netdev - Re: NAT regression in next tree

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Date:	Fri, 19 Feb 2010 08:20:56 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Patrick McHardy <kaber@...sh.net>
Cc:	Stephen Hemminger <shemminger@...tta.com>,
	David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
	netfilter-devel@...r.kernel.org
Subject: Re: NAT regression in next tree

Le vendredi 19 février 2010 à 08:06 +0100, Patrick McHardy a écrit :
> Stephen Hemminger wrote:
> > On Fri, 19 Feb 2010 06:45:43 +0100
> > Patrick McHardy <kaber@...sh.net> wrote:
> > 
> >> Stephen Hemminger wrote:
> >>> Something in net-next tree broke bridging of virtual nets.
> >>> My local VM's can no longer access external networks.
> >>>
> >>> It is a NAT problem. One of the recent netfilter changes is causing
> >>> the packets to not have there source address rewritten.
> >>>
> >>> I see:
> >>>     VM1  -- 192.168.100.0/24 -- HOST -- 192.168.1.0/24 -- ROUTER
> >>>                            virbr0    eth0
> >>>
> >>> Even a simple ping from VM1 doesn't get responded to because
> >>> the 192.168.100.X source address is not getting rewritten.
> >> I'll try to reproduce it locally. What is the HEAD of the broken
> >> tree you're running?
> > 
> > commit 37ee3d5b3e979a168536e7e2f15bd1e769cb4122
> > Author: Patrick McHardy <kaber@...sh.net>
> > Date:   Thu Feb 18 19:04:44 2010 +0100
> > 
> >     netfilter: nf_defrag_ipv4: fix compilation error with NF_CONNTRACK=n
> 
> This patch should fix it.
> 
> pièce jointe document texte brut (x)
> commit 4bac6b180771f7ef5275b1a6d88e630ca3a3d6f0
> Author: Patrick McHardy <kaber@...sh.net>
> Date:   Fri Feb 19 08:03:28 2010 +0100
> 
>     netfilter: restore POST_ROUTING hook in NF_HOOK_COND
>     
>     Commit 2249065 ("netfilter: get rid of the grossness in netfilter.h")
>     inverted the logic for conditional hook invocation, breaking the
>     POST_ROUTING hook invoked by ip_output().
>     
>     Correct the logic and remove an unnecessary initialization.
>     
>     Reported-by: Stephen Hemminger <shemminger@...tta.com>
>     Signed-off-by: Patrick McHardy <kaber@...sh.net>
> 
> diff --git a/include/linux/netfilter.h b/include/linux/netfilter.h
> index 7007945..89341c3 100644
> --- a/include/linux/netfilter.h
> +++ b/include/linux/netfilter.h
> @@ -212,8 +212,9 @@ NF_HOOK_COND(uint8_t pf, unsigned int hook, struct sk_buff *skb,
>  	     struct net_device *in, struct net_device *out,
>  	     int (*okfn)(struct sk_buff *), bool cond)
>  {
> -	int ret = 1;
> -	if (cond ||
> +	int ret;
> +
> +	if (!cond ||
>  	    (ret = nf_hook_thresh(pf, hook, skb, in, out, okfn, INT_MIN) == 1))
>  		ret = okfn(skb);
>  	return ret;

I dont quite get it

Original code was :


#define NF_HOOK_COND(pf, hook, skb, indev, outdev, okfn, cond)                \
({int __ret;                                                                  \
if ((cond) || (__ret = nf_hook_thresh(pf, hook, (skb), indev, outdev, okfn, INT_MIN)) == 1)\
       __ret = (okfn)(skb);                                                   \
__ret;})


There was no condition inversion.



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