netdev - Re: [PATCH net v2 2/3] net/sched: act_ipt: add sanity checks on skb before calling target

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Date: Thu, 8 Jun 2023 20:34:31 +0200
From: Florian Westphal <fw@...len.de>
To: Davide Caratti <dcaratti@...hat.com>
Cc: Florian Westphal <fw@...len.de>, netdev@...r.kernel.org,
	kuba@...nel.org, edumazet@...gle.com, davem@...emloft.net,
	pabeni@...hat.com, jhs@...atatu.com, xiyou.wangcong@...il.com,
	jiri@...nulli.us, Simon Horman <simon.horman@...igine.com>
Subject: Re: [PATCH net v2 2/3] net/sched: act_ipt: add sanity checks on skb
 before calling target

Davide Caratti <dcaratti@...hat.com> wrote:
> hello Florian,
> 
> On Thu, Jun 8, 2023 at 4:04 PM Florian Westphal <fw@...len.de> wrote:
> >
> > Netfilter targets make assumptions on the skb state, for example
> > iphdr is supposed to be in the linear area.
> >
> [...]
> 
> > @@ -244,9 +264,22 @@ TC_INDIRECT_SCOPE int tcf_ipt_act(struct sk_buff *skb,
> >                 .pf     = NFPROTO_IPV4,
> >         };
> >
> > +       if (skb->protocol != htons(ETH_P_IP))
> > +               return TC_ACT_UNSPEC;
> > +
> 
> maybe this can be converted to skb_protocol(skb, ...)  so that it's
> clear how VLAN packets are treated ?

Not sure how to handle this.

act_ipt claims NFPROTO_IPV4; for iptables/nftables one has to use
the interface name ("-i vlan0") to match on the vlan interface.

I don't really want to add code that pulls/pops the vlan headers
in act_ipt...