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Hannes Eder wrote:
> Update the nf_conntrack tuple in reply direction, as we will see
> traffic from the real server (RIP) to the client (CIP). Once this is
> done we can use netfilters SNAT in POSTROUTING, especially with
> xt_ipvs, to do source NAT, e.g.:
>
> % iptables -t nat -A POSTROUTING -m ipvs --vaddr 192.168.100.30/32 --vport
> 8080 \
>> -j SNAT --to-source 192.168.10.10
>
> +static void
> +ip_vs_update_conntrack(struct sk_buff *skb, struct ip_vs_conn *cp)
> +{
> + struct nf_conn *ct = (struct nf_conn *)skb->nfct;
> +
> + if (ct == NULL || ct == &nf_conntrack_untracked ||
> + nf_ct_is_confirmed(ct))
> + return;
> +
> + /*
> + * The connection is not yet in the hashtable, so we update it.
> + * CIP->VIP will remain the same, so leave the tuple in
> + * IP_CT_DIR_ORIGINAL untouched. When the reply comes back from the
> + * real-server we will see RIP->DIP.
> + */
> + ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u3 = cp->daddr;
> + /*
> + * This will also take care of UDP and other protocols.
> + */
> + ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u.tcp.port = cp->dport;
> +}
How does IPVS interact with conntrack helpers? If it does actually
intend to use them (which will happen automatically), it might make
sense to use nf_conntrack_alter_reply(), which will perform a new
helper lookup based on the changed tuple.
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