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_recovery.go

@@ -0,0 +1,68 @@
+// Copyright 2020 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
+
+// renoRecovery stores the variables related to TCP Reno loss recovery
+// algorithm.
+//
+// +stateify savable
+type renoRecovery struct {
+	s *sender
+}
+
+func newRenoRecovery(s *sender) *renoRecovery {
+	return &renoRecovery{s: s}
+}
+
+// +checklocks:rr.s.ep.mu
+func (rr *renoRecovery) DoRecovery(rcvdSeg *segment, fastRetransmit bool) {
+	ack := rcvdSeg.ackNumber
+	snd := rr.s
+
+	// We are in fast recovery mode. Ignore the ack if it's out of range.
+	if !ack.InRange(snd.SndUna, snd.SndNxt+1) {
+		return
+	}
+
+	// Don't count this as a duplicate if it is carrying data or
+	// updating the window.
+	if rcvdSeg.logicalLen() != 0 || snd.SndWnd != rcvdSeg.window {
+		return
+	}
+
+	// Inflate the congestion window if we're getting duplicate acks
+	// for the packet we retransmitted.
+	if !fastRetransmit && ack == snd.FastRecovery.First {
+		// We received a dup, inflate the congestion window by 1 packet
+		// if we're not at the max yet. Only inflate the window if
+		// regular FastRecovery is in use, RFC6675 does not require
+		// inflating cwnd on duplicate ACKs.
+		if snd.SndCwnd < snd.FastRecovery.MaxCwnd {
+			snd.SndCwnd++
+		}
+		return
+	}
+
+	// A partial ack was received. Retransmit this packet and remember it
+	// so that we don't retransmit it again.
+	//
+	// We don't inflate the window because we're putting the same packet
+	// back onto the wire.
+	//
+	// N.B. The retransmit timer will be reset by the caller.
+	snd.FastRecovery.First = ack
+	snd.DupAckCount = 0
+	snd.resendSegment()
+}