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

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Date:	Fri, 7 Feb 2014 02:04:57 -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: Friday, February 7, 2014 10:33 AM
> Subject: Re: [PATCH net-next v2] ipv6: enable anycast addresses as source addresses in ICMPv6 error messages
> 
> Le 06/02/2014 15:30, François-Xavier Le Bail a écrit :
> 
>>>  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)
> It's ok with this function. Do you submit the corresponding patch?

Yes, thanks you for the report and the tests.
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