netdev - Re: [PATCH net-next v2 3/4] net: sched: em_ipt: keep the user-specified nfproto and use it

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Message-ID: <92B812B3-C5FB-452B-809A-1367349DB29A@cumulusnetworks.com>
Date:   Wed, 26 Jun 2019 19:33:48 +0300
From:   nikolay@...ulusnetworks.com
To:     Eyal Birger <eyal.birger@...il.com>
CC:     netdev@...r.kernel.org, roopa@...ulusnetworks.com,
        pablo@...filter.org, xiyou.wangcong@...il.com, davem@...emloft.net,
        jiri@...nulli.us, jhs@...atatu.com
Subject: Re: [PATCH net-next v2 3/4] net: sched: em_ipt: keep the user-specified nfproto and use it

On 26 June 2019 19:18:35 EEST, Eyal Birger <eyal.birger@...il.com> wrote:
>Hi Nik,
>
>On Wed, 26 Jun 2019 18:56:14 +0300
>Nikolay Aleksandrov <nikolay@...ulusnetworks.com> wrote:
>
>> For NFPROTO_UNSPEC xt_matches there's no way to restrict the matching
>> to a specific family, in order to do so we record the user-specified
>> family and later enforce it while doing the match.
>> 
>> v2: adjust changes to missing patch, was patch 04 in v1
>> 
>> Signed-off-by: Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
>> ---
>>  net/sched/em_ipt.c | 17 +++++++++++++++--
>>  1 file changed, 15 insertions(+), 2 deletions(-)
>> 
>..snip..
>> @@ -182,8 +195,8 @@ static int em_ipt_match(struct sk_buff *skb,
>> struct tcf_ematch *em, const struct em_ipt_match *im = (const void
>> *)em->data; struct xt_action_param acpar = {};
>>  	struct net_device *indev = NULL;
>> -	u8 nfproto = im->match->family;
>>  	struct nf_hook_state state;
>> +	u8 nfproto = im->nfproto;
>
>Maybe I'm missing something now - but it's not really clear to me now
>why keeping im->nfproto would be useful:
>
>If NFPROTO_UNSPEC was provided by userspace then the actual nfproto
>used
>will be taken from the packet, and if NFPROTO_IPV4/IPV6 was specified
>from userspace then it will equal im->match->family.
>
>Is there any case where the resulting nfproto would differ as a result
>of this patch?
>
>Otherwise the patchset looks excellent to me.
>
>Thanks!
>Eyal.

Hi,
It's needed to limit the match only to the user-specified family
for unspec xt matches. The problem is otherwise im->match->family
stays at nfproto_unspec regardless of the user choice.

Thanks for reviewing the set. 

Cheers,
  Nik