netdev - Re: [PATCH net] bonding: stop the device in bond_setup_by

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Date: Sat, 11 Nov 2023 14:34:47 +0800
From: Hangbin Liu <liuhangbin@...il.com>
To: Jay Vosburgh <jay.vosburgh@...onical.com>
Cc: Eric Dumazet <edumazet@...gle.com>,
	"David S . Miller" <davem@...emloft.net>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Andy Gospodarek <andy@...yhouse.net>, netdev@...r.kernel.org,
	eric.dumazet@...il.com, syzbot <syzkaller@...glegroups.com>
Subject: Re: [PATCH net] bonding: stop the device in bond_setup_by_slave()

On Fri, Nov 10, 2023 at 11:19:22AM +0200, Jay Vosburgh wrote:
> >Do we need also do this if the bond changed to ether device from other dev
> >type? e.g.
> >
> >    if (slave_dev->type != ARPHRD_ETHER)
> >            bond_setup_by_slave(bond_dev, slave_dev);
> >    else
> >            bond_ether_setup(bond_dev);
> 
> 	I'm not sure I follow your comment; bond_enslave() already has
> the above logic.  If the bond is not ARPHRD_ETHER and an ARPHRD_ETHER
> device is added to the bond, the above will take the bond_ether_setup()
> path, which will call ether_setup() which will set the device to
> ARPHRD_ETHER.
> 
> 	However, my recollection is that the bond device itself should
> be unregistered if the last interface of a non-ARPHRD_ETHER bond is
> removed.  This dates back to d90a162a4ee2 ("net/bonding: Destroy bonding
> master when last slave is gone"), but I don't know if the logic still
> works correctly (I've not heard much about IPoIB with bonding in a
> while).  The bond cannot be initially created as non-ARPHRD_ETHER; the
> type changes when the first such interface is added to the bond.

Ah, thanks for this info. I just tried and it still works. Which looks
there is no need to close bond dev before bond_ether_setup().

BTW, I tried to set gre0's master to bond0 and change the types. After that,
`ip link del gre0` will return 0 but gre0 is actually not deleted. I have to
remove the gre mode to delete the link. Is that expected?

```
# ip link add bond0 type bond mode 1 miimon 100
# ip link add gre0 type gre
# ip link set gre0 master bond0
# ip link show bond0
21: bond0: <BROADCAST,MULTICAST,MASTER> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000
    link/gre 0.0.0.0 brd 0.0.0.0
# ip link del gre0
# echo $?
0
# ip link show gre0
18: gre0@...E: <NOARP,SLAVE,UP,LOWER_UP> mtu 1500 qdisc noqueue master bond0 state UNKNOWN mode DEFAULT group default qlen 1000
    link/gre 0.0.0.0 brd 0.0.0.0

```

Thanks
Hangbin