3 files changed, 16 insertions, 2 deletions
diff --git a/pkg/tcpip/network/ipv4/ipv4.go b/pkg/tcpip/network/ipv4/ipv4.go
index da07a39e5..44b1d5b9b 100644
--- a/pkg/tcpip/network/ipv4/ipv4.go
+++ b/pkg/tcpip/network/ipv4/ipv4.go
@@ -215,7 +215,9 @@ func (e *endpoint) WritePacket(r *stack.Route, gso *stack.GSO, hdr buffer.Prepen
 		views[0] = hdr.View()
 		views = append(views, payload.Views()...)
 		vv := buffer.NewVectorisedView(len(views[0])+payload.Size(), views)
-		e.HandlePacket(r, vv)
+		loopedR := r.MakeLoopedRoute()
+		e.HandlePacket(&loopedR, vv)
+		loopedR.Release()
 	}
 	if loop&stack.PacketOut == 0 {
 		return nil
diff --git a/pkg/tcpip/network/ipv6/ipv6.go b/pkg/tcpip/network/ipv6/ipv6.go
index 4b8cd496b..bcae98e1f 100644
--- a/pkg/tcpip/network/ipv6/ipv6.go
+++ b/pkg/tcpip/network/ipv6/ipv6.go
@@ -108,7 +108,9 @@ func (e *endpoint) WritePacket(r *stack.Route, gso *stack.GSO, hdr buffer.Prepen
 		views[0] = hdr.View()
 		views = append(views, payload.Views()...)
 		vv := buffer.NewVectorisedView(len(views[0])+payload.Size(), views)
-		e.HandlePacket(r, vv)
+		loopedR := r.MakeLoopedRoute()
+		e.HandlePacket(&loopedR, vv)
+		loopedR.Release()
 	}
 	if loop&stack.PacketOut == 0 {
 		return nil
diff --git a/pkg/tcpip/stack/route.go b/pkg/tcpip/stack/route.go
index 3d4c282a9..55ed02479 100644
--- a/pkg/tcpip/stack/route.go
+++ b/pkg/tcpip/stack/route.go
@@ -187,3 +187,13 @@ func (r *Route) Clone() Route {
 	r.ref.incRef()
 	return *r
 }
+
+// MakeLoopedRoute duplicates the given route and tweaks it in case of multicast.
+func (r *Route) MakeLoopedRoute() Route {
+	l := r.Clone()
+	if header.IsV4MulticastAddress(r.RemoteAddress) || header.IsV6MulticastAddress(r.RemoteAddress) {
+		l.RemoteAddress, l.LocalAddress = l.LocalAddress, l.RemoteAddress
+		l.RemoteLinkAddress = l.LocalLinkAddress
+	}
+	return l
+}