Function IcmpAliasOut1

freebsd/netinet/libalias/alias.c:478–520

}

static int
IcmpAliasOut1(struct libalias *la, struct ip *pip, int create)
{
/*
    Alias outgoing echo and timestamp requests.
    De-alias outgoing echo and timestamp replies.
*/
	struct alias_link *lnk;
	struct icmp *ic;

	LIBALIAS_LOCK_ASSERT(la);
	ic = (struct icmp *)ip_next(pip);

/* Save overwritten data for when echo packet returns */
	lnk = FindIcmpOut(la, pip->ip_src, pip->ip_dst, ic->icmp_id, create);
	if (lnk != NULL) {
		u_short alias_id;
		int accumulate;

		alias_id = GetAliasPort(lnk);

/* Since data field is being modified, adjust ICMP checksum */
		accumulate = ic->icmp_id;
		accumulate -= alias_id;
		ADJUST_CHECKSUM(accumulate, ic->icmp_cksum);

/* Alias sequence number */
		ic->icmp_id = alias_id;

/* Change source address */
		{
			struct in_addr alias_address;

			alias_address = GetAliasAddress(lnk);
			DifferentialChecksum(&pip->ip_sum,
			    &alias_address, &pip->ip_src, 2);
			pip->ip_src = alias_address;
		}

		return (PKT_ALIAS_OK);
	}
	return (PKT_ALIAS_IGNORED);
}

static int
IcmpAliasOut2(struct libalias *la, struct ip *pip)