Subject: Re: [PATCH V2 09/12] bridge: Add the ability to configure untagged vlans

From: Vlad Yasevich <[email-masked]>
Date: Tue, 18 Dec 2012 20:06:45 -0500

On 12/18/2012 06:04 PM, Michael S. Tsirkin wrote:
> On Tue, Dec 18, 2012 at 02:01:00PM -0500, Vlad Yasevich wrote:
>> A user may designate a certain vlan as untagged.  This means that
>> any ingress frame is assigned to this vlan and any forwarding decisions
>> are made with this vlan in mind.  On egress, any frames tagged/labeled
>> with untagged vlan have the vlan tag removed and are send as regular
>> ethernet frames.
>>
>> Signed-off-by: Vlad Yasevich <[email-masked]>
>> ---
>>   include/uapi/linux/if_bridge.h |    3 +
>>   net/bridge/br_if.c             |  146 +++++++++++++++++++++++++++++++++++++---
>>   net/bridge/br_netlink.c        |    6 +-
>>   net/bridge/br_private.h        |    2 +
>>   4 files changed, 144 insertions(+), 13 deletions(-)
>>
>> diff --git a/include/uapi/linux/if_bridge.h b/include/uapi/linux/if_bridge.h
>> index d0b4f5c..988d858 100644
>> --- a/include/uapi/linux/if_bridge.h
>> +++ b/include/uapi/linux/if_bridge.h
>> @@ -127,6 +127,9 @@ enum {
>>   	BR_VLAN_DEL,
>>   };
>>
>> +#define BRIDGE_VLAN_INFO_MASTER		1
>> +#define BRIDGE_VLAN_INFO_UNTAGGED	2
>> +
>>   struct bridge_vlan_info {
>>   	u16 op_code;
>>   	u16 flags;
>> diff --git a/net/bridge/br_if.c b/net/bridge/br_if.c
>> index 57bbb35..14563fb 100644
>> --- a/net/bridge/br_if.c
>> +++ b/net/bridge/br_if.c
>> @@ -108,6 +108,34 @@ static void br_vlan_put(struct net_bridge_vlan *vlan)
>>   		br_vlan_destroy(vlan);
>>   }
>>
>> +/* Must be protected by RTNL */
>> +static void br_vlan_add_untagged(struct net_bridge *br,
>> +				 struct net_bridge_vlan *vlan)
>> +{
>> +	ASSERT_RTNL();
>> +	if (br->untagged == vlan)
>> +		return;
>> +	else if (br->untagged) {
>> +		/* Untagged vlan is already set on the master,
>> +		 * so drop the ref since we'll be replacing it.
>> +		 */
>> +		br_vlan_put(br->untagged);
>> +	}
>> +	br_vlan_hold(vlan);
>> +	rcu_assign_pointer(br->untagged, vlan);
>> +}
>> +
>> +/* Must be protected by RTNL */
>> +static void br_vlan_del_untagged(struct net_bridge *br,
>> +				 struct net_bridge_vlan *vlan)
>> +{
>> +	ASSERT_RTNL();
>> +	if (br->untagged == vlan) {
>> +		br_vlan_put(vlan);
>> +		rcu_assign_pointer(br->untagged, NULL);
>> +	}
>> +}
>> +
>>   struct net_bridge_vlan *br_vlan_find(struct net_bridge *br, u16 vid)
>>   {
>>   	struct net_bridge_vlan *vlan;
>> @@ -132,7 +160,7 @@ struct net_bridge_vlan *br_vlan_add(struct net_bridge *br, u16 vid,
>>
>>   	vlan = br_vlan_find(br, vid);
>>   	if (vlan)
>> -		return vlan;
>> +		goto untagged;
>>
>>   	vlan = kzalloc(sizeof(struct net_bridge_vlan), GFP_KERNEL);
>>   	if (!vlan)
>> @@ -141,7 +169,7 @@ struct net_bridge_vlan *br_vlan_add(struct net_bridge *br, u16 vid,
>>   	vlan->vid = vid;
>>   	atomic_set(&vlan->refcnt, 1);
>>
>> -	if (flags & BRIDGE_FLAGS_SELF) {
>> +	if (flags & BRIDGE_VLAN_INFO_MASTER) {
>>   		/* Set bit 0 that is associated with the bridge master
>>   		 * device.  Port numbers start with 1.
