From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexander Duyck Subject: Re: [Intel-wired-lan] [Patch net] igb: pass the correct maxlen for eth_get_headlen() Date: Thu, 23 Apr 2015 12:45:21 -0700 Message-ID: <55394BD1.5040006@redhat.com> References: <1429724760-10075-1-git-send-email-xiyou.wangcong@gmail.com> <5537F9F1.1080008@gmail.com> <553802DA.4050709@gmail.com> <553815DF.4000109@gmail.com> <553821E4.5010901@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Cc: Cong Wang , intel-wired-lan@lists.osuosl.org, netdev To: Cong Wang , Alexander Duyck Return-path: Received: from mx1.redhat.com ([209.132.183.28]:56451 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1030357AbbDWTpW (ORCPT ); Thu, 23 Apr 2015 15:45:22 -0400 In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: On 04/23/2015 12:30 PM, Cong Wang wrote: > (Off-topic...) > > On Wed, Apr 22, 2015 at 4:23 PM, Cong Wang wrote: >> The code looks correct to me now, except it is suspicious skb->len >> is not updated after skb_copy_to_linear_data() while skb->tail is >> advanced already. I need to think more before submitting a patch. > I feel like we need the following patch, maybe skb->len is updated somewhere > else by "skb->tail - skb->head", otherwise we are screwed? Maybe in skb_add_rx_frag? You might take a look at it. > > diff --git a/drivers/net/ethernet/intel/igb/igb_main.c > b/drivers/net/ethernet/intel/igb/igb_main.c > index a0a9b1f..66e6fb6 100644 > --- a/drivers/net/ethernet/intel/igb/igb_main.c > +++ b/drivers/net/ethernet/intel/igb/igb_main.c > @@ -6843,7 +6843,6 @@ static void igb_pull_tail(struct igb_ring *rx_ring, > skb_frag_size_sub(frag, IGB_TS_HDR_LEN); > frag->page_offset += IGB_TS_HDR_LEN; > skb->data_len -= IGB_TS_HDR_LEN; > - skb->len -= IGB_TS_HDR_LEN; > > /* move va to start of packet data */ > va += IGB_TS_HDR_LEN; > @@ -6856,12 +6855,12 @@ static void igb_pull_tail(struct igb_ring *rx_ring, > > /* align pull length to size of long to optimize memcpy performance */ > skb_copy_to_linear_data(skb, va, ALIGN(pull_len, sizeof(long))); > + __skb_put(skb, pull_len); > > /* update all of the pointers */ > skb_frag_size_sub(frag, pull_len); > frag->page_offset += pull_len; > skb->data_len -= pull_len; > - skb->tail += pull_len; > } > > /** Seriously? Are you even reading the code? The fragment is already a part of the skb, as such it is already included in skb->len. By re-adding the header you are adding bytes that aren't there. All we were doing is moving data from a fragment to the linear portion. No offense but your starting to waste my time with these silly patch ideas. The patches I submitted to intel-wired-lan fix the issue that you found, and there aren't any new issues that it creates so the issue is resolved. And like I said if you need to fix this in stable just subtract IGB_TS_HDR_LEN from the header length scanned in eth_get_headlen and it will resolve the issue you reported and that way we can fix the issue and avoid pulling a fragment down to size 0. - Alex