netdev - Re: [RFC 03/12] net: cls_bpf: limit hardware offload by software-only flag

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Message-ID: <20160601222608.04c7b707@jkicinski-Precision-T1700>
Date:	Wed, 1 Jun 2016 22:26:08 +0100
From:	Jakub Kicinski <jakub.kicinski@...ronome.com>
To:	Daniel Borkmann <daniel@...earbox.net>
Cc:	netdev@...r.kernel.org, ast@...nel.org,
	dinan.gunawardena@...ronome.com
Subject: Re: [RFC 03/12] net: cls_bpf: limit hardware offload by
 software-only flag

On Wed, 01 Jun 2016 23:21:40 +0200, Daniel Borkmann wrote:
> On 06/01/2016 11:05 PM, Jakub Kicinski wrote:
> > On Wed, 01 Jun 2016 21:40:23 +0200, Daniel Borkmann wrote:  
> [...]
> >>> @@ -400,8 +406,11 @@ static int cls_bpf_modify_existing(struct net *net, struct tcf_proto *tp,
> >>>
> >>>    		have_exts = bpf_flags & TCA_BPF_FLAG_ACT_DIRECT;
> >>>    	}
> >>> +	if (tb[TCA_BPF_GEN_TCA_FLAGS])
> >>> +		gen_flags = nla_get_u32(tb[TCA_BPF_GEN_TCA_FLAGS]);
> >>>
> >>>    	prog->exts_integrated = have_exts;
> >>> +	prog->gen_flags = gen_flags & CLS_BPF_SUPPORTED_GEN_FLAGS;  
> >>
> >> Invalid flags should probably be rejected here with -EINVAL or something.  
> >
> > Indeed, that would be more in line with what is done for "the other"
> > flags attribute, but not so much with how flower and u32 handles
> > flags. I like the stricter approach better, though, so unless someone
> > speaks up I'll do as you suggest.  
> 
> If I see this correctly, in patch 4 you're already following up on that
> with the tc_flags_valid() check, it's probably okay to leave it as-is then.

My concern was that if someone adds a new flag for u32/flower
tc_flags_valid() will have to accept it but cls_bpf will ignore it.  So
I went with clearing things we don't support so that the user can at
least see in tc show that the flags he thrown at us did not stick...