Subject: Re: [net-next PATCH v2 1/1] net_sched fix: reclassification needs to consider ether protocol changes

From: Jamal Hadi Salim <[email-masked]>
Date: Wed, 17 Feb 2016 06:19:59 -0500

On 16-02-16 10:20 AM, Daniel Borkmann wrote:
> On 02/16/2016 01:37 PM, Jamal Hadi Salim wrote:
>> From: Jamal Hadi Salim <[email-masked]>
>>
>> actions could change the etherproto in particular with ethernet
>> tunnelled data. Typically such actions, after peeling the outer header,
>> will ask for the packet to be  reclassified. We then need to restart
>> the classification with the new proto header.
>>
>> Example setup used to catch this:
>> sudo tc qdisc add dev $ETH ingress
>> sudo $TC filter add dev $ETH parent ffff: pref 1 protocol 802.1Q \
>> u32 match u32 0 0 flowid 1:1 \
>> action vlan pop reclassify
>>
>> Fixes: 3b3ae880266d ("net: sched: consolidate tc_classify{,_compat}")
>> Signed-off-by: Jamal Hadi Salim <[email-masked]>
>> ---
>>   net/sched/sch_api.c | 7 ++++---
>>   1 file changed, 4 insertions(+), 3 deletions(-)
>>
>> diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
>> index b5c2cf2..22ab634 100644
>> --- a/net/sched/sch_api.c
>> +++ b/net/sched/sch_api.c
>> @@ -1818,13 +1818,14 @@ done:
>>   int tc_classify(struct sk_buff *skb, const struct tcf_proto *tp,
>>           struct tcf_result *res, bool compat_mode)
>>   {
>> -    __be16 protocol = tc_skb_protocol(skb);
>>   #ifdef CONFIG_NET_CLS_ACT
>> -    const struct tcf_proto *old_tp = tp;
>>       int limit = 0;
>> +#endif
>> +    const struct tcf_proto *old_tp = tp;
>> +    __be16 protocol;
>>
>>   reclassify:
>> -#endif
>> +    protocol = tc_skb_protocol(skb);
>>       for (; tp; tp = rcu_dereference_bh(tp->next)) {
>>           int err;
>>
>
> But, how is that better than the one-liner I suggested to you in
> my earlier mail?
>

Thats how the original code was (and what i tested). I dont have time
to test right now but i will send an update with your suggestion.

cheers,
jamal