From patchwork Tue Oct 2 09:26:44 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ben Dooks X-Patchwork-Id: 10623309 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id AECCF14BD for ; Tue, 2 Oct 2018 09:27:16 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 9ACDD287C6 for ; Tue, 2 Oct 2018 09:27:16 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 8ECF6287CE; Tue, 2 Oct 2018 09:27:16 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 3B237287C6 for ; Tue, 2 Oct 2018 09:27:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727530AbeJBQJb (ORCPT ); Tue, 2 Oct 2018 12:09:31 -0400 Received: from imap1.codethink.co.uk ([176.9.8.82]:50409 "EHLO imap1.codethink.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727160AbeJBQJM (ORCPT ); Tue, 2 Oct 2018 12:09:12 -0400 Received: from [148.252.241.226] (helo=rainbowdash) by imap1.codethink.co.uk with esmtpsa (Exim 4.84_2 #1 (Debian)) id 1g7Gx6-0002zb-Di; Tue, 02 Oct 2018 10:26:48 +0100 Received: from ben by rainbowdash with local (Exim 4.91) (envelope-from ) id 1g7Gx6-0000Jh-5c; Tue, 02 Oct 2018 10:26:48 +0100 From: Ben Dooks To: netdev@vger.kernel.org Cc: oneukum@suse.com, davem@davemloft.net, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kernel@lists.codethink.co.uk, Ben Dooks Subject: [PATCH 3/4] usbnet: smsc95xx: check for csum being in last four bytes Date: Tue, 2 Oct 2018 10:26:44 +0100 Message-Id: <20181002092645.1115-4-ben.dooks@codethink.co.uk> X-Mailer: git-send-email 2.19.0 In-Reply-To: <20181002092645.1115-1-ben.dooks@codethink.co.uk> References: <20181002092645.1115-1-ben.dooks@codethink.co.uk> MIME-Version: 1.0 Sender: linux-usb-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP The manual states that the checksum cannot lie in the last DWORD of the transmission, so add a basic check for this and fall back to software checksumming the packet. This only seems to trigger for ACK packets with no options or data to return to the other end, and the use of the tx-alignment option makes it more likely to happen. Signed-off-by: Ben Dooks --- drivers/net/usb/smsc95xx.c | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-) diff --git a/drivers/net/usb/smsc95xx.c b/drivers/net/usb/smsc95xx.c index d244357bf1ad..46385a4b8b98 100644 --- a/drivers/net/usb/smsc95xx.c +++ b/drivers/net/usb/smsc95xx.c @@ -2003,6 +2003,20 @@ static u32 smsc95xx_calc_csum_preamble(struct sk_buff *skb) return (high_16 << 16) | low_16; } +/* The CSUM won't work if the checksum lies in the last 4 bytes of the + * transmission. This is fairly unlikely, only seems to trigger with some + * short TCP ACK packets sent. + * + * Note, this calculation should probably check for the alignment of the + * data as well, but a straight chec for csum being in the last four bytes + * of the packet should be ok for now. +*/ +static bool smsc95xx_can_checksum(struct sk_buff *skb) +{ + unsigned int len = skb->len - skb_checksum_start_offset(skb); + return skb->csum_offset < (len - (4 + 1)); +} + static struct sk_buff *smsc95xx_tx_fixup(struct usbnet *dev, struct sk_buff *skb, gfp_t flags) { @@ -2031,7 +2045,8 @@ static struct sk_buff *smsc95xx_tx_fixup(struct usbnet *dev, } if (csum) { - if (skb->len <= 45) { + /* note, csum does not work if csum in last DWORD of packet */ + if (skb->len <= 45 || !smsc95xx_can_checksum(skb)) { /* workaround - hardware tx checksum does not work * properly with extremely small packets */ long csstart = skb_checksum_start_offset(skb);