Re: [PATCHv3 net 1/3] bonding: set AD_RX_PORT_DISABLED when disabling a port

Hangbin Liu [off-list ref] wrote:

On Thu, Feb 26, 2026 at 05:16:55PM -0800, Jay Vosburgh wrote:

quoted

Hangbin Liu [off-list ref] wrote:

quoted

When disabling a port’s collecting and distributing states, updating only
rx_disabled is not sufficient. We also need to set AD_RX_PORT_DISABLED
so that the rx_machine transitions into the AD_RX_EXPIRED state.

One example is in ad_agg_selection_logic(): when a new aggregator is
selected and old active aggregator is disabled, if AD_RX_PORT_DISABLED is
not set, the disabled port may remain stuck in AD_RX_CURRENT due to
continuing to receive partner LACP messages.

	I'm not sure I'm seeing the problem here, is there an actual
misbehavior being fixed here?  The port is receiving LACPDUs, and from
the receive state machine point of view (Figure 6-18) there's no issue.
The "port_enabled" variable (6.4.7) also informs the state machine
behavior, but that's not the same as what's changed by bonding's
__disable_port function.

Yes, the reason I do it here is we select another aggregator and called
__disable_port() for the old one. If we don't update sm_rx_state, the port
will be keep in collecting/distributing state, and the partner will also
keep in the c/d state.

Here we entered a logical paradox, on one hand we want to disable the port,
on the other hand we keep the port in collecting/distributing state.

	"disable" the port here really means from bonding's perspective,
so, generally equivalent to the backup interface of an active-backup
mode bond.

	Such a backup interface is typically carrier up and able to send
or receive packets.  The peer generally won't send packets to the backup
interface, however, as no traffic is sent from the backup, and the MAC
for the bond uses a different interface, so no forwarding entries will
direct to the backup interface.

	There are a couple of special cases, like LLDP, that are handled
as an exception, but in general, if a peer does send packets to the
backup interface (due to a switch flood, for example), they're dropped.

quoted

	Where I'm going with this is that, when multiple aggregator
support was originally implemented, the theory was to keep aggregators
other than the active agg in a state such that they could be put into
service immediately, without having to do LACPDU exchanges in order to
transition into the appropriate state.  A hot standby, basically,
analogous to an active-backup mode backup interface with link state up.

This sounds good. But without LACPDU exchange, the hot standby actor and
partner should be in collecting/distributing state. What should we do when
partner start send packets to us?

	Did you mean "should not be in c/d state" above?  I.e., without
LACPDU exchage, ... not in c/d state?

	Regardless, as above, the situation is generally equivalent to a
backup interface in active-backup mode: incoming traffic that isn't a
special case is dropped.  Normal traffic (bearing the bond source MAC)
isn't sent, as that would update the peer's forwarding table.

	Nothing in the standard prohibits us from having multiple
aggregators in c/d state simultaneously.  A configuration with two
separate bonds, each with interfaces successfully aggregated together
with their respective peers, wherein those two bonds are placed into a
third bond in active-backup mode is essentially the same thing as what
we're discussing.

	-J

quoted

	I haven't tested this in some time, though, so my question is
whether this change affects the failover time when an active aggregator
is de-selected in favor of another aggregator.  By "failover time," I
mean how long transmission and/or reception are interrupted when
changing from one aggregator to another.  I presume that if aggregator
failover ater this change requires LACPDU exchanges, etc, it will take
longer to fail over.

I haven't tested it yet. I think the failover time should be in 1 second.
Let me do some testing today.

Thanks
Hangbin

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	-Jay Vosburgh, jv@jvosburgh.net