extract_prefix
int extract_prefix(const u_char *, int, void *, uint8_t, uint8_t);
extract_prefix(abuf + 2, ablen - 2, &a, clen, sizeof(a));
extract_prefix(bbuf + 2, bblen - 2, &b, clen, sizeof(b));
extract_prefix(abuf + 3, ablen - 3, &a, clen, sizeof(a));
extract_prefix(bbuf + 3, bblen - 3, &b, clen, sizeof(b));
if (extract_prefix(comp + 1, complen - 1, &addr->v4, comp[0],
if (extract_prefix(comp + 2, complen - 2, buf, xlen,