Add support for Multipath TCP

src/admin/getpeers.go

@@ -24,6 +24,7 @@ type PeerEntry struct {
 	PublicKey     string        `json:"key"`
 	Port          uint64        `json:"port"`
 	Priority      uint64        `json:"priority"`
+	Multipath     bool          `json:"multipath,omitempty"`
 	RXBytes       DataUnit      `json:"bytes_recvd,omitempty"`
 	TXBytes       DataUnit      `json:"bytes_sent,omitempty"`
 	Uptime        float64       `json:"uptime,omitempty"`
@@ -37,14 +38,15 @@ func (a *AdminSocket) getPeersHandler(req *GetPeersRequest, res *GetPeersRespons
 	res.Peers = make([]PeerEntry, 0, len(peers))
 	for _, p := range peers {
 		peer := PeerEntry{
-			Port:     p.Port,
-			Up:       p.Up,
-			Inbound:  p.Inbound,
-			Priority: uint64(p.Priority), // can't be uint8 thanks to gobind
-			URI:      p.URI,
-			RXBytes:  DataUnit(p.RXBytes),
-			TXBytes:  DataUnit(p.TXBytes),
-			Uptime:   p.Uptime.Seconds(),
+			Port:      p.Port,
+			Up:        p.Up,
+			Inbound:   p.Inbound,
+			Priority:  uint64(p.Priority), // can't be uint8 thanks to gobind
+			Multipath: p.Multipath,
+			URI:       p.URI,
+			RXBytes:   DataUnit(p.RXBytes),
+			TXBytes:   DataUnit(p.TXBytes),
+			Uptime:    p.Uptime.Seconds(),
 		}
 		if p.Latency > 0 {
 			peer.Latency = p.Latency

src/core/api.go

@@ -30,6 +30,7 @@ type PeerInfo struct {
 	Coords        []uint64
 	Port          uint64
 	Priority      uint8
+	Multipath     bool
 	RXBytes       uint64
 	TXBytes       uint64
 	Uptime        time.Duration
@@ -87,6 +88,7 @@ func (c *Core) GetPeers() []PeerInfo {
 				peerinfo.RXBytes = atomic.LoadUint64(&c.rx)
 				peerinfo.TXBytes = atomic.LoadUint64(&c.tx)
 				peerinfo.Uptime = time.Since(c.up)
+				peerinfo.Multipath = isMPTCP(c)
 			}
 			if p, ok := conns[conn]; ok {
 				peerinfo.Key = p.Key

src/core/link.go

@@ -44,7 +44,7 @@ type links struct {
 
 type linkProtocol interface {
 	dial(ctx context.Context, url *url.URL, info linkInfo, options linkOptions) (net.Conn, error)
-	listen(ctx context.Context, url *url.URL, sintf string) (net.Listener, error)
+	listen(ctx context.Context, url *url.URL, sintf string, options linkOptions) (net.Listener, error)
 }
 
 // linkInfo is used as a map key
@@ -72,6 +72,7 @@ type linkOptions struct {
 	tlsSNI            string
 	password          []byte
 	maxBackoff        time.Duration
+	multipath         bool
 }
 
 type Listener struct {
@@ -140,6 +141,7 @@ const ErrLinkPinnedKeyInvalid = linkError("pinned public key is invalid")
 const ErrLinkPasswordInvalid = linkError("password is invalid")
 const ErrLinkUnrecognisedSchema = linkError("link schema unknown")
 const ErrLinkMaxBackoffInvalid = linkError("max backoff duration invalid")
+const ErrLinkMultipathInvalid = linkError("multipath invalid")
 
 func (l *links) add(u *url.URL, sintf string, linkType linkType) error {
 	var retErr error
@@ -193,6 +195,17 @@ func (l *links) add(u *url.URL, sintf string, linkType linkType) error {
 			}
 			options.maxBackoff = d
 		}
+		if p := u.Query().Get("multipath"); p != "" {
+			switch p {
+			case "true", "1":
+				options.multipath = true
+			case "false", "0":
+				options.multipath = false
+			default:
+				retErr = ErrLinkMultipathInvalid
+				return
+			}
+		}
 		// SNI headers must contain hostnames and not IP addresses, so we must make sure
 		// that we do not populate the SNI with an IP literal. We do this by splitting
 		// the host-port combo from the query option and then seeing if it parses to an
@@ -379,7 +392,7 @@ func (l *links) add(u *url.URL, sintf string, linkType linkType) error {
 	return retErr
 }
 
