From: Matt Joiner <anacrolix@gmail.com>
Date: Wed, 12 Jan 2022 03:22:42 +0000 (+1100)
Subject: Use webrtc selected ICE candidate for peer addresses
X-Git-Tag: v1.41.0~21
X-Git-Url: http://www.git.stargrave.org/?a=commitdiff_plain;h=c47e6b1f605143e1f0f8d2172c2b5dfadd8fff71;p=btrtrc.git

Use webrtc selected ICE candidate for peer addresses
---

diff --git a/torrent.go b/torrent.go
index 8e83d3d3..3e74df63 100644
--- a/torrent.go
+++ b/torrent.go
@@ -1532,13 +1532,21 @@ func (t *Torrent) onWebRtcConn(
 	dcc webtorrent.DataChannelContext,
 ) {
 	defer c.Close()
+	netConn := webrtcNetConn{
+		ReadWriteCloser:    c,
+		DataChannelContext: dcc,
+	}
+	peerRemoteAddr := netConn.RemoteAddr()
+	if t.cl.badPeerAddr(peerRemoteAddr) {
+		return
+	}
 	pc, err := t.cl.initiateProtocolHandshakes(
 		context.Background(),
-		webrtcNetConn{c, dcc},
+		netConn,
 		t,
 		dcc.LocalOffered,
 		false,
-		webrtcNetAddr{dcc.Remote},
+		netConn.RemoteAddr(),
 		webrtcNetwork,
 		fmt.Sprintf("webrtc offer_id %x", dcc.OfferId),
 	)
diff --git a/webrtc.go b/webrtc.go
index e8b0213c..44ef6ca2 100644
--- a/webrtc.go
+++ b/webrtc.go
@@ -1,13 +1,13 @@
 package torrent
 
 import (
+	"fmt"
 	"net"
 	"time"
 
+	"github.com/anacrolix/torrent/webtorrent"
 	"github.com/pion/datachannel"
 	"github.com/pion/webrtc/v3"
-
-	"github.com/anacrolix/torrent/webtorrent"
 )
 
 const webrtcNetwork = "webrtc"
@@ -18,34 +18,51 @@ type webrtcNetConn struct {
 }
 
 type webrtcNetAddr struct {
-	webrtc.SessionDescription
+	*webrtc.ICECandidate
 }
 
+var _ net.Addr = webrtcNetAddr{}
+
 func (webrtcNetAddr) Network() string {
+	// Now that we have the ICE candidate, we can tell if it's over udp or tcp. But should we use
+	// that for the network?
 	return webrtcNetwork
 }
 
 func (me webrtcNetAddr) String() string {
-	// TODO: What can I show here that's more like other protocols?
-	return "<WebRTC>"
+	// Probably makes sense to return the IP:port expected of most net.Addrs. I'm not sure if
+	// Address would be quoted for IPv6 already. If not, net.JoinHostPort might be appropriate.
+	return fmt.Sprintf("%s:%d", me.Address, me.Port)
 }
 
 func (me webrtcNetConn) LocalAddr() net.Addr {
-	return webrtcNetAddr{me.Local}
+	// I'm not sure if this evolves over time. It might also be unavailable if the PeerConnection is
+	// closed or closes itself. The same concern applies to RemoteAddr.
+	pair, err := me.DataChannelContext.GetSelectedIceCandidatePair()
+	if err != nil {
+		panic(err)
+	}
+	return webrtcNetAddr{pair.Local}
 }
 
 func (me webrtcNetConn) RemoteAddr() net.Addr {
-	return webrtcNetAddr{me.Remote}
+	// See comments on LocalAddr.
+	pair, err := me.DataChannelContext.GetSelectedIceCandidatePair()
+	if err != nil {
+		panic(err)
+	}
+	return webrtcNetAddr{pair.Remote}
 }
 
+// Do we need these for WebRTC connections exposed as net.Conns? Can we set them somewhere inside
+// PeerConnection or on the channel or some transport?
+
 func (w webrtcNetConn) SetDeadline(t time.Time) error {
 	return nil
 }
-
 func (w webrtcNetConn) SetReadDeadline(t time.Time) error {
 	return nil
 }
-
 func (w webrtcNetConn) SetWriteDeadline(t time.Time) error {
 	return nil
 }
diff --git a/webtorrent/tracker-client.go b/webtorrent/tracker-client.go
index 9f02c7e7..1ec4b9d9 100644
--- a/webtorrent/tracker-client.go
+++ b/webtorrent/tracker-client.go
@@ -58,10 +58,17 @@ type outboundOffer struct {
 }
 
 type DataChannelContext struct {
+	// Can these be obtained by just calling the relevant methods on peerConnection?
 	Local, Remote webrtc.SessionDescription
 	OfferId       string
 	LocalOffered  bool
 	InfoHash      [20]byte
+	// This is private as some methods might not be appropriate with data channel context.
+	peerConnection *wrappedPeerConnection
+}
+
+func (me *DataChannelContext) GetSelectedIceCandidatePair() (*webrtc.ICECandidatePair, error) {
+	return me.peerConnection.SCTP().Transport().ICETransport().GetSelectedCandidatePair()
 }
 
 type onDataChannelOpen func(_ datachannel.ReadWriteCloser, dcc DataChannelContext)
@@ -318,11 +325,12 @@ func (tc *TrackerClient) handleOffer(
 			tc.stats.ConvertedInboundConns++
 			tc.mu.Unlock()
 			tc.OnConn(dc, DataChannelContext{
-				Local:        answer,
-				Remote:       offer,
-				OfferId:      offerId,
-				LocalOffered: false,
-				InfoHash:     infoHash,
+				Local:          answer,
+				Remote:         offer,
+				OfferId:        offerId,
+				LocalOffered:   false,
+				InfoHash:       infoHash,
+				peerConnection: peerConnection,
 			})
 		})
 	})
@@ -345,11 +353,12 @@ func (tc *TrackerClient) handleAnswer(offerId string, answer webrtc.SessionDescr
 		tc.stats.ConvertedOutboundConns++
 		tc.mu.Unlock()
 		tc.OnConn(dc, DataChannelContext{
-			Local:        offer.originalOffer,
-			Remote:       answer,
-			OfferId:      offerId,
-			LocalOffered: true,
-			InfoHash:     offer.infoHash,
+			Local:          offer.originalOffer,
+			Remote:         answer,
+			OfferId:        offerId,
+			LocalOffered:   true,
+			InfoHash:       offer.infoHash,
+			peerConnection: offer.peerConnection,
 		})
 	})
 	if err != nil {