snapshot: sagernet/gvisor v0.0.0-20250811.0-sing-box-mod.1

Содержимое пина, зафиксированного в go.mod sing-box-lx, одним коммитом
без истории. Полная история SagerNet/gvisor — 1.45 ГБ и клонируется в
каждой CI-джобе; наша дельта — одна вставка в одну функцию, история для
неё не нужна.

Module path github.com/sagernet/gvisor сохранён намеренно: на него
опирается replace-директива суперпроекта.

Патч поверх — отдельным коммитом, чтобы дельта читалась одним git show
и переносилась на новый пин копированием.

SPECS/TASKS/048-GVISOR_HANDSHAKE_NIL_CRASH

pkg/xdp/umem.go

@@ -0,0 +1,107 @@
+// Copyright 2022 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//go:build amd64 || arm64
+// +build amd64 arm64
+
+package xdp
+
+import (
+	"fmt"
+
+	"github.com/sagernet/gvisor/pkg/sync"
+	"golang.org/x/sys/unix"
+)
+
+// TODO(b/240191988): There's some kind of memory corruption bug that occurs
+// occasionally. This occurred even before TX was supported.
+
+// TODO(b/240191988): We can hold locks for less time if we accept a more
+// obtuse API. For example, CompletionQueue.FreeAll doesn't need to hold a
+// mutex for its entire duration.
+
+// UMEM is the shared memory area that the kernel and userspace put packets in.
+type UMEM struct {
+	// mem is the mmap'd area shared with the kernel.
+	mem []byte
+
+	// sockfd is the underlying AF_XDP socket.
+	sockfd uint32
+
+	// frameMask masks the lower bits of an address to get the frame's
+	// address.
+	frameMask uint64
+
+	// mu protects frameAddresses and nFreeFrames.
+	mu sync.Mutex
+
+	// frameAddresses is a stack of available frame addresses.
+	// +checklocks:mu
+	frameAddresses []uint64
+
+	// nFreeFrames is the number of frames available and is used to index
+	// into frameAddresses.
+	// +checklocks:mu
+	nFreeFrames uint32
+}
+
+// SockFD returns the underlying AF_XDP socket FD.
+func (um *UMEM) SockFD() uint32 {
+	return um.sockfd
+}
+
+// Lock locks the UMEM.
+//
+// +checklocksacquire:um.mu
+func (um *UMEM) Lock() {
+	um.mu.Lock()
+}
+
+// Unlock unlocks the UMEM.
+//
+// +checklocksrelease:um.mu
+func (um *UMEM) Unlock() {
+	um.mu.Unlock()
+}
+
+// FreeFrame returns the frame containing addr to the set of free frames.
+//
+// The UMEM must be locked during the call to FreeFrame.
+//
+// +checklocks:um.mu
+func (um *UMEM) FreeFrame(addr uint64) {
+	um.frameAddresses[um.nFreeFrames] = addr
+	um.nFreeFrames++
+}
+
+// AllocFrame returns the address of a frame that can be enqueued to the fill
+// or TX queue. It will panic if there are no frames left, so callers must call
+// it no more than the number of buffers reserved via TXQueue.Reserve().
+//
+// The UMEM must be locked during the call to AllocFrame.
+//
+// +checklocks:um.mu
+func (um *UMEM) AllocFrame() uint64 {
+	um.nFreeFrames--
+	return um.frameAddresses[um.nFreeFrames] & um.frameMask
+}
+
+// Get gets the bytes of the packet pointed to by desc.
+func (um *UMEM) Get(desc unix.XDPDesc) []byte {
+	end := desc.Addr + uint64(desc.Len)
+	if desc.Addr&um.frameMask != (end-1)&um.frameMask {
+		panic(fmt.Sprintf("UMEM (%+v) access crosses frame boundaries: %+v", um, desc))
+	}
+	return um.mem[desc.Addr:end]
+}