netdev - Re: [net-next PATCH] net: allow vlan traffic to be received under bond

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Date:	Mon, 10 Oct 2011 19:07:14 -0700
From:	John Fastabend <john.r.fastabend@...el.com>
To:	Jiri Pirko <jpirko@...hat.com>,
	"jesse@...ira.com" <jesse@...ira.com>
CC:	"davem@...emloft.net" <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"fubar@...ibm.com" <fubar@...ibm.com>
Subject: Re: [net-next PATCH] net: allow vlan traffic to be received under
 bond

On 10/10/2011 3:37 PM, Jiri Pirko wrote:
> Mon, Oct 10, 2011 at 09:16:41PM CEST, john.r.fastabend@...el.com wrote:
>> The following configuration used to work as I expected. At least
>> we could use the fcoe interfaces to do MPIO and the bond0 iface
>> to do load balancing or failover.
>>
>>       ---eth2.228-fcoe
>>       |
>> eth2 -----|
>>          |
>>          |---- bond0
>>          |
>> eth3 -----|
>>       |
>>       ---eth3.228-fcoe
>>
>> This worked because of a change we added to allow inactive slaves
>> to rx 'exact' matches. This functionality was kept intact with the
>> rx_handler mechanism. However now the vlan interface attached to the
>> active slave never receives traffic because the bonding rx_handler
>> updates the skb->dev and goto's another_round. Previously, the
>> vlan_do_receive() logic was called before the bonding rx_handler.
>>
>> Now by the time vlan_do_receive calls vlan_find_dev() the
>> skb->dev is set to bond0 and it is clear no vlan is attached
>> to this iface. The vlan lookup fails.
>>
>> This patch moves the VLAN check above the rx_handler. A VLAN
>> tagged frame is now routed to the eth2.228-fcoe iface in the
>> above schematic. Untagged frames continue to the bond0 as
>> normal. This case also remains intact,
>>
>> eth2 --> bond0 --> vlan.228
>>
>> Here the skb is VLAN tagged but the vlan lookup fails on eth2
>> causing the bonding rx_handler to be called. On the second
>> pass the vlan lookup is on the bond0 iface and completes as
>> expected.
>>
>> Putting a VLAN.228 on both the bond0 and eth2 device will
>> result in eth2.228 receiving the skb. I don't think this is
>> completely unexpected and was the result prior to the rx_handler
>> result.
>>
>> Note, the same setup is also used for other storage traffic that
>> MPIO is used with eg. iSCSI and similar setups can be contrived
>> without storage protocols.
>>
>> Signed-off-by: John Fastabend <john.r.fastabend@...el.com>
>> ---
>>
>> net/core/dev.c |   22 +++++++++++-----------
>> 1 files changed, 11 insertions(+), 11 deletions(-)
>>
>> diff --git a/net/core/dev.c b/net/core/dev.c
>> index 70ecb86..8b6118a 100644
>> --- a/net/core/dev.c
>> +++ b/net/core/dev.c
>> @@ -3231,6 +3231,17 @@ another_round:
>> ncls:
>> #endif
>>
>> +	if (vlan_tx_tag_present(skb)) {
>> +		if (pt_prev) {
>> +			ret = deliver_skb(skb, pt_prev, orig_dev);
>> +			pt_prev = NULL;
>> +		}
>> +		if (vlan_do_receive(&skb))
>> +			goto another_round;
>> +		else if (unlikely(!skb))
>> +			goto out;
>> +	}
>> +
>> 	rx_handler = rcu_dereference(skb->dev->rx_handler);
>> 	if (rx_handler) {
>> 		if (pt_prev) {
>> @@ -3251,17 +3262,6 @@ ncls:
>> 		}
>> 	}
>>
>> -	if (vlan_tx_tag_present(skb)) {
>> -		if (pt_prev) {
>> -			ret = deliver_skb(skb, pt_prev, orig_dev);
>> -			pt_prev = NULL;
>> -		}
>> -		if (vlan_do_receive(&skb))
>> -			goto another_round;
>> -		else if (unlikely(!skb))
>> -			goto out;
>> -	}
>> -
>> 	/* deliver only exact match when indicated */
>> 	null_or_dev = deliver_exact ? skb->dev : NULL;
>>
>>
> 
> Hmm, I must look at this again tomorrow but I have strong feeling this
> will break some some scenario including vlan-bridge-macvlan.

Yes please review... I tested cases with vlan, bridge, and macvlan
components and believe this works unless I missed something.

Maybe Jesse, can comment though on why this commit that moved (and
cleaned up) the vlan tag handling put the vlan_do_receive below the
rx_handler rather than above it. Was this intended to fix something?

commit 3701e51382a026cba10c60b03efabe534fba4ca4
Author: Jesse Gross <jesse@...ira.com>
Date:   Wed Oct 20 13:56:06 2010 +0000

    vlan: Centralize handling of hardware acceleration.


Thanks,
John.
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