| Message ID | 20211226132930.7220-1-ott@mirix.org |
|---|---|
| State | New |
| Headers | show |
| Series | net: usb: pegasus: Do not drop long Ethernet frames | expand |
On 26/12/2021 17:31, Andrew Lunn wrote: >>> I've nothing against this patch, but if you are working on the driver, >>> it would be nice to replace these hex numbers with #defines using BIT, >>> or FIELD. It will make the code more readable. >> >> Replacing the constants with macros is on my list of things that I want >> to do. In this case, I did not do it because I wanted to a have small >> patch that gets easily accepted and allows me to figure out the current >> process to submit patches after years of inactivity. > > Agreed, keep fixes simple. > > A few other hints. If you consider this a fix which should be back > ported, please add a Fixes: tag, where the issue started. This can be > back as far as the first commit for the driver. Fixes should also be > sent to the net tree, not net-next. See the netdev FAQ about the two > different trees. I made a v2 of the patch and also added the prefix flag to indicate that the patch is destined for the "next" tree. There is still something that can be improved a about it, please let me know. Otherwise, I will also resend the other patch that I sent for the driver to indicate that it is destined for the "next" tree. Kind regards, Matthias-Christian Ott
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++;
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 <ott@mirix.org> --- drivers/net/usb/pegasus.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)