lx: re-graft AmneziaWG 2.0 obfuscation onto sagernet/wireguard-go v0.0.3

Migrate the AmneziaWG graft from the old sagernet base (506b763) onto v0.0.3,
the base sing-box 1.14 uses. Strategy: start from v0.0.3, copy the net-new
obfuscation files verbatim from the proven graft (27290b6), take the 6 modified
device/ files wholesale from the graft, keep all tun/* and conn/* from v0.0.3.

Net-new (copied from 27290b6): device/magic-header.go + device/obf*.go (9).
Modified (from 27290b6): device/{send,receive,uapi,device,noise-protocol,cookie}.go.
  - receive.go: reverted two Go-1.22 'range int' loops to the v0.0.3 form (go 1.20).
  - cookie.go: keeps the 4-arg CreateReply(msgType) the grafted send.go calls.
  - noise-protocol.go: MessageEncapsulatingTransportSize=0 (AWG composes without
    the sagernet Bind.Send headroom prepend).

§010 android UDP_GRO guard (fb8d8d8) intentionally DROPPED: v0.0.3 fixes the
receive split-brain at source — bind_std.go now gates all 5 RX/offload paths on
linux||android, and gso_linux.go splits coalesced packets on android. Re-inserting
the guard would disable a now-working android RX-offload path. Requires on-device
re-verification before release.

go.mod: go 1.20, golang.org/x/sys v0.21.0 (v0.0.3 baseline). No amnezia-vpn import
paths remain. Builds clean for linux/android/windows/darwin (library packages).

.github/workflows/build-if-tag.yml

@@ -1,41 +0,0 @@
-name: build-if-tag
-
-on:
-  push:
-    tags:
-      - 'v[0-9]+.[0-9]+.[0-9]+'
-
-env:
-  APP: amneziawg-go
-
-jobs:
-  build:
-    runs-on: ubuntu-latest
-    name: build
-    steps:
-      - name: Checkout
-        uses: actions/checkout@v4
-        with:
-          ref: ${{ github.ref_name }}
-
-      - name: Login to Docker Hub
-        uses: docker/login-action@v3
-        with:
-          username: ${{ secrets.DOCKERHUB_USERNAME }}
-          password: ${{ secrets.DOCKERHUB_TOKEN }}
-
-      - name: Setup metadata
-        uses: docker/metadata-action@v5
-        id: metadata
-        with:
-          images: amneziavpn/${{ env.APP }}
-          tags: type=semver,pattern={{version}}
-
-      - name: Set up Docker Buildx
-        uses: docker/setup-buildx-action@v3
-
-      - name: Build
-        uses: docker/build-push-action@v5
-        with:
-          push: true
-          tags: ${{ steps.metadata.outputs.tags }}

Dockerfile

@@ -1,18 +0,0 @@
-FROM golang:1.24.4 as awg
-COPY . /awg
-WORKDIR /awg
-RUN go mod download && \
-    go mod verify && \
-    go build -ldflags '-linkmode external -extldflags "-fno-PIC -static"' -v -o /usr/bin
-
-FROM alpine:3.19
-ARG AWGTOOLS_RELEASE="1.0.20250901"
-
-RUN apk --no-cache add iproute2 iptables bash && \
-    cd /usr/bin/ && \
-    wget https://github.com/amnezia-vpn/amneziawg-tools/releases/download/v${AWGTOOLS_RELEASE}/alpine-3.19-amneziawg-tools.zip && \
-    unzip -j alpine-3.19-amneziawg-tools.zip && \
-    chmod +x /usr/bin/awg /usr/bin/awg-quick && \
-    ln -s /usr/bin/awg /usr/bin/wg && \
-    ln -s /usr/bin/awg-quick /usr/bin/wg-quick
-COPY --from=awg /usr/bin/amneziawg-go /usr/bin/amneziawg-go

LICENSE

@@ -1,5 +1,3 @@
-Copyright (C) 2017-2025 WireGuard LLC. All Rights Reserved.
-
 Permission is hereby granted, free of charge, to any person obtaining a copy of
 this software and associated documentation files (the "Software"), to deal in
 the Software without restriction, including without limitation the rights to

Makefile

@@ -9,23 +9,23 @@ MAKEFLAGS += --no-print-directory
 
 generate-version-and-build:
 	@export GIT_CEILING_DIRECTORIES="$(realpath $(CURDIR)/..)" && \
-	tag="$$(git describe --tags --dirty 2>/dev/null)" && \
+	tag="$$(git describe --dirty 2>/dev/null)" && \
 	ver="$$(printf 'package main\n\nconst Version = "%s"\n' "$$tag")" && \
 	[ "$$(cat version.go 2>/dev/null)" != "$$ver" ] && \
 	echo "$$ver" > version.go && \
 	git update-index --assume-unchanged version.go || true
-	@$(MAKE) amneziawg-go
+	@$(MAKE) wireguard-go
 
-amneziawg-go: $(wildcard *.go) $(wildcard */*.go)
+wireguard-go: $(wildcard *.go) $(wildcard */*.go)
 	go build -v -o "$@"
 
-install: amneziawg-go
+install: wireguard-go
-	@install -v -d "$(DESTDIR)$(BINDIR)" && install -v -m 0755 "$<" "$(DESTDIR)$(BINDIR)/amneziawg-go"
+	@install -v -d "$(DESTDIR)$(BINDIR)" && install -v -m 0755 "$<" "$(DESTDIR)$(BINDIR)/wireguard-go"
 
 test:
 	go test ./...
 
 clean:
-	rm -f amneziawg-go
+	rm -f wireguard-go
 
 .PHONY: all clean test install generate-version-and-build

README.md

@@ -1,93 +0,0 @@
-**English** · [Русский](README.ru.md)
-
-# wireguard-go (lx fork) — sagernet + AmneziaWG 2.0
-
-The WireGuard-Go runtime used by **[sing-box-lx](https://github.com/Leadaxe/sing-box-lx)**:
-**[sagernet/wireguard-go](https://github.com/sagernet/wireguard-go)** (the fork sing-box builds on) **+ AmneziaWG 2.0 obfuscation**, merged together.
-
-This is **not** a general-purpose project. It exists for one reason — see below — and lives on the **`lx`** branch.
-
----
-
-## Why this fork exists
-
-sing-box's WireGuard endpoint needs **sagernet/wireguard-go**'s additions (the `conn.Bind.Send(…, offset)` contract, `device.InputPacket`, reserved/control). AmneziaWG's DPI-evasion obfuscation lives in **[amnezia-vpn/amneziawg-go](https://github.com/amnezia-vpn/amneziawg-go)**, which is a fork of *upstream* wireguard-go and therefore **lacks** those sagernet additions.
-
-So neither fork alone works for sing-box-lx:
-
-| | sing-box-compat API | AmneziaWG obfuscation |
-|---|:---:|:---:|
-| `sagernet/wireguard-go` | ✅ | ❌ |
-| `amnezia-vpn/amneziawg-go` | ❌ | ✅ |
-| **this fork** | ✅ | ✅ |
-
-Each existing fork gives exactly **half** of what's needed:
-
-- **Take `sagernet/wireguard-go`** → sing-box-lx compiles and runs, but the AWG fields (`jc`/`h1`/`i1`…) do nothing → **no obfuscation**; AmneziaWG doesn't actually work.
-- **Take `amnezia-vpn/amneziawg-go`** → the obfuscation is there, but sing-box-lx **won't even compile** (the sagernet functions are missing).
-
-We need **both** ✅ at once, and no ready-made fork has them — so we built one by **merging**: sagernet (for the API) + amnezia (for the obfuscation). That is exactly the **"this fork"** row above.
-
-The approach: **keep the sagernet base and graft the obfuscation onto it** — rather than the reverse (adding sagernet's APIs to amneziawg-go, which would route even plain WireGuard through a foreign device). This way sing-box compiles unchanged, the obfuscation is additive and off by default, and a config without AWG fields behaves exactly like plain WireGuard.
-
-## How the merge works
-
-Both `sagernet/wireguard-go` and `amneziawg-go` descend from the same upstream `git.zx2c4.com/wireguard-go`, so they share git history — which makes a real **3-way merge** possible (not a hand-port).
-
-- **Base:** `sagernet/wireguard-go` (the exact commit sing-box pins — currently `506b7631853c`).
-- **Merged in:** `amnezia-vpn/amneziawg-go` (a tip with AWG2 / I1–I5 + the S4-keepalive fix).
-- **Key trick:** `MessageEncapsulatingTransportSize` is set to **`0`** in `device/noise-protocol.go`. sing-box-lx does not use sagernet's 8-byte `Bind.Send` headroom, and zeroing it makes the AmneziaWG obfuscation compose cleanly with no weave conflicts in the packet send path.
-- **Isolation:** the obfuscation is confined to `device/` — new files `device/obf*.go`, `device/magic-header.go`, plus grafts in `device/{send,receive,device,uapi}.go`. **`conn/`, `tun/`, `ipc/` stay pure sagernet.**
-- **Module path is unchanged** (`module github.com/sagernet/wireguard-go`) so the consumer plugs it in with a `replace` directive and needs **no import edits**.
-
-## Consumed by
-
-[sing-box-lx](https://github.com/Leadaxe/sing-box-lx) wires this in as a git submodule + a `replace`:
-
-```
-# sing-box-lx/.gitmodules
-[submodule "submodules/wireguard-go"]
-    url = https://github.com/Leadaxe/wireguard-go-awg2-lx
-    branch = lx
-
-# sing-box-lx/go.mod   (// lx)
-replace github.com/sagernet/wireguard-go => ./submodules/wireguard-go
-```
-
-Built with the `with_awg` tag, it has been **live-validated** against a real AmneziaWG 2.0 server (handshake + keepalive + outbound traffic) and cross-compiles on linux/darwin/windows × amd64/arm64.
-
-## Maintaining it (rebase onto a new sagernet tag)
-
-When sing-box bumps `sagernet/wireguard-go`, redo the merge:
-
-```sh
-git remote add origin  https://github.com/sagernet/wireguard-go    # base
-git remote add amnezia https://github.com/amnezia-vpn/amneziawg-go # obfuscation source
-git fetch --all
-git checkout -b lx <new-sagernet-commit>
-git merge amnezia/master          # real 3-way merge via the shared upstream ancestor
-```
-
-Conflict resolution recipe:
-
-1. New `device/obf*.go` + `device/magic-header.go` come in clean.
-2. **Mechanical** conflicts (amnezia → sagernet import paths, `queueconstants*`, `sticky*`, `tun.go`) → take **ours** (sagernet).
-3. Remove amnezia-added infra duplicates: `conn/gso_*.go`, `outline/*`, `tun/*_test.go`.
-4. `device/device.go` → **union** (sagernet `pauseManager` + amnezia obf fields).
-5. `device/send.go` / `receive.go` → take amnezia's obfuscation, set `MessageEncapsulatingTransportSize = 0`, and keep the 3-arg `bind.Send(…, 0)` calls.
-6. `conn/`, `tun/`, `ipc/`, `go.mod` module path → **ours** (sagernet).
-
-Then in sing-box-lx: bump the submodule, `make -f Makefile.lx lx-build`, and re-test against an AWG2 server.
-
-## Links
-
-| | |
-|---|---|
-| Consumer | [Leadaxe/sing-box-lx](https://github.com/Leadaxe/sing-box-lx) |
-| Base | [sagernet/wireguard-go](https://github.com/sagernet/wireguard-go) |
-| Obfuscation source | [amnezia-vpn/amneziawg-go](https://github.com/amnezia-vpn/amneziawg-go) · [docs.amnezia.org](https://docs.amnezia.org/documentation/amnezia-wg/) |
-| Original | [WireGuard/wireguard-go](https://git.zx2c4.com/wireguard-go/about/) |
-
-## License
-
-MIT, inherited from WireGuard-Go (see [`LICENSE`](LICENSE)). The AmneziaWG obfuscation is likewise MIT (from amneziawg-go). This is an unofficial fork, not affiliated with WireGuard, SagerNet, or Amnezia.

README.ru.md

@@ -1,93 +0,0 @@
-[English](README.md) · **Русский**
-
-# wireguard-go (lx-форк) — sagernet + AmneziaWG 2.0
-
-Рантайм WireGuard-Go для **[sing-box-lx](https://github.com/Leadaxe/sing-box-lx)**:
-**[sagernet/wireguard-go](https://github.com/sagernet/wireguard-go)** (форк, на котором собирается sing-box) **+ обфускация AmneziaWG 2.0**, слитые вместе.
-
-Это **не** универсальный проект. Он существует ради одной задачи (см. ниже) и живёт на ветке **`lx`**.
-
----
-
-## Зачем этот форк
-
-WireGuard-endpoint sing-box нуждается в добавках **sagernet/wireguard-go** (контракт `conn.Bind.Send(…, offset)`, `device.InputPacket`, reserved/control). Обфускация против DPI у AmneziaWG живёт в **[amnezia-vpn/amneziawg-go](https://github.com/amnezia-vpn/amneziawg-go)**, который форкнут от *upstream* wireguard-go и потому этих sagernet-добавок **не имеет**.
-
-Значит для sing-box-lx ни один форк по отдельности не подходит:
-
-| | API под sing-box | обфускация AmneziaWG |
-|---|:---:|:---:|
-| `sagernet/wireguard-go` | ✅ | ❌ |
-| `amnezia-vpn/amneziawg-go` | ❌ | ✅ |
-| **этот форк** | ✅ | ✅ |
-
-Каждый существующий форк даёт ровно **половину** нужного:
-
-- **возьмёшь `sagernet/wireguard-go`** → sing-box-lx соберётся и запустится, но AWG-поля (`jc`/`h1`/`i1`…) ничего не сделают → **обфускации нет**; AmneziaWG не работает;
-- **возьмёшь `amnezia-vpn/amneziawg-go`** → обфускация есть, но sing-box-lx **не скомпилируется** (нет sagernet-функций).
-
-Нужны **обе** ✅ сразу, а готового форка с двумя галочками не существует — поэтому мы собрали его **слиянием**: sagernet (за API) + amnezia (за обфускацию). Это ровно строка **«этот форк»** выше.
-
-Подход: **берём sagernet-базу и граффтим обфускацию на неё** — а не наоборот (не дотачиваем sagernet-API к amneziawg-go, иначе даже обычный WireGuard шёл бы через чужой device). Так sing-box компилируется без изменений, обфускация аддитивна и выключена по умолчанию, а конфиг без AWG-полей ведёт себя как обычный WireGuard.
-
-## Как устроен merge
-
-И `sagernet/wireguard-go`, и `amneziawg-go` происходят от одного upstream `git.zx2c4.com/wireguard-go`, поэтому делят git-историю — а значит возможен настоящий **3-way merge** (а не ручной перенос).
-
-- **База:** `sagernet/wireguard-go` (тот коммит, что пинит sing-box — сейчас `506b7631853c`).
-- **Вливаем:** `amnezia-vpn/amneziawg-go` (тип с AWG2 / I1–I5 + фикс S4-keepalive).
-- **Ключевой трюк:** `MessageEncapsulatingTransportSize` выставлен в **`0`** в `device/noise-protocol.go`. sing-box-lx не использует 8-байтный headroom sagernet для `Bind.Send`, и обнуление позволяет обфускации AmneziaWG встать чисто, без конфликтов в send-пути.
-- **Изоляция:** обфускация замкнута в `device/` — новые файлы `device/obf*.go`, `device/magic-header.go` + графты в `device/{send,receive,device,uapi}.go`. **`conn/`, `tun/`, `ipc/` остаются чистым sagernet.**
-- **Module-path не меняется** (`module github.com/sagernet/wireguard-go`), поэтому потребитель подключает форк через `replace` без правки импортов.
-
-## Кто потребляет
-
-[sing-box-lx](https://github.com/Leadaxe/sing-box-lx) подключает это как git submodule + `replace`:
-
-```
-# sing-box-lx/.gitmodules
-[submodule "submodules/wireguard-go"]
-    url = https://github.com/Leadaxe/wireguard-go-awg2-lx
-    branch = lx
-
-# sing-box-lx/go.mod   (// lx)
-replace github.com/sagernet/wireguard-go => ./submodules/wireguard-go
-```
-
-Собранный с тегом `with_awg`, он **проверен живым** сервером AmneziaWG 2.0 (handshake + keepalive + трафик наружу) и кросс-компилируется на linux/darwin/windows × amd64/arm64.
-
-## Сопровождение (ребейз на новый sagernet-тег)
-
-Когда sing-box бампит `sagernet/wireguard-go`, повторяем merge:
-
-```sh
-git remote add origin  https://github.com/sagernet/wireguard-go    # база
-git remote add amnezia https://github.com/amnezia-vpn/amneziawg-go # источник обфускации
-git fetch --all
-git checkout -b lx <новый-sagernet-коммит>
-git merge amnezia/master          # настоящий 3-way merge через общего upstream-предка
-```
-
-Рецепт разрешения конфликтов:
-
-1. Новые `device/obf*.go` + `device/magic-header.go` приходят чисто.
-2. **Механические** конфликты (import-path amnezia → sagernet, `queueconstants*`, `sticky*`, `tun.go`) → берём **наши** (sagernet).
-3. Удаляем amnezia-инфра-дубликаты: `conn/gso_*.go`, `outline/*`, `tun/*_test.go`.
-4. `device/device.go` → **union** (sagernet `pauseManager` + obf-поля amnezia).
-5. `device/send.go` / `receive.go` → берём обфускацию amnezia, ставим `MessageEncapsulatingTransportSize = 0`, сохраняем 3-арг `bind.Send(…, 0)`.
-6. `conn/`, `tun/`, `ipc/`, module-path в `go.mod` → **наши** (sagernet).
-
-Затем в sing-box-lx: бампим submodule, `make -f Makefile.lx lx-build` и пере-тест против AWG2-сервера.
-
-## Ссылки
-
-| | |
-|---|---|
-| Потребитель | [Leadaxe/sing-box-lx](https://github.com/Leadaxe/sing-box-lx) |
-| База | [sagernet/wireguard-go](https://github.com/sagernet/wireguard-go) |
-| Источник обфускации | [amnezia-vpn/amneziawg-go](https://github.com/amnezia-vpn/amneziawg-go) · [docs.amnezia.org](https://docs.amnezia.org/documentation/amnezia-wg/) |
-| Оригинал | [WireGuard/wireguard-go](https://git.zx2c4.com/wireguard-go/about/) |
-
-## Лицензия
-
-MIT, унаследована от WireGuard-Go (см. [`LICENSE`](LICENSE)). Обфускация AmneziaWG — тоже MIT (из amneziawg-go). Это неофициальный форк, не аффилирован с WireGuard, SagerNet или Amnezia.

conn/bind_std.go

@@ -1,6 +1,6 @@
 /* SPDX-License-Identifier: MIT
  *
- * Copyright (C) 2017-2023 WireGuard LLC. All Rights Reserved.
+ * Copyright (C) 2017-2025 WireGuard LLC. All Rights Reserved.
  */
 
 package conn
@@ -23,10 +23,7 @@ import (
 	"golang.org/x/net/ipv6"
 )
 
-var (
+var _ Bind = (*StdNetBind)(nil)
-	_ Bind     = (*StdNetBind)(nil)
-	_ Endpoint = (*StdNetEndpoint)(nil)
-)
 
 // StdNetBind implements Bind for all platforms. While Windows has its own Bind
 // (see bind_windows.go), it may fall back to StdNetBind.
@@ -70,10 +67,12 @@ func NewStdNetBind(externalControl control.Func) Bind {
 
 		msgsPool: sync.Pool{
 			New: func() any {
+				// ipv6.Message and ipv4.Message are interchangeable as they are
+				// both aliases for x/net/internal/socket.Message.
 				msgs := make([]ipv6.Message, IdealBatchSize)
 				for i := range msgs {
 					msgs[i].Buffers = make(net.Buffers, 1)
-					msgs[i].OOB = make([]byte, controlSize)
+					msgs[i].OOB = make([]byte, 0, stickyControlSize+gsoControlSize)
 				}
 				return &msgs
 			},
@@ -116,7 +115,7 @@ func (e *StdNetEndpoint) DstIP() netip.Addr {
 	return e.AddrPort.Addr()
 }
 
-// See sticky_default,linux, etc for implementations of SrcIP and SrcIfidx.
+// See control_default,linux, etc for implementations of SrcIP and SrcIfidx.
 
 func (e *StdNetEndpoint) DstToBytes() []byte {
 	b, _ := e.AddrPort.MarshalBinary()
@@ -166,11 +165,6 @@ func listenNet(externalControl control.Func, network string, port int) (*net.UDP
 	return conn.(*net.UDPConn), uaddr.Port, nil
 }
 
-// errEADDRINUSE is syscall.EADDRINUSE, boxed into an interface once
-// in erraddrinuse.go on almost all platforms. For other platforms,
-// it's at least non-nil.
-var errEADDRINUSE error = errors.New("")
-
 func (s *StdNetBind) Open(uport uint16) ([]ReceiveFunc, uint16, error) {
 	s.mu.Lock()
 	defer s.mu.Unlock()
@@ -197,7 +191,7 @@ again:
 
 	// Listen on the same port as we're using for ipv4.
 	v6conn, port, err = listenNet(s.externalControl, "udp6", port)
-	if uport == 0 && errors.Is(err, errEADDRINUSE) && tries < 100 {
+	if uport == 0 && errors.Is(err, syscall.EADDRINUSE) && tries < 100 {
 		v4conn.Close()
 		tries++
 		goto again
@@ -209,7 +203,7 @@ again:
 	var fns []ReceiveFunc
 	if v4conn != nil {
 		s.ipv4TxOffload, s.ipv4RxOffload = supportsUDPOffload(v4conn)
-		if runtime.GOOS == "linux" {
+		if runtime.GOOS == "linux" || runtime.GOOS == "android" {
 			v4pc = ipv4.NewPacketConn(v4conn)
 			s.ipv4PC = v4pc
 		}
@@ -218,7 +212,7 @@ again:
 	}
 	if v6conn != nil {
 		s.ipv6TxOffload, s.ipv6RxOffload = supportsUDPOffload(v6conn)
-		if runtime.GOOS == "linux" {
+		if runtime.GOOS == "linux" || runtime.GOOS == "android" {
 			v6pc = ipv6.NewPacketConn(v6conn)
 			s.ipv6PC = v6pc
 		}
@@ -234,6 +228,7 @@ again:
 
 func (s *StdNetBind) putMessages(msgs *[]ipv6.Message) {
 	for i := range *msgs {
+		(*msgs)[i].OOB = (*msgs)[i].OOB[:0]
 		(*msgs)[i] = ipv6.Message{Buffers: (*msgs)[i].Buffers, OOB: (*msgs)[i].OOB}
 	}
 	s.msgsPool.Put(msgs)
@@ -269,9 +264,9 @@ func (s *StdNetBind) receiveIP(
 	}
 	defer s.putMessages(msgs)
 	var numMsgs int
-	if runtime.GOOS == "linux" {
+	if runtime.GOOS == "linux" || runtime.GOOS == "android" {
 		if rxOffload {
-			readAt := len(*msgs) - 2
+			readAt := len(*msgs) - (IdealBatchSize / udpSegmentMaxDatagrams)
 			numMsgs, err = br.ReadBatch((*msgs)[readAt:], 0)
 			if err != nil {
 				return 0, err
@@ -325,7 +320,7 @@ func (s *StdNetBind) makeReceiveIPv6(pc *ipv6.PacketConn, conn *net.UDPConn, rxO
 // TODO: When all Binds handle IdealBatchSize, remove this dynamic function and
 // rename the IdealBatchSize constant to BatchSize.
 func (s *StdNetBind) BatchSize() int {
-	if runtime.GOOS == "linux" {
+	if runtime.GOOS == "linux" || runtime.GOOS == "android" {
 		return IdealBatchSize
 	}
 	return 1
@@ -460,7 +455,7 @@ func (s *StdNetBind) send(conn *net.UDPConn, pc batchWriter, msgs []ipv6.Message
 		err   error
 		start int
 	)
-	if runtime.GOOS == "linux" {
+	if runtime.GOOS == "linux" || runtime.GOOS == "android" {
 		for {
 			n, err = pc.WriteBatch(msgs[start:], 0)
 			if err != nil || n == len(msgs[start:]) {

conn/bind_windows.go

@@ -1,6 +1,6 @@
 /* SPDX-License-Identifier: MIT
  *
- * Copyright (C) 2017-2023 WireGuard LLC. All Rights Reserved.
+ * Copyright (C) 2017-2025 WireGuard LLC. All Rights Reserved.
  */
 
 package conn

conn/controlfns_linux.go

@@ -1,6 +1,6 @@
 /* SPDX-License-Identifier: MIT
  *
- * Copyright (C) 2017-2023 WireGuard LLC. All Rights Reserved.
+ * Copyright (C) 2017-2025 WireGuard LLC. All Rights Reserved.
  */
 
 package conn
@@ -13,6 +13,35 @@ import (
 	"golang.org/x/sys/unix"
 )
 
