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quic: remember which remote connection IDs have been retired
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Keep track of which peer-provided connection ID sequence numbers
we have sent a RETIRE_CONNECTION_ID for, received an ack, and
removed from our set of tracked IDs.

Rework how we track retired connection IDs in general:
Rather than keeping all state for retired IDs, just keep a
set of the sequence numbers of IDs which we're in the process
of retiring.

Change-Id: I14da8b5295d5fbe8318c8afe556cbd2c8a56d856
Reviewed-on: https://go-review.googlesource.com/c/net/+/635717
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Jonathan Amsterdam <jba@google.com>
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@neild
neild committed Dec 30, 2024
1 parent dfc720d commit c2be992
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Showing 3 changed files with 119 additions and 67 deletions.
129 changes: 62 additions & 67 deletions quic/conn_id.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -9,6 +9,7 @@ package quic
import (
"bytes"
"crypto/rand"
"slices"
)

// connIDState is a conn's connection IDs.
Expand All @@ -25,8 +26,16 @@ type connIDState struct {
remote []remoteConnID

nextLocalSeq int64
retireRemotePriorTo int64 // largest Retire Prior To value sent by the peer
peerActiveConnIDLimit int64 // peer's active_connection_id_limit transport parameter
peerActiveConnIDLimit int64 // peer's active_connection_id_limit

// Handling of retirement of remote connection IDs.
// The rangesets track ID sequence numbers.
// IDs in need of retirement are added to remoteRetiring,
// moved to remoteRetiringSent once we send a RETIRE_CONECTION_ID frame,
// and removed from the set once retirement completes.
retireRemotePriorTo int64 // largest Retire Prior To value sent by the peer
remoteRetiring rangeset[int64] // remote IDs in need of retirement
remoteRetiringSent rangeset[int64] // remote IDs waiting for ack of retirement

originalDstConnID []byte // expected original_destination_connection_id param
retrySrcConnID []byte // expected retry_source_connection_id param
Expand All @@ -45,9 +54,6 @@ type connID struct {
// For the transient destination ID in a client's Initial packet, this is -1.
seq int64

// retired is set when the connection ID is retired.
retired bool

// send is set when the connection ID's state needs to be sent to the peer.
//
// For local IDs, this indicates a new ID that should be sent
Expand Down Expand Up @@ -144,24 +150,20 @@ func (s *connIDState) srcConnID() []byte {
// dstConnID is the Destination Connection ID to use in a sent packet.
func (s *connIDState) dstConnID() (cid []byte, ok bool) {
for i := range s.remote {
if !s.remote[i].retired {
return s.remote[i].cid, true
}
return s.remote[i].cid, true
}
return nil, false
}

// isValidStatelessResetToken reports whether the given reset token is
// associated with a non-retired connection ID which we have used.
func (s *connIDState) isValidStatelessResetToken(resetToken statelessResetToken) bool {
for i := range s.remote {
// We currently only use the first available remote connection ID,
// so any other reset token is not valid.
if !s.remote[i].retired {
return s.remote[i].resetToken == resetToken
}
if len(s.remote) == 0 {
return false
}
return false
// We currently only use the first available remote connection ID,
// so any other reset token is not valid.
return s.remote[0].resetToken == resetToken
}

// setPeerActiveConnIDLimit sets the active_connection_id_limit
Expand All @@ -174,7 +176,7 @@ func (s *connIDState) setPeerActiveConnIDLimit(c *Conn, lim int64) error {
func (s *connIDState) issueLocalIDs(c *Conn) error {
toIssue := min(int(s.peerActiveConnIDLimit), maxPeerActiveConnIDLimit)
for i := range s.local {
if s.local[i].seq != -1 && !s.local[i].retired {
if s.local[i].seq != -1 {
toIssue--
}
}
Expand Down Expand Up @@ -271,7 +273,7 @@ func (s *connIDState) handlePacket(c *Conn, ptype packetType, srcConnID []byte)
}
}
case ptype == packetTypeHandshake && c.side == serverSide:
if len(s.local) > 0 && s.local[0].seq == -1 && !s.local[0].retired {
if len(s.local) > 0 && s.local[0].seq == -1 {
// We're a server connection processing the first Handshake packet from
// the client. Discard the transient, client-chosen connection ID used
// for Initial packets; the client will never send it again.
Expand Down Expand Up @@ -304,23 +306,29 @@ func (s *connIDState) handleNewConnID(c *Conn, seq, retire int64, cid []byte, re
}
}