>>   		 */
>> @@ -149,15 +177,24 @@ struct net_bridge_vlan *br_vlan_add(struct net_bridge *br, u16 vid,
>>   	}
>>
>>   	hlist_add_head_rcu(&vlan->hlist, &br->vlan_hlist[br_vlan_hash(vid)]);
>> +
>> +untagged:
>> +	if (flags & BRIDGE_VLAN_INFO_UNTAGGED)
>> +		br_vlan_add_untagged(br, vlan);
>> +
>>   	return vlan;
>>   }
>>
>>   /* Must be protected by RTNL */
>> -static void br_vlan_del(struct net_bridge_vlan *vlan, u16 flags)
>> +static void br_vlan_del(struct net_bridge *br, struct net_bridge_vlan *vlan,
>> +			u16 flags)
>>   {
>>   	ASSERT_RTNL();
>>
>> -	if (flags & BRIDGE_FLAGS_SELF) {
>> +	if (flags & BRIDGE_VLAN_INFO_UNTAGGED)
>> +		br_vlan_del_untagged(br, vlan);
>> +
>> +	if (flags & BRIDGE_VLAN_INFO_MASTER) {
>>   		/* Clear bit 0 that is associated with the bridge master
>>   		 * device.
>>   		 */
>> @@ -172,6 +209,14 @@ static void br_vlan_del(struct net_bridge_vlan *vlan, u16 flags)
>>
>>   	vlan->vid = BR_INVALID_VID;
>>
>> +	/* If, for whatever reason, bridge still has a ref on this vlan
>> +	 * through the @untagged pointer, drop that ref and clear untagged.
>> +	 */
>> +	if (br->untagged == vlan) {
>> +		br_vlan_put(vlan);
>> +		rcu_assign_pointer(br->untagged, NULL);
>
> Is something doing an rcu sync after this point?
> If yes maybe add a comment saying where it is, if not - some rcu read
> side could still be using it through this pointer.

yes, at this point, all references from the ports have been dropped and
we are trying to destroy the element.  The put below will trigger the
destruction path which will do kfree_rcu().  Thus there is a grace
period...

-vlad

>
>> +	}
>> +
>>   	/* Drop the self-ref to trigger descrution. */
>>   	br_vlan_put(vlan);
>>   }
>> @@ -187,7 +232,7 @@ int br_vlan_delete(struct net_bridge *br, u16 vid, u16 flags)
>>   	if (!vlan)
>>   		return -ENOENT;
>>
>> -	br_vlan_del(vlan, flags);
>> +	br_vlan_del(br, vlan, flags);
>>   	return 0;
>>   }
>>
>> @@ -204,7 +249,9 @@ static void br_vlan_flush(struct net_bridge *br)
>>   	for (i = 0; i < BR_VID_HASH_SIZE; i++) {
>>   		hlist_for_each_entry_safe(vlan, node, tmp,
>>   					  &br->vlan_hlist[i], hlist) {
>> -			br_vlan_del(vlan, BRIDGE_FLAGS_SELF);
>> +			br_vlan_del(br, vlan,
>> +				    (BRIDGE_VLAN_INFO_MASTER |
>> +				     BRIDGE_VLAN_INFO_UNTAGGED));
>>   		}
>>   	}
>>   }
>> @@ -224,10 +271,70 @@ struct net_port_vlan *nbp_vlan_find(const struct net_bridge_port *p, u16 vid)
>>   	return NULL;
>>   }
>>
>> +static int nbp_vlan_add_untagged(struct net_bridge_port *p,
>> +			  struct net_bridge_vlan *vlan,
>> +			  u16 flags)
>> +{
>> +	struct net_device *dev = p->dev;
>> +
>> +	if (p->untagged) {
>> +		/* Port already has untagged vlan set.  Drop the ref
>> +		 * to the old one since we'll be replace it.
