netdev - Re: [PATCH 1/1] Reverse sense of promisc tests in ip6_mc

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Date:	Sat, 12 May 2007 17:21:10 -0700
From:	David Stevens <dlstevens@...ibm.com>
To:	Corey Mutter <crm-netdev@...-machine.mutternet.com>
Cc:	davem@...emloft.net, netdev@...r.kernel.org,
	yoshfuji@...ux-ipv6.org
Subject: Re: [PATCH 1/1] Reverse sense of promisc tests in ip6_mc_input

Your patch looks correct to me.

                        +-DLS

Signed-off-by: David L Stevens <dlstevens@...ibm.com>

netdev-owner@...r.kernel.org wrote on 05/12/2007 03:51:35 PM:

> From: Corey Mutter <crm-netdev@...ternet.com>
> 
> Reverse the sense of the promiscuous-mode tests in ip6_mc_input(). 
> 
> Signed-off-by: Corey Mutter <crm-netdev@...ternet.com>
> 
> ---
> 
> I had been suspicious of this code for a while, but just assumed I must 
> have been missing something. However, I did some tests and, sure enough, 

> I can open a socket and it will see IPv6 multicast packets come in, then 

> the packets will stop coming in when I turn on IFF_ALLMULTI on the 
> interface. 
> 
> In my tests, this change works more like I'd expect; I can open a 
> socket, and it doesn't see any multicast packets (unless I join a group 
> or something) until after I turn on IFF_ALLMULTI. 
> 
> --- linux-2.6.21.1/net/ipv6/ip6_input.c   2007-04-27 17:49:26.000000000 
-0400
> +++ linux/net/ipv6/ip6_input.c   2007-05-12 18:19:09.597750000 -0400
> @@ -235,7 +235,7 @@ int ip6_mc_input(struct sk_buff *skb)
>     IP6_INC_STATS_BH(ip6_dst_idev(skb->dst), IPSTATS_MIB_INMCASTPKTS);
> 
>     hdr = skb->nh.ipv6h;
> -   deliver = likely(!(skb->dev->flags & (IFF_PROMISC|IFF_ALLMULTI))) ||
> +   deliver = unlikely(skb->dev->flags & (IFF_PROMISC|IFF_ALLMULTI)) ||
>         ipv6_chk_mcast_addr(skb->dev, &hdr->daddr, NULL);
> 
>     /*
> -
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