net: dsa: targeted MTU notifiers should only match on one port
dsa_slave_change_mtu() calls dsa_port_mtu_change() twice:
- it sends a cross-chip notifier with the MTU of the CPU port which is
used to update the DSA links.
- it sends one targeted MTU notifier which is supposed to only match the
user port on which we are changing the MTU. The "propagate_upstream"
variable is used here to bypass the cross-chip notifier system from
switch.c
But due to a mistake, the second, targeted notifier matches not only on
the user port, but also on the DSA link which is a member of the same
switch, if that exists.
And because the DSA links of the entire dst were programmed in a
previous round to the largest_mtu via a "propagate_upstream == true"
notification, then the dsa_port_mtu_change(propagate_upstream == false)
call that is immediately upcoming will break the MTU on the one DSA link
which is chip-wise local to the dp whose MTU is changing right now.
Example given this daisy chain topology:
sw0p0 sw0p1 sw0p2 sw0p3 sw0p4
[ cpu ] [ user ] [ user ] [ dsa ] [ user ]
[ x ] [ ] [ ] [ x ] [ ]
|
+---------+
|
sw1p0 sw1p1 sw1p2 sw1p3 sw1p4
[ user ] [ user ] [ user ] [ dsa ] [ dsa ]
[ ] [ ] [ ] [ ] [ x ]
ip link set sw0p1 mtu 9000
ip link set sw1p1 mtu 9000 # at this stage, sw0p1 and sw1p1 can talk
# to one another using jumbo frames
ip link set sw0p2 mtu 1500 # this programs the sw0p3 DSA link first to
# the largest_mtu of 9000, then reprograms it to
# 1500 with the "propagate_upstream == false"
# notifier, breaking communication between
# sw0p1 and sw1p1
To escape from this situation, make the targeted match really match on a
single port - the user port, and rename the "propagate_upstream"
variable to "targeted_match" to clarify the intention and avoid future
issues.
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/dsa/slave.c b/net/dsa/slave.c
index ac2ca5f..5e668e5 100644
--- a/net/dsa/slave.c
+++ b/net/dsa/slave.c
@@ -1586,14 +1586,15 @@ int dsa_slave_change_mtu(struct net_device *dev, int new_mtu)
goto out_master_failed;
/* We only need to propagate the MTU of the CPU port to
- * upstream switches.
+ * upstream switches, so create a non-targeted notifier which
+ * updates all switches.
*/
- err = dsa_port_mtu_change(cpu_dp, cpu_mtu, true);
+ err = dsa_port_mtu_change(cpu_dp, cpu_mtu, false);
if (err)
goto out_cpu_failed;
}
- err = dsa_port_mtu_change(dp, new_mtu, false);
+ err = dsa_port_mtu_change(dp, new_mtu, true);
if (err)
goto out_port_failed;
@@ -1607,7 +1608,7 @@ int dsa_slave_change_mtu(struct net_device *dev, int new_mtu)
if (new_master_mtu != old_master_mtu)
dsa_port_mtu_change(cpu_dp, old_master_mtu -
dsa_tag_protocol_overhead(cpu_dp->tag_ops),
- true);
+ false);
out_cpu_failed:
if (new_master_mtu != old_master_mtu)
dev_set_mtu(master, old_master_mtu);
