netdev - Re: [PATCH v2] ipv6: Fix protocol resubmission

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Message-ID: <CALx6S34mG6HTtJ5sofLKayMgtJ9EhwCnk9RFX-He8sVBpO9ovg@mail.gmail.com>
Date:	Fri, 29 May 2015 14:48:27 -0700
From:	Tom Herbert <tom@...bertland.com>
To:	Josh Hunt <johunt@...mai.com>
Cc:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
	"David S. Miller" <davem@...emloft.net>,
	Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: [PATCH v2] ipv6: Fix protocol resubmission

Hi Josh,

Why did you need to move the resubmit label?


On Fri, May 29, 2015 at 2:43 PM, Josh Hunt <johunt@...mai.com> wrote:
> On 05/29/2015 03:27 PM, Sergei Shtylyov wrote:
>>
>> Hello.
>>
>> On 05/29/2015 11:04 PM, Josh Hunt wrote:
>>
>>> I came across this problem while trying to use UDP encapsulation with
>>> IPv6. The
>>> change below fixes that, but it was not immediately apparent if there
>>> are any
>>> other protocols relying on this broken behavior. FWIW the behavior
>>> below now
>>> matches IPv4.
>>
>>
>>> Josh
>>
>>
>>     Need "Signed-off-by:" line insted of this.
>>
>>> v2: Actually sets nexthdr so we can use it ;)
>>
>>
>>     Normally goes after ---, not before.
>>
>>> ---
>>
>>
>>> UDP encapsulation is broken on IPv6 because it expects when it returns
>>> a negative
>>> value that the packet will be resubmitted to the stack with the
>>> handler corresponding
>>> to the return value. The check currently looks for return values > 0
>>> and then resubmits.
>>
>>
>>> This patch fixes that check and also moves the resubmit label to take
>>> advantage of
>>> the return code identifying the next protocol we want to process.
>>
>>
>>> Signed-off-by: Josh Hunt <johunt@...mai.com>
>>> ---
>>>   net/ipv6/ip6_input.c |    7 ++++---
>>>   1 file changed, 4 insertions(+), 3 deletions(-)
>>
>>
>>> diff --git a/net/ipv6/ip6_input.c b/net/ipv6/ip6_input.c
>>> index f2e464e..e16c289 100644
>>> --- a/net/ipv6/ip6_input.c
>>> +++ b/net/ipv6/ip6_input.c
>>
>> [...]
>>>
>>> @@ -246,9 +246,10 @@ resubmit:
>>>               goto discard;
>>>
>>>           ret = ipprot->handler(skb);
>>> -        if (ret > 0)
>>> +        if (ret < 0) {
>>> +            nexthdr = -ret;
>>>               goto resubmit;
>>> -        else if (ret == 0)
>>> +        } else if (ret == 0)
>>>               IP6_INC_STATS_BH(net, idev, IPSTATS_MIB_INDELIVERS);
>>
>>
>>     The CodingStyle dictates that all branches must have {} if at least
>> one has them.
>
>
> Thanks Sergei, I appreciate the review. I will make these changes in a v3
> after I get feedback this is the correct fix for the problem.
>
> Josh
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