After upgrading compute's kernel OR after a contrail version upgrade, sometimes vRouter continuously restarts with Exec format error.

Logs:

INFO: load vrouter kernel module, options=''

modprobe: ERROR: could not insert 'vrouter': Exec format error

Contrail vrouter continuously restarts after compute kernel upgrade, with error "modprobe: ERROR: could not insert 'vrouter': Exec format error"

This is a bug in lower contrail version and is fixed in 21.4L4.45 build and later versions.

Workaround:

Workaround is to create vrouter.ko manually. (for ubuntu deployments)

Steps:

1. docker run --rm -it --privileged --net=host -v /etc/resolv.conf:/etc/resolv.conf -v /lib/modules:/lib/modules -v /usr/src:/usr/src --entrypoint bash enterprise-hub.juniper.net/contrail-container-prod/contrail-vrouter-kernel-build-init:<tag>
2. cd vrouter_src/
3. make
4. cp vrouter.ko /usr/src/
5. exit from the container
6. modinfo vrouter | grep filename
7. backup vrouter.ko original file and then replace it with /usr/src/vrouter.ko
8. replace the existing vrouter kernel module at /lib/modules/<kernel-version>-generic/updates/dkms/vrouter.ko with the newly built kernel module at /usr/src/vrouter.ko
9. docker restart vrouter-vrouter_agent-1