netdev - Re: [PATCH net-next v2] ipv6: enable anycast addresses as source addresses in ICMPv6 error messages

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Date:	Thu, 6 Feb 2014 06:30:41 -0800 (PST)
From:	François-Xavier Le Bail <fx.lebail@...oo.com>
To:	"nicolas.dichtel@...nd.com" <nicolas.dichtel@...nd.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Cc:	David Stevens <dlstevens@...ibm.com>,
	Bill Fink <billfink@...dspring.com>,
	Hannes Frederic Sowa <hannes@...essinduktion.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 v2] ipv6: enable anycast addresses as source addresses in ICMPv6 error messages

> From: Nicolas Dichtel <nicolas.dichtel@...nd.com>

> To: François-Xavier Le Bail <fx.lebail@...oo.com>; "netdev@...r.kernel.org" <netdev@...r.kernel.org>
> Cc: David Stevens <dlstevens@...ibm.com>; Bill Fink <billfink@...dspring.com>; Hannes Frederic Sowa <hannes@...essinduktion.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>
> Sent: Thursday, February 6, 2014 3:01 PM
> Subject: Re: [PATCH net-next v2] ipv6: enable anycast addresses as source addresses in ICMPv6 error messages
> 
> Le 06/02/2014 13:38, François-Xavier Le Bail a écrit :
>>>  From: Nicolas Dichtel <nicolas.dichtel@...nd.com>
>> 
>> 
>>>  Subject: Re: [PATCH net-next v2] ipv6: enable anycast addresses as 
> source addresses in ICMPv6 error messages
>>> 
>>>  Le 19/01/2014 17:00, Francois-Xavier Le Bail a écrit :
>>> 
>>>>    - Uses ipv6_anycast_destination() in icmp6_send().
>>>> 
>>>>    Suggested-by: Bill Fink <billfink@...dspring.com>
>>>>    Signed-off-by: Francois-Xavier Le Bail 
> <fx.lebail@...oo.com>
>>>  This patch causes an Oops on my target.
>> 
>>  What is your target ?
> x86 32bits
> 
>> 
>>>  Here is the step to reproduce it:
>>>  modprobe sit
>>>  ip link add sit1 type sit remote 10.16.0.121 local 10.16.0.249
>>>  ip l s sit1 up
>>>  ip -6 a a dev sit1 2001:1234::123 remote 2001:1234::121
>>>  ping6 2001:1234::121
>> 
>>  I cannot reproduce this in my target (updated net-next x86_64) and
>>  iproute2 from git.
> I use linus tree (3.14-rc1+).
> 
>>  Can you send me your config file ?
> See attachment.
> 
> 
>> 
>>>  The problem is that ipv6_anycast_destination() uses unconditionally
>>>  skb_dst(skb), which is NULL in this case.
>>> 
>>>  Not sure what is the best way to fix this, any suggestions?
>> 
>>  I will try to reproduce first and see.
> Note that the peer was not set up, hence the ping didn't work.
> ipip6_err() calls ipip6_err_gen_icmpv6_unreach() which will drop the dst
> before calling icmpv6_send().
> 
> 
> Here is the backtrace:
> [  387.786155] BUG: unable to handle kernel NULL pointer dereference at 00000096
> [  387.787291] IP: [<c12f1568>] icmp6_send+0x79/0x596

[...]

> [  387.790055]  [<f85ce03b>] ? tunnel64_err+0x16/0x25 [tunnel4]

Thanks for these informations.

Can you test an alternative replacing:

test on: ipv6_anycast_destination(skb)
by
test on: ipv6_chk_acast_addr_src(net, skb->dev, &hdr->daddr)

Greetings

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