Subject: Re: [PATCH net] bonding: Fix stacked device detection in arp monitoring

From: Vlad Yasevich <[email-masked]>
Date: Wed, 07 May 2014 09:20:04 -0400

On 05/06/2014 03:22 PM, Jay Vosburgh wrote:
> Vlad Yasevich <[email-masked]> wrote:
> 
>> Prior to commit fbd929f2dce460456807a51e18d623db3db9f077
>> 	bonding: support QinQ for bond arp interval
>>
>> the arp monitoring code allowed for proper detection of devices
>> stacked on top of vlans.  Since the above commit, the
>> code can still detect a device stacked on top of single
>> vlan, but not a device stacked on top of Q-in-Q configuration.
>> The search will only set the inner vlan tag if the route
>> device is the vlan device.  However, this is not always the
>> case, as it is possible to extend the stacked configuration.
>>
>> With this patch it is possible to provision devices on
>> top Q-in-Q vlan configuration that should be used as
>> a source of ARP monitoring information.
>>
>> For example:
>> ip link add link bond0 vlan10 type vlan proto 802.1q id 10
>> ip link add link vlan10 vlan100 type vlan proto 802.1q id 100
>> ip link add link vlan100 type macvlan
>>
>> Note:  This patch limits the number of stacked VLANs to 2,
>> just like before.  The original, however had another issue
>> in that if we had more then 2 levels of VLANs, we would end
>> up generating incorrectly tagged traffic.  This is no longer
>> possible.
> 
> 	I like this in general, with one minor exception: we lose the
> "inner" and "outer" nomenclature, which I think made the code clearer.

I can completely remove the inner/outer nomenclature if you wish, or can
save it for follow-on patch.

> I think the bond_collect_vlans function deserves at least a sentence or
> two of commentary explaining that we're walking up the layers from
> bottom to top, and collecting the outer tag and then the inner tag,
> thus, outer is tags[0] and inner is tags[1].

Will do.

> 
> 	And, just as a random observation, it looks like it will do the
> right thing (or at least not crash) if things are layered in odd ways,
> e.g., if the macvlan is nested between the vlans.

Right.  There is a slight bug though that I found last night.  I'll fix
that in v2 as well.

