write_rule("uint8_t orig_tos = ip->tos;")
write_rule("ip->tos = (ip->tos & 3) | " + str(low_bytes << 2) + ";")
write_rule("chk = (chk - orig_tos + ip->tos);")
write_rule("uint8_t orig_tos = ip->tos;")
write_rule("ip->tos = (ip->tos & 3) | " + str(low_bytes << 2) + ";")
write_rule("chk = (chk - orig_tos + ip->tos);")