implement issuing and retiring of connection IDs

conn_id_generator.go

@@ -0,0 +1,86 @@
+package quic
+
+import (
+	"fmt"
+
+	"github.com/lucas-clemente/quic-go/internal/protocol"
+	"github.com/lucas-clemente/quic-go/internal/qerr"
+	"github.com/lucas-clemente/quic-go/internal/utils"
+	"github.com/lucas-clemente/quic-go/internal/wire"
+)
+
+type connIDGenerator struct {
+	connIDLen  int
+	highestSeq uint64
+
+	activeSrcConnIDs map[uint64]protocol.ConnectionID
+
+	addConnectionID    func(protocol.ConnectionID) [16]byte
+	retireConnectionID func(protocol.ConnectionID)
+	queueControlFrame  func(wire.Frame)
+}
+
+func newConnIDGenerator(
+	initialConnectionID protocol.ConnectionID,
+	addConnectionID func(protocol.ConnectionID) [16]byte,
+	retireConnectionID func(protocol.ConnectionID),
+	queueControlFrame func(wire.Frame),
+) *connIDGenerator {
+	m := &connIDGenerator{
+		connIDLen:          initialConnectionID.Len(),
+		activeSrcConnIDs:   make(map[uint64]protocol.ConnectionID),
+		addConnectionID:    addConnectionID,
+		retireConnectionID: retireConnectionID,
+		queueControlFrame:  queueControlFrame,
+	}
+	m.activeSrcConnIDs[0] = initialConnectionID
+	return m
+}
+
+func (m *connIDGenerator) SetMaxActiveConnIDs(limit uint64) error {
+	if m.connIDLen == 0 {
+		return nil
+	}
+	// The active_connection_id_limit transport parameter is the number of
+	// connection IDs issued in NEW_CONNECTION_IDs frame that the peer will store.
+	for i := uint64(0); i < utils.MinUint64(limit, protocol.MaxIssuedConnectionIDs); i++ {
+		if err := m.issueNewConnID(); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (m *connIDGenerator) Retire(seq uint64) error {
+	if seq > m.highestSeq {
+		return qerr.Error(qerr.ProtocolViolation, fmt.Sprintf("tried to retire connection ID %d. Highest issued: %d", seq, m.highestSeq))
+	}
+	connID, ok := m.activeSrcConnIDs[seq]
+	// We might already have deleted this connection ID, if this is a duplicate frame.
+	if !ok {
+		return nil
+	}
+	m.retireConnectionID(connID)
+	delete(m.activeSrcConnIDs, seq)
+	// Don't issue a replacement for the initial connection ID.
+	if seq == 0 {
+		return nil
+	}
+	return m.issueNewConnID()
+}
+
+func (m *connIDGenerator) issueNewConnID() error {
+	connID, err := protocol.GenerateConnectionID(m.connIDLen)
+	if err != nil {
+		return err
+	}
+	m.activeSrcConnIDs[m.highestSeq+1] = connID
+	token := m.addConnectionID(connID)
+	m.queueControlFrame(&wire.NewConnectionIDFrame{
+		SequenceNumber:      m.highestSeq + 1,
+		ConnectionID:        connID,
+		StatelessResetToken: token,
+	})
+	m.highestSeq++
+	return nil
+}