+// Taken from go/src/internal/syscall/unix/kernel_version_linux.go
+func kernelVersion() (major, minor int) {
+	var uname unix.Utsname
+	if err := unix.Uname(&uname); err != nil {
+		return
+	}
+
+	var (
+		values    [2]int
+		value, vi int
+	)
+	for _, c := range uname.Release {
+		if '0' <= c && c <= '9' {
+			value = (value * 10) + int(c-'0')
+		} else {
+			// Note that we're assuming N.N.N here.
+			// If we see anything else, we are likely to mis-parse it.
+			values[vi] = value
+			vi++
+			if vi >= len(values) {
+				break
+			}
+			value = 0
+		}
+	}
+
+	return values[0], values[1]
+}
+
 func init() {
 	controlFns = append(controlFns,
 
@@ -60,17 +89,19 @@ func init() {
 
 		// Attempt to enable UDP_GRO
 		func(network, address string, c syscall.RawConn) error {
-			// lx(010): skip UDP_GRO on android. The GRO receive path in bind_std.go
+			// Kernels below 5.12 are missing 98184612aca0 ("net:
-			// is gated on runtime.GOOS=="linux", which is false on android — so a
+			// udp: Add support for getsockopt(..., ..., UDP_GRO,
-			// coalesced super-packet is never split and corrupts the WG stream
+			// ..., ...);"), which means we can't read this back
-			// (download dies). Belt-and-suspenders with the rxOffload guard in
+			// later. We could pipe the return value through to
-			// features_linux.go. TX/GSO untouched.
+			// the rest of the code, but UDP_GRO is kind of buggy
-			// See SPECS/010-WG_ENDPOINT_GRO_SPLIT_BRAIN.
+			// anyway, so just gate this here.
-			if runtime.GOOS == "android" {
+			major, minor := kernelVersion()
+			if major < 5 || (major == 5 && minor < 12) {
 				return nil
 			}
+
 			c.Control(func(fd uintptr) {
-				_ = unix.SetsockoptInt(int(fd), unix.IPPROTO_UDP, socketOptionUDPGRO, 1)
+				_ = unix.SetsockoptInt(int(fd), unix.IPPROTO_UDP, unix.UDP_GRO, 1)
 			})
 			return nil
 		},

conn/controlfns_unix.go

@@ -1,4 +1,4 @@
-//go:build !windows && !linux && !wasm && !plan9 && !tamago
+//go:build !windows && !linux && !wasm
 
 /* SPDX-License-Identifier: MIT
  *

conn/erraddrinuse.go

@@ -1,14 +0,0 @@
-//go:build !plan9
-
-/* SPDX-License-Identifier: MIT
- *
- * Copyright (C) 2017-2025 WireGuard LLC. All Rights Reserved.
- */
-
-package conn
-
-import "syscall"
-
-func init() {
-	errEADDRINUSE = syscall.EADDRINUSE
-}

conn/errors_default.go

@@ -7,6 +7,6 @@
 
 package conn
 
-func errShouldDisableUDPGSO(err error) bool {
+func errShouldDisableUDPGSO(_ error) bool {
 	return false
 }

conn/errors_linux.go

@@ -1,6 +1,6 @@
 /* SPDX-License-Identifier: MIT
  *
- * Copyright (C) 2017-2023 WireGuard LLC. All Rights Reserved.
+ * Copyright (C) 2017-2025 WireGuard LLC. All Rights Reserved.
  */
 
 package conn

conn/features_default.go

@@ -3,13 +3,13 @@
 
 /* SPDX-License-Identifier: MIT
  *
- * Copyright (C) 2017-2023 WireGuard LLC. All Rights Reserved.
+ * Copyright (C) 2017-2025 WireGuard LLC. All Rights Reserved.
  */
 
 package conn
 
 import "net"
 
-func supportsUDPOffload(conn *net.UDPConn) (txOffload, rxOffload bool) {
+func supportsUDPOffload(_ *net.UDPConn) (txOffload, rxOffload bool) {
 	return
 }

conn/features_linux.go

@@ -1,49 +1,26 @@
 /* SPDX-License-Identifier: MIT
  *
- * Copyright (C) 2017-2023 WireGuard LLC. All Rights Reserved.
+ * Copyright (C) 2017-2025 WireGuard LLC. All Rights Reserved.
  */
 
 package conn
 
 import (
 	"net"
-	"runtime"
 
 	"golang.org/x/sys/unix"
 )
 
-const (
-	// TODO: upstream to x/sys/unix
-	socketOptionLevelUDP   = 17
-	socketOptionUDPSegment = 103
-	socketOptionUDPGRO     = 104
-)
-
 func supportsUDPOffload(conn *net.UDPConn) (txOffload, rxOffload bool) {
 	rc, err := conn.SyscallConn()
 	if err != nil {
 		return
 	}
 	err = rc.Control(func(fd uintptr) {
-		_, errSyscall := unix.GetsockoptInt(int(fd), unix.IPPROTO_UDP, socketOptionUDPSegment)
+		_, errSyscall := unix.GetsockoptInt(int(fd), unix.IPPROTO_UDP, unix.UDP_SEGMENT)
-		if errSyscall != nil {
+		txOffload = errSyscall == nil
-			return
+		opt, errSyscall := unix.GetsockoptInt(int(fd), unix.IPPROTO_UDP, unix.UDP_GRO)
-		}
+		rxOffload = errSyscall == nil && opt == 1
-		txOffload = true
-		// lx(010): never advertise RX offload on android. runtime.GOOS=="android"
-		// (not "linux"), so the GRO receive dispatcher in bind_std.go (gated on
-		// GOOS=="linux") is dead there — a coalesced GRO super-packet would be read
-		// as one datagram and corrupt the WG transport stream, killing download.
-		// Confirmed on device (CPH2411/Android-15: rxOffload=true, dispatch=single).
-		// TX is left untouched. See SPECS/010-WG_ENDPOINT_GRO_SPLIT_BRAIN.
-		if runtime.GOOS == "android" {
-			return
-		}
-		opt, errSyscall := unix.GetsockoptInt(int(fd), unix.IPPROTO_UDP, socketOptionUDPGRO)
-		if errSyscall != nil {
-			return
-		}
-		rxOffload = opt == 1
 	})
 	if err != nil {
 		return false, false

conn/gso_default.go

@@ -0,0 +1,21 @@
+//go:build !linux
+
+/* SPDX-License-Identifier: MIT
+ *
+ * Copyright (C) 2017-2025 WireGuard LLC. All Rights Reserved.
+ */
+
+package conn
+
+// getGSOSize parses control for UDP_GRO and if found returns its GSO size data.
+func getGSOSize(control []byte) (int, error) {
+	return 0, nil
+}
+
+// setGSOSize sets a UDP_SEGMENT in control based on gsoSize.
+func setGSOSize(control *[]byte, gsoSize uint16) {
+}
+
+// gsoControlSize returns the recommended buffer size for pooling sticky and UDP
+// offloading control data.
+const gsoControlSize = 0

conn/gso_linux.go

@@ -0,0 +1,65 @@
+//go:build linux
+
+/* SPDX-License-Identifier: MIT
+ *
+ * Copyright (C) 2017-2025 WireGuard LLC. All Rights Reserved.
+ */
+
+package conn
+
+import (
+	"fmt"
+	"unsafe"
+
+	"golang.org/x/sys/unix"
+)
+
+const (
+	sizeOfGSOData = 2
+)
+
+// getGSOSize parses control for UDP_GRO and if found returns its GSO size data.
+func getGSOSize(control []byte) (int, error) {
+	var (
+		hdr  unix.Cmsghdr
+		data []byte
+		rem  = control
+		err  error
+	)
+
+	for len(rem) > unix.SizeofCmsghdr {
+		hdr, data, rem, err = unix.ParseOneSocketControlMessage(rem)
+		if err != nil {
+			return 0, fmt.Errorf("error parsing socket control message: %w", err)
+		}
+		if hdr.Level == unix.SOL_UDP && hdr.Type == unix.UDP_GRO && len(data) >= sizeOfGSOData {
+			var gso uint16
+			copy(unsafe.Slice((*byte)(unsafe.Pointer(&gso)), sizeOfGSOData), data[:sizeOfGSOData])
+			return int(gso), nil
+		}
+	}
+	return 0, nil
+}
+
+// setGSOSize sets a UDP_SEGMENT in control based on gsoSize. It leaves existing
+// data in control untouched.
+func setGSOSize(control *[]byte, gsoSize uint16) {
+	existingLen := len(*control)
+	avail := cap(*control) - existingLen
+	space := unix.CmsgSpace(sizeOfGSOData)
+	if avail < space {
+		return
+	}
+	*control = (*control)[:cap(*control)]
+	gsoControl := (*control)[existingLen:]
+	hdr := (*unix.Cmsghdr)(unsafe.Pointer(&(gsoControl)[0]))
+	hdr.Level = unix.SOL_UDP
+	hdr.Type = unix.UDP_SEGMENT
+	hdr.SetLen(unix.CmsgLen(sizeOfGSOData))
+	copy((gsoControl)[unix.CmsgLen(0):], unsafe.Slice((*byte)(unsafe.Pointer(&gsoSize)), sizeOfGSOData))
+	*control = (*control)[:existingLen+space]
+}
+
+// gsoControlSize returns the recommended buffer size for pooling UDP
+// offloading control data.
+var gsoControlSize = unix.CmsgSpace(sizeOfGSOData)

conn/sticky_default.go

@@ -1,8 +1,8 @@
-//go:build !(linux && !android)
+//go:build !linux || android
 
 /* SPDX-License-Identifier: MIT
  *
- * Copyright (C) 2017-2023 WireGuard LLC. All Rights Reserved.
+ * Copyright (C) 2017-2025 WireGuard LLC. All Rights Reserved.
  */
 
 package conn
@@ -22,7 +22,7 @@ func (e *StdNetEndpoint) SrcToString() string {
 }
 
 // TODO: macOS, FreeBSD and other BSDs likely do support the sticky sockets
-// ({get,set}srcControl feature set, but use alternatively named flags and need
+// {get,set}srcControl feature set, but use alternatively named flags and need
 // ports and require testing.
 
 // getSrcFromControl parses the control for PKTINFO and if found updates ep with
@@ -35,17 +35,8 @@ func getSrcFromControl(control []byte, ep *StdNetEndpoint) {
 func setSrcControl(control *[]byte, ep *StdNetEndpoint) {
 }
 
-// getGSOSize parses control for UDP_GRO and if found returns its GSO size data.
+// stickyControlSize returns the recommended buffer size for pooling sticky
-func getGSOSize(control []byte) (int, error) {
-	return 0, nil
-}
-
-// setGSOSize sets a UDP_SEGMENT in control based on gsoSize.
-func setGSOSize(control *[]byte, gsoSize uint16) {
-}
-
-// controlSize returns the recommended buffer size for pooling sticky and UDP
 // offloading control data.
-const controlSize = 0
+const stickyControlSize = 0
 
 const StdNetSupportsStickySockets = false

conn/sticky_linux.go

@@ -2,13 +2,12 @@
 
 /* SPDX-License-Identifier: MIT
  *
- * Copyright (C) 2017-2023 WireGuard LLC. All Rights Reserved.
+ * Copyright (C) 2017-2025 WireGuard LLC. All Rights Reserved.
  */
 
 package conn
 
 import (
-	"fmt"
 	"net/netip"
 	"unsafe"
 
@@ -106,54 +105,8 @@ func setSrcControl(control *[]byte, ep *StdNetEndpoint) {
 	*control = append(*control, ep.src...)
 }
 
-const (
+// stickyControlSize returns the recommended buffer size for pooling sticky
-	sizeOfGSOData = 2
-)
-
-// getGSOSize parses control for UDP_GRO and if found returns its GSO size data.
-func getGSOSize(control []byte) (int, error) {
-	var (
-		hdr  unix.Cmsghdr
-		data []byte
-		rem  = control
-		err  error
-	)
-
-	for len(rem) > unix.SizeofCmsghdr {
-		hdr, data, rem, err = unix.ParseOneSocketControlMessage(rem)
-		if err != nil {
-			return 0, fmt.Errorf("error parsing socket control message: %w", err)
-		}
-		if hdr.Level == socketOptionLevelUDP && hdr.Type == socketOptionUDPGRO && len(data) >= sizeOfGSOData {
-			var gso uint16
-			copy(unsafe.Slice((*byte)(unsafe.Pointer(&gso)), sizeOfGSOData), data[:sizeOfGSOData])
-			return int(gso), nil
-		}
-	}
-	return 0, nil
-}
-
-// setGSOSize sets a UDP_SEGMENT in control based on gsoSize. It leaves existing
-// data in control untouched.
-func setGSOSize(control *[]byte, gsoSize uint16) {
-	existingLen := len(*control)
-	avail := cap(*control) - existingLen
-	space := unix.CmsgSpace(sizeOfGSOData)
-	if avail < space {
-		return
-	}
-	*control = (*control)[:cap(*control)]
-	gsoControl := (*control)[existingLen:]
-	hdr := (*unix.Cmsghdr)(unsafe.Pointer(&(gsoControl)[0]))
-	hdr.Level = socketOptionLevelUDP
-	hdr.Type = socketOptionUDPSegment
-	hdr.SetLen(unix.CmsgLen(sizeOfGSOData))
-	copy((gsoControl)[unix.SizeofCmsghdr:], unsafe.Slice((*byte)(unsafe.Pointer(&gsoSize)), sizeOfGSOData))
-	*control = (*control)[:existingLen+space]
-}
-
-// controlSize returns the recommended buffer size for pooling sticky and UDP
 // offloading control data.
-var controlSize = unix.CmsgSpace(unix.SizeofInet6Pktinfo) + unix.CmsgSpace(sizeOfGSOData)
+var stickyControlSize = unix.CmsgSpace(unix.SizeofInet6Pktinfo)
 
 const StdNetSupportsStickySockets = true

device/keypair.go

@@ -1,6 +1,6 @@
 /* SPDX-License-Identifier: MIT
  *
- * Copyright (C) 2017-2023 WireGuard LLC. All Rights Reserved.
+ * Copyright (C) 2017-2025 WireGuard LLC. All Rights Reserved.
  */
 
 package device

device/queueconstants_android.go

@@ -1,6 +1,6 @@
 /* SPDX-License-Identifier: MIT
  *
- * Copyright (C) 2017-2023 WireGuard LLC. All Rights Reserved.
+ * Copyright (C) 2017-2025 WireGuard LLC. All Rights Reserved.
  */
 
 package device
@@ -14,6 +14,6 @@ const (
 	QueueOutboundSize          = 1024
 	QueueInboundSize           = 1024
 	QueueHandshakeSize         = 1024
-	MaxSegmentSize             = 2200
+	MaxSegmentSize             = (1 << 16) - 1 // largest possible UDP datagram
 	PreallocatedBuffersPerPool = 4096
 )

device/queueconstants_default.go

@@ -2,7 +2,7 @@
 
 /* SPDX-License-Identifier: MIT
  *
- * Copyright (C) 2017-2023 WireGuard LLC. All Rights Reserved.
+ * Copyright (C) 2017-2025 WireGuard LLC. All Rights Reserved.
  */
 
 package device

device/receive.go

@@ -96,13 +96,13 @@ func (device *Device) RoutineReceiveIncoming(
 		elemsByPeer = make(map[*Peer]*QueueInboundElementsContainer, maxBatchSize)
 	)
 
-	for i := range maxBatchSize {
+	for i := range bufsArrs {
 		bufsArrs[i] = device.GetMessageBuffer()
 		bufs[i] = bufsArrs[i][:]
 	}
 
 	defer func() {
-		for i := range maxBatchSize {
+		for i := 0; i < maxBatchSize; i++ {
 			if bufsArrs[i] != nil {
 				device.PutMessageBuffer(bufsArrs[i])
 			}

device/sticky_default.go

@@ -7,6 +7,6 @@ import (
 	"github.com/sagernet/wireguard-go/rwcancel"
 )
 
-func (device *Device) startRouteListener(bind conn.Bind) (*rwcancel.RWCancel, error) {
+func (device *Device) startRouteListener(_ conn.Bind) (*rwcancel.RWCancel, error) {
 	return nil, nil
 }

device/sticky_linux.go

@@ -1,6 +1,6 @@
 /* SPDX-License-Identifier: MIT
  *
- * Copyright (C) 2017-2023 WireGuard LLC. All Rights Reserved.
+ * Copyright (C) 2017-2025 WireGuard LLC. All Rights Reserved.
  *
  * This implements userspace semantics of "sticky sockets", modeled after
  * WireGuard's kernelspace implementation. This is more or less a straight port
@@ -9,7 +9,7 @@
  *
  * Currently there is no way to achieve this within the net package:
  * See e.g. https://github.com/golang/go/issues/17930
- * So this code is remains platform dependent.
+ * So this code remains platform dependent.
  */
 
 package device
@@ -46,7 +46,7 @@ func (device *Device) startRouteListener(bind conn.Bind) (*rwcancel.RWCancel, er
 	return netlinkCancel, nil
 }
 
-func (device *Device) routineRouteListener(bind conn.Bind, netlinkSock int, netlinkCancel *rwcancel.RWCancel) {
+func (device *Device) routineRouteListener(_ conn.Bind, netlinkSock int, netlinkCancel *rwcancel.RWCancel) {
 	type peerEndpointPtr struct {
 		peer     *Peer
 		endpoint *conn.Endpoint

device/tun.go

@@ -1,6 +1,6 @@
 /* SPDX-License-Identifier: MIT
  *
- * Copyright (C) 2017-2023 WireGuard LLC. All Rights Reserved.
+ * Copyright (C) 2017-2025 WireGuard LLC. All Rights Reserved.
  */
 
 package device

go.mod

@@ -1,11 +1,11 @@
 module github.com/sagernet/wireguard-go
 
-go 1.24
+go 1.20
 
 require (
 	github.com/sagernet/sing v0.7.10
 	golang.org/x/crypto v0.13.0
 	golang.org/x/net v0.15.0
-	golang.org/x/sys v0.12.0
+	golang.org/x/sys v0.21.0
 	golang.zx2c4.com/wintun v0.0.0-20230126152724-0fa3db229ce2
 )

go.sum

@@ -4,7 +4,7 @@ golang.org/x/crypto v0.13.0 h1:mvySKfSWJ+UKUii46M40LOvyWfN0s2U+46/jDd0e6Ck=
 golang.org/x/crypto v0.13.0/go.mod h1:y6Z2r+Rw4iayiXXAIxJIDAJ1zMW4yaTpebo8fPOliYc=
 golang.org/x/net v0.15.0 h1:ugBLEUaxABaB5AJqW9enI0ACdci2RUd4eP51NTBvuJ8=
 golang.org/x/net v0.15.0/go.mod h1:idbUs1IY1+zTqbi8yxTbhexhEEk5ur9LInksu6HrEpk=
-golang.org/x/sys v0.12.0 h1:CM0HF96J0hcLAwsHPJZjfdNzs0gftsLfgKt57wWHJ0o=
+golang.org/x/sys v0.21.0 h1:rF+pYz3DAGSQAxAu1CbC7catZg4ebC4UIeIhKxBZvws=
-golang.org/x/sys v0.12.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.21.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
 golang.zx2c4.com/wintun v0.0.0-20230126152724-0fa3db229ce2 h1:B82qJJgjvYKsXS9jeunTOisW56dUokqW/FOteYJJ/yg=
 golang.zx2c4.com/wintun v0.0.0-20230126152724-0fa3db229ce2/go.mod h1:deeaetjYA+DHMHg+sMSMI58GrEteJUUzzw7en6TJQcI=

ipc/uapi_fake.go

@@ -1,17 +0,0 @@
-//go:build wasm || plan9 || aix || solaris || illumos
-
-/* SPDX-License-Identifier: MIT
- *
- * Copyright (C) 2017-2023 WireGuard LLC. All Rights Reserved.
- */
-
-package ipc
-
-// Made up sentinel error codes for {js,wasip1}/wasm, and plan9.
-const (
-	IpcErrorIO        = 1
-	IpcErrorInvalid   = 2
-	IpcErrorPortInUse = 3
-	IpcErrorUnknown   = 4
-	IpcErrorProtocol  = 5
-)

ipc/uapi_linux.go

@@ -1,6 +1,6 @@
 /* SPDX-License-Identifier: MIT
  *
- * Copyright (C) 2017-2023 WireGuard LLC. All Rights Reserved.
+ * Copyright (C) 2017-2025 WireGuard LLC. All Rights Reserved.
  */
 
 package ipc

ipc/uapi_unix.go

@@ -26,7 +26,7 @@ const (
 
 // socketDirectory is variable because it is modified by a linker
 // flag in wireguard-android.
-var socketDirectory = "/var/run/amneziawg"
+var socketDirectory = "/var/run/wireguard"
 
 func sockPath(iface string) string {
 	return fmt.Sprintf("%s/%s.sock", socketDirectory, iface)

ipc/uapi_wasm.go

@@ -1,5 +1,3 @@
-//go:build tamago
-
 /* SPDX-License-Identifier: MIT
  *
  * Copyright (C) 2017-2025 WireGuard LLC. All Rights Reserved.
@@ -7,7 +5,7 @@
 
 package ipc
 
-// Made up sentinel error codes for tamago platform.
+// Made up sentinel error codes for {js,wasip1}/wasm.
 const (
 	IpcErrorIO        = 1
 	IpcErrorInvalid   = 2

ipc/uapi_windows.go

@@ -1,6 +1,6 @@
 /* SPDX-License-Identifier: MIT
  *
- * Copyright (C) 2017-2023 WireGuard LLC. All Rights Reserved.
+ * Copyright (C) 2017-2025 WireGuard LLC. All Rights Reserved.
  */
 
 package ipc

module_rename.py

@@ -1,33 +0,0 @@
-#!/usr/bin/env python3
-# -*- coding: utf-8 -*-
-
-import os
-import argparse
-import fileinput
-
-
-PKG_ORIGINAL = "github.com/tailscale/wireguard-go"
-PKG_NEW = "github.com/sagernet/wireguard-go"
-
-EXTENSIONS = [".go", ".md", ".mod", ".sh"]
-
-parser = argparse.ArgumentParser()
-parser.add_argument("-r", "--reverse", action="store_true")
-args = parser.parse_args()
-
-
-def replace_line(line):
-    if args.reverse:
-        return line.replace(PKG_NEW, PKG_ORIGINAL)
-    return line.replace(PKG_ORIGINAL, PKG_NEW)
-
-
-for dirpath, dirnames, filenames in os.walk("."):
-    # Skip hidden directories like .git
-    dirnames[:] = [d for d in dirnames if not d[0] == "."]
-    filenames = [f for f in filenames if os.path.splitext(f)[1] in EXTENSIONS]
-    for filename in filenames:
-        file_path = os.path.join(dirpath, filename)
-        with fileinput.FileInput(file_path, inplace=True) as file:
-            for line in file:
-                print(replace_line(line), end="")

reformat.sh

@@ -0,0 +1,9 @@
+#!/usr/bin/env bash
+
+set -e -o pipefail
+
+GO_FILES=$(find . -name "*.go" | grep -v .git)
+
+gofumpt -l -w $GO_FILES
+gofmt -l -w $GO_FILES
+gci write $GO_FILES

rename-module.sh

@@ -0,0 +1,37 @@
+#!/usr/bin/env bash
+
+set -e -o pipefail
+
+OLD_MODULE_NAME="github.com/tailscale/wireguard-go"
+NEW_MODULE_NAME="github.com/sagernet/wireguard-go"
+
+rules=$(cat <<EOF
+id: replace-module
+language: go
+rule:
+  kind: import_spec
+  pattern: \$OLD_IMPORT
+constraints:
+  OLD_IMPORT:
+    has:
+      field: path
+      regex: ^"$OLD_MODULE_NAME
+transform:
+  NEW_IMPORT:
+    replace:
+      source: \$OLD_IMPORT
+      replace: $OLD_MODULE_NAME(?<PATH>.*)
+      by: $NEW_MODULE_NAME\$PATH
+fix: \$NEW_IMPORT
+EOF
+)
+
+sg scan --inline-rules "$rules" -U
+
+sed -i "s|module $OLD_MODULE_NAME|module $NEW_MODULE_NAME|" go.mod
+
+go mod tidy
+
+./reformat.sh
+
+git commit -m "Rename module" -a

rwcancel/rwcancel.go

@@ -1,4 +1,4 @@
-//go:build !windows && !wasm && !plan9 && !tamago
+//go:build !windows && !wasm
 
