netdev - Re: [PATCH net-next 0/1] veth: Support bonding events

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Message-ID: <52973607-34d4-2cd8-8795-44410ca3233f@linux.ibm.com>
Date:   Tue, 29 Mar 2022 10:33:53 +0200
From:   Alexandra Winter <wintera@...ux.ibm.com>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Paolo Abeni <pabeni@...hat.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        KP Singh <kpsingh@...nel.org>, netdev@...r.kernel.org,
        linux-s390@...r.kernel.org, Heiko Carstens <hca@...ux.ibm.com>
Subject: Re: [PATCH net-next 0/1] veth: Support bonding events



On 29.03.22 04:14, Jakub Kicinski wrote:
> On Mon, 28 Mar 2022 10:14:16 +0200 Alexandra Winter wrote:
>> In case virtual instances are attached to an external network via veth
>> and a bridge, the interface to the external network can be a bond
>> interface. Bonding drivers generate specific events during failover
>> that trigger switch updates.  When a veth device is attached to a
>> bridge with a bond interface, we want external switches to learn about
>> the veth devices as well.
> 
> Can you please add an ASCII diagram of a setup your trying to describe?

	
	| veth_a2   |  veth_b2  |  veth_c2 |
	------o-----------o----------o------
	       \	  |	    /
		o	  o	   o
	      veth_a1  veth_b1  veth_c1
	      -------------------------
	      |        bridge         |
	      -------------------------
			bond0
			/  \
		     eth0  eth1

In case of failover from eth0 to eth1, the netdev_notifier needs to
be propagated, so e.g. veth_a2 can re-announce its MAC address to the
external hardware attached to eth1.

Does that help?
> 
>> Without this patch we have seen cases where recovery after bond
>> failover took an unacceptable amount of time (depending on timeout
>> settings in the network).
>>
>> Due to the symmetric nature of veth special care is required to avoid
>> endless notification loops. Therefore we only notify from a veth
>> bridgeport to a peer that is not a bridgeport.
>>
>> References:
>> Same handling as for macvlan:
>> 4c9912556867 ("macvlan: Support bonding events"
>> and vlan:
>> 4aa5dee4d999 ("net: convert resend IGMP to notifier event")
> 
> When sending a single patch change you can put all the information 
> in the commit message of the patch, the cover letter is only necessary
> for series of multiple patches.
Thank you, I will do so in v2.