Re: [conntrack-tools PATCH] nfct: helper: Extend error message for EEXIST

[Phil Sutter <phil@nwl.cc>]

On Thu, Aug 28, 2025 at 12:34:15AM +0200, Pablo Neira Ayuso wrote:
> On Mon, Aug 18, 2025 at 11:47:08AM +0800, Yi Chen wrote:
> > This patch adds a hint when:
> > 
> > # modprobe nf_conntrack_ftp
> > # nfct helper del ftp inet tcp
> > # nfct helper add ftp inet tcp
> > *nfct v1.4.8: netlink error: File exists*
> > 
> > or other type of helper.
> 
> This patch changes EEXIST by EBUSY:
> 
>   https://patchwork.ozlabs.org/project/netfilter-devel/patch/20250818112220.26641-1-phil@nwl.cc/
> 
> This userspace patch is not very useful after this.

Oh! I missed that nfnl_cthelper_create() also just passes through the
return code from nf_conntrack_helper_register().

> So maybe a follow up fix to retain EEXIST for nfnetlink_cthelper in
> the kernel is needed?
> 
> I mean, return EEXIST in nfnetlink_cthelper but EBUSY in case of
> insmod, ie. add a bool insmod flag to the helper register/unregister
> functions to return EBUSY for insmod and EEXIST for
> nfnetlink_cthelper.

Do we need to retain the old return code? I would just update the patch
to print the message for EBUSY instead of EEXIST.

Cheers, Phil