What's the error: Khelp module "ertt" unload ...

[elimelech007]

When the system shuts down, it writes the following error:

Khelp module "ertt" unload until its refcount drops from 1 to 0

 

[PMc]

That seems normal.

This is some module that allows to plug in routines into the tcp handling, in order to change anti-congestion schemes and such (and probably other things, but that is what it is commonly used for).
I doubt that the tcp stack is fully unraveled at shutdown, so probably this thing does not reach a state where it could cleanly let go.

 

[Mjölnir]

It would be interesting to know which parts of the kernel keep working when the system is shut down. IIRC the machine replies to ICMP packets and goes back online on a WOL?

 

[PMc]

It would be interesting to know which parts of the kernel keep working when the system is shut down. IIRC the machine replies to ICMP packets and goes back online on a WOL?

I'm not sure about the WOL. What I can see is undeliverable packets being reported until very late (and then I don't know if the reporting or rather the ip is shut down). I think there is just no point in removing the ip-stack, and probably nobody ever considered how it could be done.
Then these khelp/ertt things, they do congestion control in a stateful fashion, so as they keep states of things, they will always have a refcount as long as packets can flow.

 

[Cath O'Deray]

FreeBSD bug 271677 – ertt module unload error at shutdown (Closed FIXED).

I encountered the today after updating from 14.0-RELEASE-p2 to p6/p7.