 /* SPDX-License-Identifier: MIT
  *

rwcancel/rwcancel_stub.go

@@ -1,4 +1,4 @@
-//go:build windows || wasm || plan9 || tamago
+//go:build windows || wasm
 
 // SPDX-License-Identifier: MIT
 

tun/checksum.go

@@ -3,710 +3,111 @@ package tun
 import (
 	"encoding/binary"
 	"math/bits"
-	"strconv"
-
-	"golang.org/x/sys/cpu"
 )
 
-// checksumGeneric64 is a reference implementation of checksum using 64 bit
+// TODO: Explore SIMD and/or other assembly optimizations.
-// arithmetic for use in testing or when an architecture-specific implementation
+func checksumNoFold(b []byte, initial uint64) uint64 {
-// is not available.
+	tmp := make([]byte, 8)
-func checksumGeneric64(b []byte, initial uint16) uint16 {
+	binary.NativeEndian.PutUint64(tmp, initial)
-	var ac uint64
+	ac := binary.BigEndian.Uint64(tmp)
 	var carry uint64
 
-	if cpu.IsBigEndian {
-		ac = uint64(initial)
-	} else {
-		ac = uint64(bits.ReverseBytes16(initial))
-	}
-
 	for len(b) >= 128 {
-		if cpu.IsBigEndian {
+		ac, carry = bits.Add64(ac, binary.NativeEndian.Uint64(b[:8]), 0)
-			ac, carry = bits.Add64(ac, binary.BigEndian.Uint64(b[:8]), carry)
+		ac, carry = bits.Add64(ac, binary.NativeEndian.Uint64(b[8:16]), carry)
-			ac, carry = bits.Add64(ac, binary.BigEndian.Uint64(b[8:16]), carry)
+		ac, carry = bits.Add64(ac, binary.NativeEndian.Uint64(b[16:24]), carry)
-			ac, carry = bits.Add64(ac, binary.BigEndian.Uint64(b[16:24]), carry)
+		ac, carry = bits.Add64(ac, binary.NativeEndian.Uint64(b[24:32]), carry)
-			ac, carry = bits.Add64(ac, binary.BigEndian.Uint64(b[24:32]), carry)
+		ac, carry = bits.Add64(ac, binary.NativeEndian.Uint64(b[32:40]), carry)
-			ac, carry = bits.Add64(ac, binary.BigEndian.Uint64(b[32:40]), carry)
+		ac, carry = bits.Add64(ac, binary.NativeEndian.Uint64(b[40:48]), carry)
-			ac, carry = bits.Add64(ac, binary.BigEndian.Uint64(b[40:48]), carry)
+		ac, carry = bits.Add64(ac, binary.NativeEndian.Uint64(b[48:56]), carry)
-			ac, carry = bits.Add64(ac, binary.BigEndian.Uint64(b[48:56]), carry)
+		ac, carry = bits.Add64(ac, binary.NativeEndian.Uint64(b[56:64]), carry)
-			ac, carry = bits.Add64(ac, binary.BigEndian.Uint64(b[56:64]), carry)
+		ac, carry = bits.Add64(ac, binary.NativeEndian.Uint64(b[64:72]), carry)
-			ac, carry = bits.Add64(ac, binary.BigEndian.Uint64(b[64:72]), carry)
+		ac, carry = bits.Add64(ac, binary.NativeEndian.Uint64(b[72:80]), carry)
-			ac, carry = bits.Add64(ac, binary.BigEndian.Uint64(b[72:80]), carry)
+		ac, carry = bits.Add64(ac, binary.NativeEndian.Uint64(b[80:88]), carry)
-			ac, carry = bits.Add64(ac, binary.BigEndian.Uint64(b[80:88]), carry)
+		ac, carry = bits.Add64(ac, binary.NativeEndian.Uint64(b[88:96]), carry)
-			ac, carry = bits.Add64(ac, binary.BigEndian.Uint64(b[88:96]), carry)
+		ac, carry = bits.Add64(ac, binary.NativeEndian.Uint64(b[96:104]), carry)
-			ac, carry = bits.Add64(ac, binary.BigEndian.Uint64(b[96:104]), carry)
+		ac, carry = bits.Add64(ac, binary.NativeEndian.Uint64(b[104:112]), carry)
-			ac, carry = bits.Add64(ac, binary.BigEndian.Uint64(b[104:112]), carry)
+		ac, carry = bits.Add64(ac, binary.NativeEndian.Uint64(b[112:120]), carry)
-			ac, carry = bits.Add64(ac, binary.BigEndian.Uint64(b[112:120]), carry)
+		ac, carry = bits.Add64(ac, binary.NativeEndian.Uint64(b[120:128]), carry)
-			ac, carry = bits.Add64(ac, binary.BigEndian.Uint64(b[120:128]), carry)
+		ac += carry
-		} else {
-			ac, carry = bits.Add64(ac, binary.LittleEndian.Uint64(b[:8]), carry)
-			ac, carry = bits.Add64(ac, binary.LittleEndian.Uint64(b[8:16]), carry)
-			ac, carry = bits.Add64(ac, binary.LittleEndian.Uint64(b[16:24]), carry)
-			ac, carry = bits.Add64(ac, binary.LittleEndian.Uint64(b[24:32]), carry)
-			ac, carry = bits.Add64(ac, binary.LittleEndian.Uint64(b[32:40]), carry)
-			ac, carry = bits.Add64(ac, binary.LittleEndian.Uint64(b[40:48]), carry)
-			ac, carry = bits.Add64(ac, binary.LittleEndian.Uint64(b[48:56]), carry)
-			ac, carry = bits.Add64(ac, binary.LittleEndian.Uint64(b[56:64]), carry)
-			ac, carry = bits.Add64(ac, binary.LittleEndian.Uint64(b[64:72]), carry)
-			ac, carry = bits.Add64(ac, binary.LittleEndian.Uint64(b[72:80]), carry)
-			ac, carry = bits.Add64(ac, binary.LittleEndian.Uint64(b[80:88]), carry)
-			ac, carry = bits.Add64(ac, binary.LittleEndian.Uint64(b[88:96]), carry)
-			ac, carry = bits.Add64(ac, binary.LittleEndian.Uint64(b[96:104]), carry)
-			ac, carry = bits.Add64(ac, binary.LittleEndian.Uint64(b[104:112]), carry)
-			ac, carry = bits.Add64(ac, binary.LittleEndian.Uint64(b[112:120]), carry)
-			ac, carry = bits.Add64(ac, binary.LittleEndian.Uint64(b[120:128]), carry)
-		}
 		b = b[128:]
 	}
 	if len(b) >= 64 {
-		if cpu.IsBigEndian {
+		ac, carry = bits.Add64(ac, binary.NativeEndian.Uint64(b[:8]), 0)
-			ac, carry = bits.Add64(ac, binary.BigEndian.Uint64(b[:8]), carry)
+		ac, carry = bits.Add64(ac, binary.NativeEndian.Uint64(b[8:16]), carry)
-			ac, carry = bits.Add64(ac, binary.BigEndian.Uint64(b[8:16]), carry)
+		ac, carry = bits.Add64(ac, binary.NativeEndian.Uint64(b[16:24]), carry)
-			ac, carry = bits.Add64(ac, binary.BigEndian.Uint64(b[16:24]), carry)
+		ac, carry = bits.Add64(ac, binary.NativeEndian.Uint64(b[24:32]), carry)
-			ac, carry = bits.Add64(ac, binary.BigEndian.Uint64(b[24:32]), carry)
+		ac, carry = bits.Add64(ac, binary.NativeEndian.Uint64(b[32:40]), carry)
-			ac, carry = bits.Add64(ac, binary.BigEndian.Uint64(b[32:40]), carry)
+		ac, carry = bits.Add64(ac, binary.NativeEndian.Uint64(b[40:48]), carry)
-			ac, carry = bits.Add64(ac, binary.BigEndian.Uint64(b[40:48]), carry)
+		ac, carry = bits.Add64(ac, binary.NativeEndian.Uint64(b[48:56]), carry)
-			ac, carry = bits.Add64(ac, binary.BigEndian.Uint64(b[48:56]), carry)
+		ac, carry = bits.Add64(ac, binary.NativeEndian.Uint64(b[56:64]), carry)
-			ac, carry = bits.Add64(ac, binary.BigEndian.Uint64(b[56:64]), carry)
+		ac += carry
-		} else {
-			ac, carry = bits.Add64(ac, binary.LittleEndian.Uint64(b[:8]), carry)
-			ac, carry = bits.Add64(ac, binary.LittleEndian.Uint64(b[8:16]), carry)
-			ac, carry = bits.Add64(ac, binary.LittleEndian.Uint64(b[16:24]), carry)
-			ac, carry = bits.Add64(ac, binary.LittleEndian.Uint64(b[24:32]), carry)
-			ac, carry = bits.Add64(ac, binary.LittleEndian.Uint64(b[32:40]), carry)
-			ac, carry = bits.Add64(ac, binary.LittleEndian.Uint64(b[40:48]), carry)
-			ac, carry = bits.Add64(ac, binary.LittleEndian.Uint64(b[48:56]), carry)
-			ac, carry = bits.Add64(ac, binary.LittleEndian.Uint64(b[56:64]), carry)
-		}
 		b = b[64:]
 	}
 	if len(b) >= 32 {
-		if cpu.IsBigEndian {
+		ac, carry = bits.Add64(ac, binary.NativeEndian.Uint64(b[:8]), 0)
-			ac, carry = bits.Add64(ac, binary.BigEndian.Uint64(b[:8]), carry)
+		ac, carry = bits.Add64(ac, binary.NativeEndian.Uint64(b[8:16]), carry)
-			ac, carry = bits.Add64(ac, binary.BigEndian.Uint64(b[8:16]), carry)
+		ac, carry = bits.Add64(ac, binary.NativeEndian.Uint64(b[16:24]), carry)
-			ac, carry = bits.Add64(ac, binary.BigEndian.Uint64(b[16:24]), carry)
+		ac, carry = bits.Add64(ac, binary.NativeEndian.Uint64(b[24:32]), carry)
-			ac, carry = bits.Add64(ac, binary.BigEndian.Uint64(b[24:32]), carry)
+		ac += carry
-		} else {
-			ac, carry = bits.Add64(ac, binary.LittleEndian.Uint64(b[:8]), carry)
-			ac, carry = bits.Add64(ac, binary.LittleEndian.Uint64(b[8:16]), carry)
-			ac, carry = bits.Add64(ac, binary.LittleEndian.Uint64(b[16:24]), carry)
-			ac, carry = bits.Add64(ac, binary.LittleEndian.Uint64(b[24:32]), carry)
-		}
 		b = b[32:]
 	}
 	if len(b) >= 16 {
-		if cpu.IsBigEndian {
+		ac, carry = bits.Add64(ac, binary.NativeEndian.Uint64(b[:8]), 0)
-			ac, carry = bits.Add64(ac, binary.BigEndian.Uint64(b[:8]), carry)
+		ac, carry = bits.Add64(ac, binary.NativeEndian.Uint64(b[8:16]), carry)
-			ac, carry = bits.Add64(ac, binary.BigEndian.Uint64(b[8:16]), carry)
+		ac += carry
-		} else {
-			ac, carry = bits.Add64(ac, binary.LittleEndian.Uint64(b[:8]), carry)
-			ac, carry = bits.Add64(ac, binary.LittleEndian.Uint64(b[8:16]), carry)
-		}
 		b = b[16:]
 	}
 	if len(b) >= 8 {
-		if cpu.IsBigEndian {
+		ac, carry = bits.Add64(ac, binary.NativeEndian.Uint64(b[:8]), 0)
-			ac, carry = bits.Add64(ac, binary.BigEndian.Uint64(b), carry)
+		ac += carry
-		} else {
-			ac, carry = bits.Add64(ac, binary.LittleEndian.Uint64(b), carry)
-		}
 		b = b[8:]
 	}
 	if len(b) >= 4 {
-		if cpu.IsBigEndian {
+		ac, carry = bits.Add64(ac, uint64(binary.NativeEndian.Uint32(b[:4])), 0)
-			ac, carry = bits.Add64(ac, uint64(binary.BigEndian.Uint32(b)), carry)
+		ac += carry
-		} else {
-			ac, carry = bits.Add64(ac, uint64(binary.LittleEndian.Uint32(b)), carry)
-		}
 		b = b[4:]
 	}
 	if len(b) >= 2 {
-		if cpu.IsBigEndian {
+		ac, carry = bits.Add64(ac, uint64(binary.NativeEndian.Uint16(b[:2])), 0)
-			ac, carry = bits.Add64(ac, uint64(binary.BigEndian.Uint16(b)), carry)
+		ac += carry
-		} else {
-			ac, carry = bits.Add64(ac, uint64(binary.LittleEndian.Uint16(b)), carry)
-		}
 		b = b[2:]
 	}
-	if len(b) >= 1 {
+	if len(b) == 1 {
-		if cpu.IsBigEndian {
+		tmp := binary.NativeEndian.Uint16([]byte{b[0], 0})
-			ac, carry = bits.Add64(ac, uint64(b[0])<<8, carry)
+		ac, carry = bits.Add64(ac, uint64(tmp), 0)
-		} else {
+		ac += carry
-			ac, carry = bits.Add64(ac, uint64(b[0]), carry)
-		}
 	}
 
-	folded := ipChecksumFold64(ac, carry)
+	binary.NativeEndian.PutUint64(tmp, ac)
-	if !cpu.IsBigEndian {
+	return binary.BigEndian.Uint64(tmp)
-		folded = bits.ReverseBytes16(folded)
-	}
-	return folded
 }
 
-// checksumGeneric32 is a reference implementation of checksum using 32 bit
+func checksum(b []byte, initial uint64) uint16 {
-// arithmetic for use in testing or when an architecture-specific implementation
+	ac := checksumNoFold(b, initial)
-// is not available.
+	ac = (ac >> 16) + (ac & 0xffff)
-func checksumGeneric32(b []byte, initial uint16) uint16 {
+	ac = (ac >> 16) + (ac & 0xffff)
-	var ac uint32
+	ac = (ac >> 16) + (ac & 0xffff)
-	var carry uint32
+	ac = (ac >> 16) + (ac & 0xffff)
-
+	return uint16(ac)
-	if cpu.IsBigEndian {
-		ac = uint32(initial)
-	} else {
-		ac = uint32(bits.ReverseBytes16(initial))
-	}
-
-	for len(b) >= 64 {
-		if cpu.IsBigEndian {
-			ac, carry = bits.Add32(ac, binary.BigEndian.Uint32(b[:8]), carry)
-			ac, carry = bits.Add32(ac, binary.BigEndian.Uint32(b[4:8]), carry)
-			ac, carry = bits.Add32(ac, binary.BigEndian.Uint32(b[8:12]), carry)
-			ac, carry = bits.Add32(ac, binary.BigEndian.Uint32(b[12:16]), carry)
-			ac, carry = bits.Add32(ac, binary.BigEndian.Uint32(b[16:20]), carry)
-			ac, carry = bits.Add32(ac, binary.BigEndian.Uint32(b[20:24]), carry)
-			ac, carry = bits.Add32(ac, binary.BigEndian.Uint32(b[24:28]), carry)
-			ac, carry = bits.Add32(ac, binary.BigEndian.Uint32(b[28:32]), carry)
-			ac, carry = bits.Add32(ac, binary.BigEndian.Uint32(b[32:36]), carry)
-			ac, carry = bits.Add32(ac, binary.BigEndian.Uint32(b[36:40]), carry)
-			ac, carry = bits.Add32(ac, binary.BigEndian.Uint32(b[40:44]), carry)
-			ac, carry = bits.Add32(ac, binary.BigEndian.Uint32(b[44:48]), carry)
-			ac, carry = bits.Add32(ac, binary.BigEndian.Uint32(b[48:52]), carry)
-			ac, carry = bits.Add32(ac, binary.BigEndian.Uint32(b[52:56]), carry)
-			ac, carry = bits.Add32(ac, binary.BigEndian.Uint32(b[56:60]), carry)
-			ac, carry = bits.Add32(ac, binary.BigEndian.Uint32(b[60:64]), carry)
-		} else {
-			ac, carry = bits.Add32(ac, binary.LittleEndian.Uint32(b[:8]), carry)
-			ac, carry = bits.Add32(ac, binary.LittleEndian.Uint32(b[4:8]), carry)
-			ac, carry = bits.Add32(ac, binary.LittleEndian.Uint32(b[8:12]), carry)
-			ac, carry = bits.Add32(ac, binary.LittleEndian.Uint32(b[12:16]), carry)
-			ac, carry = bits.Add32(ac, binary.LittleEndian.Uint32(b[16:20]), carry)
-			ac, carry = bits.Add32(ac, binary.LittleEndian.Uint32(b[20:24]), carry)
-			ac, carry = bits.Add32(ac, binary.LittleEndian.Uint32(b[24:28]), carry)
-			ac, carry = bits.Add32(ac, binary.LittleEndian.Uint32(b[28:32]), carry)
-			ac, carry = bits.Add32(ac, binary.LittleEndian.Uint32(b[32:36]), carry)
-			ac, carry = bits.Add32(ac, binary.LittleEndian.Uint32(b[36:40]), carry)
-			ac, carry = bits.Add32(ac, binary.LittleEndian.Uint32(b[40:44]), carry)
-			ac, carry = bits.Add32(ac, binary.LittleEndian.Uint32(b[44:48]), carry)
-			ac, carry = bits.Add32(ac, binary.LittleEndian.Uint32(b[48:52]), carry)
-			ac, carry = bits.Add32(ac, binary.LittleEndian.Uint32(b[52:56]), carry)
-			ac, carry = bits.Add32(ac, binary.LittleEndian.Uint32(b[56:60]), carry)
-			ac, carry = bits.Add32(ac, binary.LittleEndian.Uint32(b[60:64]), carry)
-		}
-		b = b[64:]
-	}
-	if len(b) >= 32 {
-		if cpu.IsBigEndian {
-			ac, carry = bits.Add32(ac, binary.BigEndian.Uint32(b[:4]), carry)
-			ac, carry = bits.Add32(ac, binary.BigEndian.Uint32(b[4:8]), carry)
-			ac, carry = bits.Add32(ac, binary.BigEndian.Uint32(b[8:12]), carry)
-			ac, carry = bits.Add32(ac, binary.BigEndian.Uint32(b[12:16]), carry)
-			ac, carry = bits.Add32(ac, binary.BigEndian.Uint32(b[16:20]), carry)
-			ac, carry = bits.Add32(ac, binary.BigEndian.Uint32(b[20:24]), carry)
-			ac, carry = bits.Add32(ac, binary.BigEndian.Uint32(b[24:28]), carry)
-			ac, carry = bits.Add32(ac, binary.BigEndian.Uint32(b[28:32]), carry)
-		} else {
-			ac, carry = bits.Add32(ac, binary.LittleEndian.Uint32(b[:4]), carry)
-			ac, carry = bits.Add32(ac, binary.LittleEndian.Uint32(b[4:8]), carry)
-			ac, carry = bits.Add32(ac, binary.LittleEndian.Uint32(b[8:12]), carry)
-			ac, carry = bits.Add32(ac, binary.LittleEndian.Uint32(b[12:16]), carry)
-			ac, carry = bits.Add32(ac, binary.LittleEndian.Uint32(b[16:20]), carry)
-			ac, carry = bits.Add32(ac, binary.LittleEndian.Uint32(b[20:24]), carry)
-			ac, carry = bits.Add32(ac, binary.LittleEndian.Uint32(b[24:28]), carry)
-			ac, carry = bits.Add32(ac, binary.LittleEndian.Uint32(b[28:32]), carry)
-		}
-		b = b[32:]
-	}
-	if len(b) >= 16 {
-		if cpu.IsBigEndian {
-			ac, carry = bits.Add32(ac, binary.BigEndian.Uint32(b[:4]), carry)
-			ac, carry = bits.Add32(ac, binary.BigEndian.Uint32(b[4:8]), carry)
-			ac, carry = bits.Add32(ac, binary.BigEndian.Uint32(b[8:12]), carry)
-			ac, carry = bits.Add32(ac, binary.BigEndian.Uint32(b[12:16]), carry)
-		} else {
-			ac, carry = bits.Add32(ac, binary.LittleEndian.Uint32(b[:4]), carry)
-			ac, carry = bits.Add32(ac, binary.LittleEndian.Uint32(b[4:8]), carry)
-			ac, carry = bits.Add32(ac, binary.LittleEndian.Uint32(b[8:12]), carry)
-			ac, carry = bits.Add32(ac, binary.LittleEndian.Uint32(b[12:16]), carry)
-		}
-		b = b[16:]
-	}
-	if len(b) >= 8 {
-		if cpu.IsBigEndian {
-			ac, carry = bits.Add32(ac, binary.BigEndian.Uint32(b[:4]), carry)
-			ac, carry = bits.Add32(ac, binary.BigEndian.Uint32(b[4:8]), carry)
-		} else {
-			ac, carry = bits.Add32(ac, binary.LittleEndian.Uint32(b[:4]), carry)
-			ac, carry = bits.Add32(ac, binary.LittleEndian.Uint32(b[4:8]), carry)
-		}
-		b = b[8:]
-	}
-	if len(b) >= 4 {
-		if cpu.IsBigEndian {
-			ac, carry = bits.Add32(ac, binary.BigEndian.Uint32(b), carry)
-		} else {
-			ac, carry = bits.Add32(ac, binary.LittleEndian.Uint32(b), carry)
-		}
-		b = b[4:]
-	}
-	if len(b) >= 2 {
-		if cpu.IsBigEndian {
-			ac, carry = bits.Add32(ac, uint32(binary.BigEndian.Uint16(b)), carry)
-		} else {
-			ac, carry = bits.Add32(ac, uint32(binary.LittleEndian.Uint16(b)), carry)
-		}
-		b = b[2:]
-	}
-	if len(b) >= 1 {
-		if cpu.IsBigEndian {
-			ac, carry = bits.Add32(ac, uint32(b[0])<<8, carry)
-		} else {
-			ac, carry = bits.Add32(ac, uint32(b[0]), carry)
-		}
-	}
-
-	folded := ipChecksumFold32(ac, carry)
-	if !cpu.IsBigEndian {
-		folded = bits.ReverseBytes16(folded)
-	}
-	return folded
 }
 
