From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752645AbaEVTHt (ORCPT ); Thu, 22 May 2014 15:07:49 -0400 Received: from relay1.mentorg.com ([192.94.38.131]:46847 "EHLO relay1.mentorg.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751057AbaEVTHr (ORCPT ); Thu, 22 May 2014 15:07:47 -0400 Message-ID: <537E4AFD.20304@mentor.com> Date: Thu, 22 May 2014 20:07:41 +0100 From: Jim Baxter User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.5.0 MIME-Version: 1.0 To: , , "netdev@vger.kernel.org" CC: "David S. Miller" , , Ben Hutchings , , , Subject: skbuff truesize incorrect. Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit X-Originating-IP: [137.202.0.76] X-OriginalArrivalTime: 22 May 2014 19:07:43.0788 (UTC) FILETIME=[1C35A6C0:01CF75F1] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, I was hoping you can help me with some questions. I have been investigating a network issue with bursts of network traffic over USB CDC-NCM, the issue is that the kernel is dropping packets because sk_rcvqueues_full() returns true due to skb2->truesize is always 32960 instead of SKB_TRUESIZE(skb2->len) which is about 1800. The code I am trying to fix is this code below, it is splitting a set of multiple network packets compressed into a single 16k packet into individual skb's and sending them up the network stack. skb2 = skb_clone(skb, GFP_ATOMIC); if (skb2 == NULL) goto err; if (!skb_pull(skb2, index)) { ret = -EOVERFLOW; goto err; } skb_trim(skb2, dg_len - crc_len); My questions are: 1) Which buffer size does truesize represent, is it the total buffer or just the data related to the relevant skb? 2) If truesize is for the skb it is contained within should it be updated during the call to skb_trim? 3) Why does the truesize default to 32960? Thank you for any help, Jim Baxter.