netdev - Re: Failing to attach bond(created with two interfaces from different NICs) to a bridge

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Date:   Sun, 6 Sep 2020 14:12:49 +0300
From:   Ido Schimmel <idosch@...sch.org>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     Vasundhara Volam <vasundhara-v.volam@...adcom.com>,
        Jiri Pirko <jiri@...lanox.com>,
        Michael Chan <michael.chan@...adcom.com>, jtoppins@...hat.com,
        Netdev <netdev@...r.kernel.org>, Andrew Lunn <andrew@...n.ch>
Subject: Re: Failing to attach bond(created with two interfaces from
 different NICs) to a bridge

On Thu, Sep 03, 2020 at 12:14:28PM -0700, Jakub Kicinski wrote:
> On Thu, 3 Sep 2020 12:52:25 +0530 Vasundhara Volam wrote:
> > Hello Jiri,
> > 
> > After the following set of upstream commits, the user fails to attach
> > a bond to the bridge, if the user creates the bond with two interfaces
> > from different bnxt_en NICs. Previously bnxt_en driver does not
> > advertise the switch_id for legacy mode as part of
> > ndo_get_port_parent_id cb but with the following patches, switch_id is
> > returned even in legacy mode which is causing the failure.
> > 
> > ---------------
> > 7e1146e8c10c00f859843817da8ecc5d902ea409 net: devlink: introduce
> > devlink_compat_switch_id_get() helper
> > 6605a226781eb1224c2dcf974a39eea11862b864 bnxt: pass switch ID through
> > devlink_port_attrs_set()
> > 56d9f4e8f70e6f47ad4da7640753cf95ae51a356 bnxt: remove
> > ndo_get_port_parent_id implementation for physical ports
> > ----------------
> > 
> > As there is a plan to get rid of ndo_get_port_parent_id in future, I
> > think there is a need to fix devlink_compat_switch_id_get() to return
> > the switch_id only when device is in SWITCHDEV mode and this effects
> > all the NICs.
> > 
> > Please let me know your thoughts. Thank you.
> 
> I'm not Jiri, but I'd think that hiding switch_id from devices should
> not be the solution here. Especially that no NICs offload bridging
> today. 
> 
> Could you describe the team/bridge failure in detail, I'm not that
> familiar with this code.

Maybe:

br_add_slave()
	br_add_if()
		nbp_switchdev_mark_set()
			dev_get_port_parent_id()

I believe the last call will return '-ENODATA' because the two bnxt
netdevs member in the bond have different switch IDs. Perhaps the
function can be changed to return '-EOPNOTSUPP' when it's called for an
upper device that have multiple parent IDs beneath it:

diff --git a/net/core/dev.c b/net/core/dev.c
index d42c9ea0c3c0..7932594ca437 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -8646,7 +8646,7 @@ int dev_get_port_parent_id(struct net_device *dev,
                if (!first.id_len)
                        first = *ppid;
                else if (memcmp(&first, ppid, sizeof(*ppid)))
-                       return -ENODATA;
+                       return -EOPNOTSUPP;
        }
 
        return err;