add a flag to disable conn ID generation and the check for retired conn IDs

conn_id_generator.go

@@ -76,7 +76,7 @@ func (m *connIDGenerator) Retire(seq uint64, sentWithDestConnID protocol.Connect
 	if !ok {
 		return nil
 	}
-	if connID.Equal(sentWithDestConnID) {
+	if connID.Equal(sentWithDestConnID) && !RetireBugBackwardsCompatibilityMode {
 		return qerr.NewError(qerr.ProtocolViolation, fmt.Sprintf("tried to retire connection ID %d (%s), which was used as the Destination Connection ID on this packet", seq, connID))
 	}
 	m.retireConnectionID(connID)
@@ -89,6 +89,9 @@ func (m *connIDGenerator) Retire(seq uint64, sentWithDestConnID protocol.Connect
 }
 
 func (m *connIDGenerator) issueNewConnID() error {
+	if RetireBugBackwardsCompatibilityMode {
+		return nil
+	}
 	connID, err := protocol.GenerateConnectionID(m.connIDLen)
 	if err != nil {
 		return err

conn_id_generator_test.go

@@ -62,6 +62,15 @@ var _ = Describe("Connection ID Generator", func() {
 		}
 	})
 
+	It("doesn't issue new connection IDs in RetireBugBackwardsCompatibilityMode", func() {
+		RetireBugBackwardsCompatibilityMode = true
+		defer func() { RetireBugBackwardsCompatibilityMode = false }()
+
+		Expect(g.SetMaxActiveConnIDs(4)).To(Succeed())
+		Expect(retiredConnIDs).To(BeEmpty())
+		Expect(addedConnIDs).To(BeEmpty())
+	})
+
 	It("limits the number of connection IDs that it issues", func() {
 		Expect(g.SetMaxActiveConnIDs(9999999)).To(Succeed())
 		Expect(retiredConnIDs).To(BeEmpty())
@@ -81,6 +90,18 @@ var _ = Describe("Connection ID Generator", func() {
 		Expect(g.Retire(f.SequenceNumber, f.ConnectionID)).To(MatchError(fmt.Sprintf("PROTOCOL_VIOLATION: tried to retire connection ID %d (%s), which was used as the Destination Connection ID on this packet", f.SequenceNumber, f.ConnectionID)))
 	})
 
+	It("doesn't error if the peers tries to retire a connection ID in a packet with that connection ID in RetireBugBackwardsCompatibilityMode", func() {
+		Expect(g.SetMaxActiveConnIDs(4)).To(Succeed())
+		Expect(queuedFrames).ToNot(BeEmpty())
+		Expect(queuedFrames[0]).To(BeAssignableToTypeOf(&wire.NewConnectionIDFrame{}))
+
+		RetireBugBackwardsCompatibilityMode = true
+		defer func() { RetireBugBackwardsCompatibilityMode = false }()
+
+		f := queuedFrames[0].(*wire.NewConnectionIDFrame)
+		Expect(g.Retire(f.SequenceNumber, f.ConnectionID)).To(Succeed())
+	})
+
 	It("issues new connection IDs, when old ones are retired", func() {
 		Expect(g.SetMaxActiveConnIDs(5)).To(Succeed())
 		queuedFrames = nil

interface.go

@@ -13,6 +13,16 @@ import (
 	"github.com/lucas-clemente/quic-go/quictrace"
 )
 
+// RetireBugBackwardsCompatibilityMode controls a backwards compatibility mode, necessary due to a bug in
+// quic-go v0.17.2 (and earlier), where under certain circumstances, an endpoint would retire the connection
+// ID it is currently using. See https://github.com/lucas-clemente/quic-go/issues/2658.
+// The bug has now been fixed, and new deployments have nothing to worry about.
+// Deployments that already have quic-go <= v0.17.2 deployed should active RetireBugBackwardsCompatibilityMode.
+// If activated, quic-go will take steps to avoid the bug from triggering when connected to endpoints that are still
+// running quic-go <= v0.17.2.
+// This flag will be removed in a future version of quic-go.
+var RetireBugBackwardsCompatibilityMode bool
+
 // The StreamID is the ID of a QUIC stream.
 type StreamID = protocol.StreamID