From mboxrd@z Thu Jan 1 00:00:00 1970 From: Johannes Berg Subject: Re: [PATCH v3 net-next RFC] Generic XDP Date: Thu, 13 Apr 2017 08:10:56 +0200 Message-ID: <1492063856.19193.4.camel@sipsolutions.net> References: <20170412.145415.1441440342830198148.davem@davemloft.net> <20170413042036.GA46229@ast-mbp.thefacebook.com> (sfid-20170413_062046_605774_F92D4B7B) Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, xdp-newbies@vger.kernel.org To: Alexei Starovoitov , David Miller Return-path: Received: from s3.sipsolutions.net ([5.9.151.49]:50150 "EHLO sipsolutions.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755978AbdDMGLA (ORCPT ); Thu, 13 Apr 2017 02:11:00 -0400 In-Reply-To: <20170413042036.GA46229@ast-mbp.thefacebook.com> (sfid-20170413_062046_605774_F92D4B7B) Sender: netdev-owner@vger.kernel.org List-ID: On Wed, 2017-04-12 at 21:20 -0700, Alexei Starovoitov wrote: > > + if (skb_linearize(skb)) > > + goto do_drop; > > when we discussed supporting jumbo frames in XDP, the idea > was that the program would need to look at first 3+k bytes only > and the rest of the packet will be in non-contiguous pages. > If we do that, it means that XDP program would have to assume > that the packet is more than [data, data_end] and this range > only covers linear part. > If that's the future, we don't need to linearize the skb here > and can let the program access headlen only. I'm not sure how you think that would work - at least with our (wifi) driver, the headlen should be maybe ETH_HLEN or so at this point. We'd let the program know that it can only look at so much, but then the program can't do anything at all with those frames. At some point then we go back to bpf_skb_load_bytes() being necessary in one form or another, no? johannes