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

From: "Michael S. Tsirkin" <[email-masked]>
Date: Wed, 19 Dec 2012 01:10:49 +0200

On Tue, Dec 18, 2012 at 06:03:25PM -0500, Vlad Yasevich wrote:
> On 12/18/2012 06:01 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);
> >
> >Is there a reason for rcu here but not else where? If all users are under
> >rtnl you can just assign in a simple way.
> >If not then rcu_dereference_protected would be more appropriate.
> 
> Everywhere that the pointer changes rcu_assign_pointer is used.
> 
> Now, if we hold an RTNL, we can technically read the pointer with
> rcu since it's guaranteed not to change since it only changes under
> RTNL.
> I'll check that this is consistent.

Check what rcu_dereference_protected does. It's really just
an explicit way to say "this is accessed without rcu because I have
this lock".

> If I access the pointer without rtnl, it's always inside rcu
> critical section and with rcu_dereference().
> 
> I thought those were the basic rules of rcu.  Did that change?
> 
> -vlad

> >
> >>+}
> >>+
> >>+/* 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);
> >>+	}
> >>+
> >>  	/* 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