[CentOS] bad udp cksum

Fri Aug 10 07:34:24 UTC 2018
Simon Matter <simon.matter at invoca.ch>

> Hi,
> Recently I'm noticing an interesting issue.
> My CentOS servers are trying to send logs to a logging server via 514/udp,
> however I'm not receiving anything.
> I did the following on CentOS
> *tcpdump -vvv -nn udp -i esn160 port 514*
> In another session on the same server:
> *nc syslog-server -u 514*
> tcpdump started to show me messages like:
> *[bad udp cksum 0x3ce9 -> 0xb0f5!] SYSLOG, length: 172*
> After some research I disabled TCO (ethtool -K ens160 tx off rx off), now
> tcpdump shows:
> *[udp sum ok] [|syslog]*
> And I'm also receiving the logs. Yay!
> I have the same issue on multiple servers with CentOS versions 7.3.1611,
> 7.4.1708 & 7.5.1804. I'm having the issue no matter if it is a physical or
> virtual server (they also use different hardware and NIC's)
> Of course I could run ethtool every time a server starts but I think there
> should be a better solution. Also I enjoy having TCO giving some rest to
> the CPUs.
> Did anyone find a solution for this?

You can configure the ETHTOOL_OPTS option in the ifcfg files to
automatically assign settings on startup.