-// checksumGeneric32Alternate is an alternate reference implementation of
+// Checksum computes an IP checksum starting with the provided initial value.
-// checksum using 32 bit arithmetic for use in testing or when an
+func Checksum(data []byte, initial uint16) uint16 {
-// architecture-specific implementation is not available.
+	return checksum(data, uint64(initial))
-func checksumGeneric32Alternate(b []byte, initial uint16) uint16 {
-	var ac uint32
-
-	if cpu.IsBigEndian {
-		ac = uint32(initial)
-	} else {
-		ac = uint32(bits.ReverseBytes16(initial))
-	}
-
-	for len(b) >= 64 {
-		if cpu.IsBigEndian {
-			ac += uint32(binary.BigEndian.Uint16(b[:2]))
-			ac += uint32(binary.BigEndian.Uint16(b[2:4]))
-			ac += uint32(binary.BigEndian.Uint16(b[4:6]))
-			ac += uint32(binary.BigEndian.Uint16(b[6:8]))
-			ac += uint32(binary.BigEndian.Uint16(b[8:10]))
-			ac += uint32(binary.BigEndian.Uint16(b[10:12]))
-			ac += uint32(binary.BigEndian.Uint16(b[12:14]))
-			ac += uint32(binary.BigEndian.Uint16(b[14:16]))
-			ac += uint32(binary.BigEndian.Uint16(b[16:18]))
-			ac += uint32(binary.BigEndian.Uint16(b[18:20]))
-			ac += uint32(binary.BigEndian.Uint16(b[20:22]))
-			ac += uint32(binary.BigEndian.Uint16(b[22:24]))
-			ac += uint32(binary.BigEndian.Uint16(b[24:26]))
-			ac += uint32(binary.BigEndian.Uint16(b[26:28]))
-			ac += uint32(binary.BigEndian.Uint16(b[28:30]))
-			ac += uint32(binary.BigEndian.Uint16(b[30:32]))
-			ac += uint32(binary.BigEndian.Uint16(b[32:34]))
-			ac += uint32(binary.BigEndian.Uint16(b[34:36]))
-			ac += uint32(binary.BigEndian.Uint16(b[36:38]))
-			ac += uint32(binary.BigEndian.Uint16(b[38:40]))
-			ac += uint32(binary.BigEndian.Uint16(b[40:42]))
-			ac += uint32(binary.BigEndian.Uint16(b[42:44]))
-			ac += uint32(binary.BigEndian.Uint16(b[44:46]))
-			ac += uint32(binary.BigEndian.Uint16(b[46:48]))
-			ac += uint32(binary.BigEndian.Uint16(b[48:50]))
-			ac += uint32(binary.BigEndian.Uint16(b[50:52]))
-			ac += uint32(binary.BigEndian.Uint16(b[52:54]))
-			ac += uint32(binary.BigEndian.Uint16(b[54:56]))
-			ac += uint32(binary.BigEndian.Uint16(b[56:58]))
-			ac += uint32(binary.BigEndian.Uint16(b[58:60]))
-			ac += uint32(binary.BigEndian.Uint16(b[60:62]))
-			ac += uint32(binary.BigEndian.Uint16(b[62:64]))
-		} else {
-			ac += uint32(binary.LittleEndian.Uint16(b[:2]))
-			ac += uint32(binary.LittleEndian.Uint16(b[2:4]))
-			ac += uint32(binary.LittleEndian.Uint16(b[4:6]))
-			ac += uint32(binary.LittleEndian.Uint16(b[6:8]))
-			ac += uint32(binary.LittleEndian.Uint16(b[8:10]))
-			ac += uint32(binary.LittleEndian.Uint16(b[10:12]))
-			ac += uint32(binary.LittleEndian.Uint16(b[12:14]))
-			ac += uint32(binary.LittleEndian.Uint16(b[14:16]))
-			ac += uint32(binary.LittleEndian.Uint16(b[16:18]))
-			ac += uint32(binary.LittleEndian.Uint16(b[18:20]))
-			ac += uint32(binary.LittleEndian.Uint16(b[20:22]))
-			ac += uint32(binary.LittleEndian.Uint16(b[22:24]))
-			ac += uint32(binary.LittleEndian.Uint16(b[24:26]))
-			ac += uint32(binary.LittleEndian.Uint16(b[26:28]))
-			ac += uint32(binary.LittleEndian.Uint16(b[28:30]))
-			ac += uint32(binary.LittleEndian.Uint16(b[30:32]))
-			ac += uint32(binary.LittleEndian.Uint16(b[32:34]))
-			ac += uint32(binary.LittleEndian.Uint16(b[34:36]))
-			ac += uint32(binary.LittleEndian.Uint16(b[36:38]))
-			ac += uint32(binary.LittleEndian.Uint16(b[38:40]))
-			ac += uint32(binary.LittleEndian.Uint16(b[40:42]))
-			ac += uint32(binary.LittleEndian.Uint16(b[42:44]))
-			ac += uint32(binary.LittleEndian.Uint16(b[44:46]))
-			ac += uint32(binary.LittleEndian.Uint16(b[46:48]))
-			ac += uint32(binary.LittleEndian.Uint16(b[48:50]))
-			ac += uint32(binary.LittleEndian.Uint16(b[50:52]))
-			ac += uint32(binary.LittleEndian.Uint16(b[52:54]))
-			ac += uint32(binary.LittleEndian.Uint16(b[54:56]))
-			ac += uint32(binary.LittleEndian.Uint16(b[56:58]))
-			ac += uint32(binary.LittleEndian.Uint16(b[58:60]))
-			ac += uint32(binary.LittleEndian.Uint16(b[60:62]))
-			ac += uint32(binary.LittleEndian.Uint16(b[62:64]))
-		}
-		b = b[64:]
-	}
-	if len(b) >= 32 {
-		if cpu.IsBigEndian {
-			ac += uint32(binary.BigEndian.Uint16(b[:2]))
-			ac += uint32(binary.BigEndian.Uint16(b[2:4]))
-			ac += uint32(binary.BigEndian.Uint16(b[4:6]))
-			ac += uint32(binary.BigEndian.Uint16(b[6:8]))
-			ac += uint32(binary.BigEndian.Uint16(b[8:10]))
-			ac += uint32(binary.BigEndian.Uint16(b[10:12]))
-			ac += uint32(binary.BigEndian.Uint16(b[12:14]))
-			ac += uint32(binary.BigEndian.Uint16(b[14:16]))
-			ac += uint32(binary.BigEndian.Uint16(b[16:18]))
-			ac += uint32(binary.BigEndian.Uint16(b[18:20]))
-			ac += uint32(binary.BigEndian.Uint16(b[20:22]))
-			ac += uint32(binary.BigEndian.Uint16(b[22:24]))
-			ac += uint32(binary.BigEndian.Uint16(b[24:26]))
-			ac += uint32(binary.BigEndian.Uint16(b[26:28]))
-			ac += uint32(binary.BigEndian.Uint16(b[28:30]))
-			ac += uint32(binary.BigEndian.Uint16(b[30:32]))
-		} else {
-			ac += uint32(binary.LittleEndian.Uint16(b[:2]))
-			ac += uint32(binary.LittleEndian.Uint16(b[2:4]))
-			ac += uint32(binary.LittleEndian.Uint16(b[4:6]))
-			ac += uint32(binary.LittleEndian.Uint16(b[6:8]))
-			ac += uint32(binary.LittleEndian.Uint16(b[8:10]))
-			ac += uint32(binary.LittleEndian.Uint16(b[10:12]))
-			ac += uint32(binary.LittleEndian.Uint16(b[12:14]))
-			ac += uint32(binary.LittleEndian.Uint16(b[14:16]))
-			ac += uint32(binary.LittleEndian.Uint16(b[16:18]))
-			ac += uint32(binary.LittleEndian.Uint16(b[18:20]))
-			ac += uint32(binary.LittleEndian.Uint16(b[20:22]))
-			ac += uint32(binary.LittleEndian.Uint16(b[22:24]))
-			ac += uint32(binary.LittleEndian.Uint16(b[24:26]))
-			ac += uint32(binary.LittleEndian.Uint16(b[26:28]))
-			ac += uint32(binary.LittleEndian.Uint16(b[28:30]))
-			ac += uint32(binary.LittleEndian.Uint16(b[30:32]))
-		}
-		b = b[32:]
-	}
-	if len(b) >= 16 {
-		if cpu.IsBigEndian {
-			ac += uint32(binary.BigEndian.Uint16(b[:2]))
-			ac += uint32(binary.BigEndian.Uint16(b[2:4]))
-			ac += uint32(binary.BigEndian.Uint16(b[4:6]))
-			ac += uint32(binary.BigEndian.Uint16(b[6:8]))
-			ac += uint32(binary.BigEndian.Uint16(b[8:10]))
-			ac += uint32(binary.BigEndian.Uint16(b[10:12]))
-			ac += uint32(binary.BigEndian.Uint16(b[12:14]))
-			ac += uint32(binary.BigEndian.Uint16(b[14:16]))
-		} else {
-			ac += uint32(binary.LittleEndian.Uint16(b[:2]))
-			ac += uint32(binary.LittleEndian.Uint16(b[2:4]))
-			ac += uint32(binary.LittleEndian.Uint16(b[4:6]))
-			ac += uint32(binary.LittleEndian.Uint16(b[6:8]))
-			ac += uint32(binary.LittleEndian.Uint16(b[8:10]))
-			ac += uint32(binary.LittleEndian.Uint16(b[10:12]))
-			ac += uint32(binary.LittleEndian.Uint16(b[12:14]))
-			ac += uint32(binary.LittleEndian.Uint16(b[14:16]))
-		}
-		b = b[16:]
-	}
-	if len(b) >= 8 {
-		if cpu.IsBigEndian {
-			ac += uint32(binary.BigEndian.Uint16(b[:2]))
-			ac += uint32(binary.BigEndian.Uint16(b[2:4]))
-			ac += uint32(binary.BigEndian.Uint16(b[4:6]))
-			ac += uint32(binary.BigEndian.Uint16(b[6:8]))
-		} else {
-			ac += uint32(binary.LittleEndian.Uint16(b[:2]))
-			ac += uint32(binary.LittleEndian.Uint16(b[2:4]))
-			ac += uint32(binary.LittleEndian.Uint16(b[4:6]))
-			ac += uint32(binary.LittleEndian.Uint16(b[6:8]))
-		}
-		b = b[8:]
-	}
-	if len(b) >= 4 {
-		if cpu.IsBigEndian {
-			ac += uint32(binary.BigEndian.Uint16(b[:2]))
-			ac += uint32(binary.BigEndian.Uint16(b[2:4]))
-		} else {
-			ac += uint32(binary.LittleEndian.Uint16(b[:2]))
-			ac += uint32(binary.LittleEndian.Uint16(b[2:4]))
-		}
-		b = b[4:]
-	}
-	if len(b) >= 2 {
-		if cpu.IsBigEndian {
-			ac += uint32(binary.BigEndian.Uint16(b))
-		} else {
-			ac += uint32(binary.LittleEndian.Uint16(b))
-		}
-		b = b[2:]
-	}
-	if len(b) >= 1 {
-		if cpu.IsBigEndian {
-			ac += uint32(b[0]) << 8
-		} else {
-			ac += uint32(b[0])
-		}
-	}
-
-	folded := ipChecksumFold32(ac, 0)
-	if !cpu.IsBigEndian {
-		folded = bits.ReverseBytes16(folded)
-	}
-	return folded
 }
 
-// checksumGeneric64Alternate is an alternate reference implementation of
+func pseudoHeaderChecksumNoFold(protocol uint8, srcAddr, dstAddr []byte, totalLen uint16) uint64 {
-// checksum using 64 bit arithmetic for use in testing or when an
+	sum := checksumNoFold(srcAddr, 0)
-// architecture-specific implementation is not available.
+	sum = checksumNoFold(dstAddr, sum)
-func checksumGeneric64Alternate(b []byte, initial uint16) uint16 {
+	sum = checksumNoFold([]byte{0, protocol}, sum)
-	var ac uint64
+	tmp := make([]byte, 2)
-
+	binary.BigEndian.PutUint16(tmp, totalLen)
-	if cpu.IsBigEndian {
+	return checksumNoFold(tmp, sum)
-		ac = uint64(initial)
-	} else {
-		ac = uint64(bits.ReverseBytes16(initial))
-	}
-
-	for len(b) >= 64 {
-		if cpu.IsBigEndian {
-			ac += uint64(binary.BigEndian.Uint32(b[:4]))
-			ac += uint64(binary.BigEndian.Uint32(b[4:8]))
-			ac += uint64(binary.BigEndian.Uint32(b[8:12]))
-			ac += uint64(binary.BigEndian.Uint32(b[12:16]))
-			ac += uint64(binary.BigEndian.Uint32(b[16:20]))
-			ac += uint64(binary.BigEndian.Uint32(b[20:24]))
-			ac += uint64(binary.BigEndian.Uint32(b[24:28]))
-			ac += uint64(binary.BigEndian.Uint32(b[28:32]))
-			ac += uint64(binary.BigEndian.Uint32(b[32:36]))
-			ac += uint64(binary.BigEndian.Uint32(b[36:40]))
-			ac += uint64(binary.BigEndian.Uint32(b[40:44]))
-			ac += uint64(binary.BigEndian.Uint32(b[44:48]))
-			ac += uint64(binary.BigEndian.Uint32(b[48:52]))
-			ac += uint64(binary.BigEndian.Uint32(b[52:56]))
-			ac += uint64(binary.BigEndian.Uint32(b[56:60]))
-			ac += uint64(binary.BigEndian.Uint32(b[60:64]))
-		} else {
-			ac += uint64(binary.LittleEndian.Uint32(b[:4]))
-			ac += uint64(binary.LittleEndian.Uint32(b[4:8]))
-			ac += uint64(binary.LittleEndian.Uint32(b[8:12]))
-			ac += uint64(binary.LittleEndian.Uint32(b[12:16]))
-			ac += uint64(binary.LittleEndian.Uint32(b[16:20]))
-			ac += uint64(binary.LittleEndian.Uint32(b[20:24]))
-			ac += uint64(binary.LittleEndian.Uint32(b[24:28]))
-			ac += uint64(binary.LittleEndian.Uint32(b[28:32]))
-			ac += uint64(binary.LittleEndian.Uint32(b[32:36]))
-			ac += uint64(binary.LittleEndian.Uint32(b[36:40]))
-			ac += uint64(binary.LittleEndian.Uint32(b[40:44]))
-			ac += uint64(binary.LittleEndian.Uint32(b[44:48]))
-			ac += uint64(binary.LittleEndian.Uint32(b[48:52]))
-			ac += uint64(binary.LittleEndian.Uint32(b[52:56]))
-			ac += uint64(binary.LittleEndian.Uint32(b[56:60]))
-			ac += uint64(binary.LittleEndian.Uint32(b[60:64]))
-		}
-		b = b[64:]
-	}
-	if len(b) >= 32 {
-		if cpu.IsBigEndian {
-			ac += uint64(binary.BigEndian.Uint32(b[:4]))
-			ac += uint64(binary.BigEndian.Uint32(b[4:8]))
-			ac += uint64(binary.BigEndian.Uint32(b[8:12]))
-			ac += uint64(binary.BigEndian.Uint32(b[12:16]))
-			ac += uint64(binary.BigEndian.Uint32(b[16:20]))
-			ac += uint64(binary.BigEndian.Uint32(b[20:24]))
-			ac += uint64(binary.BigEndian.Uint32(b[24:28]))
-			ac += uint64(binary.BigEndian.Uint32(b[28:32]))
-		} else {
-			ac += uint64(binary.LittleEndian.Uint32(b[:4]))
-			ac += uint64(binary.LittleEndian.Uint32(b[4:8]))
-			ac += uint64(binary.LittleEndian.Uint32(b[8:12]))
-			ac += uint64(binary.LittleEndian.Uint32(b[12:16]))
-			ac += uint64(binary.LittleEndian.Uint32(b[16:20]))
-			ac += uint64(binary.LittleEndian.Uint32(b[20:24]))
-			ac += uint64(binary.LittleEndian.Uint32(b[24:28]))
-			ac += uint64(binary.LittleEndian.Uint32(b[28:32]))
-		}
-		b = b[32:]
-	}
-	if len(b) >= 16 {
-		if cpu.IsBigEndian {
-			ac += uint64(binary.BigEndian.Uint32(b[:4]))
-			ac += uint64(binary.BigEndian.Uint32(b[4:8]))
-			ac += uint64(binary.BigEndian.Uint32(b[8:12]))
-			ac += uint64(binary.BigEndian.Uint32(b[12:16]))
-		} else {
-			ac += uint64(binary.LittleEndian.Uint32(b[:4]))
-			ac += uint64(binary.LittleEndian.Uint32(b[4:8]))
-			ac += uint64(binary.LittleEndian.Uint32(b[8:12]))
-			ac += uint64(binary.LittleEndian.Uint32(b[12:16]))
-		}
-		b = b[16:]
-	}
-	if len(b) >= 8 {
-		if cpu.IsBigEndian {
-			ac += uint64(binary.BigEndian.Uint32(b[:4]))
-			ac += uint64(binary.BigEndian.Uint32(b[4:8]))
-		} else {
-			ac += uint64(binary.LittleEndian.Uint32(b[:4]))
-			ac += uint64(binary.LittleEndian.Uint32(b[4:8]))
-		}
-		b = b[8:]
-	}
-	if len(b) >= 4 {
-		if cpu.IsBigEndian {
-			ac += uint64(binary.BigEndian.Uint32(b))
-		} else {
-			ac += uint64(binary.LittleEndian.Uint32(b))
-		}
-		b = b[4:]
-	}
-	if len(b) >= 2 {
-		if cpu.IsBigEndian {
-			ac += uint64(binary.BigEndian.Uint16(b))
-		} else {
-			ac += uint64(binary.LittleEndian.Uint16(b))
-		}
-		b = b[2:]
-	}
-	if len(b) >= 1 {
-		if cpu.IsBigEndian {
-			ac += uint64(b[0]) << 8
-		} else {
-			ac += uint64(b[0])
-		}
-	}
-
-	folded := ipChecksumFold64(ac, 0)
-	if !cpu.IsBigEndian {
-		folded = bits.ReverseBytes16(folded)
-	}
-	return folded
-}
-
-func ipChecksumFold64(unfolded uint64, initialCarry uint64) uint16 {
-	sum, carry := bits.Add32(uint32(unfolded>>32), uint32(unfolded&0xffff_ffff), uint32(initialCarry))
-	// if carry != 0, sum <= 0xffff_fffe, otherwise sum <= 0xffff_ffff
-	// therefore (sum >> 16) + (sum & 0xffff) + carry <= 0x1_fffe; so there is
-	// no need to save the carry flag
-	sum = (sum >> 16) + (sum & 0xffff) + carry
-	// sum <= 0x1_fffe therefore this is the last fold needed:
-	//   if (sum >> 16) > 0 then
-	//     (sum >> 16) == 1 && (sum & 0xffff) <= 0xfffe and therefore
-	//     the addition will not overflow
-	// otherwise (sum >> 16) == 0 and sum will be unchanged
-	sum = (sum >> 16) + (sum & 0xffff)
-	return uint16(sum)
-}
-
-func ipChecksumFold32(unfolded uint32, initialCarry uint32) uint16 {
-	sum := (unfolded >> 16) + (unfolded & 0xffff) + initialCarry
-	// sum <= 0x1_ffff:
-	//   0xffff + 0xffff = 0x1_fffe
-	//   initialCarry is 0 or 1, for a combined maximum of 0x1_ffff
-	sum = (sum >> 16) + (sum & 0xffff)
-	// sum <= 0x1_0000 therefore this is the last fold needed:
-	//   if (sum >> 16) > 0 then
-	//     (sum >> 16) == 1 && (sum & 0xffff) == 0 and therefore
-	//     the addition will not overflow
-	// otherwise (sum >> 16) == 0 and sum will be unchanged
-	sum = (sum >> 16) + (sum & 0xffff)
-	return uint16(sum)
-}
-
-func addrPartialChecksum64(addr []byte, initial, carryIn uint64) (sum, carry uint64) {
-	sum, carry = initial, carryIn
-	switch len(addr) {
-	case 4: // IPv4
-		if cpu.IsBigEndian {
-			sum, carry = bits.Add64(sum, uint64(binary.BigEndian.Uint32(addr)), carry)
-		} else {
-			sum, carry = bits.Add64(sum, uint64(binary.LittleEndian.Uint32(addr)), carry)
-		}
-	case 16: // IPv6
-		if cpu.IsBigEndian {
-			sum, carry = bits.Add64(sum, binary.BigEndian.Uint64(addr), carry)
-			sum, carry = bits.Add64(sum, binary.BigEndian.Uint64(addr[8:]), carry)
-		} else {
-			sum, carry = bits.Add64(sum, binary.LittleEndian.Uint64(addr), carry)
-			sum, carry = bits.Add64(sum, binary.LittleEndian.Uint64(addr[8:]), carry)
-		}
-	default:
-		panic("bad addr length")
-	}
-	return sum, carry
-}
-
-func addrPartialChecksum32(addr []byte, initial, carryIn uint32) (sum, carry uint32) {
-	sum, carry = initial, carryIn
-	switch len(addr) {
-	case 4: // IPv4
-		if cpu.IsBigEndian {
-			sum, carry = bits.Add32(sum, binary.BigEndian.Uint32(addr), carry)
-		} else {
-			sum, carry = bits.Add32(sum, binary.LittleEndian.Uint32(addr), carry)
-		}
-	case 16: // IPv6
-		if cpu.IsBigEndian {
-			sum, carry = bits.Add32(sum, binary.BigEndian.Uint32(addr), carry)
-			sum, carry = bits.Add32(sum, binary.BigEndian.Uint32(addr[4:8]), carry)
-			sum, carry = bits.Add32(sum, binary.BigEndian.Uint32(addr[8:12]), carry)
-			sum, carry = bits.Add32(sum, binary.BigEndian.Uint32(addr[12:16]), carry)
-		} else {
-			sum, carry = bits.Add32(sum, binary.LittleEndian.Uint32(addr), carry)
-			sum, carry = bits.Add32(sum, binary.LittleEndian.Uint32(addr[4:8]), carry)
-			sum, carry = bits.Add32(sum, binary.LittleEndian.Uint32(addr[8:12]), carry)
-			sum, carry = bits.Add32(sum, binary.LittleEndian.Uint32(addr[12:16]), carry)
-		}
-	default:
-		panic("bad addr length")
-	}
-	return sum, carry
-}
-
-func pseudoHeaderChecksum64(protocol uint8, srcAddr, dstAddr []byte, totalLen uint16) uint16 {
-	var sum uint64
-	if cpu.IsBigEndian {
-		sum = uint64(totalLen) + uint64(protocol)
-	} else {
-		sum = uint64(bits.ReverseBytes16(totalLen)) + uint64(protocol)<<8
-	}
-	sum, carry := addrPartialChecksum64(srcAddr, sum, 0)
-	sum, carry = addrPartialChecksum64(dstAddr, sum, carry)
-
-	foldedSum := ipChecksumFold64(sum, carry)
-	if !cpu.IsBigEndian {
-		foldedSum = bits.ReverseBytes16(foldedSum)
-	}
-	return foldedSum
-}
-
-func pseudoHeaderChecksum32(protocol uint8, srcAddr, dstAddr []byte, totalLen uint16) uint16 {
-	var sum uint32
-	if cpu.IsBigEndian {
-		sum = uint32(totalLen) + uint32(protocol)
-	} else {
-		sum = uint32(bits.ReverseBytes16(totalLen)) + uint32(protocol)<<8
-	}
-	sum, carry := addrPartialChecksum32(srcAddr, sum, 0)
-	sum, carry = addrPartialChecksum32(dstAddr, sum, carry)
-
-	foldedSum := ipChecksumFold32(sum, carry)
-	if !cpu.IsBigEndian {
-		foldedSum = bits.ReverseBytes16(foldedSum)
-	}
-	return foldedSum
 }
 