>> +		 */
>> +		br_vlan_put(p->untagged);
>> +	} else {
>> +		int err;
>> +
>> +		/* Add vid 0 to filter if filter is available. */
>> +		if ((dev->features & NETIF_F_HW_VLAN_FILTER) &&
>> +		    dev->netdev_ops->ndo_vlan_rx_add_vid &&
>> +		    dev->netdev_ops->ndo_vlan_rx_kill_vid) {
>> +			err = dev->netdev_ops->ndo_vlan_rx_add_vid(dev, 0);
>> +			if (err)
>> +				return err;
>> +		}
>> +	}
>> +
>> +	/* This VLAN is handled as untagged/native. Save an
>> +	 * additional ref.
>> +	 */
>> +	br_vlan_hold(vlan);
>> +	rcu_assign_pointer(p->untagged, vlan);
>> +
>> +	return 0;
>> +}
>> +
>> +static void nbp_vlan_delete_untagged(struct net_bridge_port *p,
>> +				     struct net_bridge_vlan *vlan)
>> +{
>> +	if (p->untagged != vlan)
>> +		return;
>> +
>> +	/* Remove VLAN from the device filter if it is supported. */
>> +	if ((p->dev->features & NETIF_F_HW_VLAN_FILTER) &&
>> +	    p->dev->netdev_ops->ndo_vlan_rx_kill_vid) {
>> +		int err;
>> +
>> +		err = p->dev->netdev_ops->ndo_vlan_rx_kill_vid(p->dev, 0);
>> +		if (err) {
>> +			pr_warn("failed to kill vid %d for device %s\n",
>> +				vlan->vid, p->dev->name);
>> +		}
>> +	}
>> +
>> +	/* If this VLAN is currently functioning as untagged, clear it.
>> +	 * It's safe to drop the refcount, since the vlan is still held
>> +	 * by the port.
>> +	 */
>> +	br_vlan_put(vlan);
>> +	rcu_assign_pointer(p->untagged, NULL);
>> +
>> +}
>> +
>>   /* Must be protected by RTNL */
>>   int nbp_vlan_add(struct net_bridge_port *p, u16 vid, u16 flags)
>>   {
>> -	struct net_port_vlan *pve;
>> +	struct net_port_vlan *pve = NULL;
>>   	struct net_bridge_vlan *vlan;
>>   	struct net_device *dev = p->dev;
>>   	int err;
>> @@ -275,11 +382,21 @@ int nbp_vlan_add(struct net_bridge_port *p, u16 vid, u16 flags)
>>   	set_bit(p->port_no, vlan->port_bitmap);
>>
>>   	list_add_tail_rcu(&pve->list, &p->vlan_list);
>> +
>> +	if (flags & BRIDGE_VLAN_INFO_UNTAGGED) {
>> +		err = nbp_vlan_add_untagged(p, vlan, flags);
>> +		if (err)
>> +			goto del_vlan;
>> +	}
>> +
>>   	return 0;
>>
>>   clean_up:
>>   	kfree(pve);
>> -	br_vlan_del(vlan, flags);
>> +	br_vlan_del(p->br, vlan, flags);
>> +	return err;
>> +del_vlan:
>> +	nbp_vlan_delete(p, vid, flags);
>>   	return err;
>>   }
>>
>> @@ -296,6 +413,9 @@ int nbp_vlan_delete(struct net_bridge_port *p, u16 vid, u16 flags)
>>   	if (!pve)
>>   		return -ENOENT;
>>
>> +	if (flags & BRIDGE_VLAN_INFO_UNTAGGED)
>> +		nbp_vlan_delete_untagged(p, pve->vlan);
>> +
>>   	/* Remove VLAN from the device filter if it is supported. */
>>   	if ((dev->features & NETIF_F_HW_VLAN_FILTER) &&
>>   	    dev->netdev_ops->ndo_vlan_rx_kill_vid) {
>> @@ -306,6 +426,7 @@ int nbp_vlan_delete(struct net_bridge_port *p, u16 vid, u16 flags)
