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/flipcall/flipcall_unsafe.go

@@ -0,0 +1,87 @@
+// Copyright 2019 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.
+
+package flipcall
+
+import (
+	"reflect"
+	"unsafe"
+
+	"github.com/sagernet/gvisor/pkg/atomicbitops"
+	"github.com/sagernet/gvisor/pkg/sync"
+)
+
+// Packets consist of a 16-byte header followed by an arbitrarily-sized
+// datagram. The header consists of:
+//
+//   - A 4-byte native-endian connection state.
+//
+//   - A 4-byte native-endian datagram length in bytes.
+//
+//   - 8 reserved bytes.
+const (
+	// PacketHeaderBytes is the size of a flipcall packet header in bytes. The
+	// maximum datagram size supported by a flipcall connection is equal to the
+	// length of the packet window minus PacketHeaderBytes.
+	//
+	// PacketHeaderBytes is exported to support its use in constant
+	// expressions. Non-constant expressions may prefer to use
+	// PacketWindowLengthForDataCap().
+	PacketHeaderBytes = 16
+)
+
+func (ep *Endpoint) connState() *atomicbitops.Uint32 {
+	return (*atomicbitops.Uint32)(unsafe.Pointer(ep.packet))
+}
+
+func (ep *Endpoint) dataLen() *atomicbitops.Uint32 {
+	return (*atomicbitops.Uint32)(unsafe.Pointer(ep.packet + 4))
+}
+
+// Data returns the datagram part of ep's packet window as a byte slice.
+//
+// Note that the packet window is shared with the potentially-untrusted peer
+// Endpoint, which may concurrently mutate the contents of the packet window.
+// Thus:
+//
+//   - Readers must not assume that two reads of the same byte in Data() will
+//     return the same result. In other words, readers should read any given byte
+//     in Data() at most once.
+//
+//   - Writers must not assume that they will read back the same data that they
+//     have written. In other words, writers should avoid reading from Data() at
+//     all.
+func (ep *Endpoint) Data() (bs []byte) {
+	bshdr := (*reflect.SliceHeader)(unsafe.Pointer(&bs))
+	bshdr.Data = ep.packet + PacketHeaderBytes
+	bshdr.Len = int(ep.dataCap)
+	bshdr.Cap = int(ep.dataCap)
+	return
+}
+
+// ioSync is a dummy variable used to indicate synchronization to the Go race
+// detector. Compare syscall.ioSync.
+var ioSync int64
+
+func raceBecomeActive() {
+	if sync.RaceEnabled {
+		sync.RaceAcquire(unsafe.Pointer(&ioSync))
+	}
+}
+
+func raceBecomeInactive() {
+	if sync.RaceEnabled {
+		sync.RaceReleaseMerge(unsafe.Pointer(&ioSync))
+	}
+}