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

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Date:	Tue, 11 Oct 2011 12:57:42 +0200
From:	Jiri Pirko <jpirko@...hat.com>
To:	John Fastabend <john.r.fastabend@...el.com>
Cc:	davem@...emloft.net, netdev@...r.kernel.org, jesse@...ira.com,
	fubar@...ibm.com
Subject: Re: [net-next PATCH] net: allow vlan traffic to be received under
 bond

Tue, Oct 11, 2011 at 12:37:53AM CEST, jpirko@...hat.com 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.

I didn't find out anything.

Reviewed-by: Jiri Pirko <jpirko@...hat.com>

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