quicreuse: make it possible to use an application-constructed quic.Transport

p2p/transport/quicreuse/connmgr.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"crypto/tls"
 	"errors"
+	"io"
 	"net"
 	"sync"
 
@@ -15,6 +16,22 @@ import (
 	quicmetrics "github.com/quic-go/quic-go/metrics"
 )
 
+type QUICListener interface {
+	Accept(ctx context.Context) (quic.Connection, error)
+	Close() error
+	Addr() net.Addr
+}
+
+var _ QUICListener = &quic.Listener{}
+
+type QUICTransport interface {
+	Listen(tlsConf *tls.Config, conf *quic.Config) (QUICListener, error)
+	Dial(ctx context.Context, addr net.Addr, tlsConf *tls.Config, conf *quic.Config) (quic.Connection, error)
+	WriteTo(b []byte, addr net.Addr) (int, error)
+	ReadNonQUICPacket(ctx context.Context, b []byte) (int, net.Addr, error)
+	io.Closer
+}
+
 type ConnManager struct {
 	reuseUDP4       *reuse
 	reuseUDP6       *reuse
@@ -101,6 +118,32 @@ func (c *ConnManager) getReuse(network string) (*reuse, error) {
 	}
 }
 
+// LendTransport is an advanced method used to lend an existing QUICTransport
+// to the ConnManager. The ConnManager will close the returned channel when it
+// is done with the transport, so that the owner may safely close the transport.
+func (c *ConnManager) LendTransport(network string, tr QUICTransport, conn net.PacketConn) (<-chan struct{}, error) {
+	c.quicListenersMu.Lock()
+	defer c.quicListenersMu.Unlock()
+
+	localAddr, ok := conn.LocalAddr().(*net.UDPAddr)
+	if !ok {
+		return nil, errors.New("expected a conn.LocalAddr() to return a *net.UDPAddr")
+	}
+
+	refCountedTr := &refcountedTransport{
+		QUICTransport:    tr,
+		packetConn:       conn,
+		borrowDoneSignal: make(chan struct{}),
+	}
+
+	var reuse *reuse
+	reuse, err := c.getReuse(network)
+	if err != nil {
+		return nil, err
+	}
+	return refCountedTr.borrowDoneSignal, reuse.AddTransport(refCountedTr, localAddr)
+}
+
 func (c *ConnManager) ListenQUIC(addr ma.Multiaddr, tlsConf *tls.Config, allowWindowIncrease func(conn quic.Connection, delta uint64) bool) (Listener, error) {
 	return c.ListenQUICAndAssociate(nil, addr, tlsConf, allowWindowIncrease)
 }
@@ -175,7 +218,7 @@ func (c *ConnManager) SharedNonQUICPacketConn(network string, laddr *net.UDPAddr
 			ctx:             ctx,
 			ctxCancel:       cancel,
 			owningTransport: t,
-			tr:              &t.Transport,
+			tr:              t.QUICTransport,
 		}, nil
 	}
 	return nil, errors.New("expected to be able to share with a QUIC listener, but the QUIC listener is not using a refcountedTransport. `DisableReuseport` should not be set")
@@ -201,10 +244,12 @@ func (c *ConnManager) transportForListen(association any, network string, laddr
 	}
 	return &singleOwnerTransport{
 		packetConn: conn,
-		Transport: quic.Transport{
-			Conn:              conn,
-			StatelessResetKey: &c.srk,
-			TokenGeneratorKey: &c.tokenKey,
+		Transport: &wrappedQUICTransport{
+			&quic.Transport{
+				Conn:              conn,
+				StatelessResetKey: &c.srk,
+				TokenGeneratorKey: &c.tokenKey,
+			},
 		},
 	}, nil
 }
@@ -279,7 +324,7 @@ func (c *ConnManager) TransportWithAssociationForDial(association any, network s
 	if err != nil {
 		return nil, err
 	}
-	return &singleOwnerTransport{Transport: quic.Transport{Conn: conn, StatelessResetKey: &c.srk}, packetConn: conn}, nil
+	return &singleOwnerTransport{Transport: &wrappedQUICTransport{&quic.Transport{Conn: conn, StatelessResetKey: &c.srk}}, packetConn: conn}, nil
 }
 
