ippseudo
__CTASSERT(sizeof(struct ippseudo) == 12);
struct ippseudo ippseudo;
memset(&ippseudo, 0, sizeof(ippseudo));
ippseudo.ippseudo_src = ipovly->ih_src;
ippseudo.ippseudo_dst = ipovly->ih_dst;
ippseudo.ippseudo_pad = 0;
ippseudo.ippseudo_p = IPPROTO_TCP;
ippseudo.ippseudo_len = htons(m->m_pkthdr.len - thoff);
MD5Update(&ctx, (char *)&ippseudo, sizeof(ippseudo));