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f2f42a54e8
The qca8k patch series brings the numbering to 799. This patch renames 7xx patches to create space for more backports to be added. Signed-off-by: Matthew Hagan <mnhagan88@gmail.com> [rename 729->719] Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>
127 lines
5.7 KiB
Diff
127 lines
5.7 KiB
Diff
From 90dc8fd36078a536671adae884d0b929cce6480a Mon Sep 17 00:00:00 2001
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From: Vladimir Oltean <vladimir.oltean@nxp.com>
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Date: Wed, 6 Jan 2021 11:51:30 +0200
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Subject: [PATCH] net: bridge: notify switchdev of disappearance of old FDB
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entry upon migration
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Currently the bridge emits atomic switchdev notifications for
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dynamically learnt FDB entries. Monitoring these notifications works
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wonders for switchdev drivers that want to keep their hardware FDB in
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sync with the bridge's FDB.
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For example station A wants to talk to station B in the diagram below,
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and we are concerned with the behavior of the bridge on the DUT device:
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DUT
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+-------------------------------------+
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| br0 |
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| +------+ +------+ +------+ +------+ |
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| | | | | | | | | |
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| | swp0 | | swp1 | | swp2 | | eth0 | |
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+-------------------------------------+
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| | |
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Station A | |
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| |
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+--+------+--+ +--+------+--+
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| | | | | | | |
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| | swp0 | | | | swp0 | |
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Another | +------+ | | +------+ | Another
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switch | br0 | | br0 | switch
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| +------+ | | +------+ |
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| | | | | | | |
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| | swp1 | | | | swp1 | |
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+--+------+--+ +--+------+--+
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Station B
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Interfaces swp0, swp1, swp2 are handled by a switchdev driver that has
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the following property: frames injected from its control interface bypass
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the internal address analyzer logic, and therefore, this hardware does
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not learn from the source address of packets transmitted by the network
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stack through it. So, since bridging between eth0 (where Station B is
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attached) and swp0 (where Station A is attached) is done in software,
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the switchdev hardware will never learn the source address of Station B.
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So the traffic towards that destination will be treated as unknown, i.e.
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flooded.
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This is where the bridge notifications come in handy. When br0 on the
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DUT sees frames with Station B's MAC address on eth0, the switchdev
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driver gets these notifications and can install a rule to send frames
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towards Station B's address that are incoming from swp0, swp1, swp2,
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only towards the control interface. This is all switchdev driver private
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business, which the notification makes possible.
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All is fine until someone unplugs Station B's cable and moves it to the
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other switch:
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DUT
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+-------------------------------------+
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| br0 |
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| +------+ +------+ +------+ +------+ |
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| | | | | | | | | |
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| | swp0 | | swp1 | | swp2 | | eth0 | |
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+-------------------------------------+
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| | |
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Station A | |
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| |
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+--+------+--+ +--+------+--+
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| | | | | | | |
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| | swp0 | | | | swp0 | |
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Another | +------+ | | +------+ | Another
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switch | br0 | | br0 | switch
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| +------+ | | +------+ |
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| | | | | | | |
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| | swp1 | | | | swp1 | |
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+--+------+--+ +--+------+--+
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Station B
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Luckily for the use cases we care about, Station B is noisy enough that
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the DUT hears it (on swp1 this time). swp1 receives the frames and
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delivers them to the bridge, who enters the unlikely path in br_fdb_update
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of updating an existing entry. It moves the entry in the software bridge
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to swp1 and emits an addition notification towards that.
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As far as the switchdev driver is concerned, all that it needs to ensure
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is that traffic between Station A and Station B is not forever broken.
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If it does nothing, then the stale rule to send frames for Station B
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towards the control interface remains in place. But Station B is no
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longer reachable via the control interface, but via a port that can
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offload the bridge port learning attribute. It's just that the port is
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prevented from learning this address, since the rule overrides FDB
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updates. So the rule needs to go. The question is via what mechanism.
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It sure would be possible for this switchdev driver to keep track of all
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addresses which are sent to the control interface, and then also listen
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for bridge notifier events on its own ports, searching for the ones that
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have a MAC address which was previously sent to the control interface.
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But this is cumbersome and inefficient. Instead, with one small change,
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the bridge could notify of the address deletion from the old port, in a
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symmetrical manner with how it did for the insertion. Then the switchdev
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driver would not be required to monitor learn/forget events for its own
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ports. It could just delete the rule towards the control interface upon
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bridge entry migration. This would make hardware address learning be
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possible again. Then it would take a few more packets until the hardware
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and software FDB would be in sync again.
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Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
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Acked-by: Nikolay Aleksandrov <nikolay@nvidia.com>
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Reviewed-by: Ido Schimmel <idosch@nvidia.com>
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Reviewed-by: Andrew Lunn <andrew@lunn.ch>
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Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
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Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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---
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net/bridge/br_fdb.c | 1 +
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1 file changed, 1 insertion(+)
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--- a/net/bridge/br_fdb.c
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+++ b/net/bridge/br_fdb.c
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@@ -602,6 +602,7 @@ void br_fdb_update(struct net_bridge *br
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/* fastpath: update of existing entry */
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if (unlikely(source != fdb->dst &&
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!test_bit(BR_FDB_STICKY, &fdb->flags))) {
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+ br_switchdev_fdb_notify(fdb, RTM_DELNEIGH);
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fdb->dst = source;
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fdb_modified = true;
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/* Take over HW learned entry */
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