On Tue, Aug 10, 2021 at 01:15:32PM +0300, Nikolay Aleksandrov wrote: > On 10/08/2021 13:09, Vladimir Oltean wrote: > > On Tue, Aug 10, 2021 at 09:46:34AM +0300, Ido Schimmel wrote: > >> On Mon, Aug 09, 2021 at 04:05:22PM +0000, Vladimir Oltean wrote: > >>> On Mon, Aug 09, 2021 at 03:16:40PM +0300, Ido Schimmel wrote: > >>>> I have at least once selftest where I forgot the 'static' keyword: > >>>> > >>>> bridge fdb add de:ad:be:ef:13:37 dev $swp1 master extern_learn vlan 1 > >>>> > >>>> This patch breaks the test when run against both the kernel and hardware > >>>> data paths. I don't mind patching these tests, but we might get more > >>>> reports in the future. > >>> > >>> Is it the 'static' keyword that you forgot, or 'dynamic'? The > >>> tools/testing/selftests/net/forwarding/bridge_vlan_aware.sh selftest > >>> looks to me like it's testing the behavior of an FDB entry which should > >>> roam, and which without the extern_learn flag would be ageable. > >> > >> static - no aging, no roaming > >> dynamic - aging, roaming > >> extern_learn - no aging, roaming > >> > >> So these combinations do not make any sense and the kernel will ignore > >> static/dynamic when extern_learn is specified. It's needed to work > >> around iproute2 behavior of "assume permanent" > > > > Since NTF_EXT_LEARNED is part of ndm->ndm_flags and NUD_REACHABLE/NUD_NOARP > > are part of ndm->ndm_state, it is not at all clear to me that 'extern_learn' > > belongs to the same class of bridge neighbor attributes as 'static'/'dynamic', > > and that it is invalid to have the full degree of freedom. If it isn't, > > shouldn't the kernel validate that, instead of just ignoring the ndm->ndm_state? > > If it's too late to validate, shouldn't we at least document somewhere > > that the ndm_state is ignored in the presence of ndm_flags & NTF_EXT_LEARNED? > > It is user API after all, easter eggs like this aren't very enjoyable. > > > > It's too late unfortunately, ignoring other flags in that case has been the standard > behaviour for a long time (it has never made sense to specify flags for extern_learn > entries). I'll send a separate patch that adds a comment to document it or if you have > another thing in mind feel free to send a patch. No, I don't have anything else in mind, but since the topic is the same as the "net: bridge: fix flags interpretation for extern learn fdb entries" patch you already sent, you could as well just send a v2 for that and add an extra phrase in a comment somewhere near a NTF_EXT_LEARNED uapi definition, or perhaps extend this comment right here: /* NUD_NOARP & NUD_PERMANENT are pseudostates, they never change and make no address resolution or NUD. NUD_PERMANENT also cannot be deleted by garbage collectors. */
