Re: [PATCH net-next v2 01/13] net: sched: support skb chain ext in tc classification path

From: Jiri Pirko <jiri@resnulli.us>
To: Jakub Kicinski <kuba@kernel.org>
Cc: Paul Blakey <paulb@mellanox.com>,
	Saeed Mahameed <saeedm@mellanox.com>,
	Oz Shlomo <ozsh@mellanox.com>,
	Jakub Kicinski <jakub.kicinski@netronome.com>,
	Vlad Buslov <vladbu@mellanox.com>,
	David Miller <davem@davemloft.net>,
	"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
	Roi Dayan <roid@mellanox.com>
Subject: Re: [PATCH net-next v2 01/13] net: sched: support skb chain ext in tc classification path
Date: Thu, 23 Jan 2020 08:06:27 +0100	[thread overview]
Message-ID: <20200123070627.GB2207@nanopsycho.orion> (raw)
In-Reply-To: <20200122072916.23fc3416@cakuba>

Wed, Jan 22, 2020 at 04:29:16PM CET, kuba@kernel.org wrote:
>On Wed, 22 Jan 2020 15:52:46 +0200, Paul Blakey wrote:
>> +int tcf_classify_ingress(struct sk_buff *skb,
>> +			 const struct tcf_block *ingress_block,
>> +			 const struct tcf_proto *tp, struct tcf_result *res,
>> +			 bool compat_mode)
>> +{
>> +	const struct tcf_proto *orig_tp = tp;
>> +
>> +#if IS_ENABLED(CONFIG_NET_TC_SKB_EXT)
>> +	{
>> +		struct tc_skb_ext *ext = skb_ext_find(skb, TC_SKB_EXT);
>> +
>> +		if (ext && ext->chain && ingress_block) {
>> +			struct tcf_chain *fchain;
>> +
>> +			fchain = tcf_chain_lookup_rcu(ingress_block,
>> +						      ext->chain);
>> +			if (!fchain)
>> +				return TC_ACT_UNSPEC;
>> +
>> +			tp = rcu_dereference_bh(fchain->filter_chain);
>> +		}
>
>Doesn't this skb ext have to be somehow "consumed" by the first lookup?
>What if the skb finds its way to an ingress of another device?

You are right. Looks like it would be better to return TC_ACT_SHOT here.

>
>> +	}
>> +#endif
>> +
>> +	return tcf_classify(skb, tp, orig_tp, res, compat_mode);
>> +}
>> +EXPORT_SYMBOL(tcf_classify_ingress);