netfilter: conntrack: helper: Replace -EEXIST by -EBUSY

The helper registration return value is passed-through by module_init
callbacks which modprobe confuses with the harmless -EEXIST returned
when trying to load an already loaded module.

Make sure modprobe fails so users notice their helper has not been
registered and won't work.

Suggested-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Fixes: 12f7a50533 ("netfilter: add user-space connection tracking helper infrastructure")
Signed-off-by: Phil Sutter <phil@nwl.cc>
Signed-off-by: Florian Westphal <fw@strlen.de>
This commit is contained in:
Phil Sutter 2025-08-18 13:22:20 +02:00 • committed by Florian Westphal
commit 54416fd767