vxlan: fix default fdb entry netlink notify ordering during netdev create

Problem:
In vxlan_newlink, a default fdb entry is added before register_netdev.
The default fdb creation function also notifies user-space of the
fdb entry on the vxlan device which user-space does not know about yet.
(RTM_NEWNEIGH goes before RTM_NEWLINK for the same ifindex).

This patch fixes the user-space netlink notification ordering issue
with the following changes:
- decouple fdb notify from fdb create.
- Move fdb notify after register_netdev.
- Call rtnl_configure_link in vxlan newlink handler to notify
userspace about the newlink before fdb notify and
hence avoiding the user-space race.

Fixes: afbd8bae9c79 ("vxlan: add implicit fdb entry for default destination")
Signed-off-by: Roopa Prabhu <roopa@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/vxlan.c b/drivers/net/vxlan.c
index a7e9a4d..e857cb3 100644 (file)
--- a/drivers/net/vxlan.c
+++ b/drivers/net/vxlan.c
@@ -3195,6 +3195,7 @@ static int __vxlan_dev_create(struct net *net, struct net_device *dev,
 {
        struct vxlan_net *vn = net_generic(net, vxlan_net_id);
        struct vxlan_dev *vxlan = netdev_priv(dev);
+       struct vxlan_fdb *f = NULL;
        int err;
 
        err = vxlan_dev_configure(net, dev, conf, false, extack);
@@ -3205,27 +3206,38 @@ static int __vxlan_dev_create(struct net *net, struct net_device *dev,
 
        /* create an fdb entry for a valid default destination */
        if (!vxlan_addr_any(&vxlan->default_dst.remote_ip)) {
-               err = vxlan_fdb_update(vxlan, all_zeros_mac,
+               err = vxlan_fdb_create(vxlan, all_zeros_mac,
                                       &vxlan->default_dst.remote_ip,
                                       NUD_REACHABLE | NUD_PERMANENT,
-                                      NLM_F_EXCL | NLM_F_CREATE,
                                       vxlan->cfg.dst_port,
                                       vxlan->default_dst.remote_vni,
                                       vxlan->default_dst.remote_vni,
                                       vxlan->default_dst.remote_ifindex,
-                                      NTF_SELF);
+                                      NTF_SELF, &f);
                if (err)
                        return err;
        }
 
        err = register_netdevice(dev);
+       if (err)
+               goto errout;
+
+       err = rtnl_configure_link(dev, NULL);
        if (err) {
-               vxlan_fdb_delete_default(vxlan, vxlan->default_dst.remote_vni);
-               return err;
+               unregister_netdevice(dev);
+               goto errout;
        }
 
+       /* notify default fdb entry */
+       if (f)
+               vxlan_fdb_notify(vxlan, f, first_remote_rtnl(f), RTM_NEWNEIGH);
+
        list_add(&vxlan->next, &vn->vxlan_list);
        return 0;
+errout:
+       if (f)
+               vxlan_fdb_destroy(vxlan, f, false);
+       return err;
 }
 
 static int vxlan_nl2conf(struct nlattr *tb[], struct nlattr *data[],
@@ -3460,6 +3472,7 @@ static int vxlan_changelink(struct net_device *dev, struct nlattr *tb[],
        struct vxlan_rdst *dst = &vxlan->default_dst;
        struct vxlan_rdst old_dst;
        struct vxlan_config conf;
+       struct vxlan_fdb *f = NULL;
        int err;
 
        err = vxlan_nl2conf(tb, data,
@@ -3485,19 +3498,19 @@ static int vxlan_changelink(struct net_device *dev, struct nlattr *tb[],
                                           old_dst.remote_ifindex, 0);
 
                if (!vxlan_addr_any(&dst->remote_ip)) {
-                       err = vxlan_fdb_update(vxlan, all_zeros_mac,
+                       err = vxlan_fdb_create(vxlan, all_zeros_mac,
                                               &dst->remote_ip,
                                               NUD_REACHABLE | NUD_PERMANENT,
-                                              NLM_F_CREATE | NLM_F_APPEND,
                                               vxlan->cfg.dst_port,
                                               dst->remote_vni,
                                               dst->remote_vni,
                                               dst->remote_ifindex,
-                                              NTF_SELF);
+                                              NTF_SELF, &f);
                        if (err) {
                                spin_unlock_bh(&vxlan->hash_lock);
                                return err;
                        }
+                       vxlan_fdb_notify(vxlan, f, first_remote_rtnl(f), RTM_NEWNEIGH);
                }
                spin_unlock_bh(&vxlan->hash_lock);
        }