netdev - Re: [PATCH net-next 1/3] netfilter: flowtable: Support GRE

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Date:   Sat, 12 Feb 2022 10:54:01 +0900
From:   Toshiaki Makita <toshiaki.makita1@...il.com>
To:     Pablo Neira Ayuso <pablo@...filter.org>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Saeed Mahameed <saeedm@...dia.com>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jiri Pirko <jiri@...nulli.us>,
        Jozsef Kadlecsik <kadlec@...filter.org>,
        Florian Westphal <fw@...len.de>, netdev@...r.kernel.org,
        netfilter-devel@...r.kernel.org, coreteam@...filter.org,
        Paul Blakey <paulb@...dia.com>
Subject: Re: [PATCH net-next 1/3] netfilter: flowtable: Support GRE

On 2022/02/09 19:01, Pablo Neira Ayuso wrote:
> On Tue, Feb 08, 2022 at 11:30:03PM +0900, Toshiaki Makita wrote:
>> On 2022/02/08 2:56, Pablo Neira Ayuso wrote:
>>> On Thu, Feb 03, 2022 at 08:59:39PM +0900, Toshiaki Makita wrote:
> [...]
>>>> diff --git a/net/netfilter/nf_flow_table_ip.c b/net/netfilter/nf_flow_table_ip.c
>>>> index 889cf88..48e2f58 100644
>>>> --- a/net/netfilter/nf_flow_table_ip.c
>>>> +++ b/net/netfilter/nf_flow_table_ip.c
> [...]
>>>> @@ -202,15 +209,25 @@ static int nf_flow_tuple_ip(struct sk_buff *skb, const struct net_device *dev,
>>>>    	if (!pskb_may_pull(skb, thoff + *hdrsize))
>>>>    		return -1;
>>>> +	if (ipproto == IPPROTO_GRE) {
>>>
>>> No ifdef here? Maybe remove these ifdef everywhere?
>>
>> I wanted to avoid adding many ifdefs and I expect this to be compiled out
>> when CONFIG_NF_CT_PROTO_GRE=n as this block is unreachable anyway. It rather
>> may have been unintuitive though.
>>
>> Removing all of these ifdefs will cause inconsistent behavior between
>> CONFIG_NF_CT_PROTO_GRE=n/y.
>> When CONFIG_NF_CT_PROTO_GRE=n, conntrack cannot determine GRE version, thus
>> it will track GREv1 without key infomation, and the flow will be offloaded.
>> When CONFIG_NF_CT_PROTO_GRE=y, GREv1 will have key information and will not
>> be offloaded.
>> I wanted to just refuse offloading of GRE to avoid this inconsistency.
>> Anyway this kind of inconsistency seems to happen in software conntrack, so
>> if you'd like to remove ifdefs, I will do.
> 
> Good point, thanks for explaining. LGTM.

Let me confirm, did you agree to keep ifdefs, or delete them?

Toshiaki Makita