-func (l *links) remove(u *url.URL, sintf string, linkType linkType) error {
+func (l *links) remove(u *url.URL, sintf string, _ linkType) error {
 	var retErr error
 	phony.Block(l, func() {
 		// Generate the link info and see whether we think we already
@@ -422,31 +435,45 @@ func (l *links) listen(u *url.URL, sintf string) (*Listener, error) {
 		cancel()
 		return nil, ErrLinkUnrecognisedSchema
 	}
-	listener, err := protocol.listen(ctx, u, sintf)
-	if err != nil {
-		cancel()
-		return nil, err
-	}
-	li := &Listener{
-		listener: listener,
-		ctx:      ctx,
-		Cancel:   cancel,
-	}
 
 	var options linkOptions
 	if p := u.Query().Get("priority"); p != "" {
 		pi, err := strconv.ParseUint(p, 10, 8)
 		if err != nil {
+			cancel()
 			return nil, ErrLinkPriorityInvalid
 		}
 		options.priority = uint8(pi)
 	}
 	if p := u.Query().Get("password"); p != "" {
 		if len(p) > blake2b.Size {
+			cancel()
 			return nil, ErrLinkPasswordInvalid
 		}
 		options.password = []byte(p)
 	}
+	if p := u.Query().Get("multipath"); p != "" {
+		switch p {
+		case "true", "1":
+			options.multipath = true
+		case "false", "0":
+			options.multipath = false
+		default:
+			cancel()
+			return nil, ErrLinkMultipathInvalid
+		}
+	}
+
+	listener, err := protocol.listen(ctx, u, sintf, options)
+	if err != nil {
+		cancel()
+		return nil, err
+	}
+	li := &Listener{
+		listener: listener,
+		ctx:      ctx,
+		Cancel:   cancel,
+	}
 
 	go func() {
 		l.core.log.Infof("%s listener started on %s", strings.ToUpper(u.Scheme), listener.Addr())
@@ -567,7 +594,7 @@ func (l *links) handler(linkType linkType, options linkOptions, conn net.Conn, s
 	switch {
 	case err != nil:
 		return fmt.Errorf("write handshake: %w", err)
-	case err == nil && n != len(metaBytes):
+	case n != len(metaBytes):
 		return fmt.Errorf("incomplete handshake send")
 	}
 	meta = version_metadata{}

src/core/link_quic.go

@@ -65,7 +65,7 @@ func (l *linkQUIC) dial(ctx context.Context, url *url.URL, info linkInfo, option
 	}, nil
 }
 
-func (l *linkQUIC) listen(ctx context.Context, url *url.URL, _ string) (net.Listener, error) {
+func (l *linkQUIC) listen(ctx context.Context, url *url.URL, _ string, _ linkOptions) (net.Listener, error) {
 	ql, err := quic.ListenAddr(url.Host, l.tlsconfig, l.quicconfig)
 	if err != nil {
 		return nil, err

src/core/link_socks.go

@@ -47,6 +47,6 @@ func (l *linkSOCKS) dial(_ context.Context, url *url.URL, info linkInfo, options
 	return conn, nil
 }
 
-func (l *linkSOCKS) listen(ctx context.Context, url *url.URL, _ string) (net.Listener, error) {
+func (l *linkSOCKS) listen(ctx context.Context, url *url.URL, _ string, _ linkOptions) (net.Listener, error) {
 	return nil, fmt.Errorf("SOCKS listener not supported")
 }

src/core/link_tcp.go

@@ -36,7 +36,7 @@ type tcpDialer struct {
 	addr   *net.TCPAddr
 }
 
-func (l *linkTCP) dialersFor(url *url.URL, info linkInfo) ([]*tcpDialer, error) {
+func (l *linkTCP) dialersFor(url *url.URL, info linkInfo, options linkOptions) ([]*tcpDialer, error) {
 	host, p, err := net.SplitHostPort(url.Host)
 	if err != nil {
 		return nil, err
@@ -55,7 +55,7 @@ func (l *linkTCP) dialersFor(url *url.URL, info linkInfo) ([]*tcpDialer, error)
 			IP:   ip,
 			Port: port,
 		}
-		dialer, err := l.dialerFor(addr, info.sintf)
+		dialer, err := l.dialerFor(addr, info.sintf, options.multipath)
 		if err != nil {
 			continue
 		}
@@ -69,7 +69,7 @@ func (l *linkTCP) dialersFor(url *url.URL, info linkInfo) ([]*tcpDialer, error)
 }
 
 func (l *linkTCP) dial(ctx context.Context, url *url.URL, info linkInfo, options linkOptions) (net.Conn, error) {
-	dialers, err := l.dialersFor(url, info)
+	dialers, err := l.dialersFor(url, info, options)
 	if err != nil {
 		return nil, err
 	}
@@ -88,17 +88,21 @@ func (l *linkTCP) dial(ctx context.Context, url *url.URL, info linkInfo, options
 	return nil, err
 }
 
