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/pipe/rx.go

@@ -0,0 +1,108 @@
+// 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 pipe
+
+// Rx is the receive side of the shared memory ring buffer.
+//
+// +stateify savable
+type Rx struct {
+	p pipe
+
+	tail uint64
+	head uint64
+}
+
+// Init initializes the receive end of the pipe. In the initial state, the next
+// slot to be inspected is the very first one.
+func (r *Rx) Init(b []byte) {
+	r.p.init(b)
+	r.tail = 0xfffffffe * jump
+	r.head = r.tail
+}
+
+// Pull reads the next buffer from the pipe, returning nil if there isn't one
+// currently available.
+//
+// The returned slice is available until Flush() is next called. After that, it
+// must not be touched.
+func (r *Rx) Pull() []byte {
+	if r.head == r.tail+jump {
+		// We've already pulled the whole pipe.
+		return nil
+	}
+
+	header := r.p.readAtomic(r.head)
+	if header&slotFree != 0 {
+		// The next slot is free, we can't pull it yet.
+		return nil
+	}
+
+	payloadSize := header & slotSizeMask
+	newHead := r.head + payloadToSlotSize(payloadSize)
+	headWrap := (r.head & revolutionMask) | uint64(len(r.p.buffer))
+
+	// Check if this is a wrapping slot. If that's the case, it carries no
+	// data, so we just skip it and try again from the first slot.
+	if int64(newHead-headWrap) >= 0 {
+		// If newHead passes the tail, the pipe is either damaged or the
+		// RX view of the pipe has completely wrapped without an
+		// intervening flush.
+		if int64(newHead-(r.tail+jump)) > 0 {
+			return nil
+		}
+		// The pipe is damaged if newHead doesn't point to the start of
+		// the ring.
+		if newHead&offsetMask != 0 {
+			return nil
+		}
+
+		if r.tail == r.head {
+			// If this is the first pull since the last Flush()
+			// call, we flush the state so that the sender can use
+			// this space if it needs to.
+			r.p.writeAtomic(r.head, slotFree|slotToPayloadSize(newHead-r.head))
+			r.tail = newHead
+		}
+
+		r.head = newHead
+		return r.Pull()
+	}
+
+	// Grab the buffer before updating r.head.
+	b := r.p.data(r.head, payloadSize)
+	r.head = newHead
+	return b
+}
+
+// Flush tells the transmitter that all buffers pulled since the last Flush()
+// have been used, so the transmitter is free to used their slots for further
+// transmission.
+func (r *Rx) Flush() {
+	if r.head == r.tail {
+		return
+	}
+	r.p.writeAtomic(r.tail, slotFree|slotToPayloadSize(r.head-r.tail))
+	r.tail = r.head
+}
+
+// Abort unpulls any pulled buffers.
+func (r *Rx) Abort() {
+	r.head = r.tail
+}
+
+// Bytes returns the byte slice on which the pipe operates.
+func (r *Rx) Bytes() []byte {
+	return r.p.buffer
+}