Re: [net-next,v15,06/12] selftests/vsock: prepare vm management helpers for namespaces

[Jakub Kicinski <kuba@kernel.org>]

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---
selftests/vsock: prepare vm management helpers for namespaces

This commit adds namespace support to VM management helpers and wrapper
functions, requiring callers to explicitly pass "init_ns" for the init
namespace. The commit message states "No functional changes for existing
tests. All have been updated to pass 'init_ns' explicitly."

> diff --git a/tools/testing/selftests/vsock/vmtest.sh b/tools/testing/selftests/vsock/vmtest.sh
> index c2bdc293b94c..1d03acb62347 100755
> --- a/tools/testing/selftests/vsock/vmtest.sh
> +++ b/tools/testing/selftests/vsock/vmtest.sh
> @@ -135,7 +135,18 @@ del_namespaces() {
>  }
>
>  vm_ssh() {
> -	ssh -q -o UserKnownHostsFile=/dev/null -p ${SSH_HOST_PORT} localhost "$@"
> +	local ns_exec
> +
> +	if [[ "${1}" == init_ns ]]; then
> +		ns_exec=""
> +	else
> +		ns_exec="ip netns exec ${1}"
> +	fi
> +
> +	shift
> +
> +	${ns_exec} ssh -q -o UserKnownHostsFile=/dev/null -p "${SSH_HOST_PORT}" localhost "$@"
> +
>  	return $?
>  }

The vm_ssh() function now expects a namespace as its first argument, but
run_shared_vm_test() still calls vm_ssh without this parameter:

    vm_oops_cnt_before=$(vm_ssh -- dmesg | grep -c -i 'Oops')
    vm_warn_cnt_before=$(vm_ssh -- dmesg --level=warn | grep -c -i 'vsock')
    vm_oops_cnt_after=$(vm_ssh -- dmesg | grep -i 'Oops' | wc -l)
    vm_warn_cnt_after=$(vm_ssh -- dmesg --level=warn | grep -c -i 'vsock')

When called as "vm_ssh -- dmesg", the "--" is interpreted as the namespace
argument. Since "--" does not equal "init_ns", the function sets
ns_exec="ip netns exec --" which is invalid. The shift then consumes "--"
and the command becomes "ip netns exec -- ssh ... dmesg" which will fail.

Interestingly, the v9 version of this patch on lore correctly updated these
calls to pass "init_ns", but this change appears to have been lost between
v9 and v15. The fix for this regression is present later in the series in
commit 3ae984505e00 ("selftests/vsock: add vm_dmesg_{warn,oops}_count()
helpers").

[ ... ]