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/tcpip/link/sharedmem/sharedmem_unsafe.go

@@ -0,0 +1,59 @@
+// Copyright 2018 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 sharedmem
+
+import (
+	"fmt"
+	"reflect"
+	"unsafe"
+
+	"github.com/sagernet/gvisor/pkg/atomicbitops"
+	"github.com/sagernet/gvisor/pkg/memutil"
+	"golang.org/x/sys/unix"
+)
+
+// sharedDataPointer converts the shared data slice into a pointer so that it
+// can be used in atomic operations.
+func sharedDataPointer(sharedData []byte) *atomicbitops.Uint32 {
+	return (*atomicbitops.Uint32)(unsafe.Pointer(&sharedData[0:4][0]))
+}
+
+// getBuffer returns a memory region mapped to the full contents of the given
+// file descriptor.
+func getBuffer(fd int) ([]byte, error) {
+	var s unix.Stat_t
+	if err := unix.Fstat(fd, &s); err != nil {
+		return nil, err
+	}
+
+	// Check that size doesn't overflow an int.
+	if s.Size > int64(^uint(0)>>1) {
+		return nil, unix.EDOM
+	}
+
+	addr, err := memutil.MapFile(0 /* addr */, uintptr(s.Size), unix.PROT_READ|unix.PROT_WRITE, unix.MAP_SHARED|unix.MAP_FILE, uintptr(fd), 0 /*offset*/)
+	if err != nil {
+		return nil, fmt.Errorf("failed to map memory for buffer fd: %d, error: %s", fd, err)
+	}
+
+	// Use unsafe to convert addr into a []byte.
+	var b []byte
+	hdr := (*reflect.SliceHeader)(unsafe.Pointer(&b))
+	hdr.Data = addr
+	hdr.Len = int(s.Size)
+	hdr.Cap = int(s.Size)
+
+	return b, nil
+}