>>   			pr_warn("failed to kill vid %d for device %s\n",
>>   				vid, dev->name);
>>   	}
>> +
>>   	pve->vid = BR_INVALID_VID;
>>
>>   	vlan = pve->vlan;
>> @@ -316,7 +437,7 @@ int nbp_vlan_delete(struct net_bridge_port *p, u16 vid, u16 flags)
>>   	list_del_rcu(&pve->list);
>>   	kfree_rcu(pve, rcu);
>>
>> -	br_vlan_del(vlan, flags);
>> +	br_vlan_del(p->br, vlan, flags);
>>
>>   	return 0;
>>   }
>> @@ -328,8 +449,11 @@ static void nbp_vlan_flush(struct net_bridge_port *p)
>>
>>   	ASSERT_RTNL();
>>
>> -	list_for_each_entry_safe(pve, tmp, &p->vlan_list, list)
>> -		nbp_vlan_delete(p, pve->vid, BRIDGE_FLAGS_SELF);
>> +	list_for_each_entry_safe(pve, tmp, &p->vlan_list, list)  {
>> +		nbp_vlan_delete(p, pve->vid,
>> +				(BRIDGE_VLAN_INFO_MASTER |
>> +				 BRIDGE_VLAN_INFO_UNTAGGED));
>> +	}
>>   }
>>
>>   static void release_nbp(struct kobject *kobj)
>> diff --git a/net/bridge/br_netlink.c b/net/bridge/br_netlink.c
>> index 9cf2879..1b302ce 100644
>> --- a/net/bridge/br_netlink.c
>> +++ b/net/bridge/br_netlink.c
>> @@ -199,7 +199,8 @@ static int br_afspec(struct net_bridge *br, struct net_bridge_port *p,
>>   			if (p)
>>   				err = nbp_vlan_add(p, vinfo->vid, vinfo->flags);
>>   			else {
>> -				u16 flags = vinfo->flags | BRIDGE_FLAGS_SELF;
>> +				u16 flags = vinfo->flags |
>> +					    BRIDGE_VLAN_INFO_MASTER;
>>   				if (!br_vlan_add(br, vinfo->vid, flags))
>>   					err = -ENOMEM;
>>   			}
>> @@ -210,7 +211,8 @@ static int br_afspec(struct net_bridge *br, struct net_bridge_port *p,
>>   				err = nbp_vlan_delete(p, vinfo->vid,
>>   						      vinfo->flags);
>>   			else {
>> -				u16 flags = vinfo->flags | BRIDGE_FLAGS_SELF;
>> +				u16 flags = vinfo->flags |
>> +					    BRIDGE_VLAN_INFO_MASTER;
>>   				err = br_vlan_delete(br, vinfo->vid, flags);
>>   			}
>>   			break;
>> diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
>> index cc75212..9328463 100644
>> --- a/net/bridge/br_private.h
>> +++ b/net/bridge/br_private.h
>> @@ -179,6 +179,7 @@ struct net_bridge_port
>>   	struct netpoll			*np;
>>   #endif
>>   	struct list_head		vlan_list;
>> +	struct net_bridge_vlan __rcu	*untagged;
>>   };
>>
>>   #define br_port_exists(dev) (dev->priv_flags & IFF_BRIDGE_PORT)
>> @@ -298,6 +299,7 @@ struct net_bridge
>>   	struct timer_list		gc_timer;
>>   	struct kobject			*ifobj;
>>   	struct hlist_head		vlan_hlist[BR_VID_HASH_SIZE];
>> +	struct net_bridge_vlan __rcu	*untagged;
>>   };
>>
>>   struct br_input_skb_cb {
>> --
>> 1.7.7.6
> --
> To unsubscribe from this list: send the line "unsubscribe netdev" in
> the body of a message to [email-masked]
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>