Remove restrictions on the sending address

It is quite legal to send from the ANY address (it is required for
DHCP). I can't figure out why the broadcast address was included here,
so removing that as well.

PiperOrigin-RevId: 275541954

pkg/tcpip/network/ipv4/ipv4_test.go

@@ -47,10 +47,6 @@ func TestExcludeBroadcast(t *testing.T) {
 		t.Fatalf("CreateNIC failed: %v", err)
 	}
 
-	if err := s.AddAddress(1, ipv4.ProtocolNumber, header.IPv4Any); err != nil {
-		t.Fatalf("AddAddress failed: %v", err)
-	}
-
 	s.SetRouteTable([]tcpip.Route{{
 		Destination: header.IPv4EmptySubnet,
 		NIC:         1,

pkg/tcpip/stack/nic.go

@@ -173,11 +173,6 @@ func (n *NIC) primaryEndpoint(protocol tcpip.NetworkProtocolNumber) *referencedN
 
 	for e := list.Front(); e != nil; e = e.Next() {
 		r := e.(*referencedNetworkEndpoint)
-		// TODO(crawshaw): allow broadcast address when SO_BROADCAST is set.
-		switch r.ep.ID().LocalAddress {
-		case header.IPv4Broadcast, header.IPv4Any:
-			continue
-		}
 		if r.isValidForOutgoing() && r.tryIncRef() {
 			return r
 		}