snapshot: sagernet/gvisor v0.0.0-20260727.0-sing-box-mod.1 + SPEC 048 guard

Обновление снапшота с v0.0.0-20250811.0 на пин, которого требует
sing-box после мержа 235 коммитов (upstream d620bbbf2 "Update gvisor to
20260727.0"). Прежний снапшот был взят 2026-08-04 ровно с той версии,
на которой тогда стоял апстрим; разрыв возник 2026-08-05 вместе с его
бампом.

За год апстрим-gvisor изменил ~14 000 строк в 292 файлах. Значимое для
нас — сетевой стек: tcp/connect.go (PMTU-discovery + исправление
начального RTT/RTO: раньше задержка ACK внутри стека завышала стартовый
таймаут на несколько RTT), tcp/snd.go, tcp/rcv.go, stack/conntrack.go,
stack/packet_buffer.go. Всего 30 файлов в TCP и 37 в stack.

Баг SPEC 048 апстрим НЕ исправил — проверено по коду новой версии:
handleConnecting по-прежнему проверяет состояние endpoint'а, но не ep.h,
а performHandshake так же зануляет h и отпускает мьютекс до Close().
Поэтому guard перенесён (12 строк) вместе со своим тестом (45 строк).

Red/green проверен на новой базе: без guard'а тест падает с той же
nil-паникой, что в полевом крашдампе; с ним зелёный.

pkg/hostarch/addr.go

@@ -101,6 +101,18 @@ func (v Addr) ToRange(length uint64) (AddrRange, bool) {
 	return AddrRange{v, end}, ok
 }
 
+// MustToRange is equivalent to ToRange, but panics if the end of the range
+// wraps around.
+//
+//go:nosplit
+func (v Addr) MustToRange(length uint64) AddrRange {
+	ar, ok := v.ToRange(length)
+	if !ok {
+		panic("hostarch.Addr.ToRange() wraps")
+	}
+	return ar
+}
+
 // IsPageAligned returns true if ar.Start.IsPageAligned() and
 // ar.End.IsPageAligned().
 func (ar AddrRange) IsPageAligned() bool {

pkg/hostarch/hostarch.go

@@ -4,5 +4,23 @@
 // license that can be found in the LICENSE file or at
 // https://developers.google.com/open-source/licenses/bsd.
 
-// Package hostarch contains host arch address operations for user memory.
+// Package hostarch contains machine architecture parameters.
 package hostarch
+
+import (
+	"encoding/binary"
+	"fmt"
+)
+
+// EndianString returns "little" if the invoking process is little-endian and
+// "big" if the invoking process is big-endian.
+func EndianString() string {
+	switch val := binary.NativeEndian.Uint32([]byte{0x01, 0x02, 0x03, 0x04}); val {
+	case 0x01020304:
+		return "big"
+	case 0x04030201:
+		return "little"
+	default:
+		panic(fmt.Sprintf("unknown endianness: [01 02 03 04] => %#x", val))
+	}
+}

pkg/hostarch/hostarch_arm64.go

@@ -13,36 +13,30 @@
 // limitations under the License.
 
 //go:build arm64
-// +build arm64
 
 package hostarch
 
-import (
-	"encoding/binary"
-
-	"golang.org/x/sys/unix"
-)
+import "encoding/binary"
 
 const (
 	// PageSize is the system page size.
 	// arm64 support 4K/16K/64K page size,
 	// which can be get by unix.Getpagesize().
-	// Currently, only 4K page size is supported.
+	// Currently, only 4K page size is supported by default,
+	// or 64K pages by using the pagesize_64k build tag.
 	PageSize = 1 << PageShift
 
 	// HugePageSize is the system huge page size.
 	HugePageSize = 1 << HugePageShift
 
+	// JumboPageSize is the 1GB jumbo page size.
+	JumboPageSize = 1 << JumboPageShift
+
 	// CacheLineSize is the size of the cache line.
 	CacheLineSize = 1 << CacheLineShift
 
-	// PageShift is the binary log of the system page size.
-	PageShift = 12
-
-	// HugePageShift is the binary log of the system huge page size.
-	// Should be calculated by "PageShift + (PageShift - 3)"
-	// when multiple page size support is ready.
-	HugePageShift = 21
+	// JumboPageShift is the binary log of jumbo page whose size is 1GB.
+	JumboPageShift = 30
 
