udp_print
extern void udp_print(const u_char *, u_int, const void *);
udp_print(cp, len, (const u_char *)ip);
udp_print(cp, len + sizeof(struct ip6_hdr) - (cp - bp),
udp_print(data, len, bp2);
udp_print(bp + pl_len, len - pl_len,