diff options
Diffstat (limited to 'target/linux/generic/backport-5.15/720-v5.12-net-bridge-notify-switchdev-of-disappearance-of-old-.patch')
| -rw-r--r-- | target/linux/generic/backport-5.15/720-v5.12-net-bridge-notify-switchdev-of-disappearance-of-old-.patch | 126 |
1 files changed, 126 insertions, 0 deletions
diff --git a/target/linux/generic/backport-5.15/720-v5.12-net-bridge-notify-switchdev-of-disappearance-of-old-.patch b/target/linux/generic/backport-5.15/720-v5.12-net-bridge-notify-switchdev-of-disappearance-of-old-.patch new file mode 100644 index 0000000000..c43cb4d1f2 --- /dev/null +++ b/target/linux/generic/backport-5.15/720-v5.12-net-bridge-notify-switchdev-of-disappearance-of-old-.patch @@ -0,0 +1,126 @@ +From 90dc8fd36078a536671adae884d0b929cce6480a Mon Sep 17 00:00:00 2001 +From: Vladimir Oltean <vladimir.oltean@nxp.com> +Date: Wed, 6 Jan 2021 11:51:30 +0200 +Subject: [PATCH] net: bridge: notify switchdev of disappearance of old FDB + entry upon migration + +Currently the bridge emits atomic switchdev notifications for +dynamically learnt FDB entries. Monitoring these notifications works +wonders for switchdev drivers that want to keep their hardware FDB in +sync with the bridge's FDB. + +For example station A wants to talk to station B in the diagram below, +and we are concerned with the behavior of the bridge on the DUT device: + + DUT + +-------------------------------------+ + | br0 | + | +------+ +------+ +------+ +------+ | + | | | | | | | | | | + | | swp0 | | swp1 | | swp2 | | eth0 | | + +-------------------------------------+ + | | | + Station A | | + | | + +--+------+--+ +--+------+--+ + | | | | | | | | + | | swp0 | | | | swp0 | | + Another | +------+ | | +------+ | Another + switch | br0 | | br0 | switch + | +------+ | | +------+ | + | | | | | | | | + | | swp1 | | | | swp1 | | + +--+------+--+ +--+------+--+ + | + Station B + +Interfaces swp0, swp1, swp2 are handled by a switchdev driver that has +the following property: frames injected from its control interface bypass +the internal address analyzer logic, and therefore, this hardware does +not learn from the source address of packets transmitted by the network +stack through it. So, since bridging between eth0 (where Station B is +attached) and swp0 (where Station A is attached) is done in software, +the switchdev hardware will never learn the source address of Station B. +So the traffic towards that destination will be treated as unknown, i.e. +flooded. + +This is where the bridge notifications come in handy. When br0 on the +DUT sees frames with Station B's MAC address on eth0, the switchdev +driver gets these notifications and can install a rule to send frames +towards Station B's address that are incoming from swp0, swp1, swp2, +only towards the control interface. This is all switchdev driver private +business, which the notification makes possible. + +All is fine until someone unplugs Station B's cable and moves it to the +other switch: + + DUT + +-------------------------------------+ + | br0 | + | +------+ +------+ +------+ +------+ | + | | | | | | | | | | + | | swp0 | | swp1 | | swp2 | | eth0 | | + +-------------------------------------+ + | | | + Station A | | + | | + +--+------+--+ +--+------+--+ + | | | | | | | | + | | swp0 | | | | swp0 | | + Another | +------+ | | +------+ | Another + switch | br0 | | br0 | switch + | +------+ | | +------+ | + | | | | | | | | + | | swp1 | | | | swp1 | | + +--+------+--+ +--+------+--+ + | + Station B + +Luckily for the use cases we care about, Station B is noisy enough that +the DUT hears it (on swp1 this time). swp1 receives the frames and +delivers them to the bridge, who enters the unlikely path in br_fdb_update +of updating an existing entry. It moves the entry in the software bridge +to swp1 and emits an addition notification towards that. + +As far as the switchdev driver is concerned, all that it needs to ensure +is that traffic between Station A and Station B is not forever broken. +If it does nothing, then the stale rule to send frames for Station B +towards the control interface remains in place. But Station B is no +longer reachable via the control interface, but via a port that can +offload the bridge port learning attribute. It's just that the port is +prevented from learning this address, since the rule overrides FDB +updates. So the rule needs to go. The question is via what mechanism. + +It sure would be possible for this switchdev driver to keep track of all +addresses which are sent to the control interface, and then also listen +for bridge notifier events on its own ports, searching for the ones that +have a MAC address which was previously sent to the control interface. +But this is cumbersome and inefficient. Instead, with one small change, +the bridge could notify of the address deletion from the old port, in a +symmetrical manner with how it did for the insertion. Then the switchdev +driver would not be required to monitor learn/forget events for its own +ports. It could just delete the rule towards the control interface upon +bridge entry migration. This would make hardware address learning be +possible again. Then it would take a few more packets until the hardware +and software FDB would be in sync again. + +Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com> +Acked-by: Nikolay Aleksandrov <nikolay@nvidia.com> +Reviewed-by: Ido Schimmel <idosch@nvidia.com> +Reviewed-by: Andrew Lunn <andrew@lunn.ch> +Reviewed-by: Florian Fainelli <f.fainelli@gmail.com> +Signed-off-by: Jakub Kicinski <kuba@kernel.org> +--- + net/bridge/br_fdb.c | 1 + + 1 file changed, 1 insertion(+) + +--- a/net/bridge/br_fdb.c ++++ b/net/bridge/br_fdb.c +@@ -602,6 +602,7 @@ void br_fdb_update(struct net_bridge *br + /* fastpath: update of existing entry */ + if (unlikely(source != fdb->dst && + !test_bit(BR_FDB_STICKY, &fdb->flags))) { ++ br_switchdev_fdb_notify(fdb, RTM_DELNEIGH); + fdb->dst = source; + fdb_modified = true; + /* Take over HW learned entry */ |