 	// CacheLineShift is the binary log of the cache line size.
 	CacheLineShift = 6
@@ -89,10 +83,3 @@ func ESRAccessType(code uint64) AccessType {
 func UntaggedUserAddr(addr Addr) Addr {
 	return Addr(int64(addr<<8) >> 8)
 }
-
-func init() {
-	// Make sure the page size is 4K on arm64 platform.
-	if size := unix.Getpagesize(); size != PageSize {
-		panic("Only 4K page size is supported on arm64!")
-	}
-}

pkg/hostarch/hostarch_arm64_4k.go

@@ -0,0 +1,36 @@
+// Copyright 2026 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 arm64 && !pagesize_64k
+
+package hostarch
+
+import "golang.org/x/sys/unix"
+
+const (
+	// PageShift is the binary log of the system page size.
+	// 4K pages: 2^12 = 4096
+	PageShift = 12
+
+	// HugePageShift is the binary log of the system huge page size.
+	// For 4K pages: PageShift + (PageShift - 3) = 12 + 9 = 21
+	// This gives 2MB huge pages.
+	HugePageShift = 21
+)
+
+func init() {
+	if size := unix.Getpagesize(); size != PageSize {
+		println("WARNING: host page size mismatch - running on non-4K host")
+	}
+}

pkg/hostarch/hostarch_arm64_4k_state_autogen.go

@@ -0,0 +1,6 @@
+// automatically generated by stateify.
+
+//go:build arm64 && !pagesize_64k
+// +build arm64,!pagesize_64k
+
+package hostarch

pkg/hostarch/hostarch_arm64_64k.go

@@ -0,0 +1,36 @@
+// Copyright 2026 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 arm64 && pagesize_64k
+
+package hostarch
+
+import "golang.org/x/sys/unix"
+
+const (
+	// PageShift is the binary log of the system page size.
+	// 64K pages: 2^16 = 65536
+	PageShift = 16
+
+	// HugePageShift is the binary log of the system huge page size.
+	// For 64K pages: PageShift + (PageShift - 3) = 16 + 13 = 29
+	// This gives 512MB huge pages.
+	HugePageShift = 29
+)
+
+func init() {
+	if size := unix.Getpagesize(); size != PageSize {
+		println("WARNING: host page size mismatch - running on non-64K host")
+	}
+}

pkg/hostarch/hostarch_arm64_64k_state_autogen.go

@@ -0,0 +1,6 @@
+// automatically generated by stateify.
+
+//go:build arm64 && pagesize_64k
+// +build arm64,pagesize_64k
+
+package hostarch

pkg/hostarch/hostarch_x86.go

@@ -26,6 +26,9 @@ const (
 	// HugePageSize is the system huge page size.
 	HugePageSize = 1 << HugePageShift
 
+	// JumboPageSize is the 1GB jumbo page size.
+	JumboPageSize = 1 << JumboPageShift
+
 	// CacheLineSize is the size of the cache line.
 	CacheLineSize = 1 << CacheLineShift
 
@@ -35,6 +38,9 @@ const (
 	// HugePageShift is the binary log of the system huge page size.
 	HugePageShift = 21
 
+	// JumboPageShift is the binary log of jumbo page whose size is 1GB.
+	JumboPageShift = 30
+
 	// CacheLineShift is the binary log of the cache line size.
 	CacheLineShift = 6
 )

pkg/hostarch/sizes_util.go

@@ -11,10 +11,11 @@ const (
 	PageMask      = PageSize - 1
 	HugePageMask  = HugePageSize - 1
 	CacheLineMask = CacheLineSize - 1
+	JumboPageMask = ^uintptr(JumboPageSize - 1)
 )
 
 type bytecount interface {
-	~uint | ~uint16 | ~uint32 | ~uint64 | ~uintptr
+	~uint | ~uint32 | ~uint64 | ~uintptr
 }
 
 type hugebytecount interface {
@@ -112,3 +113,13 @@ func CacheLineRoundUp[T bytecount](x T) (val T, ok bool) {
 	ok = val >= x
 	return
 }
+
+// MustCacheLineRoundUp is equivalent to CacheLineRoundUp, but panics if
+// rounding up overflows.
+func MustCacheLineRoundUp[T bytecount](x T) T {
+	val, ok := CacheLineRoundUp(x)
+	if !ok {
+		panic("CacheLineRoundUp overflows")
+	}
+	return val
+}