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

From: Veaceslav Falico <[email-masked]>
Date: Wed, 7 May 2014 15:32:39 +0200

On Tue, May 06, 2014 at 01:41:15PM -0400, Vlad Yasevich 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.
>
>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++;

Won't idx here skyrocket if we have more than 1 vlan on top of bonding?

Otherwise I like this approach, from the first view.

>+		}
>+		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]);
> 	}
> }
>
>-- 
>1.9.0
>