 // PseudoHeaderChecksum computes an IP pseudo-header checksum. srcAddr and
 // dstAddr must be 4 or 16 bytes in length.
 func PseudoHeaderChecksum(protocol uint8, srcAddr, dstAddr []byte, totalLen uint16) uint16 {
-	if strconv.IntSize < 64 {
+	return checksum([]byte{}, pseudoHeaderChecksumNoFold(protocol, srcAddr, dstAddr, totalLen))
-		return pseudoHeaderChecksum32(protocol, srcAddr, dstAddr, totalLen)
-	}
-	return pseudoHeaderChecksum64(protocol, srcAddr, dstAddr, totalLen)
 }

tun/checksum_amd64.go

@@ -1,23 +0,0 @@
-package tun
-
-import "golang.org/x/sys/cpu"
-
-var checksum = checksumAMD64
-
-// Checksum computes an IP checksum starting with the provided initial value.
-// The length of data should be at least 128 bytes for best performance. Smaller
-// buffers will still compute a correct result.
-func Checksum(data []byte, initial uint16) uint16 {
-	return checksum(data, initial)
-}
-
-func init() {
-	if cpu.X86.HasAVX && cpu.X86.HasAVX2 && cpu.X86.HasBMI2 {
-		checksum = checksumAVX2
-		return
-	}
-	if cpu.X86.HasSSE2 {
-		checksum = checksumSSE2
-		return
-	}
-}

tun/checksum_generated_amd64.go

@@ -1,18 +0,0 @@
-// Code generated by command: go run generate_amd64.go -out checksum_generated_amd64.s -stubs checksum_generated_amd64.go. DO NOT EDIT.
-
-package tun
-
-// checksumAVX2 computes an IP checksum using amd64 v3 instructions (AVX2, BMI2)
-//
-//go:noescape
-func checksumAVX2(b []byte, initial uint16) uint16
-
-// checksumSSE2 computes an IP checksum using amd64 baseline instructions (SSE2)
-//
-//go:noescape
-func checksumSSE2(b []byte, initial uint16) uint16
-
-// checksumAMD64 computes an IP checksum using amd64 baseline instructions
-//
-//go:noescape
-func checksumAMD64(b []byte, initial uint16) uint16

tun/checksum_generated_amd64.s

@@ -1,851 +0,0 @@
-// Code generated by command: go run generate_amd64.go -out checksum_generated_amd64.s -stubs checksum_generated_amd64.go. DO NOT EDIT.
-
-#include "textflag.h"
-
-DATA xmmLoadMasks<>+0(SB)/16, $"\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xff\xff"
-DATA xmmLoadMasks<>+16(SB)/16, $"\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xff\xff\xff\xff"
-DATA xmmLoadMasks<>+32(SB)/16, $"\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xff\xff\xff\xff\xff\xff"
-DATA xmmLoadMasks<>+48(SB)/16, $"\x00\x00\x00\x00\x00\x00\x00\x00\xff\xff\xff\xff\xff\xff\xff\xff"
-DATA xmmLoadMasks<>+64(SB)/16, $"\x00\x00\x00\x00\x00\x00\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff"
-DATA xmmLoadMasks<>+80(SB)/16, $"\x00\x00\x00\x00\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff"
-DATA xmmLoadMasks<>+96(SB)/16, $"\x00\x00\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff"
-GLOBL xmmLoadMasks<>(SB), RODATA|NOPTR, $112
-
-// func checksumAVX2(b []byte, initial uint16) uint16
-// Requires: AVX, AVX2, BMI2
-TEXT ·checksumAVX2(SB), NOSPLIT|NOFRAME, $0-34
-	MOVWQZX initial+24(FP), AX
-	XCHGB   AH, AL
-	MOVQ    b_base+0(FP), DX
-	MOVQ    b_len+8(FP), BX
-
-	// handle odd length buffers; they are difficult to handle in general
-	TESTQ   $0x00000001, BX
-	JZ      lengthIsEven
-	MOVBQZX -1(DX)(BX*1), CX
-	DECQ    BX
-	ADDQ    CX, AX
-
-lengthIsEven:
-	// handle tiny buffers (<=31 bytes) specially
-	CMPQ BX, $0x1f
-	JGT  bufferIsNotTiny
-	XORQ CX, CX
-	XORQ SI, SI
-	XORQ DI, DI
-
-	// shift twice to start because length is guaranteed to be even
-	// n = n >> 2; CF = originalN & 2
-	SHRQ $0x02, BX
-	JNC  handleTiny4
-
-	// tmp2 = binary.LittleEndian.Uint16(buf[:2]); buf = buf[2:]
-	MOVWQZX (DX), CX
-	ADDQ    $0x02, DX
-
-handleTiny4:
-	// n = n >> 1; CF = originalN & 4
-	SHRQ $0x01, BX
-	JNC  handleTiny8
-
-	// tmp4 = binary.LittleEndian.Uint32(buf[:4]); buf = buf[4:]
-	MOVLQZX (DX), SI
-	ADDQ    $0x04, DX
-
-handleTiny8:
-	// n = n >> 1; CF = originalN & 8
-	SHRQ $0x01, BX
-	JNC  handleTiny16
-
-	// tmp8 = binary.LittleEndian.Uint64(buf[:8]); buf = buf[8:]
-	MOVQ (DX), DI
-	ADDQ $0x08, DX
-
-handleTiny16:
-	// n = n >> 1; CF = originalN & 16
-	// n == 0 now, otherwise we would have branched after comparing with tinyBufferSize
-	SHRQ $0x01, BX
-	JNC  handleTinyFinish
-	ADDQ (DX), AX
-	ADCQ 8(DX), AX
-
-handleTinyFinish:
-	// CF should be included from the previous add, so we use ADCQ.
-	// If we arrived via the JNC above, then CF=0 due to the branch condition,
-	// so ADCQ will still produce the correct result.
-	ADCQ CX, AX
-	ADCQ SI, AX
-	ADCQ DI, AX
-	JMP  foldAndReturn
-
-bufferIsNotTiny:
-	// skip all SIMD for small buffers
-	CMPQ BX, $0x00000100
-	JGE  startSIMD
-
-	// Accumulate carries in this register. It is never expected to overflow.
-	XORQ SI, SI
-
-	// We will perform an overlapped read for buffers with length not a multiple of 8.
-	// Overlapped in this context means some memory will be read twice, but a shift will
-	// eliminate the duplicated data. This extra read is performed at the end of the buffer to
-	// preserve any alignment that may exist for the start of the buffer.
-	MOVQ BX, CX
-	SHRQ $0x03, BX
-	ANDQ $0x07, CX
-	JZ   handleRemaining8
-	LEAQ (DX)(BX*8), DI
-	MOVQ -8(DI)(CX*1), DI
-
-	// Shift out the duplicated data: overlapRead = overlapRead >> (64 - leftoverBytes*8)
-	SHLQ $0x03, CX
-	NEGQ CX
-	ADDQ $0x40, CX
-	SHRQ CL, DI
-	ADDQ DI, AX
-	ADCQ $0x00, SI
-
-handleRemaining8:
-	SHRQ $0x01, BX
-	JNC  handleRemaining16
-	ADDQ (DX), AX
-	ADCQ $0x00, SI
-	ADDQ $0x08, DX
-
-handleRemaining16:
-	SHRQ $0x01, BX
-	JNC  handleRemaining32
-	ADDQ (DX), AX
-	ADCQ 8(DX), AX
-	ADCQ $0x00, SI
-	ADDQ $0x10, DX
-
-handleRemaining32:
-	SHRQ $0x01, BX
-	JNC  handleRemaining64
-	ADDQ (DX), AX
-	ADCQ 8(DX), AX
-	ADCQ 16(DX), AX
-	ADCQ 24(DX), AX
-	ADCQ $0x00, SI
-	ADDQ $0x20, DX
-
-handleRemaining64:
-	SHRQ $0x01, BX
-	JNC  handleRemaining128
-	ADDQ (DX), AX
-	ADCQ 8(DX), AX
-	ADCQ 16(DX), AX
-	ADCQ 24(DX), AX
-	ADCQ 32(DX), AX
-	ADCQ 40(DX), AX
-	ADCQ 48(DX), AX
-	ADCQ 56(DX), AX
-	ADCQ $0x00, SI
-	ADDQ $0x40, DX
-
-handleRemaining128:
-	SHRQ $0x01, BX
-	JNC  handleRemainingComplete
-	ADDQ (DX), AX
-	ADCQ 8(DX), AX
-	ADCQ 16(DX), AX
-	ADCQ 24(DX), AX
-	ADCQ 32(DX), AX
-	ADCQ 40(DX), AX
-	ADCQ 48(DX), AX
-	ADCQ 56(DX), AX
-	ADCQ 64(DX), AX
-	ADCQ 72(DX), AX
-	ADCQ 80(DX), AX
-	ADCQ 88(DX), AX
-	ADCQ 96(DX), AX
-	ADCQ 104(DX), AX
-	ADCQ 112(DX), AX
-	ADCQ 120(DX), AX
-	ADCQ $0x00, SI
-	ADDQ $0x80, DX
-
-handleRemainingComplete:
-	ADDQ SI, AX
-	JMP  foldAndReturn
-
-startSIMD:
-	VPXOR Y0, Y0, Y0
-	VPXOR Y1, Y1, Y1
-	VPXOR Y2, Y2, Y2
-	VPXOR Y3, Y3, Y3
-	MOVQ  BX, CX
-
-	// Update number of bytes remaining after the loop completes
-	ANDQ $0xff, BX
-
-	// Number of 256 byte iterations
-	SHRQ $0x08, CX
-	JZ   smallLoop
-
-bigLoop:
-	VPMOVZXWD (DX), Y4
-	VPADDD    Y4, Y0, Y0
-	VPMOVZXWD 16(DX), Y4
-	VPADDD    Y4, Y1, Y1
-	VPMOVZXWD 32(DX), Y4
-	VPADDD    Y4, Y2, Y2
-	VPMOVZXWD 48(DX), Y4
-	VPADDD    Y4, Y3, Y3
-	VPMOVZXWD 64(DX), Y4
-	VPADDD    Y4, Y0, Y0
-	VPMOVZXWD 80(DX), Y4
-	VPADDD    Y4, Y1, Y1
-	VPMOVZXWD 96(DX), Y4
-	VPADDD    Y4, Y2, Y2
-	VPMOVZXWD 112(DX), Y4
-	VPADDD    Y4, Y3, Y3
-	VPMOVZXWD 128(DX), Y4
-	VPADDD    Y4, Y0, Y0
-	VPMOVZXWD 144(DX), Y4
-	VPADDD    Y4, Y1, Y1
-	VPMOVZXWD 160(DX), Y4
-	VPADDD    Y4, Y2, Y2
-	VPMOVZXWD 176(DX), Y4
-	VPADDD    Y4, Y3, Y3
-	VPMOVZXWD 192(DX), Y4
-	VPADDD    Y4, Y0, Y0
-	VPMOVZXWD 208(DX), Y4
-	VPADDD    Y4, Y1, Y1
-	VPMOVZXWD 224(DX), Y4
-	VPADDD    Y4, Y2, Y2
-	VPMOVZXWD 240(DX), Y4
-	VPADDD    Y4, Y3, Y3
-	ADDQ      $0x00000100, DX
-	DECQ      CX
-	JNZ       bigLoop
-	CMPQ      BX, $0x10
-	JLT       doneSmallLoop
-
-	// now read a single 16 byte unit of data at a time
-smallLoop:
-	VPMOVZXWD (DX), Y4
-	VPADDD    Y4, Y0, Y0
-	ADDQ      $0x10, DX
-	SUBQ      $0x10, BX
-	CMPQ      BX, $0x10
-	JGE       smallLoop
-
-doneSmallLoop:
-	CMPQ BX, $0x00
-	JE   doneSIMD
-
-	// There are between 1 and 15 bytes remaining. Perform an overlapped read.
-	LEAQ      xmmLoadMasks<>+0(SB), CX
-	VMOVDQU   -16(DX)(BX*1), X4
-	VPAND     -16(CX)(BX*8), X4, X4
-	VPMOVZXWD X4, Y4
-	VPADDD    Y4, Y0, Y0
-
-doneSIMD:
-	// Multi-chain loop is done, combine the accumulators
-	VPADDD Y1, Y0, Y0
-	VPADDD Y2, Y0, Y0
-	VPADDD Y3, Y0, Y0
-
-	// extract the YMM into a pair of XMM and sum them
-	VEXTRACTI128 $0x01, Y0, X1
-	VPADDD       X0, X1, X0
-
-	// extract the XMM into GP64
-	VPEXTRQ $0x00, X0, CX
-	VPEXTRQ $0x01, X0, DX
-
-	// no more AVX code, clear upper registers to avoid SSE slowdowns
-	VZEROUPPER
-	ADDQ CX, AX
-	ADCQ DX, AX
-
-foldAndReturn:
-	// add CF and fold
-	RORXQ $0x20, AX, CX
-	ADCL  CX, AX
-	RORXL $0x10, AX, CX
-	ADCW  CX, AX
-	ADCW  $0x00, AX
-	XCHGB AH, AL
-	MOVW  AX, ret+32(FP)
-	RET
-
-// func checksumSSE2(b []byte, initial uint16) uint16
-// Requires: SSE2
-TEXT ·checksumSSE2(SB), NOSPLIT|NOFRAME, $0-34
-	MOVWQZX initial+24(FP), AX
-	XCHGB   AH, AL
-	MOVQ    b_base+0(FP), DX
-	MOVQ    b_len+8(FP), BX
-
-	// handle odd length buffers; they are difficult to handle in general
-	TESTQ   $0x00000001, BX
-	JZ      lengthIsEven
-	MOVBQZX -1(DX)(BX*1), CX
-	DECQ    BX
-	ADDQ    CX, AX
-
-lengthIsEven:
-	// handle tiny buffers (<=31 bytes) specially
-	CMPQ BX, $0x1f
-	JGT  bufferIsNotTiny
-	XORQ CX, CX
-	XORQ SI, SI
-	XORQ DI, DI
-
-	// shift twice to start because length is guaranteed to be even
-	// n = n >> 2; CF = originalN & 2
-	SHRQ $0x02, BX
-	JNC  handleTiny4
-
-	// tmp2 = binary.LittleEndian.Uint16(buf[:2]); buf = buf[2:]
-	MOVWQZX (DX), CX
-	ADDQ    $0x02, DX
-
-handleTiny4:
-	// n = n >> 1; CF = originalN & 4
-	SHRQ $0x01, BX
-	JNC  handleTiny8
-
-	// tmp4 = binary.LittleEndian.Uint32(buf[:4]); buf = buf[4:]
-	MOVLQZX (DX), SI
-	ADDQ    $0x04, DX
-
-handleTiny8:
-	// n = n >> 1; CF = originalN & 8
-	SHRQ $0x01, BX
-	JNC  handleTiny16
-
-	// tmp8 = binary.LittleEndian.Uint64(buf[:8]); buf = buf[8:]
-	MOVQ (DX), DI
-	ADDQ $0x08, DX
-
-handleTiny16:
-	// n = n >> 1; CF = originalN & 16
-	// n == 0 now, otherwise we would have branched after comparing with tinyBufferSize
-	SHRQ $0x01, BX
-	JNC  handleTinyFinish
-	ADDQ (DX), AX
-	ADCQ 8(DX), AX
-
-handleTinyFinish:
-	// CF should be included from the previous add, so we use ADCQ.
-	// If we arrived via the JNC above, then CF=0 due to the branch condition,
-	// so ADCQ will still produce the correct result.
-	ADCQ CX, AX
-	ADCQ SI, AX
-	ADCQ DI, AX
-	JMP  foldAndReturn
-
-bufferIsNotTiny:
-	// skip all SIMD for small buffers
-	CMPQ BX, $0x00000100
-	JGE  startSIMD
-
-	// Accumulate carries in this register. It is never expected to overflow.
-	XORQ SI, SI
-
-	// We will perform an overlapped read for buffers with length not a multiple of 8.
-	// Overlapped in this context means some memory will be read twice, but a shift will
-	// eliminate the duplicated data. This extra read is performed at the end of the buffer to
-	// preserve any alignment that may exist for the start of the buffer.
-	MOVQ BX, CX
-	SHRQ $0x03, BX
-	ANDQ $0x07, CX
-	JZ   handleRemaining8
-	LEAQ (DX)(BX*8), DI
-	MOVQ -8(DI)(CX*1), DI
-
-	// Shift out the duplicated data: overlapRead = overlapRead >> (64 - leftoverBytes*8)
-	SHLQ $0x03, CX
-	NEGQ CX
-	ADDQ $0x40, CX
-	SHRQ CL, DI
-	ADDQ DI, AX
-	ADCQ $0x00, SI
-
-handleRemaining8:
-	SHRQ $0x01, BX
-	JNC  handleRemaining16
-	ADDQ (DX), AX
-	ADCQ $0x00, SI
-	ADDQ $0x08, DX
-
-handleRemaining16:
-	SHRQ $0x01, BX
-	JNC  handleRemaining32
-	ADDQ (DX), AX
-	ADCQ 8(DX), AX
-	ADCQ $0x00, SI
-	ADDQ $0x10, DX
-
-handleRemaining32:
-	SHRQ $0x01, BX
-	JNC  handleRemaining64
-	ADDQ (DX), AX
-	ADCQ 8(DX), AX
-	ADCQ 16(DX), AX
-	ADCQ 24(DX), AX
-	ADCQ $0x00, SI
-	ADDQ $0x20, DX
-
-handleRemaining64:
-	SHRQ $0x01, BX
-	JNC  handleRemaining128
-	ADDQ (DX), AX
-	ADCQ 8(DX), AX
-	ADCQ 16(DX), AX
-	ADCQ 24(DX), AX
-	ADCQ 32(DX), AX
-	ADCQ 40(DX), AX
-	ADCQ 48(DX), AX
-	ADCQ 56(DX), AX
-	ADCQ $0x00, SI
-	ADDQ $0x40, DX
-
-handleRemaining128:
-	SHRQ $0x01, BX
-	JNC  handleRemainingComplete
-	ADDQ (DX), AX
-	ADCQ 8(DX), AX
-	ADCQ 16(DX), AX
-	ADCQ 24(DX), AX
-	ADCQ 32(DX), AX
-	ADCQ 40(DX), AX
-	ADCQ 48(DX), AX
-	ADCQ 56(DX), AX
-	ADCQ 64(DX), AX
-	ADCQ 72(DX), AX
-	ADCQ 80(DX), AX
-	ADCQ 88(DX), AX
-	ADCQ 96(DX), AX
-	ADCQ 104(DX), AX
-	ADCQ 112(DX), AX
-	ADCQ 120(DX), AX
-	ADCQ $0x00, SI
-	ADDQ $0x80, DX
-
-handleRemainingComplete:
-	ADDQ SI, AX
-	JMP  foldAndReturn
-
-startSIMD:
-	PXOR X0, X0
-	PXOR X1, X1
-	PXOR X2, X2
-	PXOR X3, X3
-	PXOR X4, X4
-	MOVQ BX, CX
-
-	// Update number of bytes remaining after the loop completes
-	ANDQ $0xff, BX
-
-	// Number of 256 byte iterations
-	SHRQ $0x08, CX
-	JZ   smallLoop
-
-bigLoop:
-	MOVOU     (DX), X5
-	MOVOA     X5, X6
-	PUNPCKHWL X4, X5
-	PUNPCKLWL X4, X6
-	PADDD     X5, X0
-	PADDD     X6, X2
-	MOVOU     16(DX), X5
-	MOVOA     X5, X6
-	PUNPCKHWL X4, X5
-	PUNPCKLWL X4, X6
-	PADDD     X5, X1
-	PADDD     X6, X3
-	MOVOU     32(DX), X5
-	MOVOA     X5, X6
-	PUNPCKHWL X4, X5
-	PUNPCKLWL X4, X6
-	PADDD     X5, X2
-	PADDD     X6, X0
-	MOVOU     48(DX), X5
-	MOVOA     X5, X6
-	PUNPCKHWL X4, X5
-	PUNPCKLWL X4, X6
-	PADDD     X5, X3
-	PADDD     X6, X1
-	MOVOU     64(DX), X5
-	MOVOA     X5, X6
-	PUNPCKHWL X4, X5
-	PUNPCKLWL X4, X6
-	PADDD     X5, X0
-	PADDD     X6, X2
-	MOVOU     80(DX), X5
-	MOVOA     X5, X6
-	PUNPCKHWL X4, X5
-	PUNPCKLWL X4, X6
-	PADDD     X5, X1
-	PADDD     X6, X3
-	MOVOU     96(DX), X5
-	MOVOA     X5, X6
-	PUNPCKHWL X4, X5
-	PUNPCKLWL X4, X6
-	PADDD     X5, X2
-	PADDD     X6, X0
-	MOVOU     112(DX), X5
-	MOVOA     X5, X6
-	PUNPCKHWL X4, X5
-	PUNPCKLWL X4, X6
-	PADDD     X5, X3
-	PADDD     X6, X1
-	MOVOU     128(DX), X5
-	MOVOA     X5, X6
-	PUNPCKHWL X4, X5
-	PUNPCKLWL X4, X6
-	PADDD     X5, X0
-	PADDD     X6, X2
-	MOVOU     144(DX), X5
-	MOVOA     X5, X6
-	PUNPCKHWL X4, X5
-	PUNPCKLWL X4, X6
-	PADDD     X5, X1
-	PADDD     X6, X3
-	MOVOU     160(DX), X5
-	MOVOA     X5, X6
-	PUNPCKHWL X4, X5
-	PUNPCKLWL X4, X6
-	PADDD     X5, X2
-	PADDD     X6, X0
-	MOVOU     176(DX), X5
-	MOVOA     X5, X6
-	PUNPCKHWL X4, X5
-	PUNPCKLWL X4, X6
-	PADDD     X5, X3
-	PADDD     X6, X1
-	MOVOU     192(DX), X5
-	MOVOA     X5, X6
-	PUNPCKHWL X4, X5
-	PUNPCKLWL X4, X6
-	PADDD     X5, X0
-	PADDD     X6, X2
-	MOVOU     208(DX), X5
-	MOVOA     X5, X6
-	PUNPCKHWL X4, X5
-	PUNPCKLWL X4, X6
-	PADDD     X5, X1
-	PADDD     X6, X3
-	MOVOU     224(DX), X5
-	MOVOA     X5, X6
-	PUNPCKHWL X4, X5
-	PUNPCKLWL X4, X6
-	PADDD     X5, X2
-	PADDD     X6, X0
-	MOVOU     240(DX), X5
-	MOVOA     X5, X6
-	PUNPCKHWL X4, X5
-	PUNPCKLWL X4, X6
-	PADDD     X5, X3
-	PADDD     X6, X1
-	ADDQ      $0x00000100, DX
-	DECQ      CX
-	JNZ       bigLoop
-	CMPQ      BX, $0x10
-	JLT       doneSmallLoop
-
-	// now read a single 16 byte unit of data at a time
-smallLoop:
-	MOVOU     (DX), X5
-	MOVOA     X5, X6
-	PUNPCKHWL X4, X5
-	PUNPCKLWL X4, X6
-	PADDD     X5, X0
-	PADDD     X6, X1
-	ADDQ      $0x10, DX
-	SUBQ      $0x10, BX
-	CMPQ      BX, $0x10
-	JGE       smallLoop
-
-doneSmallLoop:
-	CMPQ BX, $0x00
-	JE   doneSIMD
-
-	// There are between 1 and 15 bytes remaining. Perform an overlapped read.
-	LEAQ      xmmLoadMasks<>+0(SB), CX
-	MOVOU     -16(DX)(BX*1), X5
-	PAND      -16(CX)(BX*8), X5
-	MOVOA     X5, X6
-	PUNPCKHWL X4, X5
-	PUNPCKLWL X4, X6
-	PADDD     X5, X0
-	PADDD     X6, X1
-
-doneSIMD:
-	// Multi-chain loop is done, combine the accumulators
-	PADDD X1, X0
-	PADDD X2, X0
-	PADDD X3, X0
-
-	// extract the XMM into GP64
-	MOVQ   X0, CX
-	PSRLDQ $0x08, X0
-	MOVQ   X0, DX
-	ADDQ   CX, AX
-	ADCQ   DX, AX
-
-foldAndReturn:
-	// add CF and fold
-	MOVL    AX, CX
-	ADCQ    $0x00, CX
-	SHRQ    $0x20, AX
-	ADDQ    CX, AX
-	MOVWQZX AX, CX
-	SHRQ    $0x10, AX
-	ADDQ    CX, AX
-	MOVW    AX, CX
-	SHRQ    $0x10, AX
-	ADDW    CX, AX
-	ADCW    $0x00, AX
-	XCHGB   AH, AL
-	MOVW    AX, ret+32(FP)
-	RET
-
-// func checksumAMD64(b []byte, initial uint16) uint16
-TEXT ·checksumAMD64(SB), NOSPLIT|NOFRAME, $0-34
-	MOVWQZX initial+24(FP), AX
-	XCHGB   AH, AL
-	MOVQ    b_base+0(FP), DX
-	MOVQ    b_len+8(FP), BX
-
-	// handle odd length buffers; they are difficult to handle in general
-	TESTQ   $0x00000001, BX
-	JZ      lengthIsEven
-	MOVBQZX -1(DX)(BX*1), CX
-	DECQ    BX
-	ADDQ    CX, AX
-
-lengthIsEven:
-	// handle tiny buffers (<=31 bytes) specially
-	CMPQ BX, $0x1f
-	JGT  bufferIsNotTiny
-	XORQ CX, CX
-	XORQ SI, SI
-	XORQ DI, DI
-
-	// shift twice to start because length is guaranteed to be even
-	// n = n >> 2; CF = originalN & 2
-	SHRQ $0x02, BX
-	JNC  handleTiny4
-
-	// tmp2 = binary.LittleEndian.Uint16(buf[:2]); buf = buf[2:]
-	MOVWQZX (DX), CX
-	ADDQ    $0x02, DX
-
-handleTiny4:
-	// n = n >> 1; CF = originalN & 4
-	SHRQ $0x01, BX
-	JNC  handleTiny8
-
-	// tmp4 = binary.LittleEndian.Uint32(buf[:4]); buf = buf[4:]
-	MOVLQZX (DX), SI
-	ADDQ    $0x04, DX
-
-handleTiny8:
-	// n = n >> 1; CF = originalN & 8
-	SHRQ $0x01, BX
-	JNC  handleTiny16
-
-	// tmp8 = binary.LittleEndian.Uint64(buf[:8]); buf = buf[8:]
-	MOVQ (DX), DI
-	ADDQ $0x08, DX
-
-handleTiny16:
-	// n = n >> 1; CF = originalN & 16
-	// n == 0 now, otherwise we would have branched after comparing with tinyBufferSize
-	SHRQ $0x01, BX
-	JNC  handleTinyFinish
-	ADDQ (DX), AX
-	ADCQ 8(DX), AX
-
-handleTinyFinish:
-	// CF should be included from the previous add, so we use ADCQ.
-	// If we arrived via the JNC above, then CF=0 due to the branch condition,
-	// so ADCQ will still produce the correct result.
-	ADCQ CX, AX
-	ADCQ SI, AX
-	ADCQ DI, AX
-	JMP  foldAndReturn
-
-bufferIsNotTiny:
-	// Number of 256 byte iterations into loop counter
-	MOVQ BX, CX
-
-	// Update number of bytes remaining after the loop completes
-	ANDQ $0xff, BX
-	SHRQ $0x08, CX
-	JZ   startCleanup
-	CLC
-	XORQ SI, SI
-	XORQ DI, DI
-	XORQ R8, R8
-	XORQ R9, R9
-	XORQ R10, R10
-	XORQ R11, R11
-	XORQ R12, R12
-
-bigLoop:
-	ADDQ (DX), AX
-	ADCQ 8(DX), AX
-	ADCQ 16(DX), AX
-	ADCQ 24(DX), AX
-	ADCQ $0x00, SI
-	ADDQ 32(DX), DI
-	ADCQ 40(DX), DI
-	ADCQ 48(DX), DI
-	ADCQ 56(DX), DI
-	ADCQ $0x00, R8
-	ADDQ 64(DX), R9
-	ADCQ 72(DX), R9
-	ADCQ 80(DX), R9
-	ADCQ 88(DX), R9
-	ADCQ $0x00, R10
-	ADDQ 96(DX), R11
-	ADCQ 104(DX), R11
-	ADCQ 112(DX), R11
-	ADCQ 120(DX), R11
-	ADCQ $0x00, R12
-	ADDQ 128(DX), AX
-	ADCQ 136(DX), AX
-	ADCQ 144(DX), AX
-	ADCQ 152(DX), AX
-	ADCQ $0x00, SI
-	ADDQ 160(DX), DI
-	ADCQ 168(DX), DI
-	ADCQ 176(DX), DI
-	ADCQ 184(DX), DI
-	ADCQ $0x00, R8
-	ADDQ 192(DX), R9
-	ADCQ 200(DX), R9
-	ADCQ 208(DX), R9
-	ADCQ 216(DX), R9
-	ADCQ $0x00, R10
-	ADDQ 224(DX), R11
-	ADCQ 232(DX), R11
-	ADCQ 240(DX), R11
-	ADCQ 248(DX), R11
-	ADCQ $0x00, R12
-	ADDQ $0x00000100, DX
-	SUBQ $0x01, CX
-	JNZ  bigLoop
-	ADDQ SI, AX
-	ADCQ DI, AX
-	ADCQ R8, AX
-	ADCQ R9, AX
-	ADCQ R10, AX
-	ADCQ R11, AX
-	ADCQ R12, AX
-
-	// accumulate CF (twice, in case the first time overflows)
-	ADCQ $0x00, AX
-	ADCQ $0x00, AX
-
-startCleanup:
-	// Accumulate carries in this register. It is never expected to overflow.
-	XORQ SI, SI
-
-	// We will perform an overlapped read for buffers with length not a multiple of 8.
-	// Overlapped in this context means some memory will be read twice, but a shift will
-	// eliminate the duplicated data. This extra read is performed at the end of the buffer to
-	// preserve any alignment that may exist for the start of the buffer.
-	MOVQ BX, CX
-	SHRQ $0x03, BX
-	ANDQ $0x07, CX
-	JZ   handleRemaining8
-	LEAQ (DX)(BX*8), DI
-	MOVQ -8(DI)(CX*1), DI
-
-	// Shift out the duplicated data: overlapRead = overlapRead >> (64 - leftoverBytes*8)
-	SHLQ $0x03, CX
-	NEGQ CX
-	ADDQ $0x40, CX
-	SHRQ CL, DI
-	ADDQ DI, AX
-	ADCQ $0x00, SI
-
-handleRemaining8:
-	SHRQ $0x01, BX
-	JNC  handleRemaining16
-	ADDQ (DX), AX
-	ADCQ $0x00, SI
-	ADDQ $0x08, DX
-
-handleRemaining16:
-	SHRQ $0x01, BX
-	JNC  handleRemaining32
-	ADDQ (DX), AX
-	ADCQ 8(DX), AX
-	ADCQ $0x00, SI
-	ADDQ $0x10, DX
-
-handleRemaining32:
-	SHRQ $0x01, BX
-	JNC  handleRemaining64
-	ADDQ (DX), AX
-	ADCQ 8(DX), AX
-	ADCQ 16(DX), AX
-	ADCQ 24(DX), AX
-	ADCQ $0x00, SI
-	ADDQ $0x20, DX
-
-handleRemaining64:
-	SHRQ $0x01, BX
-	JNC  handleRemaining128
-	ADDQ (DX), AX
-	ADCQ 8(DX), AX
-	ADCQ 16(DX), AX
-	ADCQ 24(DX), AX
-	ADCQ 32(DX), AX
-	ADCQ 40(DX), AX
-	ADCQ 48(DX), AX
-	ADCQ 56(DX), AX
-	ADCQ $0x00, SI
-	ADDQ $0x40, DX
-
-handleRemaining128:
-	SHRQ $0x01, BX
-	JNC  handleRemainingComplete
-	ADDQ (DX), AX
-	ADCQ 8(DX), AX
-	ADCQ 16(DX), AX
-	ADCQ 24(DX), AX
-	ADCQ 32(DX), AX
-	ADCQ 40(DX), AX
-	ADCQ 48(DX), AX
-	ADCQ 56(DX), AX
-	ADCQ 64(DX), AX
-	ADCQ 72(DX), AX
-	ADCQ 80(DX), AX
-	ADCQ 88(DX), AX
-	ADCQ 96(DX), AX
-	ADCQ 104(DX), AX
-	ADCQ 112(DX), AX
-	ADCQ 120(DX), AX
-	ADCQ $0x00, SI
-	ADDQ $0x80, DX
-
-handleRemainingComplete:
-	ADDQ SI, AX
-
-foldAndReturn:
-	// add CF and fold
-	MOVL    AX, CX
-	ADCQ    $0x00, CX
-	SHRQ    $0x20, AX
-	ADDQ    CX, AX
-	MOVWQZX AX, CX
-	SHRQ    $0x10, AX
-	ADDQ    CX, AX
-	MOVW    AX, CX
-	SHRQ    $0x10, AX
-	ADDW    CX, AX
-	ADCW    $0x00, AX
-	XCHGB   AH, AL
-	MOVW    AX, ret+32(FP)
-	RET

