[PATCH net V2] net: bridge: br_fdb_external_learn_add(): always set EXT_LEARN

[PATCH net V2] net: bridge: br_fdb_external_learn_add(): always set EXT_LEARN

[Jonas Gorski]

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.

Fix this by always allowing to set BR_FDB_ADDED_BY_EXT_LEARN regardless
if this was a user fdb entry or not.

Fixes: 710ae7287737 ("net: bridge: Mark FDB entries that were added by user as such")
Signed-off-by: Jonas Gorski <jonas.gorski@bisdn.de>
---
Changelog:
V2:
 * always allow setting EXT_LEARN regardless if user entry
 * reworded the commit message a bit to match the new behavior
 * dropped the redundant code excerpt from the commit message as it's
   already in the context

 net/bridge/br_fdb.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

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;
 		}
 
-- 
2.46.0


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Re: [PATCH net V2] net: bridge: br_fdb_external_learn_add(): always set EXT_LEARN

[Nikolay Aleksandrov]

On 9/3/24 11:19, 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.
> 
> Fix this by always allowing to set BR_FDB_ADDED_BY_EXT_LEARN regardless
> if this was a user fdb entry or not.
> 
> Fixes: 710ae7287737 ("net: bridge: Mark FDB entries that were added by user as such")
> Signed-off-by: Jonas Gorski <jonas.gorski@bisdn.de>
> ---
> Changelog:
> V2:
>  * always allow setting EXT_LEARN regardless if user entry
>  * reworded the commit message a bit to match the new behavior
>  * dropped the redundant code excerpt from the commit message as it's
>    already in the context
> 
>  net/bridge/br_fdb.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
> 
> 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;
>  		}
>  

Although the curly braces aren't needed, I don't mind in this case.

Acked-by: Nikolay Aleksandrov <razor@blackwall.org>

Re: [PATCH net V2] net: bridge: br_fdb_external_learn_add(): always set EXT_LEARN

[Ido Schimmel]

On Tue, Sep 03, 2024 at 10:19:57AM +0200, 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.
> 
> Fix this by always allowing to set BR_FDB_ADDED_BY_EXT_LEARN regardless
> if this was a user fdb entry or not.
> 
> Fixes: 710ae7287737 ("net: bridge: Mark FDB entries that were added by user as such")
> Signed-off-by: Jonas Gorski <jonas.gorski@bisdn.de>

Reviewed-by: Ido Schimmel <idosch@nvidia.com>

Re: [PATCH net V2] net: bridge: br_fdb_external_learn_add(): always set EXT_LEARN

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Tue,  3 Sep 2024 10:19:57 +0200 you 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.
> 
> [...]

Here is the summary with links:
  - [net,V2] net: bridge: br_fdb_external_learn_add(): always set EXT_LEARN
    https://git.kernel.org/netdev/net/c/bee2ef946d31

You are awesome, thank you!
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