From patchwork Fri Oct 12 08:34:01 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ben Dooks X-Patchwork-Id: 10638035 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 9AB961869 for ; Fri, 12 Oct 2018 08:34:28 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 874A92B3D7 for ; Fri, 12 Oct 2018 08:34:28 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 78F932B3DF; Fri, 12 Oct 2018 08:34:28 +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 22E4E2B3D7 for ; Fri, 12 Oct 2018 08:34:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728045AbeJLQFf (ORCPT ); Fri, 12 Oct 2018 12:05:35 -0400 Received: from imap1.codethink.co.uk ([176.9.8.82]:48207 "EHLO imap1.codethink.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727808AbeJLQFd (ORCPT ); Fri, 12 Oct 2018 12:05:33 -0400 Received: from [148.252.241.226] (helo=rainbowdash) by imap1.codethink.co.uk with esmtpsa (Exim 4.84_2 #1 (Debian)) id 1gAstc-0005Ta-Mg; Fri, 12 Oct 2018 09:34:08 +0100 Received: from ben by rainbowdash with local (Exim 4.91) (envelope-from ) id 1gAstc-00052e-6s; Fri, 12 Oct 2018 09:34:08 +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 4/8] usbnet: smsc95xx: check for csum being in last four bytes Date: Fri, 12 Oct 2018 09:34:01 +0100 Message-Id: <20181012083405.19246-5-ben.dooks@codethink.co.uk> X-Mailer: git-send-email 2.19.1 In-Reply-To: <20181012083405.19246-1-ben.dooks@codethink.co.uk> References: <20181012083405.19246-1-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 --- Fixes for v2: - Fix spelling of check at Sergei's suggestion - Move skb->len check into smsc95xx_can_tx_checksum() - Change name of smsc95xx_can_checksum to explicitly say it is tx-csum --- drivers/net/usb/smsc95xx.c | 19 ++++++++++++++++++- 1 file changed, 18 insertions(+), 1 deletion(-) diff --git a/drivers/net/usb/smsc95xx.c b/drivers/net/usb/smsc95xx.c index 0c083d1b7f34..19e71fe15f6c 100644 --- a/drivers/net/usb/smsc95xx.c +++ b/drivers/net/usb/smsc95xx.c @@ -2000,6 +2000,23 @@ static u32 smsc95xx_calc_csum_preamble(struct sk_buff *skb) return (high_16 << 16) | low_16; } +/* The TX 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 check for csum being in the last four bytes + * of the packet should be ok for now. +*/ +static bool smsc95xx_can_tx_checksum(struct sk_buff *skb) +{ + unsigned int len = skb->len - skb_checksum_start_offset(skb); + + if (skb->len <= 45) + return false; + return skb->csum_offset < (len - (4 + 1)); +} + static struct sk_buff *smsc95xx_tx_fixup(struct usbnet *dev, struct sk_buff *skb, gfp_t flags) { @@ -2024,7 +2041,7 @@ static struct sk_buff *smsc95xx_tx_fixup(struct usbnet *dev, tx_cmd_a = tx_cmd_b | TX_CMD_A_FIRST_SEG_ | TX_CMD_A_LAST_SEG_; if (csum) { - if (skb->len <= 45) { + if (!smsc95xx_can_tx_checksum(skb)) { /* workaround - hardware tx checksum does not work * properly with extremely small packets */ long csstart = skb_checksum_start_offset(skb);