CM-ITC, pch_can/c_can_pci, sendto() returning ENOBUFS

[Jacob Kroon <jacob.kroon@gmail.com>]

Hi,

I am using a CM-ITC board 
(https://www.compulab.com/products/computer-on-modules/cm-itc/) with an 
application that uses the CAN interface. After a while of successfully 
sending packets, sendto() starts returning ENOBUFS. I wait a whole 
second and try to send, several retries, but I get ENOBUFS every time. 
I'm using kernel 5.15.59, and I've tried both the pch_can and c_can_pci 
driver, but both show the same error.

In the console I see several of:
can0: can_put_echo_skb: BUG! echo_skb 0 is occupied

I've also tried to increase the txqueuelen to 1000, as suggested here

https://stackoverflow.com/questions/40424433/write-no-buffer-space-available-socket-can-linux-can

but I think that if I increase the queuelen the threads just block 
forever in sendto() (sockets are opened in blocking mode)

If I bring down the interface with

ifconfig can0 down
ifconfig can0 up

the transmitting does get unblocked.

Is there anything I can do to debug this further ? Any other ideas ?

Thanks,
Jacob