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/transport/tcp/reno.go

@@ -0,0 +1,118 @@
+// 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 tcp
+
+import (
+	"time"
+)
+
+// renoState stores the variables related to TCP New Reno congestion
+// control algorithm.
+//
+// +stateify savable
+type renoState struct {
+	s *sender
+}
+
+// newRenoCC initializes the state for the NewReno congestion control algorithm.
+func newRenoCC(s *sender) *renoState {
+	return &renoState{s: s}
+}
+
+// updateSlowStart will update the congestion window as per the slow-start
+// algorithm used by NewReno. If after adjusting the congestion window
+// we cross the SSthreshold then it will return the number of packets that
+// must be consumed in congestion avoidance mode.
+//
+// +checklocks:r.s.ep.mu
+func (r *renoState) updateSlowStart(packetsAcked int) int {
+	// Don't let the congestion window cross into the congestion
+	// avoidance range.
+	newcwnd := r.s.SndCwnd + packetsAcked
+	if newcwnd >= r.s.Ssthresh {
+		newcwnd = r.s.Ssthresh
+		r.s.SndCAAckCount = 0
+	}
+
+	packetsAcked -= newcwnd - r.s.SndCwnd
+	r.s.SndCwnd = newcwnd
+	return packetsAcked
+}
+
+// updateCongestionAvoidance will update congestion window in congestion
+// avoidance mode as described in RFC5681 section 3.1
+//
+// +checklocks:r.s.ep.mu
+func (r *renoState) updateCongestionAvoidance(packetsAcked int) {
+	// Consume the packets in congestion avoidance mode.
+	r.s.SndCAAckCount += packetsAcked
+	if r.s.SndCAAckCount >= r.s.SndCwnd {
+		r.s.SndCwnd += r.s.SndCAAckCount / r.s.SndCwnd
+		r.s.SndCAAckCount = r.s.SndCAAckCount % r.s.SndCwnd
+	}
+}
+
+// reduceSlowStartThreshold reduces the slow-start threshold per RFC 5681,
+// page 6, eq. 4. It is called when we detect congestion in the network.
+//
+// +checklocks:r.s.ep.mu
+func (r *renoState) reduceSlowStartThreshold() {
+	r.s.Ssthresh = r.s.Outstanding / 2
+	if r.s.Ssthresh < 2 {
+		r.s.Ssthresh = 2
+	}
+}
+
+// Update updates the congestion state based on the number of packets that
+// were acknowledged.
+// Update implements congestionControl.Update.
+//
+// +checklocks:r.s.ep.mu
+func (r *renoState) Update(packetsAcked int, _ time.Duration) {
+	if r.s.SndCwnd < r.s.Ssthresh {
+		packetsAcked = r.updateSlowStart(packetsAcked)
+		if packetsAcked == 0 {
+			return
+		}
+	}
+	r.updateCongestionAvoidance(packetsAcked)
+}
+
+// HandleLossDetected implements congestionControl.HandleLossDetected.
+//
+// +checklocks:r.s.ep.mu
+func (r *renoState) HandleLossDetected() {
+	// A retransmit was triggered due to nDupAckThreshold or when RACK
+	// detected loss. Reduce our slow start threshold.
+	r.reduceSlowStartThreshold()
+}
+
+// HandleRTOExpired implements congestionControl.HandleRTOExpired.
+//
+// +checklocks:r.s.ep.mu
+func (r *renoState) HandleRTOExpired() {
+	// We lost a packet, so reduce ssthresh.
+	r.reduceSlowStartThreshold()
+
+	// Reduce the congestion window to 1, i.e., enter slow-start. Per
+	// RFC 5681, page 7, we must use 1 regardless of the value of the
+	// initial congestion window.
+	r.s.SndCwnd = 1
+}
+
+// PostRecovery implements congestionControl.PostRecovery.
+func (r *renoState) PostRecovery() {
+	// noop.
+}