Re: Re-routing packets via netfilter (ip_rt_bug)

[Ric Wheeler <ric@emc.com>]

Patrick, Hebert,

This issues stills seems to be in the latest trees - is this patch or a 
variation on it still bumping around?

Thanks!

Yair Itzhaki wrote:

> Can anyone propose a patch that I can start checking?
>
> I have come up with the following:
>
> --- net/core/netfilter.c.orig   2005-04-18 21:55:30.000000000 +0300
> +++ net/core/netfilter.c        2005-05-02 17:35:20.000000000 +0300
> @@ -622,9 +622,10 @@
>        /* some non-standard hacks like ipt_REJECT.c:send_reset() can cause
>         * packets with foreign saddr to appear on the NF_IP_LOCAL_OUT hook.
>         */
> -       if (inet_addr_type(iph->saddr) == RTN_LOCAL) {
> +       if ((inet_addr_type(iph->saddr) == RTN_LOCAL) ||
> +           (inet_addr_type(iph->daddr) == RTN_LOCAL)) {
>                fl.nl_u.ip4_u.daddr = iph->daddr;
> -               fl.nl_u.ip4_u.saddr = iph->saddr;
> +               fl.nl_u.ip4_u.saddr = 0;
>                fl.nl_u.ip4_u.tos = RT_TOS(iph->tos);
>                fl.oif = (*pskb)->sk ? (*pskb)->sk->sk_bound_dev_if : 0;
> #ifdef CONFIG_IP_ROUTE_FWMARK
>
> Please advise,
> Yair
>
>
>  
>
> > -----Original Message-----
> > From: Patrick McHardy [mailto:kaber@trash.net]
> > Sent: Wednesday, April 27, 2005 14:05
> > To: Herbert Xu
> > Cc: Jozsef Kadlecsik; netdev@oss.sgi.com; 
> > netfilter-devel@lists.netfilter.org; Yair Itzhaki; 
> > linux-kernel@vger.kernel.org
> > Subject: Re: Re-routing packets via netfilter (ip_rt_bug)
> >
> >
> > Herbert Xu wrote:
> >    
> >
> > > Here is another reason why these packets should go through FORWARD.
> > > They were generated in response to packets in INPUT/FORWARD/OUTPUT.
> > > The original packet has not undergone SNAT in any of these cases.
> > >
> > > However, if we feed the response packet through LOCAL_OUT it will
> > > be subject to DNAT.  This creates a NAT asymmetry and we may end
> > > up with the wrong destination address.
> > >
> > > By pushing it through FORWARD it will only undergo SNAT which is
> > > correct since the original packet would have undergone DNAT.
> > >      
> > This is only a problem since the recent NAT changes, but I agree
> > that we should fix it by moving these packets to FORWARD.
> >
> > Regards
> > Patrick
> >
> >    
>
>  

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