From patchwork Sun Dec 26 13:29:30 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Matthias-Christian Ott X-Patchwork-Id: 528509 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id CC945C433FE for ; Sun, 26 Dec 2021 13:29:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233573AbhLZN3n (ORCPT ); Sun, 26 Dec 2021 08:29:43 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35066 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232345AbhLZN3m (ORCPT ); Sun, 26 Dec 2021 08:29:42 -0500 X-Greylist: delayed 254 seconds by postgrey-1.37 at lindbergh.monkeyblade.net; Sun, 26 Dec 2021 05:29:42 PST Received: from mirix.in-vpn.de (mirix.in-vpn.de [IPv6:2001:67c:1407:a0::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5FE35C06173E; Sun, 26 Dec 2021 05:29:42 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=mirix.org; s=43974b1a7d21b2cf; h=Content-Transfer-Encoding:MIME-Version:Message-Id:Date: Subject:Cc:To:From:Sender:Reply-To:Content-Type:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:In-Reply-To:References:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; bh=htuYveoisK6rglAz8iXUOUxqkcJZuLcbQvz/xoYi8kM=; b=P/A6jJjv0gkVDD+z5y10YSfPaS 1SAOT61mHF8RUIQlVxE+TdZNnssy2KBu9fHdxmUhjz9/lfNihojrzHjreU+GsNM6DoW8Pat/RD7ph melBp0FWSfdaw2cly/OU8eOTTWq8Q7agFv9RUCpZ+fl8HAwdFjuROnMPxGRLUAdySJhGCDCvRb1Rw WPyYXL/lyN+i/PwwD6osMuutYwpHv8DGZnU50nUos1NoxaNCa9+ypItfUmLWogg14yD5wAA1Qfrr4 25ftZCBqrRR0XIZXzw/R5RtmvZuez16SCW/n432lggFC6sMPJBnXEl6jbw6/3DHCoP+Ak+rEBGNyB TLEzMv7Q==; Received: from [::1] (helo=localhost.localdomain) by mirix.in-vpn.de with esmtpsa (TLS1.3:ECDHE_X25519__RSA_PSS_RSAE_SHA256__AES_256_GCM:256) (Exim) id 1n1Tal-0005oZ-OR; Sun, 26 Dec 2021 13:29:39 +0000 From: Matthias-Christian Ott To: Petko Manolov Cc: linux-usb@vger.kernel.org, netdev@vger.kernel.org, Matthias-Christian Ott Subject: [PATCH] net: usb: pegasus: Do not drop long Ethernet frames Date: Sun, 26 Dec 2021 14:29:30 +0100 Message-Id: <20211226132930.7220-1-ott@mirix.org> X-Mailer: git-send-email 2.30.2 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org The D-Link DSB-650TX (2001:4002) is unable to receive Ethernet frames that are longer than 1518 octets, for example, Ethernet frames that contain 802.1Q VLAN tags. The frames are sent to the pegasus driver via USB but the driver discards them because they have the Long_pkt field set to 1 in the received status report. The function read_bulk_callback of the pegasus driver treats such received "packets" (in the terminology of the hardware) as errors but the field simply does just indicate that the Ethernet frame (MAC destination to FCS) is longer than 1518 octets. It seems that in the 1990s there was a distinction between "giant" (> 1518) and "runt" (< 64) frames and the hardware includes flags to indicate this distinction. It seems that the purpose of the distinction "giant" frames was to not allow infinitely long frames due to transmission errors and to allow hardware to have an upper limit of the frame size. However, the hardware already has such limit with its 2048 octet receive buffer and, therefore, Long_pkt is merely a convention and should not be treated as a receive error. Actually, the hardware is even able to receive Ethernet frames with 2048 octets which exceeds the claimed limit frame size limit of the driver of 1536 octets (PEGASUS_MTU). Signed-off-by: Matthias-Christian Ott --- drivers/net/usb/pegasus.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/net/usb/pegasus.c b/drivers/net/usb/pegasus.c index 140d11ae6688..2582daf23015 100644 --- a/drivers/net/usb/pegasus.c +++ b/drivers/net/usb/pegasus.c @@ -499,11 +499,11 @@ static void read_bulk_callback(struct urb *urb) goto goon; rx_status = buf[count - 2]; - if (rx_status & 0x1e) { + if (rx_status & 0x1c) { netif_dbg(pegasus, rx_err, net, "RX packet error %x\n", rx_status); net->stats.rx_errors++; - if (rx_status & 0x06) /* long or runt */ + if (rx_status & 0x04) /* runt */ net->stats.rx_length_errors++; if (rx_status & 0x08) net->stats.rx_crc_errors++;