SMSC9514 eth0: hw csum failure - NOT Pi3b+

[6by9]

Raised to avoid confusion with #2659.

Report from @ricardosalveti of seeing eth0: hw csum failure messages from the kernel on 3B (ie SMSC9514) with 4.18 kernel.

lso started to see this issue lately, but I'm using the 3 model B, which uses smsc95xx.
This is with the latest 4.18 kernel tree (rpi patches + stable).

#2659 (comment)
#2659 (comment)
are the relevant comments.

New issue raised to avoid confusing lan78xx issues vs smsc95xx issues.

[6by9]

Looking at my local network, the service generating this issue was iceccd (running on ubuntu 16.04).
After disabling iceccd on the ubuntu machine I'm not not getting the hw csum errors anymore.
Logs from tcpdump:

21:12:03.771275 IP (tos 0x0, ttl 64, id 57986, offset 0, flags [DF], proto UDP (17), length 29)
    192.168.1.44.58909 > 192.168.1.255.8765: UDP, length 1
E.....@.@......,......"=.       S. ............../..

Unclear if this is really an issue at the sender or if an issue at the receiver side.

A UDP packet of length 29 would fall into the category of the UDP checksum being in the last 4 words of the packet, however the patch that had been posted was for checksum offload failure on transmit, not receive.
I'll see if I can find the relevant reference docs for SMSC9514 as to the details on that offload issue.

[6by9]

Closing as this does seem to be a common issue in the main IP core and not a driver related thing.

There is a check in the SMSC9514 driver that s/w checks buffers under 45 bytes, so I'd expect this to be trapped there.