From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jesse Brandeburg Subject: Re: WARN trace - skb_warn_bad_offload - vxlan - large udp packet - udp checksum disabled Date: Wed, 6 Jan 2016 18:23:54 -0800 Message-ID: <20160106182354.000044e9@unknown> References: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: Tom Herbert , Jesse Gross , "Jiri Benc" , David Miller , netdev , jesse.brandeburg@intel.com To: "Nelson, Shannon" Return-path: Received: from mga09.intel.com ([134.134.136.24]:19511 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752291AbcAGCX6 (ORCPT ); Wed, 6 Jan 2016 21:23:58 -0500 In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: On Tue, 15 Dec 2015 01:35:27 +0000 "Nelson, Shannon" wrote: > Using a slightly modified version of udpspam (see diff below - hopefully > not mangled by corporate email servers), where I set the SO_NO_CHECK > socket option and can specify a large buffer size, I can reliably get > the following WARN trace. I have reproduced this on both ixgbe and > i40e drivers using "udpspam-no-check 6000". > > It looks to me like this is in the Tx path before we get to the actual > NIC drivers, but I may be wrong. > > > [ 1757.644324] ------------[ cut here ]------------ > [ 1757.644333] WARNING: CPU: 22 PID: 5537 at net/core/dev.c:2423 skb_warn_bad_offload+0x104/0x111() Was anyone able to take a look at this? There is a pretty clear reproducer in the original mail. I know SO_NO_CHECK is a lightly used option, but it does exist and we found a userspace program that tries to use it.