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

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Date:	Fri, 28 Oct 2011 13:06:26 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	jesse@...ira.com, john.r.fastabend@...el.com,
	hans.schillstrom@...csson.com, jpirko@...hat.com,
	mbizon@...ebox.fr, netdev@...r.kernel.org, fubar@...ibm.com
Subject: Re: [net-next PATCH] net: allow vlan traffic to be received under
 bond

Le vendredi 28 octobre 2011 à 12:00 +0200, Eric Dumazet a écrit :

> Oh well, this broke my setup, a very basic one.
> 
> eth1 and eth2 on a bonding device, bond0, active-backup
> 
> some vlans on top of bond0, say vlan.103
> 
> $ ip link show dev vlan.103
> 8: vlan.103@...d0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc
> pfifo_fast state UP qlen 100
>     link/ether 00:1e:0b:ec:d3:d2 brd ff:ff:ff:ff:ff:ff
> 
> 
> arp_rcv() now gets packets with skb->type PACKET_OTHERHOST and drops
> such packets.
> 
>      [000] 52870.115435: skb_gro_reset_offset <-napi_gro_receive
>      [000] 52870.115435: dev_gro_receive <-napi_gro_receive
>      [000] 52870.115435: napi_skb_finish <-napi_gro_receive
>      [000] 52870.115435: netif_receive_skb <-napi_skb_finish
>      [000] 52870.115435: get_rps_cpu <-netif_receive_skb
>      [000] 52870.115435: __netif_receive_skb <-netif_receive_skb
>      [000] 52870.115436: vlan_do_receive <-__netif_receive_skb
>      [000] 52870.115436: bond_handle_frame <-__netif_receive_skb
>      [000] 52870.115436: vlan_do_receive <-__netif_receive_skb
>      [000] 52870.115436: arp_rcv <-__netif_receive_skb
>      [000] 52870.115436: kfree_skb <-arp_rcv
>      [000] 52870.115437: __kfree_skb <-kfree_skb
>      [000] 52870.115437: skb_release_head_state <-__kfree_skb
>      [000] 52870.115437: skb_release_data <-__kfree_skb
>      [000] 52870.115437: kfree <-skb_release_data
>      [000] 52870.115437: kmem_cache_free <-__kfree_skb
> 
> 
> By the way, we have no SNMP counter here so I spent some time to track
> this. I'll send a patch for this.
> 
> If this host initiates the trafic, all is well.
> 
> Please guys, can we get back ARP or revert this patch ?

Following patch cures the problem, I am not sure its the right fix.

Problem is we dont know how many times vlan_do_receive() can be called
for a packet.

Only last call should set/mess pkt_type to PACKET_OTHERHOST.

So the caller should be responsible for this, not vlan_do_receive()


Alternative would be to check skb->dev->rx_handler being NULL,
but its not clean.

Following patch is a hack because it handles multicast/broadcast trafic
only. Unicast is already handled in lines 26-33, this is why we didnt
catch the problem.

diff --git a/net/8021q/vlan_core.c b/net/8021q/vlan_core.c
index f1f2f7b..6861899 100644
--- a/net/8021q/vlan_core.c
+++ b/net/8021q/vlan_core.c
@@ -13,7 +13,7 @@ bool vlan_do_receive(struct sk_buff **skbp)
 
 	vlan_dev = vlan_find_dev(skb->dev, vlan_id);
 	if (!vlan_dev) {
-		if (vlan_id)
+		if (vlan_id && skb->pkt_type == PACKET_HOST)
 			skb->pkt_type = PACKET_OTHERHOST;
 		return false;
 	}


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