tun/checksum_generic.go

@@ -1,15 +0,0 @@
-// This file contains IP checksum algorithms that are not specific to any
-// architecture and don't use hardware acceleration.
-
-//go:build !amd64
-
-package tun
-
-import "strconv"
-
-func Checksum(data []byte, initial uint16) uint16 {
-	if strconv.IntSize < 64 {
-		return checksumGeneric32(data, initial)
-	}
-	return checksumGeneric64(data, initial)
-}

tun/generate_amd64.go

@@ -1,579 +0,0 @@
-//go:build ignore
-
-//go:generate go run generate_amd64.go -out checksum_generated_amd64.s -stubs checksum_generated_amd64.go
-
-package main
-
-import (
-	"fmt"
-	"math"
-	"math/bits"
-
-	. "github.com/mmcloughlin/avo/build"
-	"github.com/mmcloughlin/avo/operand"
-	"github.com/mmcloughlin/avo/reg"
-)
-
-const checksumSignature = "func(b []byte, initial uint16) uint16"
-
-func loadParams() (accum, buf, n reg.GPVirtual) {
-	accum, buf, n = GP64(), GP64(), GP64()
-	Load(Param("initial"), accum)
-	XCHGB(accum.As8H(), accum.As8L())
-	Load(Param("b").Base(), buf)
-	Load(Param("b").Len(), n)
-	return
-}
-
-type simdStrategy int
-
-const (
-	sse2 = iota
-	avx2
-)
-
-const tinyBufferSize = 31 // A buffer is tiny if it has at most 31 bytes.
-
-func generateSIMDChecksum(name, doc string, minSIMDSize, chains int, strategy simdStrategy) {
-	TEXT(name, NOSPLIT|NOFRAME, checksumSignature)
-	Pragma("noescape")
-	Doc(doc)
-
-	accum64, buf, n := loadParams()
-
-	handleOddLength(n, buf, accum64)
-	// no chance of overflow because accum64 was initialized by a uint16 and
-	// handleOddLength adds at most a uint8
-	handleTinyBuffers(n, buf, accum64, operand.LabelRef("foldAndReturn"), operand.LabelRef("bufferIsNotTiny"))
-	Label("bufferIsNotTiny")
-
-	const simdReadSize = 16
-
-	if minSIMDSize > tinyBufferSize {
-		Comment("skip all SIMD for small buffers")
-		if minSIMDSize <= math.MaxUint8 {
-			CMPQ(n, operand.U8(minSIMDSize))
-		} else {
-			CMPQ(n, operand.U32(minSIMDSize))
-		}
-		JGE(operand.LabelRef("startSIMD"))
-
-		handleRemaining(n, buf, accum64, minSIMDSize-1)
-		JMP(operand.LabelRef("foldAndReturn"))
-	}
-
-	Label("startSIMD")
-
-	// chains is the number of accumulators to use. This improves speed via
-	// reduced data dependency. We combine the accumulators once when the big
-	// loop is complete.
-	simdAccumulate := make([]reg.VecVirtual, chains)
-	for i := range simdAccumulate {
-		switch strategy {
-		case sse2:
-			simdAccumulate[i] = XMM()
-			PXOR(simdAccumulate[i], simdAccumulate[i])
-		case avx2:
-			simdAccumulate[i] = YMM()
-			VPXOR(simdAccumulate[i], simdAccumulate[i], simdAccumulate[i])
-		}
-	}
-	var zero reg.VecVirtual
-	if strategy == sse2 {
-		zero = XMM()
-		PXOR(zero, zero)
-	}
-
-	// Number of loads per big loop
-	const unroll = 16
-	// Number of bytes
-	loopSize := uint64(simdReadSize * unroll)
-	if bits.Len64(loopSize) != bits.Len64(loopSize-1)+1 {
-		panic("loopSize is not a power of 2")
-	}
-	loopCount := GP64()
-
-	MOVQ(n, loopCount)
-	Comment("Update number of bytes remaining after the loop completes")
-	ANDQ(operand.Imm(loopSize-1), n)
-	Comment(fmt.Sprintf("Number of %d byte iterations", loopSize))
-	SHRQ(operand.Imm(uint64(bits.Len64(loopSize-1))), loopCount)
-	JZ(operand.LabelRef("smallLoop"))
-	Label("bigLoop")
-	for i := 0; i < unroll; i++ {
-		chain := i % chains
-		switch strategy {
-		case sse2:
-			sse2AccumulateStep(i*simdReadSize, buf, zero, simdAccumulate[chain], simdAccumulate[(chain+chains/2)%chains])
-		case avx2:
-			avx2AccumulateStep(i*simdReadSize, buf, simdAccumulate[chain])
-		}
-	}
-	ADDQ(operand.U32(loopSize), buf)
-	DECQ(loopCount)
-	JNZ(operand.LabelRef("bigLoop"))
-
-	Label("bigCleanup")
-
-	CMPQ(n, operand.Imm(uint64(simdReadSize)))
-	JLT(operand.LabelRef("doneSmallLoop"))
-
-	Commentf("now read a single %d byte unit of data at a time", simdReadSize)
-	Label("smallLoop")
-
-	switch strategy {
-	case sse2:
-		sse2AccumulateStep(0, buf, zero, simdAccumulate[0], simdAccumulate[1])
-	case avx2:
-		avx2AccumulateStep(0, buf, simdAccumulate[0])
-	}
-	ADDQ(operand.Imm(uint64(simdReadSize)), buf)
-	SUBQ(operand.Imm(uint64(simdReadSize)), n)
-	CMPQ(n, operand.Imm(uint64(simdReadSize)))
-	JGE(operand.LabelRef("smallLoop"))
-
-	Label("doneSmallLoop")
-	CMPQ(n, operand.Imm(0))
-	JE(operand.LabelRef("doneSIMD"))
-
-	Commentf("There are between 1 and %d bytes remaining. Perform an overlapped read.", simdReadSize-1)
-
-	maskDataPtr := GP64()
-	LEAQ(operand.NewDataAddr(operand.NewStaticSymbol("xmmLoadMasks"), 0), maskDataPtr)
-	dataAddr := operand.Mem{Index: n, Scale: 1, Base: buf, Disp: -simdReadSize}
-	// scale 8 is only correct here because n is guaranteed to be even and we
-	// do not generate masks for odd lengths
-	maskAddr := operand.Mem{Base: maskDataPtr, Index: n, Scale: 8, Disp: -16}
-	remainder := XMM()
-
-	switch strategy {
-	case sse2:
-		MOVOU(dataAddr, remainder)
-		PAND(maskAddr, remainder)
-		low := XMM()
-		MOVOA(remainder, low)
-		PUNPCKHWL(zero, remainder)
-		PUNPCKLWL(zero, low)
-		PADDD(remainder, simdAccumulate[0])
-		PADDD(low, simdAccumulate[1])
-	case avx2:
-		// Note: this is very similar to the sse2 path but MOVOU has a massive
-		// performance hit if used here, presumably due to switching between SSE
-		// and AVX2 modes.
-		VMOVDQU(dataAddr, remainder)
-		VPAND(maskAddr, remainder, remainder)
-
-		temp := YMM()
-		VPMOVZXWD(remainder, temp)
-		VPADDD(temp, simdAccumulate[0], simdAccumulate[0])
-	}
-
-	Label("doneSIMD")
-
-	Comment("Multi-chain loop is done, combine the accumulators")
-	for i := range simdAccumulate {
-		if i == 0 {
-			continue
-		}
-		switch strategy {
-		case sse2:
-			PADDD(simdAccumulate[i], simdAccumulate[0])
-		case avx2:
-			VPADDD(simdAccumulate[i], simdAccumulate[0], simdAccumulate[0])
-		}
-	}
-
-	if strategy == avx2 {
-		Comment("extract the YMM into a pair of XMM and sum them")
-		tmp := YMM()
-		VEXTRACTI128(operand.Imm(1), simdAccumulate[0], tmp.AsX())
-
-		xAccumulate := XMM()
-		VPADDD(simdAccumulate[0].AsX(), tmp.AsX(), xAccumulate)
-		simdAccumulate = []reg.VecVirtual{xAccumulate}
-	}
-
-	Comment("extract the XMM into GP64")
-	low, high := GP64(), GP64()
-	switch strategy {
-	case sse2:
-		MOVQ(simdAccumulate[0], low)
-		PSRLDQ(operand.Imm(8), simdAccumulate[0])
-		MOVQ(simdAccumulate[0], high)
-	case avx2:
-		VPEXTRQ(operand.Imm(0), simdAccumulate[0], low)
-		VPEXTRQ(operand.Imm(1), simdAccumulate[0], high)
-
-		Comment("no more AVX code, clear upper registers to avoid SSE slowdowns")
-		VZEROUPPER()
-	}
-	ADDQ(low, accum64)
-	ADCQ(high, accum64)
-	Label("foldAndReturn")
-	foldWithCF(accum64, strategy == avx2)
-	XCHGB(accum64.As8H(), accum64.As8L())
-	Store(accum64.As16(), ReturnIndex(0))
-	RET()
-}
-
-// handleOddLength generates instructions to incorporate the last byte into
-// accum64 if the length is odd. CF may be set if accum64 overflows; be sure to
-// handle that if overflow is possible.
-func handleOddLength(n, buf, accum64 reg.GPVirtual) {
-	Comment("handle odd length buffers; they are difficult to handle in general")
-	TESTQ(operand.U32(1), n)
-	JZ(operand.LabelRef("lengthIsEven"))
-
-	tmp := GP64()
-	MOVBQZX(operand.Mem{Base: buf, Index: n, Scale: 1, Disp: -1}, tmp)
-	DECQ(n)
-	ADDQ(tmp, accum64)
-
-	Label("lengthIsEven")
-}
-
-func sse2AccumulateStep(offset int, buf reg.GPVirtual, zero, accumulate1, accumulate2 reg.VecVirtual) {
-	high, low := XMM(), XMM()
-	MOVOU(operand.Mem{Disp: offset, Base: buf}, high)
-	MOVOA(high, low)
-	PUNPCKHWL(zero, high)
-	PUNPCKLWL(zero, low)
-	PADDD(high, accumulate1)
-	PADDD(low, accumulate2)
-}
-
-func avx2AccumulateStep(offset int, buf reg.GPVirtual, accumulate reg.VecVirtual) {
-	tmp := YMM()
-	VPMOVZXWD(operand.Mem{Disp: offset, Base: buf}, tmp)
-	VPADDD(tmp, accumulate, accumulate)
-}
-
-func generateAMD64Checksum(name, doc string) {
-	TEXT(name, NOSPLIT|NOFRAME, checksumSignature)
-	Pragma("noescape")
-	Doc(doc)
-
-	accum64, buf, n := loadParams()
-
-	handleOddLength(n, buf, accum64)
-	// no chance of overflow because accum64 was initialized by a uint16 and
-	// handleOddLength adds at most a uint8
-	handleTinyBuffers(n, buf, accum64, operand.LabelRef("foldAndReturn"), operand.LabelRef("bufferIsNotTiny"))
-	Label("bufferIsNotTiny")
-
-	const (
-		// numChains is the number of accumulators and carry counters to use.
-		// This improves speed via reduced data dependency. We combine the
-		// accumulators and carry counters once when the loop is complete.
-		numChains = 4
-		unroll    = 32         // The number of 64-bit reads to perform per iteration of the loop.
-		loopSize  = 8 * unroll // The number of bytes read per iteration of the loop.
-	)
-	if bits.Len(loopSize) != bits.Len(loopSize-1)+1 {
-		panic("loopSize is not a power of 2")
-	}
-	loopCount := GP64()
-
-	Comment(fmt.Sprintf("Number of %d byte iterations into loop counter", loopSize))
-	MOVQ(n, loopCount)
-	Comment("Update number of bytes remaining after the loop completes")
-	ANDQ(operand.Imm(loopSize-1), n)
-	SHRQ(operand.Imm(uint64(bits.Len(loopSize-1))), loopCount)
-	JZ(operand.LabelRef("startCleanup"))
-	CLC()
-
-	chains := make([]struct {
-		accum   reg.GPVirtual
-		carries reg.GPVirtual
-	}, numChains)
-	for i := range chains {
-		if i == 0 {
-			chains[i].accum = accum64
-		} else {
-			chains[i].accum = GP64()
-			XORQ(chains[i].accum, chains[i].accum)
-		}
-		chains[i].carries = GP64()
-		XORQ(chains[i].carries, chains[i].carries)
-	}
-
-	Label("bigLoop")
-
-	var curChain int
-	for i := 0; i < unroll; i++ {
-		// It is significantly faster to use a ADCX/ADOX pair instead of plain
-		// ADC, which results in two dependency chains, however those require
-		// ADX support, which was added after AVX2. If AVX2 is available, that's
-		// even better than ADCX/ADOX.
-		//
-		// However, multiple dependency chains using multiple accumulators and
-		// occasionally storing CF into temporary counters seems to work almost
-		// as well.
-		addr := operand.Mem{Disp: i * 8, Base: buf}
-
-		if i%4 == 0 {
-			if i > 0 {
-				ADCQ(operand.Imm(0), chains[curChain].carries)
-				curChain = (curChain + 1) % len(chains)
-			}
-			ADDQ(addr, chains[curChain].accum)
-		} else {
-			ADCQ(addr, chains[curChain].accum)
-		}
-	}
-	ADCQ(operand.Imm(0), chains[curChain].carries)
-	ADDQ(operand.U32(loopSize), buf)
-	SUBQ(operand.Imm(1), loopCount)
-	JNZ(operand.LabelRef("bigLoop"))
-	for i := range chains {
-		if i == 0 {
-			ADDQ(chains[i].carries, accum64)
-			continue
-		}
-		ADCQ(chains[i].accum, accum64)
-		ADCQ(chains[i].carries, accum64)
-	}
-
-	accumulateCF(accum64)
-
-	Label("startCleanup")
-	handleRemaining(n, buf, accum64, loopSize-1)
-	Label("foldAndReturn")
-	foldWithCF(accum64, false)
-
-	XCHGB(accum64.As8H(), accum64.As8L())
-	Store(accum64.As16(), ReturnIndex(0))
-	RET()
-}
-
-// handleTinyBuffers computes checksums if the buffer length (the n parameter)
-// is less than 32. After computing the checksum, a jump to returnLabel will
-// be executed. Otherwise, if the buffer length is at least 32, nothing will be
-// modified; a jump to continueLabel will be executed instead.
-//
-// When jumping to returnLabel, CF may be set and must be accommodated e.g.
-// using foldWithCF or accumulateCF.
-//
-// Anecdotally, this appears to be faster than attempting to coordinate an
-// overlapped read (which would also require special handling for buffers
-// smaller than 8).
-func handleTinyBuffers(n, buf, accum reg.GPVirtual, returnLabel, continueLabel operand.LabelRef) {
-	Comment("handle tiny buffers (<=31 bytes) specially")
-	CMPQ(n, operand.Imm(tinyBufferSize))
-	JGT(continueLabel)
-
-	tmp2, tmp4, tmp8 := GP64(), GP64(), GP64()
-	XORQ(tmp2, tmp2)
-	XORQ(tmp4, tmp4)
-	XORQ(tmp8, tmp8)
-
-	Comment("shift twice to start because length is guaranteed to be even",
-		"n = n >> 2; CF = originalN & 2")
-	SHRQ(operand.Imm(2), n)
-	JNC(operand.LabelRef("handleTiny4"))
-	Comment("tmp2 = binary.LittleEndian.Uint16(buf[:2]); buf = buf[2:]")
-	MOVWQZX(operand.Mem{Base: buf}, tmp2)
-	ADDQ(operand.Imm(2), buf)
-
-	Label("handleTiny4")
-	Comment("n = n >> 1; CF = originalN & 4")
-	SHRQ(operand.Imm(1), n)
-	JNC(operand.LabelRef("handleTiny8"))
-	Comment("tmp4 = binary.LittleEndian.Uint32(buf[:4]); buf = buf[4:]")
-	MOVLQZX(operand.Mem{Base: buf}, tmp4)
-	ADDQ(operand.Imm(4), buf)
-
-	Label("handleTiny8")
-	Comment("n = n >> 1; CF = originalN & 8")
-	SHRQ(operand.Imm(1), n)
-	JNC(operand.LabelRef("handleTiny16"))
-	Comment("tmp8 = binary.LittleEndian.Uint64(buf[:8]); buf = buf[8:]")
-	MOVQ(operand.Mem{Base: buf}, tmp8)
-	ADDQ(operand.Imm(8), buf)
-
-	Label("handleTiny16")
-	Comment("n = n >> 1; CF = originalN & 16",
-		"n == 0 now, otherwise we would have branched after comparing with tinyBufferSize")
-	SHRQ(operand.Imm(1), n)
-	JNC(operand.LabelRef("handleTinyFinish"))
-	ADDQ(operand.Mem{Base: buf}, accum)
-	ADCQ(operand.Mem{Base: buf, Disp: 8}, accum)
-
-	Label("handleTinyFinish")
-	Comment("CF should be included from the previous add, so we use ADCQ.",
-		"If we arrived via the JNC above, then CF=0 due to the branch condition,",
-		"so ADCQ will still produce the correct result.")
-	ADCQ(tmp2, accum)
-	ADCQ(tmp4, accum)
-	ADCQ(tmp8, accum)
-
-	JMP(returnLabel)
-}
-
-// handleRemaining generates a series of conditional unrolled additions,
-// starting with 8 bytes long and doubling each time until the length reaches
-// max. This is the reverse order of what may be intuitive, but makes the branch
-// conditions convenient to compute: perform one right shift each time and test
-// against CF.
-//
-// When done, CF may be set and must be accommodated e.g., using foldWithCF or
-// accumulateCF.
-//
-// If n is not a multiple of 8, an extra 64 bit read at the end of the buffer
-// will be performed, overlapping with data that will be read later. The
-// duplicate data will be shifted off.
-//
-// The original buffer length must have been at least 8 bytes long, even if
