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Message-ID: <ZtRWACsOAnha75Ef@shredder.mtl.com>
Date: Sun, 1 Sep 2024 14:54:40 +0300
From: Ido Schimmel <idosch@...dia.com>
To: Nikolay Aleksandrov <razor@...ckwall.org>
Cc: Jonas Gorski <jonas.gorski@...dn.de>, Roopa Prabhu <roopa@...dia.com>,
"David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
Petr Machata <petrm@...lanox.com>,
Ido Schimmel <idosch@...lanox.com>, bridge@...ts.linux.dev,
netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net] net: bridge: allow users setting EXT_LEARN for user
FDB entries
On Sat, Aug 31, 2024 at 11:31:50AM +0300, Nikolay Aleksandrov wrote:
> On 30/08/2024 17:53, Jonas Gorski wrote:
> > When userspace wants to take over a fdb entry by setting it as
> > EXTERN_LEARNED, we set both flags BR_FDB_ADDED_BY_EXT_LEARN and
> > BR_FDB_ADDED_BY_USER in br_fdb_external_learn_add().
> >
> > If the bridge updates the entry later because its port changed, we clear
> > the BR_FDB_ADDED_BY_EXT_LEARN flag, but leave the BR_FDB_ADDED_BY_USER
> > flag set.
> >
> > If userspace then wants to take over the entry again,
> > br_fdb_external_learn_add() sees that BR_FDB_ADDED_BY_USER and skips
> > setting the BR_FDB_ADDED_BY_EXT_LEARN flags, thus silently ignores the
> > update:
> >
> > if (test_bit(BR_FDB_ADDED_BY_EXT_LEARN, &fdb->flags)) {
> > /* Refresh entry */
> > fdb->used = jiffies;
> > } else if (!test_bit(BR_FDB_ADDED_BY_USER, &fdb->flags)) {
> > /* Take over SW learned entry */
> > set_bit(BR_FDB_ADDED_BY_EXT_LEARN, &fdb->flags);
> > modified = true;
> > }
> >
> > Fix this by relaxing the condition for setting BR_FDB_ADDED_BY_EXT_LEARN
> > by also allowing it if swdev_notify is true, which it will only be for
> > user initiated updates.
> >
> > Fixes: 710ae7287737 ("net: bridge: Mark FDB entries that were added by user as such")
> > Signed-off-by: Jonas Gorski <jonas.gorski@...dn.de>
> > ---
> > net/bridge/br_fdb.c | 3 ++-
> > 1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/net/bridge/br_fdb.c b/net/bridge/br_fdb.c
> > index c77591e63841..c5d9ae13a6fb 100644
> > --- a/net/bridge/br_fdb.c
> > +++ b/net/bridge/br_fdb.c
> > @@ -1472,7 +1472,8 @@ int br_fdb_external_learn_add(struct net_bridge *br, struct net_bridge_port *p,
> > if (test_bit(BR_FDB_ADDED_BY_EXT_LEARN, &fdb->flags)) {
> > /* Refresh entry */
> > fdb->used = jiffies;
> > - } else if (!test_bit(BR_FDB_ADDED_BY_USER, &fdb->flags)) {
> > + } else if (swdev_notify ||
> > + !test_bit(BR_FDB_ADDED_BY_USER, &fdb->flags)) {
> > /* Take over SW learned entry */
> > set_bit(BR_FDB_ADDED_BY_EXT_LEARN, &fdb->flags);
> > modified = true;
>
> This literally means if added_by_user || !added_by_user, so you can probably
> rewrite that whole block to be more straight-forward with test_and_set_bit -
> if it was already set then refresh, if it wasn't modified = true
Hi Nik,
You mean like this [1]?
I deleted the comment about "SW learned entry" since "extern_learn" flag
not being set does not necessarily mean the entry was learned by SW.
[1]
diff --git a/net/bridge/br_fdb.c b/net/bridge/br_fdb.c
index c77591e63841..ad7a42b505ef 100644
--- a/net/bridge/br_fdb.c
+++ b/net/bridge/br_fdb.c
@@ -1469,12 +1469,10 @@ int br_fdb_external_learn_add(struct net_bridge *br, struct net_bridge_port *p,
modified = true;
}
- if (test_bit(BR_FDB_ADDED_BY_EXT_LEARN, &fdb->flags)) {
+ if (test_and_set_bit(BR_FDB_ADDED_BY_EXT_LEARN, &fdb->flags)) {
/* Refresh entry */
fdb->used = jiffies;
- } else if (!test_bit(BR_FDB_ADDED_BY_USER, &fdb->flags)) {
- /* Take over SW learned entry */
- set_bit(BR_FDB_ADDED_BY_EXT_LEARN, &fdb->flags);
+ } else {
modified = true;
}
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