 func (c *ConnManager) Protocols() []int {
@@ -299,3 +344,11 @@ func (c *ConnManager) Close() error {
 func (c *ConnManager) ClientConfig() *quic.Config {
 	return c.clientConfig
 }
+
+type wrappedQUICTransport struct {
+	*quic.Transport
+}
+
+func (t *wrappedQUICTransport) Listen(tlsConf *tls.Config, conf *quic.Config) (QUICListener, error) {
+	return t.Transport.Listen(tlsConf, conf)
+}

p2p/transport/quicreuse/connmgr_test.go

@@ -97,7 +97,7 @@ func TestConnectionPassedToQUICForListening(t *testing.T) {
 	quicTr, err := cm.transportForListen(nil, netw, naddr)
 	require.NoError(t, err)
 	defer quicTr.Close()
-	if _, ok := quicTr.(*singleOwnerTransport).Transport.Conn.(quic.OOBCapablePacketConn); !ok {
+	if _, ok := quicTr.(*singleOwnerTransport).packetConn.(quic.OOBCapablePacketConn); !ok {
 		t.Fatal("connection passed to quic-go cannot be type asserted to a *net.UDPConn")
 	}
 }
@@ -156,7 +156,7 @@ func TestConnectionPassedToQUICForDialing(t *testing.T) {
 
 	require.NoError(t, err, "dial error")
 	defer quicTr.Close()
-	if _, ok := quicTr.(*singleOwnerTransport).Transport.Conn.(quic.OOBCapablePacketConn); !ok {
+	if _, ok := quicTr.(*singleOwnerTransport).packetConn.(quic.OOBCapablePacketConn); !ok {
 		t.Fatal("connection passed to quic-go cannot be type asserted to a *net.UDPConn")
 	}
 }
@@ -257,3 +257,61 @@ func testListener(t *testing.T, enableReuseport bool) {
 
 	checkClosed(t, cm)
 }
+
+func TestExternalTransport(t *testing.T) {
+	conn, err := net.ListenUDP("udp4", &net.UDPAddr{IP: net.IPv4zero})
+	require.NoError(t, err)
+	defer conn.Close()
+	port := conn.LocalAddr().(*net.UDPAddr).Port
+	tr := &quic.Transport{Conn: conn}
+	defer tr.Close()
+
+	cm, err := NewConnManager(quic.StatelessResetKey{}, quic.TokenGeneratorKey{})
+	require.NoError(t, err)
+	doneWithTr, err := cm.LendTransport("udp4", &wrappedQUICTransport{tr}, conn)
+	require.NoError(t, err)
+
+	// make sure this transport is used when listening on the same port
+	ln, err := cm.ListenQUICAndAssociate(
+		"quic",
+		ma.StringCast(fmt.Sprintf("/ip4/0.0.0.0/udp/%d", port)),
+		&tls.Config{NextProtos: []string{"libp2p"}},
+		func(quic.Connection, uint64) bool { return false },
+	)
+	require.NoError(t, err)
+	defer ln.Close()
+	require.Equal(t, port, ln.Addr().(*net.UDPAddr).Port)
+
+	// make sure this transport is used when dialing out
+	udpLn, err := net.ListenUDP("udp4", &net.UDPAddr{IP: net.IPv4(127, 0, 0, 1)})
+	require.NoError(t, err)
+	defer udpLn.Close()
+	addrChan := make(chan net.Addr, 1)
+	go func() {
+		_, addr, _ := udpLn.ReadFrom(make([]byte, 2000))
+		addrChan <- addr
+	}()
+	ctx, cancel := context.WithTimeout(context.Background(), 20*time.Millisecond)
+	defer cancel()
+	_, err = cm.DialQUIC(
+		ctx,
+		ma.StringCast(fmt.Sprintf("/ip4/127.0.0.1/udp/%d/quic-v1", udpLn.LocalAddr().(*net.UDPAddr).Port)),
+		&tls.Config{NextProtos: []string{"libp2p"}},
+		func(quic.Connection, uint64) bool { return false },
+	)
+	require.ErrorIs(t, err, context.DeadlineExceeded)
+
+	select {
+	case addr := <-addrChan:
+		require.Equal(t, port, addr.(*net.UDPAddr).Port)
+	case <-time.After(time.Second):
+		t.Fatal("timeout")
+	}
+
+	cm.Close()
+	select {
+	case <-doneWithTr:
+	default:
+		t.Fatal("doneWithTr not closed")
+	}
+}