if seq < s.retireRemotePriorTo {
// This ID was already retired by a previous NEW_CONNECTION_ID frame.
// Nothing to do.
return nil
}

if retire > s.retireRemotePriorTo {
// Add newly-retired connection IDs to the set we need to send
// RETIRE_CONNECTION_ID frames for, and remove them from s.remote.
//
// (This might cause us to send a RETIRE_CONNECTION_ID for an ID we've
// never seen. That's fine.)
s.remoteRetiring.add(s.retireRemotePriorTo, retire)
s.retireRemotePriorTo = retire
s.needSend = true
s.remote = slices.DeleteFunc(s.remote, func(rcid remoteConnID) bool {
return rcid.seq < s.retireRemotePriorTo
})
}

have := false // do we already have this connection ID?
active := 0
for i := range s.remote {
rcid := &s.remote[i]
if !rcid.retired && rcid.seq >= 0 && rcid.seq < s.retireRemotePriorTo {
s.retireRemote(rcid)
c.endpoint.connsMap.updateConnIDs(func(conns *connsMap) {
conns.retireResetToken(c, rcid.resetToken)
})
}
if !rcid.retired {
active++
}
if rcid.seq == seq {
if !bytes.Equal(rcid.cid, cid) {
return localTransportError{
Expand All @@ -329,6 +337,7 @@ func (s *connIDState) handleNewConnID(c *Conn, seq, retire int64, cid []byte, re
}
}
have = true // yes, we've seen this sequence number
break
}
}

Expand All @@ -345,18 +354,12 @@ func (s *connIDState) handleNewConnID(c *Conn, seq, retire int64, cid []byte, re
},
resetToken: resetToken,
})
if seq < s.retireRemotePriorTo {
// This ID was already retired by a previous NEW_CONNECTION_ID frame.
s.retireRemote(&s.remote[len(s.remote)-1])
} else {
active++
c.endpoint.connsMap.updateConnIDs(func(conns *connsMap) {
conns.addResetToken(c, resetToken)
})
}
c.endpoint.connsMap.updateConnIDs(func(conns *connsMap) {
conns.addResetToken(c, resetToken)
})
}

if active > activeConnIDLimit {
if len(s.remote) > activeConnIDLimit {
// Retired connection IDs (including newly-retired ones) do not count
// against the limit.
// https://www.rfc-editor.org/rfc/rfc9000.html#section-5.1.1-5
Expand All @@ -370,25 +373,18 @@ func (s *connIDState) handleNewConnID(c *Conn, seq, retire int64, cid []byte, re
// for which RETIRE_CONNECTION_ID frames have not yet been acknowledged."
// https://www.rfc-editor.org/rfc/rfc9000#section-5.1.2-6
//
// Set a limit of four times the active_connection_id_limit for
// the total number of remote connection IDs we keep state for locally.
if len(s.remote) > 4*activeConnIDLimit {
// Set a limit of three times the active_connection_id_limit for
// the total number of remote connection IDs we keep retirement state for.
if s.remoteRetiring.size()+s.remoteRetiringSent.size() > 3*activeConnIDLimit {
return localTransportError{
code: errConnectionIDLimit,
reason: "too many unacknowledged RETIRE_CONNECTION_ID frames",
reason: "too many unacknowledged retired connection ids",
}
}

return nil
}

// retireRemote marks a remote connection ID as retired.
func (s *connIDState) retireRemote(rcid *remoteConnID) {
rcid.retired = true
rcid.send.setUnsent()
s.needSend = true
}

func (s *connIDState) handleRetireConnID(c *Conn, seq int64) error {
if seq >= s.nextLocalSeq {
return localTransportError{
Expand Down Expand Up @@ -424,20 +420,11 @@ func (s *connIDState) ackOrLossNewConnectionID(pnum packetNumber, seq int64, fat
}

