check_ip4
if ((r = check(&c, check_ip4(parser, t, &f[3], o+c, n-c))) < 0)
(r = check(&c, check_ip4(parser, type, &f[1], o+c, n-c))))
if ((r = check(&c, check_ip4(parser, t, &f[3], o+c, n-c))) < 0)
if ((r = check(&c, check_ip4(parser, type, &f[0], o, n))) ||