p2p/transport/quicreuse/listener.go

@@ -29,7 +29,7 @@ type protoConf struct {
 }
 
 type quicListener struct {
-	l         *quic.Listener
+	l         QUICListener
 	transport refCountedQuicTransport
 	running   chan struct{}
 	addrs     []ma.Multiaddr

p2p/transport/quicreuse/nonquic_packetconn.go

@@ -4,16 +4,14 @@ import (
 	"context"
 	"net"
 	"time"
-
-	"github.com/quic-go/quic-go"
 )
 
 // nonQUICPacketConn is a net.PacketConn that can be used to read and write
 // non-QUIC packets on a quic.Transport. This lets us reuse this UDP port for
 // other transports like WebRTC.
 type nonQUICPacketConn struct {
 	owningTransport refCountedQuicTransport
-	tr              *quic.Transport
+	tr              QUICTransport
 	ctx             context.Context
 	ctxCancel       context.CancelFunc
 	readCtx         context.Context
@@ -32,7 +30,7 @@ func (n *nonQUICPacketConn) Close() error {
 
 // LocalAddr implements net.PacketConn.
 func (n *nonQUICPacketConn) LocalAddr() net.Addr {
-	return n.tr.Conn.LocalAddr()
+	return n.owningTransport.LocalAddr()
 }
 
 // ReadFrom implements net.PacketConn.

p2p/transport/quicreuse/reuse.go

@@ -3,6 +3,8 @@ package quicreuse
 import (
 	"context"
 	"crypto/tls"
+	"errors"
+	"fmt"
 	"net"
 	"sync"
 	"time"
@@ -25,23 +27,30 @@ type refCountedQuicTransport interface {
 	IncreaseCount()
 
 	Dial(ctx context.Context, addr net.Addr, tlsConf *tls.Config, conf *quic.Config) (quic.Connection, error)
-	Listen(tlsConf *tls.Config, conf *quic.Config) (*quic.Listener, error)
+	Listen(tlsConf *tls.Config, conf *quic.Config) (QUICListener, error)
 }
 
 type singleOwnerTransport struct {
-	quic.Transport
+	Transport QUICTransport
 
 	// Used to write packets directly around QUIC.
 	packetConn net.PacketConn
 }
 
+var _ QUICTransport = &singleOwnerTransport{}
+
 func (c *singleOwnerTransport) IncreaseCount() {}
-func (c *singleOwnerTransport) DecreaseCount() {
-	c.Transport.Close()
+func (c *singleOwnerTransport) DecreaseCount() { c.Transport.Close() }
+func (c *singleOwnerTransport) LocalAddr() net.Addr {
+	return c.packetConn.LocalAddr()
 }
 
-func (c *singleOwnerTransport) LocalAddr() net.Addr {
-	return c.Transport.Conn.LocalAddr()
+func (c *singleOwnerTransport) Dial(ctx context.Context, addr net.Addr, tlsConf *tls.Config, conf *quic.Config) (quic.Connection, error) {
+	return c.Transport.Dial(ctx, addr, tlsConf, conf)
+}
+
+func (c *singleOwnerTransport) ReadNonQUICPacket(ctx context.Context, b []byte) (int, net.Addr, error) {
+	return c.Transport.ReadNonQUICPacket(ctx, b)
 }
 
 func (c *singleOwnerTransport) Close() error {
@@ -54,14 +63,18 @@ func (c *singleOwnerTransport) WriteTo(b []byte, addr net.Addr) (int, error) {
 	return c.Transport.WriteTo(b, addr)
 }
 
