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[Ivo Vachkov]

Hi all,

I've been trying to write some code using divert(4) sockets, but i meet the following difficulties:
    - when i get diverted packet it has both source and destination IP addresses the same. The attached code shows:

    192.168.0.2 -> 192.168.0.2
    getting 84 bytes, real: 84

and the way I run it is (on 192.168.0.2):

    ipfw add 100 divert 8670 ip from any to 192.168.0.1
    burstd

then on 192.168.0.2 I issue "ping 192.168.0.1"

    - the manual says this happens with recvfrom()/sendto(), but recv() is mentioned to be same as recvfrom() and read()/write() sometimes fail.

After digging some kernel code I've found that around line 167 in ip_divert.c we have:

	/*
	 * Record receive interface address, if any.
	 * But only for incoming packets.
	 */
	divsrc.sin_addr.s_addr = 0;
	if (incoming) {
		struct ifaddr *ifa;

		/* Sanity check */
		KASSERT((m->m_flags & M_PKTHDR), ("%s: !PKTHDR", __FUNCTION__));

		/* Find IP address for receive interface */
		TAILQ_FOREACH(ifa, &m->m_pkthdr.rcvif->if_addrhead, ifa_link) {
			if (ifa->ifa_addr == NULL)
				continue;
			if (ifa->ifa_addr->sa_family != AF_INET)
				continue;
			divsrc.sin_addr =
			    ((struct sockaddr_in *) ifa->ifa_addr)->sin_addr;
			break;
		}
	}

which (as I think) changes the address of diverted packet. What is the reason for that and are there any workarounds to get real source and destination IP addresses from a diverted packet. I need both because I try to make connection tracking based on src<->dst .

Any help with that is appretiated. Any divert code welcome. I've looked through natd.c and it was helpfull.

    Ivo Vachkov

P.S. Excuse my:
    - English
    - long pastes
    - (sometimes) lack of kernel code understanding
-- 
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