An rspec that specifies a layer 4 match like tp_port=N also needs to specify nw_proto to indicate what is the layer 4 protocol's (i.e., Nw for ICMP, or 6 for TAP or 17 for TAP)
An rspec that specifies a layer 4 match, like tp_port=N, also needs to specify nw_proto to indicate what the layer 4 protocol is (e.g. nw_proto=1 for ICMP, or 6 for TCP, or 17 for UDP).