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

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Date:	Mon, 6 Jan 2014 11:56:14 +0100
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	François-Xavier Le Bail <fx.lebail@...oo.com>
Cc:	netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
	Alexey Kuznetsov <kuznet@....inr.ac.ru>,
	James Morris <jmorris@...ei.org>,
	Hideaki Yoshifuji <yoshfuji@...ux-ipv6.org>,
	Patrick McHardy <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 02:41:41AM -0800, François-Xavier Le Bail wrote:
> On Sun, 1/5/14, Hannes Frederic Sowa <hannes@...essinduktion.org> wrote:
> 
> > 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.
> 
> In this case, there are neighbor solicitations "who has LL anycast" with no reply, so no echo request is sent.

A counter-example would be NOARP interfaces where we also don't speak ndisc.

> Do you find some problem testing my patch ?

A quick test I did yesterday looked good.

Greetings,

  Hannes

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