-// n < 8, otherwise this will access memory before the start of the buffer,
-// which may be unsafe.
-func handleRemaining(n, buf, accum64 reg.GPVirtual, max int) {
-	Comment("Accumulate carries in this register. It is never expected to overflow.")
-	carries := GP64()
-	XORQ(carries, carries)
-
-	Comment("We will perform an overlapped read for buffers with length not a multiple of 8.",
-		"Overlapped in this context means some memory will be read twice, but a shift will",
-		"eliminate the duplicated data. This extra read is performed at the end of the buffer to",
-		"preserve any alignment that may exist for the start of the buffer.")
-	leftover := reg.RCX
-	MOVQ(n, leftover)
-	SHRQ(operand.Imm(3), n)          // n is now the number of 64 bit reads remaining
-	ANDQ(operand.Imm(0x7), leftover) // leftover is now the number of bytes to read from the end
-	JZ(operand.LabelRef("handleRemaining8"))
-	endBuf := GP64()
-	// endBuf is the position near the end of the buffer that is just past the
-	// last multiple of 8: (buf + len(buf)) & ^0x7
-	LEAQ(operand.Mem{Base: buf, Index: n, Scale: 8}, endBuf)
-
-	overlapRead := GP64()
-	// equivalent to overlapRead = binary.LittleEndian.Uint64(buf[len(buf)-8:len(buf)])
-	MOVQ(operand.Mem{Base: endBuf, Index: leftover, Scale: 1, Disp: -8}, overlapRead)
-
-	Comment("Shift out the duplicated data: overlapRead = overlapRead >> (64 - leftoverBytes*8)")
-	SHLQ(operand.Imm(3), leftover)  // leftover = leftover * 8
-	NEGQ(leftover)                  // leftover = -leftover; this completes the (-leftoverBytes*8) part of the expression
-	ADDQ(operand.Imm(64), leftover) // now we have (64 - leftoverBytes*8)
-	SHRQ(reg.CL, overlapRead)       // shift right by (64 - leftoverBytes*8); CL is the low 8 bits of leftover (set to RCX above) and variable shift only accepts CL
-
-	ADDQ(overlapRead, accum64)
-	ADCQ(operand.Imm(0), carries)
-
-	for curBytes := 8; curBytes <= max; curBytes *= 2 {
-		Label(fmt.Sprintf("handleRemaining%d", curBytes))
-		SHRQ(operand.Imm(1), n)
-		if curBytes*2 <= max {
-			JNC(operand.LabelRef(fmt.Sprintf("handleRemaining%d", curBytes*2)))
-		} else {
-			JNC(operand.LabelRef("handleRemainingComplete"))
-		}
-
-		numLoads := curBytes / 8
-		for i := 0; i < numLoads; i++ {
-			addr := operand.Mem{Base: buf, Disp: i * 8}
-			// It is possible to add the multiple dependency chains trick here
-			// that generateAMD64Checksum uses but anecdotally it does not
-			// appear to outweigh the cost.
-			if i == 0 {
-				ADDQ(addr, accum64)
-				continue
-			}
-			ADCQ(addr, accum64)
-		}
-		ADCQ(operand.Imm(0), carries)
-
-		if curBytes > math.MaxUint8 {
-			ADDQ(operand.U32(uint64(curBytes)), buf)
-		} else {
-			ADDQ(operand.U8(uint64(curBytes)), buf)
-		}
-		if curBytes*2 >= max {
-			continue
-		}
-		JMP(operand.LabelRef(fmt.Sprintf("handleRemaining%d", curBytes*2)))
-	}
-	Label("handleRemainingComplete")
-	ADDQ(carries, accum64)
-}
-
-func accumulateCF(accum64 reg.GPVirtual) {
-	Comment("accumulate CF (twice, in case the first time overflows)")
-	// accum64 += CF
-	ADCQ(operand.Imm(0), accum64)
-	// accum64 += CF again if the previous add overflowed. The previous add was
-	// 0 or 1. If it overflowed, then accum64 == 0, so adding another 1 can
-	// never overflow.
-	ADCQ(operand.Imm(0), accum64)
-}
-
-// foldWithCF generates instructions to fold accum (a GP64) into a 16-bit value
-// according to ones-complement arithmetic. BMI2 instructions will be used if
-// allowBMI2 is true (requires fewer instructions).
-func foldWithCF(accum reg.GPVirtual, allowBMI2 bool) {
-	Comment("add CF and fold")
-
-	// CF|accum max value starts as 0x1_ffff_ffff_ffff_ffff
-
-	tmp := GP64()
-	if allowBMI2 {
-		// effectively, tmp = accum >> 32 (technically, this is a rotate)
-		RORXQ(operand.Imm(32), accum, tmp)
-		// accum as uint32 = uint32(accum) + uint32(tmp64) + CF; max value 0xffff_ffff + CF set
-		ADCL(tmp.As32(), accum.As32())
-		// effectively, tmp64 as uint32 = uint32(accum) >> 16 (also a rotate)
-		RORXL(operand.Imm(16), accum.As32(), tmp.As32())
-		// accum as uint16 = uint16(accum) + uint16(tmp) + CF; max value 0xffff + CF unset or 0xfffe + CF set
-		ADCW(tmp.As16(), accum.As16())
-	} else {
-		// tmp = uint32(accum); max value 0xffff_ffff
-		// MOVL clears the upper 32 bits of a GP64 so this is equivalent to the
-		// non-existent MOVLQZX.
-		MOVL(accum.As32(), tmp.As32())
-		// tmp += CF; max value 0x1_0000_0000, CF unset
-		ADCQ(operand.Imm(0), tmp)
-		// accum = accum >> 32; max value 0xffff_ffff
-		SHRQ(operand.Imm(32), accum)
-		// accum = accum + tmp; max value 0x1_ffff_ffff + CF unset
-		ADDQ(tmp, accum)
-		// tmp = uint16(accum); max value 0xffff
-		MOVWQZX(accum.As16(), tmp)
-		// accum = accum >> 16; max value 0x1_ffff
-		SHRQ(operand.Imm(16), accum)
-		// accum = accum + tmp; max value 0x2_fffe + CF unset
-		ADDQ(tmp, accum)
-		// tmp as uint16 = uint16(accum); max value 0xffff
-		MOVW(accum.As16(), tmp.As16())
-		// accum = accum >> 16; max value 0x2
-		SHRQ(operand.Imm(16), accum)
-		// accum as uint16 = uint16(accum) + uint16(tmp); max value 0xffff + CF unset or 0x2 + CF set
-		ADDW(tmp.As16(), accum.As16())
-	}
-	// accum as uint16 += CF; will not overflow: either CF was 0 or accum <= 0xfffe
-	ADCW(operand.Imm(0), accum.As16())
-}
-
-func generateLoadMasks() {
-	var offset int
-	// xmmLoadMasks is a table of masks that can be used with PAND to zero all but the last N bytes in an XMM, N=2,4,6,8,10,12,14
-	GLOBL("xmmLoadMasks", RODATA|NOPTR)
-
-	for n := 2; n < 16; n += 2 {
-		var pattern [16]byte
-		for i := 0; i < len(pattern); i++ {
-			if i < len(pattern)-n {
-				pattern[i] = 0
-				continue
-			}
-			pattern[i] = 0xff
-		}
-		DATA(offset, operand.String(pattern[:]))
-		offset += len(pattern)
-	}
-}
-
-func main() {
-	generateLoadMasks()
-	generateSIMDChecksum("checksumAVX2", "checksumAVX2 computes an IP checksum using amd64 v3 instructions (AVX2, BMI2)", 256, 4, avx2)
-	generateSIMDChecksum("checksumSSE2", "checksumSSE2 computes an IP checksum using amd64 baseline instructions (SSE2)", 256, 4, sse2)
-	generateAMD64Checksum("checksumAMD64", "checksumAMD64 computes an IP checksum using amd64 baseline instructions")
-	Generate()
-}

tun/offload.go

@@ -55,32 +55,25 @@ type GSOOptions struct {
 }
 
 const (
-	ipv4SrcAddrOffset = 12
+	gsoIPv4SrcAddrOffset = 12
-	ipv6SrcAddrOffset = 8
+	gsoIPv6SrcAddrOffset = 8
-)
+	gsoTCPFlagsOffset    = 13
-
+	gsoIPProtoTCP        = 6
-const tcpFlagsOffset = 13
+	gsoIPProtoUDP        = 17
-
-const (
-	tcpFlagFIN uint8 = 0x01
-	tcpFlagPSH uint8 = 0x08
-	tcpFlagACK uint8 = 0x10
 )
 
 const (
-	// defined here in order to avoid importation of any platform-specific pkgs
+	gsoTCPFlagFIN uint8 = 0x01
-	ipProtoTCP = 6
+	gsoTCPFlagPSH uint8 = 0x08
-	ipProtoUDP = 17
 )
 
-// GSOSplit splits packets from 'in' into outBufs[<index>][outOffset:], writing
+// GSOSplit splits packets from in into outBufs[<index>][outOffset:], writing
 // the size of each element into sizes. It returns the number of buffers
-// populated, and/or an error. Callers may pass an 'in' slice that overlaps with
+// populated, and/or an error. Callers may pass an in slice that overlaps with
-// the first element of outBuffers, i.e. &in[0] may be equal to
+// the first element of outBufs, i.e. &in[0] may be equal to
 // &outBufs[0][outOffset]. GSONone is a valid options.GSOType regardless of the
 // value of options.NeedsCsum. Length of each outBufs element must be greater
-// than or equal to the length of 'in', otherwise output may be silently
+// than or equal to the length of in, otherwise output may be silently truncated.
-// truncated.
 func GSOSplit(in []byte, options GSOOptions, outBufs [][]byte, sizes []int, outOffset int) (int, error) {
 	cSumAt := int(options.CsumStart) + int(options.CsumOffset)
 	if cSumAt+1 >= len(in) {
@@ -91,15 +84,12 @@ func GSOSplit(in []byte, options GSOOptions, outBufs [][]byte, sizes []int, outO
 		return 0, fmt.Errorf("length of packet (%d) < GSO HdrLen (%d)", len(in), options.HdrLen)
 	}
 
-	// Handle the conditions where we are copying a single element to outBuffs.
 	payloadLen := len(in) - int(options.HdrLen)
 	if options.GSOType == GSONone || payloadLen < int(options.GSOSize) {
 		if len(in) > len(outBufs[0][outOffset:]) {
 			return 0, fmt.Errorf("length of packet (%d) exceeds output element length (%d)", len(in), len(outBufs[0][outOffset:]))
 		}
 		if options.NeedsCsum {
-			// The initial value at the checksum offset should be summed with
-			// the checksum we compute. This is typically the pseudo-header sum.
 			initial := binary.BigEndian.Uint16(in[cSumAt:])
 			in[cSumAt], in[cSumAt+1] = 0, 0
 			binary.BigEndian.PutUint16(in[cSumAt:], ^Checksum(in[options.CsumStart:], initial))
@@ -133,24 +123,24 @@ func GSOSplit(in []byte, options GSOOptions, outBufs [][]byte, sizes []int, outO
 	}
 
 	iphLen := int(options.CsumStart)
-	srcAddrOffset := ipv6SrcAddrOffset
+	srcAddrOffset := gsoIPv6SrcAddrOffset
 	addrLen := 16
 	if ipVersion == 4 {
-		srcAddrOffset = ipv4SrcAddrOffset
+		srcAddrOffset = gsoIPv4SrcAddrOffset
 		addrLen = 4
 	}
 	transportCsumAt := int(options.CsumStart + options.CsumOffset)
 	var firstTCPSeqNum uint32
 	var protocol uint8
 	if options.GSOType == GSOTCPv4 || options.GSOType == GSOTCPv6 {
-		protocol = ipProtoTCP
+		protocol = gsoIPProtoTCP
 		if len(in) < int(options.CsumStart)+20 {
 			return 0, fmt.Errorf("length of packet (%d) < GSO CsumStart (%d) + minimum TCP header size (%d)",
 				len(in), options.CsumStart, 20)
 		}
 		firstTCPSeqNum = binary.BigEndian.Uint32(in[options.CsumStart+4:])
 	} else {
-		protocol = ipProtoUDP
+		protocol = gsoIPProtoUDP
 	}
 	nextSegmentDataAt := int(options.HdrLen)
 	i := 0
@@ -169,45 +159,35 @@ func GSOSplit(in []byte, options GSOOptions, outBufs [][]byte, sizes []int, outO
 
 		copy(out, in[:iphLen])
 		if ipVersion == 4 {
-			// For IPv4 we are responsible for incrementing the ID field,
-			// updating the total len field, and recalculating the header
-			// checksum.
 			if i > 0 {
 				id := binary.BigEndian.Uint16(out[4:])
 				id += uint16(i)
 				binary.BigEndian.PutUint16(out[4:], id)
 			}
-			out[10], out[11] = 0, 0 // clear ipv4 header checksum
+			out[10], out[11] = 0, 0
 			binary.BigEndian.PutUint16(out[2:], uint16(totalLen))
 			ipv4CSum := ^Checksum(out[:iphLen], 0)
 			binary.BigEndian.PutUint16(out[10:], ipv4CSum)
 		} else {
-			// For IPv6 we are responsible for updating the payload length field.
 			binary.BigEndian.PutUint16(out[4:], uint16(totalLen-iphLen))
 		}
 
-		// copy transport header
 		copy(out[options.CsumStart:options.HdrLen], in[options.CsumStart:options.HdrLen])
 
-		if protocol == ipProtoTCP {
+		if protocol == gsoIPProtoTCP {
-			// set TCP seq and adjust TCP flags
 			tcpSeq := firstTCPSeqNum + uint32(options.GSOSize*uint16(i))
 			binary.BigEndian.PutUint32(out[options.CsumStart+4:], tcpSeq)
 			if nextSegmentEnd != len(in) {
-				// FIN and PSH should only be set on last segment
+				clearFlags := gsoTCPFlagFIN | gsoTCPFlagPSH
-				clearFlags := tcpFlagFIN | tcpFlagPSH
+				out[options.CsumStart+gsoTCPFlagsOffset] &^= clearFlags
-				out[options.CsumStart+tcpFlagsOffset] &^= clearFlags
 			}
 		} else {
-			// set UDP header len
 			binary.BigEndian.PutUint16(out[options.CsumStart+4:], uint16(segmentDataLen)+(options.HdrLen-options.CsumStart))
 		}
 
-		// payload
 		copy(out[options.HdrLen:], in[nextSegmentDataAt:nextSegmentEnd])
 
-		// transport checksum
+		out[transportCsumAt], out[transportCsumAt+1] = 0, 0
-		out[transportCsumAt], out[transportCsumAt+1] = 0, 0 // clear tcp/udp checksum
 		transportHeaderLen := int(options.HdrLen - options.CsumStart)
 		lenForPseudo := uint16(transportHeaderLen + segmentDataLen)
 		transportCSum := PseudoHeaderChecksum(protocol, in[srcAddrOffset:srcAddrOffset+addrLen], in[srcAddrOffset+addrLen:srcAddrOffset+addrLen*2], lenForPseudo)

tun/offload_linux.go

@@ -1,6 +1,6 @@
 /* SPDX-License-Identifier: MIT
  *
- * Copyright (C) 2017-2023 WireGuard LLC. All Rights Reserved.
+ * Copyright (C) 2017-2025 WireGuard LLC. All Rights Reserved.
  */
 
 package tun
@@ -9,7 +9,6 @@ import (
 	"bytes"
 	"encoding/binary"
 	"errors"
-	"fmt"
 	"io"
 	"unsafe"
 
@@ -17,6 +16,14 @@ import (
 	"golang.org/x/sys/unix"
 )
 
+const tcpFlagsOffset = 13
+
+const (
+	tcpFlagFIN uint8 = 0x01
+	tcpFlagPSH uint8 = 0x08
+	tcpFlagACK uint8 = 0x10
+)
+
 // virtioNetHdr is defined in the kernel in include/uapi/linux/virtio_net.h. The
 // kernel symbol is virtio_net_hdr.
 type virtioNetHdr struct {
@@ -28,30 +35,6 @@ type virtioNetHdr struct {
 	csumOffset uint16
 }
 
-func (v *virtioNetHdr) toGSOOptions() (GSOOptions, error) {
-	var gsoType GSOType
-	switch v.gsoType {
-	case unix.VIRTIO_NET_HDR_GSO_NONE:
-		gsoType = GSONone
-	case unix.VIRTIO_NET_HDR_GSO_TCPV4:
-		gsoType = GSOTCPv4
-	case unix.VIRTIO_NET_HDR_GSO_TCPV6:
-		gsoType = GSOTCPv6
-	case unix.VIRTIO_NET_HDR_GSO_UDP_L4:
-		gsoType = GSOUDPL4
-	default:
-		return GSOOptions{}, fmt.Errorf("unsupported virtio gsoType: %d", v.gsoType)
-	}
-	return GSOOptions{
-		GSOType:    gsoType,
-		HdrLen:     v.hdrLen,
-		CsumStart:  v.csumStart,
-		CsumOffset: v.csumOffset,
-		GSOSize:    v.gsoSize,
-		NeedsCsum:  v.flags&unix.VIRTIO_NET_HDR_F_NEEDS_CSUM != 0,
-	}, nil
-}
-
 func (v *virtioNetHdr) decode(b []byte) error {
 	if len(b) < virtioNetHdrLen {
 		return io.ErrShortBuffer
@@ -410,8 +393,8 @@ func checksumValid(pkt []byte, iphLen, proto uint8, isV6 bool) bool {
 		addrSize = 16
 	}
 	lenForPseudo := uint16(len(pkt) - int(iphLen))
-	cSum := PseudoHeaderChecksum(proto, pkt[srcAddrAt:srcAddrAt+addrSize], pkt[srcAddrAt+addrSize:srcAddrAt+addrSize*2], lenForPseudo)
+	cSum := pseudoHeaderChecksumNoFold(proto, pkt[srcAddrAt:srcAddrAt+addrSize], pkt[srcAddrAt+addrSize:srcAddrAt+addrSize*2], lenForPseudo)
-	return ^Checksum(pkt[iphLen:], cSum) == 0
+	return ^checksum(pkt[iphLen:], cSum) == 0
 }
 
