Receive broadcast packets on interested endpoints

When a broadcast packet is received by the stack, the packet should be
delivered to each endpoint that may be interested in the packet. This
includes all any address and specified broadcast address listeners.

Test: integration_test.TestReuseAddrAndBroadcast
PiperOrigin-RevId: 332060652

1 files changed, 11 insertions, 7 deletions

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)
 }