From 83a8284d6aba889cc9b4d476dfc94726dd3f5c64 Mon Sep 17 00:00:00 2001
From: Matt Joiner <anacrolix@gmail.com>
Date: Wed, 12 Jan 2022 15:01:33 +1100
Subject: [PATCH] Add tests for preferred network direction

---
 peerconn.go      |  4 ++--
 peerconn_test.go | 35 +++++++++++++++++++++++++++++++++++
 torrent.go       |  2 +-
 3 files changed, 38 insertions(+), 3 deletions(-)

diff --git a/peerconn.go b/peerconn.go
index 6866d450..d1ebf3a4 100644
--- a/peerconn.go
+++ b/peerconn.go
@@ -221,12 +221,12 @@ func (cn *PeerConn) isPreferredDirection() bool {
 // Returns whether the left connection should be preferred over the right one,
 // considering only their networking properties. If ok is false, we can't
 // decide.
-func (l *PeerConn) hasPreferredNetworkOver(r *PeerConn) (left, ok bool) {
+func (l *PeerConn) hasPreferredNetworkOver(r *PeerConn) bool {
 	var ml multiLess
 	ml.NextBool(l.isPreferredDirection(), r.isPreferredDirection())
 	ml.NextBool(!l.utp(), !r.utp())
 	ml.NextBool(l.ipv6(), r.ipv6())
-	return ml.FinalOk()
+	return ml.Less()
 }
 
 func (cn *Peer) cumInterest() time.Duration {
diff --git a/peerconn_test.go b/peerconn_test.go
index 2d5aa681..b1ac1dbc 100644
--- a/peerconn_test.go
+++ b/peerconn_test.go
@@ -1,7 +1,9 @@
 package torrent
 
 import (
+	"encoding/binary"
 	"errors"
+	"fmt"
 	"io"
 	"net"
 	"sync"
@@ -246,3 +248,36 @@ func TestApplyRequestStateWriteBufferConstraints(t *testing.T) {
 	c.Check(maxLocalToRemoteRequests >= 8, qt.IsTrue)
 	c.Logf("max local to remote requests: %v", maxLocalToRemoteRequests)
 }
+
+func peerConnForPreferredNetworkDirection(localPeerId, remotePeerId int, outgoing, utp, ipv6 bool) *PeerConn {
+	pc := PeerConn{}
+	pc.outgoing = outgoing
+	if utp {
+		pc.Network = "udp"
+	}
+	if ipv6 {
+		pc.RemoteAddr = &net.TCPAddr{IP: net.ParseIP(fmt.Sprintf("::420"))}
+	} else {
+		pc.RemoteAddr = &net.TCPAddr{IP: net.IPv4(1, 2, 3, 4)}
+	}
+	binary.BigEndian.PutUint64(pc.PeerID[:], uint64(remotePeerId))
+	cl := Client{}
+	binary.BigEndian.PutUint64(cl.peerID[:], uint64(localPeerId))
+	pc.t = &Torrent{cl: &cl}
+	return &pc
+}
+
+func TestPreferredNetworkDirection(t *testing.T) {
+	pc := peerConnForPreferredNetworkDirection
+	c := qt.New(t)
+	// Prefer outgoing to higher peer ID
+	c.Assert(pc(1, 2, true, false, false).hasPreferredNetworkOver(pc(1, 2, false, false, false)), qt.IsTrue)
+	c.Assert(pc(1, 2, false, false, false).hasPreferredNetworkOver(pc(1, 2, true, false, false)), qt.IsFalse)
+	c.Assert(pc(2, 1, false, false, false).hasPreferredNetworkOver(pc(2, 1, true, false, false)), qt.IsTrue)
+	// Don't prefer uTP
+	c.Assert(pc(1, 2, false, true, false).hasPreferredNetworkOver(pc(1, 2, false, false, false)), qt.IsFalse)
+	// Prefer IPv6
+	c.Assert(pc(1, 2, false, false, false).hasPreferredNetworkOver(pc(1, 2, false, false, true)), qt.IsFalse)
+	// No difference
+	c.Assert(pc(1, 2, false, false, false).hasPreferredNetworkOver(pc(1, 2, false, false, false)), qt.IsFalse)
+}
diff --git a/torrent.go b/torrent.go
index fbb5f6b0..8e83d3d3 100644
--- a/torrent.go
+++ b/torrent.go
@@ -1866,7 +1866,7 @@ func (t *Torrent) addPeerConn(c *PeerConn) (err error) {
 		if !t.cl.config.DropDuplicatePeerIds {
 			continue
 		}
-		if left, ok := c.hasPreferredNetworkOver(c0); ok && left {
+		if c.hasPreferredNetworkOver(c0) {
 			c0.close()
 			t.deletePeerConn(c0)
 		} else {
-- 
2.48.1