From 1f421f981bb455a759f92a10cbd8f6ecfae2c6df Mon Sep 17 00:00:00 2001
From: Joseph Lee <joseph@jc-lab.net>
Date: Wed, 6 Dec 2023 18:59:46 +0900
Subject: [PATCH] feat: support ipv6 link-local address

---
 p2p/host/basic/basic_host.go  | 13 ++++---
 p2p/net/reuseport/dialer.go   |  2 +-
 p2p/net/swarm/swarm_dial.go   |  2 --
 p2p/transport/tcp/tcp.go      |  5 ++-
 p2p/transport/tcp/tcp_test.go | 64 +++++++++++++++++++++++++++++++++++
 5 files changed, 78 insertions(+), 8 deletions(-)

diff --git a/p2p/host/basic/basic_host.go b/p2p/host/basic/basic_host.go
index 8e6e8efe7c..354ea0af52 100644
--- a/p2p/host/basic/basic_host.go
+++ b/p2p/host/basic/basic_host.go
@@ -782,22 +782,27 @@ func (h *BasicHost) Addrs() []ma.Multiaddr {
 
 	// Copy addrs slice since we'll be modifying it.
 	addrsOld := addrs
-	addrs = make([]ma.Multiaddr, len(addrsOld))
-	copy(addrs, addrsOld)
+	addrs = make([]ma.Multiaddr, 0, len(addrsOld))
 
-	for i, addr := range addrs {
+	for _, addr := range addrsOld {
 		if ok, n := libp2pwebtransport.IsWebtransportMultiaddr(addr); ok && n == 0 {
 			t := s.TransportForListening(addr)
 			tpt, ok := t.(addCertHasher)
 			if !ok {
+				addrs = append(addrs, addr)
 				continue
 			}
 			addrWithCerthash, added := tpt.AddCertHashes(addr)
 			if !added {
+				addrs = append(addrs, addr)
 				log.Debug("Couldn't add certhashes to webtransport multiaddr because we aren't listening on webtransport")
 				continue
 			}
-			addrs[i] = addrWithCerthash
+			addrs = append(addrs, addrWithCerthash)
+		} else if manet.IsIP6LinkLocal(addr) {
+			continue
+		} else {
+			addrs = append(addrs, addr)
 		}
 	}
 	return addrs
diff --git a/p2p/net/reuseport/dialer.go b/p2p/net/reuseport/dialer.go
index 2efc02d393..102f3e75cc 100644
--- a/p2p/net/reuseport/dialer.go
+++ b/p2p/net/reuseport/dialer.go
@@ -50,7 +50,7 @@ func (d *dialer) DialContext(ctx context.Context, network, addr string) (net.Con
 			return nil, err
 		}
 		ip := tcpAddr.IP
-		if !ip.IsLoopback() && !ip.IsGlobalUnicast() {
+		if !ip.IsLoopback() && !ip.IsGlobalUnicast() && !ip.IsLinkLocalUnicast() {
 			return nil, fmt.Errorf("undialable IP: %s", ip)
 		}
 
diff --git a/p2p/net/swarm/swarm_dial.go b/p2p/net/swarm/swarm_dial.go
index 3fb15383a2..b0497650b3 100644
--- a/p2p/net/swarm/swarm_dial.go
+++ b/p2p/net/swarm/swarm_dial.go
@@ -489,8 +489,6 @@ func (s *Swarm) filterKnownUndialables(p peer.ID, addrs []ma.Multiaddr) (goodAdd
 			}
 			return true
 		},
-		// TODO: Consider allowing link-local addresses
-		func(addr ma.Multiaddr) bool { return !manet.IsIP6LinkLocal(addr) },
 		func(addr ma.Multiaddr) bool {
 			if s.gater != nil && !s.gater.InterceptAddrDial(p, addr) {
 				addrErrs = append(addrErrs, TransportError{Address: addr, Cause: ErrGaterDisallowedConnection})
diff --git a/p2p/transport/tcp/tcp.go b/p2p/transport/tcp/tcp.go
index d52bb96019..45b0274a6f 100644
--- a/p2p/transport/tcp/tcp.go
+++ b/p2p/transport/tcp/tcp.go
@@ -152,7 +152,10 @@ func NewTCPTransport(upgrader transport.Upgrader, rcmgr network.ResourceManager,
 	return tr, nil
 }
 
-var dialMatcher = mafmt.And(mafmt.IP, mafmt.Base(ma.P_TCP))
+var dialMatcher = mafmt.Or(
+	mafmt.And(mafmt.IP, mafmt.Base(ma.P_TCP)),
+	mafmt.And(mafmt.Base(ma.P_IP6ZONE), mafmt.IP, mafmt.Base(ma.P_TCP)),
+)
 
 // CanDial returns true if this transport believes it can dial the given
 // multiaddr.
diff --git a/p2p/transport/tcp/tcp_test.go b/p2p/transport/tcp/tcp_test.go
index d96c34317b..00e27c6e13 100644
--- a/p2p/transport/tcp/tcp_test.go
+++ b/p2p/transport/tcp/tcp_test.go
@@ -3,6 +3,7 @@ package tcp
 import (
 	"context"
 	"errors"
+	"net"
 	"testing"
 
 	"github.com/libp2p/go-libp2p/core/crypto"
@@ -46,6 +47,69 @@ func TestTcpTransport(t *testing.T) {
 	envReuseportVal = true
 }
 
+func TestTcpTransportCanDialToLinkLocalAddress(t *testing.T) {
+	addr := ma.StringCast("/ip6zone/eth0/ip6/fe80::fc54:ff:fe43:e553/tcp/1234")
+
+	var u transport.Upgrader
+	tpt, err := NewTCPTransport(u, nil)
+	require.NoError(t, err)
+
+	if !tpt.CanDial(addr) {
+		t.Fatal("should be able to dial ip6zone")
+	}
+}
+
+func TestTcpTransportWithLinkLocalAddress(t *testing.T) {
+	ifaces, err := net.Interfaces()
+	if err != nil {
+		t.Error(err)
+		return
+	}
+
+	var targetAddr ma.Multiaddr
+
+findInterface:
+	for _, iface := range ifaces {
+		addrs, err := iface.Addrs()
+		if err == nil {
+			for _, a := range addrs {
+				addr, err := manet.FromNetAddr(a)
+				if err == nil {
+					if manet.IsIP6LinkLocal(addr) {
+						targetAddr = ma.StringCast("/ip6zone/" + iface.Name + addr.String())
+						break findInterface
+					}
+				}
+			}
+		}
+	}
+
+	if targetAddr == nil {
+		t.Fail()
+		return
+	}
+
+	for i := 0; i < 2; i++ {
+		peerA, ia := makeInsecureMuxer(t)
+		_, ib := makeInsecureMuxer(t)
+
+		ua, err := tptu.New(ia, muxers, nil, nil, nil)
+		require.NoError(t, err)
+		ta, err := NewTCPTransport(ua, nil)
+		require.NoError(t, err)
+		ub, err := tptu.New(ib, muxers, nil, nil, nil)
+		require.NoError(t, err)
+		tb, err := NewTCPTransport(ub, nil)
+		require.NoError(t, err)
+
+		zero := targetAddr.String() + "/tcp/0"
+		ttransport.SubtestTransport(t, ta, tb, zero, peerA)
+
+		envReuseportVal = false
+	}
+	envReuseportVal = true
+}
+
 func TestTcpTransportWithMetrics(t *testing.T) {
 	peerA, ia := makeInsecureMuxer(t)
 	_, ib := makeInsecureMuxer(t)