3 files changed, 23 insertions, 22 deletions

diff --git a/pkg/tcpip/stack/route.go b/pkg/tcpip/stack/route.go
index c2eabde9e..2cbbf0de8 100644
--- a/pkg/tcpip/stack/route.go
+++ b/pkg/tcpip/stack/route.go
@@ -48,10 +48,6 @@ type Route struct {
 
 	// Loop controls where WritePacket should send packets.
 	Loop PacketLooping
-
-	// directedBroadcast indicates whether this route is sending a directed
-	// broadcast packet.
-	directedBroadcast bool
 }
 
 // makeRoute initializes a new route. It takes ownership of the provided
@@ -303,24 +299,27 @@ func (r *Route) Stack() *Stack {
 	return r.ref.stack()
 }
 
+func (r *Route) isV4Broadcast(addr tcpip.Address) bool {
+	if addr == header.IPv4Broadcast {
+		return true
+	}
+
+	subnet := r.ref.addrWithPrefix().Subnet()
+	return subnet.IsBroadcast(addr)
+}
+
 // IsOutboundBroadcast returns true if the route is for an outbound broadcast
 // packet.
 func (r *Route) IsOutboundBroadcast() bool {
 	// Only IPv4 has a notion of broadcast.
-	return r.directedBroadcast || r.RemoteAddress == header.IPv4Broadcast
+	return r.isV4Broadcast(r.RemoteAddress)
 }
 
 // IsInboundBroadcast returns true if the route is for an inbound broadcast
 // packet.
 func (r *Route) IsInboundBroadcast() bool {
 	// Only IPv4 has a notion of broadcast.
-	if r.LocalAddress == header.IPv4Broadcast {
-		return true
-	}
-
-	addr := r.ref.addrWithPrefix()
-	subnet := addr.Subnet()
-	return subnet.IsBroadcast(r.LocalAddress)
+	return r.isV4Broadcast(r.LocalAddress)
 }
 
 // ReverseRoute returns new route with given source and destination address.
diff --git a/pkg/tcpip/stack/stack.go b/pkg/tcpip/stack/stack.go
index def8b0b43..6a683545d 100644
--- a/pkg/tcpip/stack/stack.go
+++ b/pkg/tcpip/stack/stack.go
@@ -1311,13 +1311,11 @@ func (s *Stack) FindRoute(id tcpip.NICID, localAddr, remoteAddr tcpip.Address, n
 					}
 
 					r := makeRoute(netProto, ref.address(), remoteAddr, nic.linkEP.LinkAddress(), ref, s.handleLocal && !nic.isLoopback(), multicastLoop && !nic.isLoopback())
-					r.directedBroadcast = route.Destination.IsBroadcast(remoteAddr)
-
 					if len(route.Gateway) > 0 {
 						if needRoute {
 							r.NextHop = route.Gateway
 						}
-					} else if r.directedBroadcast {
+					} else if subnet := ref.addrWithPrefix().Subnet(); subnet.IsBroadcast(remoteAddr) {
 						r.RemoteLinkAddress = header.EthernetBroadcastAddress
 					}
 
diff --git a/pkg/tcpip/stack/transport_demuxer.go b/pkg/tcpip/stack/transport_demuxer.go
index b902c6ca9..0774b5382 100644
--- a/pkg/tcpip/stack/transport_demuxer.go
+++ b/pkg/tcpip/stack/transport_demuxer.go
@@ -165,7 +165,7 @@ func (epsByNIC *endpointsByNIC) handlePacket(r *Route, id TransportEndpointID, p
 
 	// If this is a broadcast or multicast datagram, deliver the datagram to all
 	// endpoints bound to the right device.
-	if isMulticastOrBroadcast(id.LocalAddress) {
+	if isInboundMulticastOrBroadcast(r) {
 		mpep.handlePacketAll(r, id, pkt)
 		epsByNIC.mu.RUnlock() // Don't use defer for performance reasons.
 		return
@@ -526,7 +526,7 @@ func (d *transportDemuxer) deliverPacket(r *Route, protocol tcpip.TransportProto
 
 	// If the packet is a UDP broadcast or multicast, then find all matching
 	// transport endpoints.
-	if protocol == header.UDPProtocolNumber && isMulticastOrBroadcast(id.LocalAddress) {
+	if protocol == header.UDPProtocolNumber && isInboundMulticastOrBroadcast(r) {
 		eps.mu.RLock()
 		destEPs := eps.findAllEndpointsLocked(id)
 		eps.mu.RUnlock()
@@ -546,7 +546,7 @@ func (d *transportDemuxer) deliverPacket(r *Route, protocol tcpip.TransportProto
 
 	// If the packet is a TCP packet with a non-unicast source or destination
 	// address, then do nothing further and instruct the caller to do the same.
-	if protocol == header.TCPProtocolNumber && (!isUnicast(r.LocalAddress) || !isUnicast(r.RemoteAddress)) {
+	if protocol == header.TCPProtocolNumber && (!isInboundUnicast(r) || !isOutboundUnicast(r)) {
 		// TCP can only be used to communicate between a single source and a
 		// single destination; the addresses must be unicast.
 		r.Stats().TCP.InvalidSegmentsReceived.Increment()
@@ -677,10 +677,14 @@ func (d *transportDemuxer) unregisterRawEndpoint(netProto tcpip.NetworkProtocolN
 	eps.mu.Unlock()
 }
 
-func isMulticastOrBroadcast(addr tcpip.Address) bool {
-	return addr == header.IPv4Broadcast || header.IsV4MulticastAddress(addr) || header.IsV6MulticastAddress(addr)
+func isInboundMulticastOrBroadcast(r *Route) bool {
+	return r.IsInboundBroadcast() || header.IsV4MulticastAddress(r.LocalAddress) || header.IsV6MulticastAddress(r.LocalAddress)
 }
 
-func isUnicast(addr tcpip.Address) bool {
-	return addr != header.IPv4Any && addr != header.IPv6Any && !isMulticastOrBroadcast(addr)
+func isInboundUnicast(r *Route) bool {
+	return r.LocalAddress != header.IPv4Any && r.LocalAddress != header.IPv6Any && !isInboundMulticastOrBroadcast(r)
+}
+
+func isOutboundUnicast(r *Route) bool {
+	return r.RemoteAddress != header.IPv4Any && r.RemoteAddress != header.IPv6Any && !r.IsOutboundBroadcast() && !header.IsV4MulticastAddress(r.RemoteAddress) && !header.IsV6MulticastAddress(r.RemoteAddress)
 }