netdev - Re: [PATCH] ipv4/route.c: respect prefsrc for local routes

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Date:	Tue, 04 Jan 2011 08:24:40 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Joel Sing <jsing@...gle.com>
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH] ipv4/route.c: respect prefsrc for local routes

Le mardi 04 janvier 2011 à 17:24 +1100, Joel Sing a écrit :
> The preferred source address is currently ignored for local routes,
> which results in all local connections having a src address that is the
> same as the local dst address. Fix this by respecting the preferred source
> address when it is provided for local routes.
> 
> This bug can be demonstrated as follows:
> 
>  # ifconfig dummy0 192.168.0.1
>  # ip route show table local | grep local.*dummy0
>  local 192.168.0.1 dev dummy0  proto kernel  scope host  src 192.168.0.1
>  # ip route change table local local 192.168.0.1 dev dummy0 \
>      proto kernel scope host src 127.0.0.1
>  # ip route show table local | grep local.*dummy0
>  local 192.168.0.1 dev dummy0  proto kernel  scope host  src 127.0.0.1
> 
> We now establish a local connection and verify the source IP
> address selection:
> 
>  # nc -l 192.168.0.1 3128 &
>  # nc 192.168.0.1 3128 &
>  # netstat -ant | grep 192.168.0.1:3128.*EST
>  tcp        0      0 192.168.0.1:3128        192.168.0.1:33228 ESTABLISHED
>  tcp        0      0 192.168.0.1:33228       192.168.0.1:3128  ESTABLISHED
> 
> Signed-off-by: Joel Sing <jsing@...gle.com>
> ---
>  net/ipv4/route.c |    8 ++++++--
>  1 files changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/net/ipv4/route.c b/net/ipv4/route.c
> index df948b0..93bfd95 100644
> --- a/net/ipv4/route.c
> +++ b/net/ipv4/route.c
> @@ -2649,8 +2649,12 @@ static int ip_route_output_slow(struct net *net, struct rtable **rp,
>  	}
>  
>  	if (res.type == RTN_LOCAL) {
> -		if (!fl.fl4_src)
> -			fl.fl4_src = fl.fl4_dst;
> +		if (!fl.fl4_src) {
> +			if (res.fi->fib_prefsrc)
> +				fl.fl4_src = res.fi->fib_prefsrc;
> +			else
> +				fl.fl4_src = fl.fl4_dst;
> +		}
>  		dev_out = net->loopback_dev;
>  		fl.oif = dev_out->ifindex;
>  		res.fi = NULL;

Please use FIB_RES_PREFSRC(res)

as we do a few lines after ;)

Thanks


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