From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nxp.com; s=selector2; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=NGtLr/xfPNKdQQi8cLqJEqaFspc5r8oK4Wf/m2YcrSs=; b=e/+Yej2JBJhFXCj1lt1W23NhlW5Gjs7ZnubKiV3TX38M8EVVKYFuqRpKlEaFiel8ITTh9kDuV3zHdukJJrv8aSN6WrFtiyABG4pboYxT/YhIcWBRKTPFkoKqjUpItceUhYC0g+0zibXEue14MUtEOTJFcIDcKwCsIVU/mRqe9SU= From: Vladimir Oltean Date: Tue, 10 Aug 2021 10:38:41 +0000 Message-ID: <20210810103840.oequsjeg5be2jkkz@skbuf> References: <20210801231730.7493-1-vladimir.oltean@nxp.com> <20210809160521.audhnv7o2tugwtmp@skbuf> <20210810100928.uk7dfstrnts2may4@skbuf> In-Reply-To: Content-Language: en-US Content-Type: text/plain; charset="us-ascii" Content-ID: Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Subject: Re: [Bridge] [PATCH net] net: bridge: validate the NUD_PERMANENT bit when adding an extern_learn FDB entry List-Id: Linux Ethernet Bridging List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Nikolay Aleksandrov Cc: "syzbot+9ba1174359adba5a5b7c@syzkaller.appspotmail.com" , Jiri Pirko , "netdev@vger.kernel.org" , "bridge@lists.linux-foundation.org" , syzkaller-bugs , Ido Schimmel , Roopa Prabhu , Jakub Kicinski , "David S. Miller" 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 hard= ware > >>>> 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 shou= ld > >>> 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" > >=20 > > Since NTF_EXT_LEARNED is part of ndm->ndm_flags and NUD_REACHABLE/NUD_N= OARP > > are part of ndm->ndm_state, it is not at all clear to me that 'extern_l= earn' > > belongs to the same class of bridge neighbor attributes as 'static'/'dy= namic', > > 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->n= dm_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_LE= ARNED? > > It is user API after all, easter eggs like this aren't very enjoyable. > >=20 >=20 > It's too late unfortunately, ignoring other flags in that case has been t= he standard > behaviour for a long time (it has never made sense to specify flags for e= xtern_learn > entries). I'll send a separate patch that adds a comment to document it o= r 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. */=