func (s *connIDState) ackOrLossRetireConnectionID(pnum packetNumber, seq int64, fate packetFate) {
for i := 0; i < len(s.remote); i++ {
if s.remote[i].seq != seq {
continue
}
if fate == packetAcked {
// We have retired this connection ID, and the peer has acked.
// Discard its state completely.
s.remote = append(s.remote[:i], s.remote[i+1:]...)
} else {
// RETIRE_CONNECTION_ID frame was lost, mark for retransmission.
s.needSend = true
s.remote[i].send.ackOrLoss(pnum, fate)
}
return
s.remoteRetiringSent.sub(seq, seq+1)
if fate == packetLost {
// RETIRE_CONNECTION_ID frame was lost, mark for retransmission.
s.remoteRetiring.add(seq, seq+1)
s.needSend = true
}
}

Expand Down Expand Up @@ -469,14 +456,22 @@ func (s *connIDState) appendFrames(c *Conn, pnum packetNumber, pto bool) bool {
}
s.local[i].send.setSent(pnum)
}
for i := range s.remote {
if !s.remote[i].send.shouldSendPTO(pto) {
continue
if pto {
for _, r := range s.remoteRetiringSent {
for cid := r.start; cid < r.end; cid++ {
if !c.w.appendRetireConnectionIDFrame(cid) {
return false
}
}
}
if !c.w.appendRetireConnectionIDFrame(s.remote[i].seq) {
}
for s.remoteRetiring.numRanges() > 0 {
cid := s.remoteRetiring.min()
if !c.w.appendRetireConnectionIDFrame(cid) {
return false
}
s.remote[i].send.setSent(pnum)
s.remoteRetiring.sub(cid, cid+1)
s.remoteRetiringSent.add(cid, cid+1)
}
s.needSend = false
return true
Expand Down
49 changes: 49 additions & 0 deletions quic/conn_id_test.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -664,3 +664,52 @@ func TestConnIDsCleanedUpAfterClose(t *testing.T) {
}
})
}

func TestConnIDRetiredConnIDResent(t *testing.T) {
tc := newTestConn(t, serverSide)
tc.handshake()
tc.ignoreFrame(frameTypeAck)
//tc.ignoreFrame(frameTypeRetireConnectionID)

// Send CID 2, retire 0-1 (negotiated during the handshake).
tc.writeFrames(packetType1RTT,
debugFrameNewConnectionID{
seq: 2,
retirePriorTo: 2,
connID: testPeerConnID(2),
token: testPeerStatelessResetToken(2),
})
tc.wantFrame("retire CID 0", packetType1RTT, debugFrameRetireConnectionID{seq: 0})
tc.wantFrame("retire CID 1", packetType1RTT, debugFrameRetireConnectionID{seq: 1})

// Send CID 3, retire 2.
tc.writeFrames(packetType1RTT,
debugFrameNewConnectionID{
seq: 3,
retirePriorTo: 3,
connID: testPeerConnID(3),
token: testPeerStatelessResetToken(3),
})
tc.wantFrame("retire CID 2", packetType1RTT, debugFrameRetireConnectionID{seq: 2})

// Acknowledge retirement of CIDs 0-2.
// The server should have state for only one CID: 3.
tc.writeAckForAll()
if got, want := len(tc.conn.connIDState.remote), 1; got != want {
t.Fatalf("connection has state for %v connection IDs, want %v", got, want)
}

// Send CID 2 again.
// The server should ignore this, since it's already retired the CID.
tc.ignoreFrames[frameTypeRetireConnectionID] = false
tc.writeFrames(packetType1RTT,
debugFrameNewConnectionID{
seq: 2,
connID: testPeerConnID(2),
token: testPeerStatelessResetToken(2),
})
if got, want := len(tc.conn.connIDState.remote), 1; got != want {
t.Fatalf("connection has state for %v connection IDs, want %v", got, want)
}
tc.wantIdle("server does not re-retire already retired CID 2")
}
8 changes: 8 additions & 0 deletions quic/rangeset.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -159,6 +159,14 @@ func (s rangeset[T]) numRanges() int {
return len(s)
}

// size returns the size of all ranges in the rangeset.
func (s rangeset[T]) size() (total T) {
for _, r := range s {
total += r.size()
}
return total
}

// isrange reports if the rangeset covers exactly the range [start, end).
func (s rangeset[T]) isrange(start, end T) bool {
switch len(s) {
Expand Down

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