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/header/gue.go

@@ -0,0 +1,73 @@
+// 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 header
+
+const (
+	typeHLen   = 0
+	encapProto = 1
+)
+
+// GUEFields contains the fields of a GUE packet. It is used to describe the
+// fields of a packet that needs to be encoded.
+type GUEFields struct {
+	// Type is the "type" field of the GUE header.
+	Type uint8
+
+	// Control is the "control" field of the GUE header.
+	Control bool
+
+	// HeaderLength is the "header length" field of the GUE header. It must
+	// be at least 4 octets, and a multiple of 4 as well.
+	HeaderLength uint8
+
+	// Protocol is the "protocol" field of the GUE header. This is one of
+	// the IPPROTO_* values.
+	Protocol uint8
+}
+
+// GUE represents a Generic UDP Encapsulation header stored in a byte array, the
+// fields are described in https://tools.ietf.org/html/draft-ietf-nvo3-gue-01.
+type GUE []byte
+
+const (
+	// GUEMinimumSize is the minimum size of a valid GUE packet.
+	GUEMinimumSize = 4
+)
+
+// TypeAndControl returns the GUE packet type (top 3 bits of the first byte,
+// which includes the control bit).
+func (b GUE) TypeAndControl() uint8 {
+	return b[typeHLen] >> 5
+}
+
+// HeaderLength returns the total length of the GUE header.
+func (b GUE) HeaderLength() uint8 {
+	return 4 + 4*(b[typeHLen]&0x1f)
+}
+
+// Protocol returns the protocol field of the GUE header.
+func (b GUE) Protocol() uint8 {
+	return b[encapProto]
+}
+
+// Encode encodes all the fields of the GUE header.
+func (b GUE) Encode(i *GUEFields) {
+	ctl := uint8(0)
+	if i.Control {
+		ctl = 1 << 5
+	}
+	b[typeHLen] = ctl | i.Type<<6 | (i.HeaderLength-4)/4
+	b[encapProto] = i.Protocol
+}