netdev - Re: [Issue] Bonding can't show correct speed if lower interface is bond 802.3ad

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Message-ID: <20230510171436.GA27945@ti139.telemetry-investments.com>
Date: Wed, 10 May 2023 13:14:36 -0400
From: "Andrew J. Schorr" <aschorr@...emetry-investments.com>
To: Hangbin Liu <liuhangbin@...il.com>
Cc: Jay Vosburgh <jay.vosburgh@...onical.com>, netdev@...r.kernel.org
Subject: Re: [Issue] Bonding can't show correct speed if lower interface is
 bond 802.3ad

Sorry -- resending from a different email address to fix a problem
with gmail rejecting it.

On Wed, May 10, 2023 at 12:57:38PM -0400, Andrew J. Schorr wrote:
> Hi Hangbin & Jay,
> 
> On Wed, May 10, 2023 at 03:50:34PM +0800, Hangbin Liu wrote:
> > On Mon, May 08, 2023 at 11:32:16AM -0700, Jay Vosburgh wrote:
> > > 	That case should work fine without the active-backup.  LACP has
> > > a concept of an "individual" port, which (in this context) would be the
> > > "normal NIC," presuming that that means its link peer isn't running
> > > LACP.
> > > 
> > > 	If all of the ports (N that are LACP to a single switch, plus 1
> > > that's the non-LACP "normal NIC") were attached to a single bond, it
> > > would create one aggregator with the LACP enabled ports, and then a
> > > separate aggregator for the indvidual port that's not.  The aggregator
> > > selection logic prefers the LACP enabled aggregator over the individual
> > > port aggregator.  The precise criteria is in the commentary within
> > > ad_agg_selection_test().
> > > 
> > 
> > cc Andrew, He add active-backup bond over LACP bond because he want to
> > use arp_ip_target to ensure that the target network is reachable...
> 
> That's correct. I prefer the ARP monitoring to ensure that the needed
> connectivity is actually there instead of relying on MII monitoring.
> 
> I also confess that I was unaware of the possibility of using an individual
> port inside an 802.3ad bond without having to stick that individual port into a
> port-channel group with LACP enabled. I want to avoid enabling LACP on that
> link because I'd like to be able to PXE boot over it, not to mention the switch
> configuration hassle.  Is that individual port configuration without LACP
> detected automatically by the kernel, or do I need to configure something to do
> that? I see the logic in drivers/net/bonding/bond_3ad.c to set is_individual,
> but it appears to depend on whether duplex is enabled. At that point, I got
> lost, since I see duplex mentioned only in ad_user_port_key, and that seems to
> be a property of the bond master, not the slaves. Is there any documentation of
> how this configuration works?
> 
> But in any case, I still prefer active-backup on top of 802.3ad so that I can
> have the ARP monitoring.
> 
> If it's too much trouble to get the top-level bond to report duplex/speed
> correctly when the underlying bond speed changes, then I think it would
> be an improvement to set duplex/speed to N/A (or -1) for a bond of
> bonds configuration instead of potentially having incorrect information.
> I imagine such a fix might be much easier than updating dynamically
> when the lower-level 802.3ad bond changes speed.
> 
> Best regards,
> Andy