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

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Date:	Tue, 11 Oct 2011 00:37:53 +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

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.
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