+func (c *singleOwnerTransport) Listen(tlsConf *tls.Config, conf *quic.Config) (QUICListener, error) {
+	return c.Transport.Listen(tlsConf, conf)
+}
+
 // Constant. Defined as variables to simplify testing.
 var (
 	garbageCollectInterval = 30 * time.Second
 	maxUnusedDuration      = 10 * time.Second
 )
 
 type refcountedTransport struct {
-	quic.Transport
+	QUICTransport
 
 	// Used to write packets directly around QUIC.
 	packetConn net.PacketConn
@@ -70,6 +83,11 @@ type refcountedTransport struct {
 	refCount    int
 	unusedSince time.Time
 
+	// Only set for transports we are borrowing.
+	// If set, we will _never_ close the underlying transport. We only close this
+	// channel to signal to the owner that we are done with it.
+	borrowDoneSignal chan struct{}
+
 	assocations map[any]struct{}
 }
 
@@ -109,17 +127,24 @@ func (c *refcountedTransport) IncreaseCount() {
 }
 
 func (c *refcountedTransport) Close() error {
-	// TODO(when we drop support for go 1.19) use errors.Join
-	c.Transport.Close()
-	return c.packetConn.Close()
+	if c.borrowDoneSignal != nil {
+		close(c.borrowDoneSignal)
+		return nil
+	}
+
+	return errors.Join(c.QUICTransport.Close(), c.packetConn.Close())
 }
 
 func (c *refcountedTransport) WriteTo(b []byte, addr net.Addr) (int, error) {
-	return c.Transport.WriteTo(b, addr)
+	return c.QUICTransport.WriteTo(b, addr)
 }
 
 func (c *refcountedTransport) LocalAddr() net.Addr {
-	return c.Transport.Conn.LocalAddr()
+	return c.packetConn.LocalAddr()
+}
+
+func (c *refcountedTransport) Listen(tlsConf *tls.Config, conf *quic.Config) (QUICListener, error) {
+	return c.QUICTransport.Listen(tlsConf, conf)
 }
 
 func (c *refcountedTransport) DecreaseCount() {
@@ -302,15 +327,34 @@ func (r *reuse) transportForDialLocked(association any, network string, source *
 	if err != nil {
 		return nil, err
 	}
-	tr := &refcountedTransport{Transport: quic.Transport{
-		Conn:              conn,
-		StatelessResetKey: r.statelessResetKey,
-		TokenGeneratorKey: r.tokenGeneratorKey,
-	}, packetConn: conn}
+	tr := &refcountedTransport{
+		QUICTransport: &wrappedQUICTransport{
+			Transport: &quic.Transport{
+				Conn:              conn,
+				StatelessResetKey: r.statelessResetKey,
+				TokenGeneratorKey: r.tokenGeneratorKey,
+			},
+		},
+		packetConn: conn,
+	}
 	r.globalDialers[conn.LocalAddr().(*net.UDPAddr).Port] = tr
 	return tr, nil
 }
 
+func (r *reuse) AddTransport(tr *refcountedTransport, laddr *net.UDPAddr) error {
+	r.mutex.Lock()
+	defer r.mutex.Unlock()
+
+	if !laddr.IP.IsUnspecified() {
+		return errors.New("adding transport for specific IP not supported")
+	}
+	if _, ok := r.globalDialers[laddr.Port]; ok {
+		return fmt.Errorf("already have global dialer for port %d", laddr.Port)
+	}
+	r.globalDialers[laddr.Port] = tr
+	return nil
+}
+
 func (r *reuse) TransportForListen(network string, laddr *net.UDPAddr) (*refcountedTransport, error) {
 	r.mutex.Lock()
 	defer r.mutex.Unlock()
@@ -351,9 +395,11 @@ func (r *reuse) TransportForListen(network string, laddr *net.UDPAddr) (*refcoun
 	}
 	localAddr := conn.LocalAddr().(*net.UDPAddr)
 	tr := &refcountedTransport{
-		Transport: quic.Transport{
-			Conn:              conn,
-			StatelessResetKey: r.statelessResetKey,
+		QUICTransport: &wrappedQUICTransport{
+			Transport: &quic.Transport{
+				Conn:              conn,
+				StatelessResetKey: r.statelessResetKey,
+			},
 		},
 		packetConn: conn,
 	}