Use unicast source for ICMP echo replies

Packets MUST NOT use a non-unicast source address for ICMP
Echo Replies.

Test: integration_test.TestPingMulticastBroadcast
PiperOrigin-RevId: 325634380

1 files changed, 22 insertions, 2 deletions

diff --git a/pkg/tcpip/stack/route.go b/pkg/tcpip/stack/route.go
index 91e0110f1..9ce0a2c22 100644
--- a/pkg/tcpip/stack/route.go
+++ b/pkg/tcpip/stack/route.go
@@ -110,6 +110,12 @@ func (r *Route) GSOMaxSize() uint32 {
 	return 0
 }
 
+// ResolveWith immediately resolves a route with the specified remote link
+// address.
+func (r *Route) ResolveWith(addr tcpip.LinkAddress) {
+	r.RemoteLinkAddress = addr
+}
+
 // Resolve attempts to resolve the link address if necessary. Returns ErrWouldBlock in
 // case address resolution requires blocking, e.g. wait for ARP reply. Waker is
 // notified when address resolution is complete (success or not).
@@ -279,12 +285,26 @@ func (r *Route) Stack() *Stack {
 	return r.ref.stack()
 }
 
-// IsBroadcast returns true if the route is to send a broadcast packet.
-func (r *Route) IsBroadcast() bool {
+// 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
 }
 
+// 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)
+}
+
 // ReverseRoute returns new route with given source and destination address.
 func (r *Route) ReverseRoute(src tcpip.Address, dst tcpip.Address) Route {
 	return Route{