netdev - Re: [PATCH net-next v2 11/12] bnxt

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Thu, 2 Feb 2017 15:57:54 -0800
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Jakub Kicinski <kubakici@...pl>
Cc:     Michael Chan <michael.chan@...adcom.com>, davem@...emloft.net,
        netdev@...r.kernel.org, Martin KaFai Lau <kafai@...com>
Subject: Re: [PATCH net-next v2 11/12] bnxt_en: Add basic XDP support.

On Thu, Feb 02, 2017 at 03:08:27PM -0800, Jakub Kicinski wrote:
> > +	rcu_read_lock();
> > +	act = bpf_prog_run_xdp(xdp_prog, &xdp);
> > +	rcu_read_unlock();
> > +
> > +	if (orig_data != xdp.data) {
> > +		offset = xdp.data - xdp.data_hard_start;
> > +		len = xdp.data_end - xdp.data;
> 
> If BPF changed the start of the packet and returned XDP_PASS you should
> make sure stack will see the modified packet.  I.e. with adjusted
> offset and len.

that is correct.
skb passed to the stack should see new packet start and len.
Though today it's only useful with tc+cls_bpf on top that can
take advantage of it. Certainly more work is needed in this area
for xdp overall. I don't think we should mix that discussion
with this patch set.