-func (l *linkTCP) listen(ctx context.Context, url *url.URL, sintf string) (net.Listener, error) {
+func (l *linkTCP) listen(ctx context.Context, url *url.URL, sintf string, options linkOptions) (net.Listener, error) {
 	hostport := url.Host
 	if sintf != "" {
 		if host, port, err := net.SplitHostPort(hostport); err == nil {
 			hostport = fmt.Sprintf("[%s%%%s]:%s", host, sintf, port)
 		}
 	}
-	return l.listenconfig.Listen(ctx, "tcp", hostport)
+	lc := *l.listenconfig
+	if options.multipath {
+		setMPTCPForListener(&lc)
+	}
+	return lc.Listen(ctx, "tcp", hostport)
 }
 
-func (l *linkTCP) dialerFor(dst *net.TCPAddr, sintf string) (*net.Dialer, error) {
+func (l *linkTCP) dialerFor(dst *net.TCPAddr, sintf string, mptcp bool) (*net.Dialer, error) {
 	if dst.IP.IsLinkLocalUnicast() {
 		if sintf != "" {
 			dst.Zone = sintf
@@ -112,6 +116,9 @@ func (l *linkTCP) dialerFor(dst *net.TCPAddr, sintf string) (*net.Dialer, error)
 		KeepAlive: -1,
 		Control:   l.tcpContext,
 	}
+	if mptcp {
+		setMPTCPForDialer(dialer)
+	}
 	if sintf != "" {
 		dialer.Control = l.getControl(sintf)
 		ief, err := net.InterfaceByName(sintf)

src/core/link_tcp_mptcp.go

@@ -0,0 +1,30 @@
+package core
+
+import (
+	"crypto/tls"
+	"net"
+)
+
+func setMPTCPForDialer(d *net.Dialer) {
+	d.SetMultipathTCP(true)
+}
+
+func setMPTCPForListener(lc *net.ListenConfig) {
+	lc.SetMultipathTCP(true)
+}
+
+func isMPTCP(c net.Conn) bool {
+	switch tc := c.(type) {
+	case *net.TCPConn:
+		mp, _ := tc.MultipathTCP()
+		return mp
+	case *tls.Conn:
+		if tc, ok := tc.NetConn().(*net.TCPConn); ok {
+			mp, _ := tc.MultipathTCP()
+			return mp
+		}
+		return false
+	default:
+		return false
+	}
+}

src/core/link_tls.go

@@ -3,7 +3,6 @@ package core
 import (
 	"context"
 	"crypto/tls"
-	"fmt"
 	"net"
 	"net/url"
 
@@ -34,7 +33,7 @@ func (l *links) newLinkTLS(tcp *linkTCP) *linkTLS {
 }
 
 func (l *linkTLS) dial(ctx context.Context, url *url.URL, info linkInfo, options linkOptions) (net.Conn, error) {
-	dialers, err := l.tcp.dialersFor(url, info)
+	dialers, err := l.tcp.dialersFor(url, info, options)
 	if err != nil {
 		return nil, err
 	}
@@ -58,17 +57,10 @@ func (l *linkTLS) dial(ctx context.Context, url *url.URL, info linkInfo, options
 	return nil, err
 }
 
-func (l *linkTLS) listen(ctx context.Context, url *url.URL, sintf string) (net.Listener, error) {
-	hostport := url.Host
-	if sintf != "" {
-		if host, port, err := net.SplitHostPort(hostport); err == nil {
-			hostport = fmt.Sprintf("[%s%%%s]:%s", host, sintf, port)
-		}
-	}
-	listener, err := l.listener.Listen(ctx, "tcp", hostport)
+func (l *linkTLS) listen(ctx context.Context, url *url.URL, sintf string, options linkOptions) (net.Listener, error) {
+	listener, err := l.tcp.listen(ctx, url, sintf, options)
 	if err != nil {
 		return nil, err
 	}
-	tlslistener := tls.NewListener(listener, l.config)
-	return tlslistener, nil
+	return tls.NewListener(listener, l.config), nil
 }

src/core/link_unix.go

@@ -40,6 +40,6 @@ func (l *linkUNIX) dial(ctx context.Context, url *url.URL, info linkInfo, option
 	return l.dialer.DialContext(ctx, "unix", addr.String())
 }
 
-func (l *linkUNIX) listen(ctx context.Context, url *url.URL, _ string) (net.Listener, error) {
+func (l *linkUNIX) listen(ctx context.Context, url *url.URL, _ string, _ linkOptions) (net.Listener, error) {
 	return l.listener.Listen(ctx, "unix", url.Path)
 }