pffindproto
prp = pffindproto(dom, proto, type);
pr = pffindproto(PF_INET, IPPROTO_RAW, SOCK_RAW);
pr = pffindproto(PF_INET6, IPPROTO_RAW, SOCK_RAW);
struct protosw *pffindproto (int family, int protocol, int type);