add user-defined conn select alg and user-defined dest select alg

best.go

@@ -0,0 +1,21 @@
+package swarm
+
+import (
+	peer "github.com/libp2p/go-libp2p-peer"
+	ma "github.com/multiformats/go-multiaddr"
+)
+
+// BestConn supports user-defined connection selection algorithm
+// BestConnFallback is BestConn's downgrade algorithm. When BestConn
+// cann't select a connection, we downgrade using BestConnFallback to
+// select the connection.
+type BestConn interface {
+	BestConn(peer.ID, []*Conn) *Conn
+	BestConnFallback(peer.ID, []*Conn) *Conn
+}
+
+// If there is multiple good address can connect to the peer,
+// We use this interface to select the best address to peer.
+type BestDest interface {
+	BestDestSelect(peer.ID, []ma.Multiaddr) []ma.Multiaddr
+}

swarm.go

@@ -18,6 +18,7 @@ import (
 	pstore "github.com/libp2p/go-libp2p-peerstore"
 	transport "github.com/libp2p/go-libp2p-transport"
 	filter "github.com/libp2p/go-maddr-filter"
+	ma "github.com/multiformats/go-multiaddr"
 	mafilter "github.com/whyrusleeping/multiaddr-filter"
 )
 
@@ -81,6 +82,9 @@ type Swarm struct {
 	// filters for addresses that shouldnt be dialed (or accepted)
 	Filters *filter.Filters
 
+	bestConn BestConn
+	bestDest BestDest
+
 	proc goprocess.Process
 	ctx  context.Context
 	bwc  metrics.Reporter
@@ -274,6 +278,16 @@ func (s *Swarm) StreamHandler() inet.StreamHandler {
 	return handler
 }
 
+// SetBestConn set the BestConn interface
+func (s *Swarm) SetBestConn(bc BestConn) {
+	s.bestConn = bc
+}
+
+// SetBestDest set the BestDest interface
+func (s *Swarm) SetBestDest(bd BestDest) {
+	s.bestDest = bd
+}
+
 // NewStream creates a new stream on any available connection to peer, dialing
 // if necessary.
 func (s *Swarm) NewStream(ctx context.Context, p peer.ID) (inet.Stream, error) {
@@ -359,6 +373,34 @@ func (s *Swarm) bestConnToPeer(p peer.ID) *Conn {
 	return best
 }
 
+// Wrapper for BestConn Interface
+func (s *Swarm) bestConnToPeerWrapper(p peer.ID) *Conn {
+	if s.bestConn == nil {
+		return s.bestConnToPeer(p)
+	}
+	s.conns.RLock()
+	defer s.conns.RUnlock()
+	return s.bestConn.BestConn(p, s.conns.m[p])
+}
+
+// Wrapper for BestConnFallback Interface
+func (s *Swarm) bestConnToPeerFallbackWrapper(p peer.ID) *Conn {
+	if s.bestConn == nil {
+		return s.bestConnToPeer(p)
+	}
+	s.conns.RLock()
+	defer s.conns.RUnlock()
+	return s.bestConn.BestConnFallback(p, s.conns.m[p])
+}
+
+// Wrapper for BestDest Interface
+func (s *Swarm) bestDestSelectWrapper(id peer.ID, addrs []ma.Multiaddr) []ma.Multiaddr {
+	if s.bestDest == nil {
+		return addrs
+	}
+	return s.bestDest.BestDestSelect(id, addrs)
+}
+
 // Connectedness returns our "connectedness" state with the given peer.
 //
 // To check if we have an open connection, use `s.Connectedness(p) ==

swarm_conn.go

@@ -48,6 +48,10 @@ func (c *Conn) Close() error {
 	return c.err
 }
 
+func (c *Conn) IsClosed() bool {
+	return c.conn.IsClosed()
+}
+
 func (c *Conn) doClose() {
 	c.swarm.removeConn(c)
 

swarm_dial.go

@@ -196,7 +196,7 @@ func (s *Swarm) dialPeer(ctx context.Context, p peer.ID) (*Conn, error) {
 	defer log.EventBegin(ctx, "swarmDialAttemptSync", p).Done()
 
 	// check if we already have an open connection first
-	conn := s.bestConnToPeer(p)
+	conn := s.bestConnToPeerWrapper(p)
 	if conn != nil {
 		return conn, nil
 	}
@@ -226,7 +226,7 @@ func (s *Swarm) doDial(ctx context.Context, p peer.ID) (*Conn, error) {
 	// Short circuit.
 	// By the time we take the dial lock, we may already *have* a connection
 	// to the peer.
-	c := s.bestConnToPeer(p)
+	c := s.bestConnToPeerWrapper(p)
 	if c != nil {
 		return c, nil
 	}
@@ -239,7 +239,7 @@ func (s *Swarm) doDial(ctx context.Context, p peer.ID) (*Conn, error) {
 
 	conn, err := s.dial(ctx, p)
 	if err != nil {
-		conn = s.bestConnToPeer(p)
+		conn = s.bestConnToPeerFallbackWrapper(p)
 		if conn != nil {
 			// Hm? What error?
 			// Could have canceled the dial because we received a
@@ -294,9 +294,18 @@ func (s *Swarm) dial(ctx context.Context, p peer.ID) (*Conn, error) {
 		return nil, errors.New("no addresses")
 	}
 	goodAddrs := s.filterKnownUndialables(peerAddrs)
+
 	if len(goodAddrs) == 0 {
 		return nil, errors.New("no good addresses")
 	}
+
+	if s.bestDest != nil {
+		// Select the best address to peer.
+		bestAddrs := s.bestDestSelectWrapper(p, goodAddrs)
+		if len(bestAddrs) != 0 {
+			goodAddrs = bestAddrs
+		}
+	}
 	goodAddrsChan := make(chan ma.Multiaddr, len(goodAddrs))
 	for _, a := range goodAddrs {
 		goodAddrsChan <- a