From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pl0-f67.google.com ([209.85.160.67]:41517 "EHLO mail-pl0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932328AbeCMX1Q (ORCPT ); Tue, 13 Mar 2018 19:27:16 -0400 Received: by mail-pl0-f67.google.com with SMTP id d9-v6so703757plo.8 for ; Tue, 13 Mar 2018 16:27:16 -0700 (PDT) Subject: Re: BUG_ON triggered in skb_segment To: Alexei Starovoitov , Eric Dumazet , Yonghong Song , Steffen Klassert Cc: Daniel Borkmann , netdev , Martin Lau , saeedm@mellanox.com, diptanu@fb.com References: <9265b93f-253d-6b8c-f2b8-4b54eff1835c@fb.com> <875f59f2-d1ec-c47c-cdd7-2ce4985c5143@gmail.com> <20180313084444.5hyu7kteswh6v5li@gauss3.secunet.de> <06bef27e-60f6-0fb4-e926-cb7ff3666a3c@fb.com> <4c0d599e-95a3-be7d-bfeb-e51a16648cc8@gmail.com> From: Eric Dumazet Message-ID: <39a56b2c-6ea8-02f7-9e9c-968b16b9aa7a@gmail.com> Date: Tue, 13 Mar 2018 16:27:03 -0700 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: netdev-owner@vger.kernel.org List-ID: On 03/13/2018 04:09 PM, Alexei Starovoitov wrote: > we have bpf_skb_proto_6_to_4() that was used by cilium for long time. > It's not clear why it's not crashing there, but we cannot just > reject changing proto in bpf programs now. > We have to fix whatever needs to be fixed in skb_segment > (if bug is there) or fix whatever necessary on mlx5 side. > In bpf helper we mark it as SKB_GSO_DODGY just like packets coming > through virtio would do, so if skb_segment() needs to do something > special with skb the SKB_GSO_DODGY flag is already there. 'Fixing' skb_segment(), I did that a long time ago and Herbert Xu was not happy with the fix and provided something else. GSO_DODGY has nothing to do with the problem really. Changing gso_size is breaking GRO since it ends up changing the number of segments on the wire. TCP is not going to be happy, so you'll also have to fix TCP eventually.