On Mon, Aug 18, 2025 at 12:07:18PM +0200, Christophe Leroy wrote: > [+ Netfilter lists] > > Hi Phil > > Le 18/08/2025 à 11:34, Phil Sutter a écrit : > > [Vous ne recevez pas souvent de courriers de p...@nwl.cc. Découvrez > > pourquoi ceci est important à https://aka.ms/LearnAboutSenderIdentification > > ] > > > > Hi Christophe, > > > > On Sun, Aug 17, 2025 at 05:54:27PM +0200, Christophe Leroy wrote: > >> Le 17/08/2025 à 01:33, Phil Sutter a écrit : > >>> [Vous ne recevez pas souvent de courriers de p...@nwl.cc. D?couvrez > >>> pourquoi ceci est important ? > >>> https://aka.ms/LearnAboutSenderIdentification ] > >>> > >>> Hi, > >>> > >>> I admittedly didn't fully analyze the cause, but on my system a call to: > >>> > >>> # insmod /lib/module/$(uname -r)/kernel/net/netfilter/nf_conntrack_ftp.ko > >>> > >>> fails with -EEXIST (due to a previous call to 'nfct add helper ftp inet > >>> tcp'). A call to: > >>> > >>> # modprobe nf_conntrack_ftp > >>> > >>> though returns 0 even though module loading fails. Is there a bug in > >>> modprobe error status handling? > >>> > >> > >> Read the man page : > >> https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Flinux.die.net%2Fman%2F8%2Fmodprobe&data=05%7C02%7Cchristophe.leroy%40csgroup.eu%7C34b49eb3d0544fc683e608ddde3a75b2%7C8b87af7d86474dc78df45f69a2011bb5%7C0%7C0%7C638911064858807750%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=%2F70LV37Zb%2FNeiBV59y9rvkLGh0xsqga08Nl3c5%2BVU5I%3D&reserved=0 > >> > >> In the man page I see: > >> > >> Normally, modprobe will succeed (and do nothing) if told to > >> insert a module which is already present or to remove a module which > >> isn't present. > > > > This is not a case of already inserted module, it is not loaded before > > the call to modprobe. It is the module_init callback > > nf_conntrack_ftp_init() which returns -EEXIST it received from > > nf_conntrack_helpers_register(). > > > > Can't user space distinguish the two causes of -EEXIST? Or in other > > words, is use of -EEXIST in module_init callbacks problematic? > > So if I understand correctly the load fails because it is in conflict > with another module ?
Yes, it tries to signal that there is already a conntrack helper for FTP. It is a stub redirecting to an implementation in user space, but that's just details. > Then I think the error returned by nf_conntrack_helpers_register() > shouldn't be EEXIST but probably EBUSY. Sounds good! We could at least adjust the module_init callback return code from EEXIST to EBUSY so the change has minimal impact. Thanks for your help, Christophe! Cheers, Phil