 // coalesceResult represents the result of attempting to coalesce two TCP
@@ -527,7 +510,9 @@ const (
 )
 
 const (
-	maxUint16 = 1<<16 - 1
+	ipv4SrcAddrOffset = 12
+	ipv6SrcAddrOffset = 8
+	maxUint16         = 1<<16 - 1
 )
 
 type groResult int
@@ -659,7 +644,7 @@ func applyTCPCoalesceAccounting(bufs [][]byte, offset int, table *tcpGROTable) e
 					hdr.gsoType = unix.VIRTIO_NET_HDR_GSO_TCPV4
 					pkt[10], pkt[11] = 0, 0
 					binary.BigEndian.PutUint16(pkt[2:], uint16(len(pkt))) // set new total length
-					iphCSum := ^Checksum(pkt[:item.iphLen], 0)            // compute IPv4 header checksum
+					iphCSum := ^checksum(pkt[:item.iphLen], 0)            // compute IPv4 header checksum
 					binary.BigEndian.PutUint16(pkt[10:], iphCSum)         // set IPv4 header checksum field
 				}
 				err := hdr.encode(bufs[item.bufsIndex][offset-virtioNetHdrLen:])
@@ -679,8 +664,8 @@ func applyTCPCoalesceAccounting(bufs [][]byte, offset int, table *tcpGROTable) e
 				srcAddrAt := offset + addrOffset
 				srcAddr := bufs[item.bufsIndex][srcAddrAt : srcAddrAt+addrLen]
 				dstAddr := bufs[item.bufsIndex][srcAddrAt+addrLen : srcAddrAt+addrLen*2]
-				psum := PseudoHeaderChecksum(unix.IPPROTO_TCP, srcAddr, dstAddr, uint16(len(pkt)-int(item.iphLen)))
+				psum := pseudoHeaderChecksumNoFold(unix.IPPROTO_TCP, srcAddr, dstAddr, uint16(len(pkt)-int(item.iphLen)))
-				binary.BigEndian.PutUint16(pkt[hdr.csumStart+hdr.csumOffset:], Checksum([]byte{}, psum))
+				binary.BigEndian.PutUint16(pkt[hdr.csumStart+hdr.csumOffset:], checksum([]byte{}, psum))
 			} else {
 				hdr := virtioNetHdr{}
 				err := hdr.encode(bufs[item.bufsIndex][offset-virtioNetHdrLen:])
@@ -716,7 +701,7 @@ func applyUDPCoalesceAccounting(bufs [][]byte, offset int, table *udpGROTable) e
 				} else {
 					pkt[10], pkt[11] = 0, 0
 					binary.BigEndian.PutUint16(pkt[2:], uint16(len(pkt))) // set new total length
-					iphCSum := ^Checksum(pkt[:item.iphLen], 0)            // compute IPv4 header checksum
+					iphCSum := ^checksum(pkt[:item.iphLen], 0)            // compute IPv4 header checksum
 					binary.BigEndian.PutUint16(pkt[10:], iphCSum)         // set IPv4 header checksum field
 				}
 				err := hdr.encode(bufs[item.bufsIndex][offset-virtioNetHdrLen:])
@@ -739,8 +724,8 @@ func applyUDPCoalesceAccounting(bufs [][]byte, offset int, table *udpGROTable) e
 				srcAddrAt := offset + addrOffset
 				srcAddr := bufs[item.bufsIndex][srcAddrAt : srcAddrAt+addrLen]
 				dstAddr := bufs[item.bufsIndex][srcAddrAt+addrLen : srcAddrAt+addrLen*2]
-				psum := PseudoHeaderChecksum(unix.IPPROTO_UDP, srcAddr, dstAddr, uint16(len(pkt)-int(item.iphLen)))
+				psum := pseudoHeaderChecksumNoFold(unix.IPPROTO_UDP, srcAddr, dstAddr, uint16(len(pkt)-int(item.iphLen)))
-				binary.BigEndian.PutUint16(pkt[hdr.csumStart+hdr.csumOffset:], Checksum([]byte{}, psum))
+				binary.BigEndian.PutUint16(pkt[hdr.csumStart+hdr.csumOffset:], checksum([]byte{}, psum))
 			} else {
 				hdr := virtioNetHdr{}
 				err := hdr.encode(bufs[item.bufsIndex][offset-virtioNetHdrLen:])
@@ -909,3 +894,100 @@ func handleGRO(bufs [][]byte, offset int, tcpTable *tcpGROTable, udpTable *udpGR
 	errUDP := applyUDPCoalesceAccounting(bufs, offset, udpTable)
 	return errors.Join(errTCP, errUDP)
 }
+
+// gsoSplit splits packets from in into outBuffs, writing the size of each
+// element into sizes. It returns the number of buffers populated, and/or an
+// error.
+func gsoSplit(in []byte, hdr virtioNetHdr, outBuffs [][]byte, sizes []int, outOffset int, isV6 bool) (int, error) {
+	iphLen := int(hdr.csumStart)
+	srcAddrOffset := ipv6SrcAddrOffset
+	addrLen := 16
+	if !isV6 {
+		in[10], in[11] = 0, 0 // clear ipv4 header checksum
+		srcAddrOffset = ipv4SrcAddrOffset
+		addrLen = 4
+	}
+	transportCsumAt := int(hdr.csumStart + hdr.csumOffset)
+	in[transportCsumAt], in[transportCsumAt+1] = 0, 0 // clear tcp/udp checksum
+	var firstTCPSeqNum uint32
+	var protocol uint8
+	if hdr.gsoType == unix.VIRTIO_NET_HDR_GSO_TCPV4 || hdr.gsoType == unix.VIRTIO_NET_HDR_GSO_TCPV6 {
+		protocol = unix.IPPROTO_TCP
+		firstTCPSeqNum = binary.BigEndian.Uint32(in[hdr.csumStart+4:])
+	} else {
+		protocol = unix.IPPROTO_UDP
+	}
+	nextSegmentDataAt := int(hdr.hdrLen)
+	i := 0
+	for ; nextSegmentDataAt < len(in); i++ {
+		if i == len(outBuffs) {
+			return i - 1, ErrTooManySegments
+		}
+		nextSegmentEnd := nextSegmentDataAt + int(hdr.gsoSize)
+		if nextSegmentEnd > len(in) {
+			nextSegmentEnd = len(in)
+		}
+		segmentDataLen := nextSegmentEnd - nextSegmentDataAt
+		totalLen := int(hdr.hdrLen) + segmentDataLen
+		sizes[i] = totalLen
+		out := outBuffs[i][outOffset:]
+
+		copy(out, in[:iphLen])
+		if !isV6 {
+			// For IPv4 we are responsible for incrementing the ID field,
+			// updating the total len field, and recalculating the header
+			// checksum.
+			if i > 0 {
+				id := binary.BigEndian.Uint16(out[4:])
+				id += uint16(i)
+				binary.BigEndian.PutUint16(out[4:], id)
+			}
+			binary.BigEndian.PutUint16(out[2:], uint16(totalLen))
+			ipv4CSum := ^checksum(out[:iphLen], 0)
+			binary.BigEndian.PutUint16(out[10:], ipv4CSum)
+		} else {
+			// For IPv6 we are responsible for updating the payload length field.
+			binary.BigEndian.PutUint16(out[4:], uint16(totalLen-iphLen))
+		}
+
+		// copy transport header
+		copy(out[hdr.csumStart:hdr.hdrLen], in[hdr.csumStart:hdr.hdrLen])
+
+		if protocol == unix.IPPROTO_TCP {
+			// set TCP seq and adjust TCP flags
+			tcpSeq := firstTCPSeqNum + uint32(hdr.gsoSize*uint16(i))
+			binary.BigEndian.PutUint32(out[hdr.csumStart+4:], tcpSeq)
+			if nextSegmentEnd != len(in) {
+				// FIN and PSH should only be set on last segment
+				clearFlags := tcpFlagFIN | tcpFlagPSH
+				out[hdr.csumStart+tcpFlagsOffset] &^= clearFlags
+			}
+		} else {
+			// set UDP header len
+			binary.BigEndian.PutUint16(out[hdr.csumStart+4:], uint16(segmentDataLen)+(hdr.hdrLen-hdr.csumStart))
+		}
+
+		// payload
+		copy(out[hdr.hdrLen:], in[nextSegmentDataAt:nextSegmentEnd])
+
+		// transport checksum
+		transportHeaderLen := int(hdr.hdrLen - hdr.csumStart)
+		lenForPseudo := uint16(transportHeaderLen + segmentDataLen)
+		transportCSumNoFold := pseudoHeaderChecksumNoFold(protocol, in[srcAddrOffset:srcAddrOffset+addrLen], in[srcAddrOffset+addrLen:srcAddrOffset+addrLen*2], lenForPseudo)
+		transportCSum := ^checksum(out[hdr.csumStart:totalLen], transportCSumNoFold)
+		binary.BigEndian.PutUint16(out[hdr.csumStart+hdr.csumOffset:], transportCSum)
+
+		nextSegmentDataAt += int(hdr.gsoSize)
+	}
+	return i, nil
+}
+
+func gsoNoneChecksum(in []byte, cSumStart, cSumOffset uint16) error {
+	cSumAt := cSumStart + cSumOffset
+	// The initial value at the checksum offset should be summed with the
+	// checksum we compute. This is typically the pseudo-header checksum.
+	initial := binary.BigEndian.Uint16(in[cSumAt:])
+	in[cSumAt], in[cSumAt+1] = 0, 0
+	binary.BigEndian.PutUint16(in[cSumAt:], ^checksum(in[cSumStart:], uint64(initial)))
+	return nil
+}

tun/tun.go

@@ -56,21 +56,12 @@ type Device interface {
 // versions may have offload bugs. Where these bugs negatively impact throughput
 // or break connectivity entirely we can use these methods to disable the
 // related offload.
-//
-// Linux has the following known, GRO bugs.
-//
-// torvalds/linux@e269d79c7d35aa3808b1f3c1737d63dab504ddc8 broke virtio_net
-// TCP & UDP GRO causing GRO writes to return EINVAL. The bug was then
-// resolved later in
-// torvalds/linux@89add40066f9ed9abe5f7f886fe5789ff7e0c50e. The offending
-// commit was pulled into various LTS releases.
-//
-// UDP GRO writes end up blackholing/dropping packets destined for a
-// vxlan/geneve interface on kernel versions prior to 6.8.5.
 type GRODevice interface {
 	Device
+
 	// DisableUDPGRO disables UDP GRO if it is enabled.
 	DisableUDPGRO()
+
 	// DisableTCPGRO disables TCP GRO if it is enabled.
 	DisableTCPGRO()
 }

tun/tun_linux.go

@@ -1,6 +1,6 @@
 /* SPDX-License-Identifier: MIT
  *
- * Copyright (C) 2017-2023 WireGuard LLC. All Rights Reserved.
+ * Copyright (C) 2017-2025 WireGuard LLC. All Rights Reserved.
  */
 
 package tun
@@ -48,7 +48,7 @@ type NativeTun struct {
 	readOpMu sync.Mutex                    // readOpMu guards readBuff
 	readBuff [virtioNetHdrLen + 65535]byte // if vnetHdr every read() is prefixed by virtioNetHdr
 
-	writeOpMu   sync.Mutex // writeOpMu guards the following fields
+	writeOpMu   sync.Mutex // writeOpMu guards toWrite, tcpGROTable, udpGROTable, gro
 	toWrite     []int
 	tcpGROTable *tcpGROTable
 	udpGROTable *udpGROTable
@@ -269,15 +269,21 @@ func (tun *NativeTun) setMTU(n int) error {
 
 	defer unix.Close(fd)
 
-	req, err := unix.NewIfreq(name)
+	// do ioctl call
-	if err != nil {
+	var ifr [ifReqSize]byte
-		return fmt.Errorf("unix.NewIfreq(%q): %w", name, err)
+	copy(ifr[:], name)
-	}
+	*(*uint32)(unsafe.Pointer(&ifr[unix.IFNAMSIZ])) = uint32(n)
-	req.SetUint32(uint32(n))
+	_, _, errno := unix.Syscall(
-	err = unix.IoctlIfreq(fd, unix.SIOCSIFMTU, req)
+		unix.SYS_IOCTL,
-	if err != nil {
+		uintptr(fd),
-		return fmt.Errorf("failed to set MTU of TUN device %q: %w", name, err)
+		uintptr(unix.SIOCSIFMTU),
+		uintptr(unsafe.Pointer(&ifr[0])),
+	)
+
+	if errno != 0 {
+		return fmt.Errorf("failed to set MTU of TUN device: %w", errno)
 	}
+
 	return nil
 }
 
@@ -396,32 +402,73 @@ func handleVirtioRead(in []byte, bufs [][]byte, sizes []int, offset int) (int, e
 		return 0, err
 	}
 	in = in[virtioNetHdrLen:]
-
+	if hdr.gsoType == unix.VIRTIO_NET_HDR_GSO_NONE {
-	options, err := hdr.toGSOOptions()
+		if hdr.flags&unix.VIRTIO_NET_HDR_F_NEEDS_CSUM != 0 {
-	if err != nil {
+			// This means CHECKSUM_PARTIAL in skb context. We are responsible
-		return 0, err
+			// for computing the checksum starting at hdr.csumStart and placing
+			// at hdr.csumOffset.
+			err = gsoNoneChecksum(in, hdr.csumStart, hdr.csumOffset)
+			if err != nil {
+				return 0, err
+			}
+		}
+		if len(in) > len(bufs[0][offset:]) {
+			return 0, fmt.Errorf("read len %d overflows bufs element len %d", len(in), len(bufs[0][offset:]))
+		}
+		n := copy(bufs[0][offset:], in)
+		sizes[0] = n
+		return 1, nil
+	}
+	if hdr.gsoType != unix.VIRTIO_NET_HDR_GSO_TCPV4 && hdr.gsoType != unix.VIRTIO_NET_HDR_GSO_TCPV6 && hdr.gsoType != unix.VIRTIO_NET_HDR_GSO_UDP_L4 {
+		return 0, fmt.Errorf("unsupported virtio GSO type: %d", hdr.gsoType)
 	}
 
-	// Don't trust HdrLen from the kernel as it can be equal to the length
+	ipVersion := in[0] >> 4
+	switch ipVersion {
+	case 4:
+		if hdr.gsoType != unix.VIRTIO_NET_HDR_GSO_TCPV4 && hdr.gsoType != unix.VIRTIO_NET_HDR_GSO_UDP_L4 {
+			return 0, fmt.Errorf("ip header version: %d, GSO type: %d", ipVersion, hdr.gsoType)
+		}
+	case 6:
+		if hdr.gsoType != unix.VIRTIO_NET_HDR_GSO_TCPV6 && hdr.gsoType != unix.VIRTIO_NET_HDR_GSO_UDP_L4 {
+			return 0, fmt.Errorf("ip header version: %d, GSO type: %d", ipVersion, hdr.gsoType)
+		}
+	default:
+		return 0, fmt.Errorf("invalid ip header version: %d", ipVersion)
+	}
+
+	// Don't trust hdr.hdrLen from the kernel as it can be equal to the length
 	// of the entire first packet when the kernel is handling it as part of a
 	// FORWARD path. Instead, parse the transport header length and add it onto
-	// CsumStart, which is synonymous for IP header length.
+	// csumStart, which is synonymous for IP header length.
-	if options.GSOType == GSOUDPL4 {
+	if hdr.gsoType == unix.VIRTIO_NET_HDR_GSO_UDP_L4 {
-		options.HdrLen = options.CsumStart + 8
+		hdr.hdrLen = hdr.csumStart + 8
-	} else if options.GSOType != GSONone {
+	} else {
-		if len(in) <= int(options.CsumStart+12) {
+		if len(in) <= int(hdr.csumStart+12) {
 			return 0, errors.New("packet is too short")
 		}
 
-		tcpHLen := uint16(in[options.CsumStart+12] >> 4 * 4)
+		tcpHLen := uint16(in[hdr.csumStart+12] >> 4 * 4)
 		if tcpHLen < 20 || tcpHLen > 60 {
 			// A TCP header must be between 20 and 60 bytes in length.
 			return 0, fmt.Errorf("tcp header len is invalid: %d", tcpHLen)
 		}
-		options.HdrLen = options.CsumStart + tcpHLen
+		hdr.hdrLen = hdr.csumStart + tcpHLen
 	}
 
-	return GSOSplit(in, options, bufs, sizes, offset)
+	if len(in) < int(hdr.hdrLen) {
+		return 0, fmt.Errorf("length of packet (%d) < virtioNetHdr.hdrLen (%d)", len(in), hdr.hdrLen)
+	}
+
+	if hdr.hdrLen < hdr.csumStart {
+		return 0, fmt.Errorf("virtioNetHdr.hdrLen (%d) < virtioNetHdr.csumStart (%d)", hdr.hdrLen, hdr.csumStart)
+	}
+	cSumAt := int(hdr.csumStart + hdr.csumOffset)
+	if cSumAt+1 >= len(in) {
+		return 0, fmt.Errorf("end of checksum offset (%d) exceeds packet length (%d)", cSumAt+1, len(in))
+	}
+
+	return gsoSplit(in, hdr, bufs, sizes, offset, ipVersion == 6)
 }
 
 func (tun *NativeTun) Read(bufs [][]byte, sizes []int, offset int) (int, error) {
@@ -478,16 +525,14 @@ func (tun *NativeTun) BatchSize() int {
 	return tun.batchSize
 }
 
-// DisableUDPGRO disables UDP GRO if it is enabled. See the GRODevice interface
+// DisableUDPGRO disables UDP GRO if it is enabled.
-// for cases where it should be called.
 func (tun *NativeTun) DisableUDPGRO() {
 	tun.writeOpMu.Lock()
 	tun.gro.disableUDPGRO()
 	tun.writeOpMu.Unlock()
 }
 
-// DisableTCPGRO disables TCP GRO if it is enabled. See the GRODevice interface
+// DisableTCPGRO disables TCP GRO if it is enabled.
-// for cases where it should be called.
 func (tun *NativeTun) DisableTCPGRO() {
 	tun.writeOpMu.Lock()
 	tun.gro.disableTCPGRO()

tun/tun_plan9.go

@@ -1,147 +0,0 @@
-/* SPDX-License-Identifier: MIT
- *
- * Copyright (C) 2017-2023 WireGuard LLC. All Rights Reserved.
- */
-
-package tun
-
-import (
-	"fmt"
-	"io"
-	"os"
-	"strconv"
-	"strings"
-	"sync"
-)
-
-type NativeTun struct {
-	name      string // "/net/ipifc/2"
-	ctlFile   *os.File
-	dataFile  *os.File
-	events    chan Event
-	errors    chan error
-	closeOnce sync.Once
-}
-
-func CreateTUN(_ string, mtu int) (Device, error) {
-	ctl, err := os.OpenFile("/net/ipifc/clone", os.O_RDWR, 0)
-	if err != nil {
-		return nil, err
-	}
-	nbuf := make([]byte, 5)
-	n, err := ctl.Read(nbuf)
-	if err != nil {
-		ctl.Close()
-		return nil, fmt.Errorf("error reading from clone file: %w", err)
-	}
-	ifn, err := strconv.Atoi(strings.TrimSpace(string(nbuf[:n])))
-	if err != nil {
-		ctl.Close()
-		return nil, fmt.Errorf("error converting clone result %q to int: %w", nbuf[:n], err)
-	}
-
-	if _, err := fmt.Fprintf(ctl, "bind pkt\n"); err != nil {
-		ctl.Close()
-		return nil, fmt.Errorf("error binding to pkt: %w", err)
-	}
-	if mtu > 0 {
-		if _, err := fmt.Fprintf(ctl, "mtu %d\n", mtu); err != nil {
-			ctl.Close()
-			return nil, fmt.Errorf("error setting MTU: %w", err)
-		}
-	}
-
-	dataFile, err := os.OpenFile(fmt.Sprintf("/net/ipifc/%d/data", ifn), os.O_RDWR, 0)
-	if err != nil {
-		ctl.Close()
-		return nil, err
-	}
-
-	tun := &NativeTun{
-		ctlFile:  ctl,
-		dataFile: dataFile,
-		name:     fmt.Sprintf("/net/ipifc/%d", ifn),
-		events:   make(chan Event, 10),
-		errors:   make(chan error, 5),
-	}
-	tun.events <- EventUp
-
-	return tun, nil
-}
-
-func (tun *NativeTun) Name() (string, error) {
-	return tun.name, nil
-}
-
-func (tun *NativeTun) File() *os.File {
-	return tun.ctlFile
-}
-
-func (tun *NativeTun) Events() <-chan Event {
-	return tun.events
-}
-
-func (tun *NativeTun) Read(bufs [][]byte, sizes []int, offset int) (int, error) {
-	select {
-	case err := <-tun.errors:
-		return 0, err
-	default:
-		n, err := tun.dataFile.Read(bufs[0][offset:])
-		if n == 1 && bufs[0][offset] == 0 {
-			// EOF
-			err = io.EOF
-			n = 0
-		}
-		sizes[0] = n
-		return 1, err
-	}
-}
-
-func (tun *NativeTun) Write(bufs [][]byte, offset int) (int, error) {
-	for i, buf := range bufs {
-		if _, err := tun.dataFile.Write(buf[offset:]); err != nil {
-			return i, err
-		}
-	}
-	return len(bufs), nil
-}
-
-func (tun *NativeTun) Close() error {
-	var err1, err2 error
-	tun.closeOnce.Do(func() {
-		_, err1 := fmt.Fprintf(tun.ctlFile, "unbind\n")
-		if err := tun.ctlFile.Close(); err != nil && err1 == nil {
-			err1 = err
-		}
-		err2 = tun.dataFile.Close()
-	})
-	if err1 != nil {
-		return err1
-	}
-	return err2
-}
-
-func (tun *NativeTun) MTU() (int, error) {
-	var buf [100]byte
-	f, err := os.Open(tun.name + "/status")
-	if err != nil {
-		return 0, err
-	}
-	defer f.Close()
-	n, err := f.Read(buf[:])
-	_, res, ok := strings.Cut(string(buf[:n]), " maxtu ")
-	if ok {
-		if mtus, _, ok := strings.Cut(res, " "); ok {
-			mtu, err := strconv.Atoi(mtus)
-			if err != nil {
-				return 0, fmt.Errorf("error converting mtu %q to int: %w", mtus, err)
-			}
-			return mtu, nil
-		}
-	}
-	return 0, fmt.Errorf("no 'maxtu' field found in %s/status", tun.name)
-}
-
-func (tun *NativeTun) BatchSize() int {
-	return 1
-}