netdev - Re: [PATCH net-next v4] IPv6: use anycast addresses as source addresses in echo reply

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Message-ID: <20140106230508.GD10204@order.stressinduktion.org>
Date:	Tue, 7 Jan 2014 00:05:08 +0100
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	François-Xavier Le Bail <fx.lebail@...oo.com>
Cc:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
	kuznet@....inr.ac.ru, jmorris@...ei.org, yoshfuji@...ux-ipv6.org,
	kaber@...sh.net
Subject: Re: [PATCH net-next v4] IPv6: use anycast addresses as source addresses in echo reply

On Mon, Jan 06, 2014 at 01:53:49PM -0800, François-Xavier Le Bail wrote:
> On Mon, 1/6/14, David Miller <davem@...emloft.net> wrote:
> 
> > From: Hannes Frederic Sowa <hannes@...essinduktion.org>
> > Date: Mon, 6 Jan 2014 00:05:05 +0100
> 
> >> On Fri, Jan 03, 2014 at 05:43:31PM +0100, Francois-Xavier Le Bail wrote:
> >>> diff --git a/net/ipv6/icmp.c b/net/ipv6/icmp.c
> >>> index 5d42009..65c8619 100644
> >>> --- a/net/ipv6/icmp.c
> >>> +++ b/net/ipv6/icmp.c
> >>> @@ -556,7 +556,9 @@ static void icmpv6_echo_reply(struct sk_buff *skb)
> >>>  
> >>>      saddr = &ipv6_hdr(skb)->daddr;
> >>>  
> >>> -    if (!ipv6_unicast_destination(skb))
> >>> +    if (!ipv6_unicast_destination(skb) &&
> >>> +        !(net->ipv6.anycast_src_echo_reply &&
> >>> +          ipv6_chk_acast_addr(net, NULL, saddr)))
> >>>          saddr = NULL;
> >> 
> >> I am not sure why you left out the device at ipv6_chk_acast_addr?
> >> 
> >> IMHO this logic is a bit more complex, we can pass NULL for ipv6 addresses of
> >> scope global but need to check the interface for scope link.
> >> 
> >> It is already possible via setsockopt JOIN_ANYCAST that an ll address is
> >> anycast on another interface which may not be checked here.
> 
> > I think we should pass a valid device in unless it breaks something
> > obvious.
> 
> The problem is that "saddr" is not necessarily an address on "skb->dev"
> in icmpv6_echo_reply(). It may be an address on another interface.

Maybe you're right, but then I don't get it. Could you make an example?

Thanks,

  Hannes

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