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From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	stable@vger.kernel.org, Matthias-Christian Ott <ott@mirix.org>,
	Andrew Lunn <andrew@lunn.ch>,
	"David S. Miller" <davem@davemloft.net>,
	Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.14 07/19] net: usb: pegasus: Do not drop long Ethernet frames
Date: Mon,  3 Jan 2022 15:21:24 +0100	[thread overview]
Message-ID: <20220103142052.301084487@linuxfoundation.org> (raw)
In-Reply-To: <20220103142052.068378906@linuxfoundation.org>

From: Matthias-Christian Ott <ott@mirix.org>

[ Upstream commit ca506fca461b260ab32952b610c3d4aadc6c11fd ]

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).

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Matthias-Christian Ott <ott@mirix.org>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 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 d18a283a0ccff..408b996ff4dfb 100644
--- a/drivers/net/usb/pegasus.c
+++ b/drivers/net/usb/pegasus.c
@@ -498,11 +498,11 @@ 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++;
-- 
2.34.1




  parent reply	other threads:[~2022-01-03 14:24 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-01-03 14:21 [PATCH 4.14 00/19] 4.14.261-rc1 review Greg Kroah-Hartman
2022-01-03 14:21 ` [PATCH 4.14 01/19] HID: asus: Add depends on USB_HID to HID_ASUS Kconfig option Greg Kroah-Hartman
2022-01-03 14:21 ` [PATCH 4.14 02/19] tee: handle lookup of shm with reference count 0 Greg Kroah-Hartman
2022-01-03 14:21 ` [PATCH 4.14 03/19] platform/x86: apple-gmux: use resource_size() with res Greg Kroah-Hartman
2022-01-03 14:21 ` [PATCH 4.14 04/19] recordmcount.pl: fix typo in s390 mcount regex Greg Kroah-Hartman
2022-01-03 14:21 ` [PATCH 4.14 05/19] selinux: initialize proto variable in selinux_ip_postroute_compat() Greg Kroah-Hartman
2022-01-03 14:21 ` [PATCH 4.14 06/19] scsi: lpfc: Terminate string in lpfc_debugfs_nvmeio_trc_write() Greg Kroah-Hartman
2022-01-03 14:21 ` Greg Kroah-Hartman [this message]
2022-01-03 14:21 ` [PATCH 4.14 08/19] NFC: st21nfca: Fix memory leak in device probe and remove Greg Kroah-Hartman
2022-01-03 14:21 ` [PATCH 4.14 09/19] fsl/fman: Fix missing put_device() call in fman_port_probe Greg Kroah-Hartman
2022-01-03 14:21 ` [PATCH 4.14 10/19] nfc: uapi: use kernel size_t to fix user-space builds Greg Kroah-Hartman
2022-01-03 14:21 ` [PATCH 4.14 11/19] uapi: fix linux/nfc.h userspace compilation errors Greg Kroah-Hartman
2022-01-03 14:21 ` [PATCH 4.14 12/19] xhci: Fresco FL1100 controller should not have BROKEN_MSI quirk set Greg Kroah-Hartman
2022-01-03 14:21 ` [PATCH 4.14 13/19] usb: gadget: f_fs: Clear ffs_eventfd in ffs_data_clear Greg Kroah-Hartman
2022-01-03 14:21 ` [PATCH 4.14 14/19] binder: fix async_free_space accounting for empty parcels Greg Kroah-Hartman
2022-01-03 14:21 ` [PATCH 4.14 15/19] scsi: vmw_pvscsi: Set residual data length conditionally Greg Kroah-Hartman
2022-01-03 14:21 ` [PATCH 4.14 16/19] Input: appletouch - initialize work before device registration Greg Kroah-Hartman
2022-01-03 14:21 ` [PATCH 4.14 17/19] Input: spaceball - fix parsing of movement data packets Greg Kroah-Hartman
2022-01-03 14:21 ` [PATCH 4.14 18/19] net: fix use-after-free in tw_timer_handler Greg Kroah-Hartman
2022-01-03 14:21 ` [PATCH 4.14 19/19] sctp: use call_rcu to free endpoint Greg Kroah-Hartman
2022-01-04  1:24 ` [PATCH 4.14 00/19] 4.14.261-rc1 review Guenter Roeck
2022-01-04  9:53 ` Jon Hunter
2022-01-04 13:39 ` Naresh Kamboju
2022-01-05  2:19 ` Shuah Khan

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