Thanks
-vlad

> 
> 	-J
> 
>> Fixes: fbd929f2dce460456807a51e18d623db3db9f077 (bonding: support QinQ for bond arp interval)
>> CC: Jay Vosburgh <[email-masked]>
>> CC: Veaceslav Falico <[email-masked]>
>> CC: Andy Gospodarek <[email-masked]>
>> CC: Ding Tianhong <[email-masked]>
>> CC: Patric McHardy <[email-masked]>
>> Signed-off-by: Vlad Yasevich <[email-masked]>
>> ---
>> drivers/net/bonding/bond_main.c | 90 +++++++++++++++++------------------------
>> 1 file changed, 37 insertions(+), 53 deletions(-)
>>
>> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
>> index 9d08e00..4822728 100644
>> --- a/drivers/net/bonding/bond_main.c
>> +++ b/drivers/net/bonding/bond_main.c
>> @@ -2164,22 +2164,46 @@ static void bond_arp_send(struct net_device *slave_dev, int arp_op,
>> 	arp_xmit(skb);
>> }
>>
>> +static bool bond_collect_vlans(struct net_device *start, struct net_device *end,
>> +				struct bond_vlan_tag *tag, int idx)
>> +{
>> +	struct net_device *upper;
>> +	struct list_head  *iter;
>> +
>> +	/* We do not support more then 2 levels of VLAN nesting */
>> +	if (idx >= 2)
>> +		return false;
>> +
>> +	netdev_for_each_all_upper_dev_rcu(start, upper, iter) {
>> +		if (is_vlan_dev(upper)) {
>> +			tag[idx].vlan_proto = vlan_dev_vlan_proto(upper);
>> +			tag[idx].vlan_id = vlan_dev_vlan_id(upper);
>> +			idx++;
>> +		}
>> +		if (upper == end)
>> +			return true;
>> +
>> +		/* Look at upper devices list only if current device
>> +		 * is a vlan
>> +		 */
>> +		if (is_vlan_dev(upper) && bond_collect_vlans(upper, end, tag, idx))
>> +			return true;
>> +	}
>> +	return false;
>> +}
>> +
>>
>> static void bond_arp_send_all(struct bonding *bond, struct slave *slave)
>> {
>> -	struct net_device *upper, *vlan_upper;
>> -	struct list_head *iter, *vlan_iter;
>> 	struct rtable *rt;
>> -	struct bond_vlan_tag inner, outer;
>> +	struct bond_vlan_tag tags[2];
>> 	__be32 *targets = bond->params.arp_targets, addr;
>> 	int i;
>> +	bool ret;
>>
>> 	for (i = 0; i < BOND_MAX_ARP_TARGETS && targets[i]; i++) {
>> 		pr_debug("basa: target %pI4\n", &targets[i]);
>> -		inner.vlan_proto = 0;
>> -		inner.vlan_id = 0;
>> -		outer.vlan_proto = 0;
>> -		outer.vlan_id = 0;
>> +		memset(tags, 0, sizeof(tags));
>>
>> 		/* Find out through which dev should the packet go */
>> 		rt = ip_route_output(dev_net(bond->dev), targets[i], 0,
>> @@ -2192,7 +2216,7 @@ static void bond_arp_send_all(struct bonding *bond, struct slave *slave)
>> 				net_warn_ratelimited("%s: no route to arp_ip_target %pI4 and arp_validate is set\n",
>> 						     bond->dev->name,
>> 						     &targets[i]);
>> -			bond_arp_send(slave->dev, ARPOP_REQUEST, targets[i], 0, &inner, &outer);
>> +			bond_arp_send(slave->dev, ARPOP_REQUEST, targets[i], 0, &tags[1], &tags[0]);
>> 			continue;
>> 		}
>>
>> @@ -2201,52 +2225,12 @@ static void bond_arp_send_all(struct bonding *bond, struct slave *slave)
>> 			goto found;
>>
>> 		rcu_read_lock();
>> -		/* first we search only for vlan devices. for every vlan
>> -		 * found we verify its upper dev list, searching for the
>> -		 * rt->dst.dev. If found we save the tag of the vlan and
>> -		 * proceed to send the packet.
>> -		 */
>> -		netdev_for_each_all_upper_dev_rcu(bond->dev, vlan_upper,
>> -						  vlan_iter) {
>> -			if (!is_vlan_dev(vlan_upper))
>> -				continue;
>> -
>> -			if (vlan_upper == rt->dst.dev) {
>> -				outer.vlan_proto = vlan_dev_vlan_proto(vlan_upper);
>> -				outer.vlan_id = vlan_dev_vlan_id(vlan_upper);
>> -				rcu_read_unlock();
>> -				goto found;
>> -			}
>> -			netdev_for_each_all_upper_dev_rcu(vlan_upper, upper,
>> -							  iter) {
>> -				if (upper == rt->dst.dev) {
>> -					/* If the upper dev is a vlan dev too,
>> -					 *  set the vlan tag to inner tag.
>> -					 */
>> -					if (is_vlan_dev(upper)) {
>> -						inner.vlan_proto = vlan_dev_vlan_proto(upper);
>> -						inner.vlan_id = vlan_dev_vlan_id(upper);
>> -					}
>> -					outer.vlan_proto = vlan_dev_vlan_proto(vlan_upper);
>> -					outer.vlan_id = vlan_dev_vlan_id(vlan_upper);
>> -					rcu_read_unlock();
>> -					goto found;
>> -				}
>> -			}
>> -		}
>> -
>> -		/* if the device we're looking for is not on top of any of
>> -		 * our upper vlans, then just search for any dev that
>> -		 * matches, and in case it's a vlan - save the id
>> -		 */
>> -		netdev_for_each_all_upper_dev_rcu(bond->dev, upper, iter) {
>> -			if (upper == rt->dst.dev) {
>> -				rcu_read_unlock();
>> -				goto found;
>> -			}
>> -		}
>> +		ret = bond_collect_vlans(bond->dev, rt->dst.dev, tags, 0);
>> 		rcu_read_unlock();
>>
>> +		if (ret)
>> +			goto found;
>> +
>> 		/* Not our device - skip */
>> 		pr_debug("%s: no path to arp_ip_target %pI4 via rt.dev %s\n",
>> 			 bond->dev->name, &targets[i],
>> @@ -2259,7 +2243,7 @@ found:
>> 		addr = bond_confirm_addr(rt->dst.dev, targets[i], 0);
>> 		ip_rt_put(rt);
>> 		bond_arp_send(slave->dev, ARPOP_REQUEST, targets[i],
>> -			      addr, &inner, &outer);
>> +			      addr, &tags[1], &tags[0]);
>> 	}
>> }
> 
> ---
> 	-Jay Vosburgh, [email-masked]
>