Re: [PATCH 2/3] IPVS: make friends with nf_conntrack

[Hannes Eder <heder@google.com>]

On Wed, Sep 2, 2009 at 16:56, Patrick McHardy<kaber@trash.net> wrote:
> 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.

Good point, I'll use nf_conntrack_alter_reply().  IHMO IPVS only deals
with ftp in a special way, I think something need to be done there as
well, I'll investigate that.