netdev - Re: [PATCH] sit: correct IP protocol used in ipip6

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Date:	Thu, 16 Jun 2016 17:23:13 +0900
From:	YOSHIFUJI Hideaki <hideaki.yoshifuji@...aclelinux.com>
To:	Simon Horman <simon.horman@...ronome.com>,
	"David S. Miller" <davem@...emloft.net>
Cc:	hideaki.yoshifuji@...aclelinux.com, netdev@...r.kernel.org
Subject: Re: [PATCH] sit: correct IP protocol used in ipip6_err

Hi, Simon,

Simon Horman wrote:
> On Thu, Jun 16, 2016 at 05:06:19PM +0900, Simon Horman wrote:
>> Since 32b8a8e59c9c ("sit: add IPv4 over IPv4 support")
>> ipip6_err() may be called for packets whose IP protocol is
>> IPPROTO_IPIP as well as those whose IP protocol is IPPROTO_IPV6.
>>
>> In the case of IPPROTO_IPIP packets the correct protocol value is not
>> passed to ipv4_update_pmtu() or ipv4_redirect().
>>
>> This patch resolves this problem by using the IP protocol of the packet
>> rather than a hard-coded value. This appears to be consistent
>> with the usage of the protocol of a packet by icmp_socket_deliver()
>> the caller of ipip6_err().
>>
>> I was able to exercise the redirect case by using a setup where an ICMP
>> redirect was received for the destination of the encapsulated packet.
>> However, it appears that although incorrect the protocol field is not used
>> in this case and thus no problem manifests.  On inspection it does not
>> appear that a problem will manifest in the fragmentation needed/update pmtu
>> case either.
>>
>> In short I believe this is a cosmetic fix. None the less, the use of
>> IPPROTO_IPV6 seems wrong and confusing.
>>
>> Reviewed-by: Dinan Gunawardena <dinan.gunawardena@...ronome.com>
>> Signed-off-by: Simon Horman <simon.horman@...ronome.com>
> 
> Apologies for not making this more obvious, this is a "net-next" patch.

Acked-by: YOSHIFUJI Hideaki <yoshfuji@...ux-ipv6.org>

BTW, we should have similar fix in -net, -stable etc. as well, no?

> 
>> ---
>>  net/ipv6/sit.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/net/ipv6/sit.c b/net/ipv6/sit.c
>> index d9f2bd6ef72d..f4356bb13f4b 100644
>> --- a/net/ipv6/sit.c
>> +++ b/net/ipv6/sit.c
>> @@ -560,13 +560,13 @@ static int ipip6_err(struct sk_buff *skb, u32 info)
>>  
>>  	if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED) {
>>  		ipv4_update_pmtu(skb, dev_net(skb->dev), info,
>> -				 t->parms.link, 0, IPPROTO_IPV6, 0);
>> +				 t->parms.link, 0, iph->protocol, 0);
>>  		err = 0;
>>  		goto out;
>>  	}
>>  	if (type == ICMP_REDIRECT) {
>>  		ipv4_redirect(skb, dev_net(skb->dev), t->parms.link, 0,
>> -			      IPPROTO_IPV6, 0);
>> +			      iph->protocol, 0);
>>  		err = 0;
>>  		goto out;
>>  	}
>> -- 
>> 2.1.4
>>

-- 
Hideaki Yoshifuji <hideaki.yoshifuji@...aclelinux.com>
Technical Division, MIRACLE LINUX CORPORATION