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Date: Mon, 27 Jul 2009 14:44:02 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Chia-chi Yeh (=?ISO-8859-1?Q?=5F=5F=5F=5F=5F=5F=5F=5F=5F?=) 
	<chiachi@android.com>
Cc: linux-kernel@vger.kernel.org, netdev@vger.kernel.org
Subject: Re: [PATCH] net: Keep interface binding when sending packets with 
 ipi_ifindex = 0
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(cc netdev)

On Thu, 23 Jul 2009 14:39:28 -0700
Chia-chi Yeh (_________) <chiachi@android.com> wrote:

> In IPv4, sending a packet with ipi_ifindex = 0 via an interface-bound
> socket will unbind the packet to that interface. This behavior is
> different from IPv6 which treats ipi6_ifindex = 0 as unspecified.
> Furthermore, IPv6 does not allow sending packets to other interface
> than the bound one, but I am not sure if it is necessary in IPv4. The
> following patch keeps the interface binding when ipi_ifindex = 0.
> 
> Thanks,
> Chia-chi
> 
> --- a/net/ipv4/ip_sockglue.c	2009-07-24 04:50:45.000000000 +0800
> +++ b/net/ipv4/ip_sockglue.c	2009-07-24 04:51:09.000000000 +0800
> @@ -213,7 +213,8 @@
>  			if (cmsg->cmsg_len != CMSG_LEN(sizeof(struct in_pktinfo)))
>  				return -EINVAL;
>  			info = (struct in_pktinfo *)CMSG_DATA(cmsg);
> -			ipc->oif = info->ipi_ifindex;
> +			if (info->ipi_ifindex)
> +				ipc->oif = info->ipi_ifindex;
>  			ipc->addr = info->ipi_spec_dst.s_addr;
>  			break;
>  		}