Disable hardware TCP segmentation offload

gjaltemba

I do not remember ever changing the following settings. These settings seem to conflict. Who wins?

System -> Advanced -> Networking
Disable hardware TCP segmentation offload = checked

System -> Advanced -> System Tunables
net.inet.tcp.tso = 1

jimp

The tunable disables it system-wide. The checkbox disables it manually on the assigned network interfaces.

When the box is checked (default), the NICs will have it disabled. The tunable can still be "1", meaning that it's possible for a NIC to use TSO still, if it had to, but it does not force it on.

kolpinkb

I'm having trouble finding the "sysctl" values for the other two options:

Disable hardware large receive offload
&
Disable hardware checksum offload

I would like to verify because I'm using Suricata and they need to be disabled for proper functionality. I've done lots of searching and can't locate the values even after scanning through all sysctl net manually.

Any thoughts anyone?

pfBasic

@gjaltemba:

System -> Advanced -> Networking

Yeah, all three offloading functions that you need to disable are there.

kolpinkb

They don't seem to be functioning properly.

Checking TSO to disabled still results in sysctl net.inet.tcp.tso returning a 1.

Manually setting net.inet.tcp.tso = 0 in loader.conf.local still returns a 1 after reboot.

That is why I was looking for the sysctl parameters for the other disabled options.

pfBasic

Re read jimps post, they are working fine.

Don't use system tunables unless you know exactly what you are doing it are told to do so by someone who does.