bridge: Fix the way to find old local fdb entries in br_fdb_changeaddr

br_fdb_changeaddr() assumes that there is at most one local entry per port
per vlan. It used to be true, but since commit 36fd2b63e3b4 ("bridge: allow
creating/deleting fdb entries via netlink"), it has not been so.
Therefore, the function might fail to search a correct previous address
to be deleted and delete an arbitrary local entry if user has added local
entries manually.

Example of problematic case:
  ip link set eth0 address ee:ff:12:34:56:78
  brctl addif br0 eth0
  bridge fdb add 12:34:56:78:90:ab dev eth0 master
  ip link set eth0 address aa:bb:cc:dd:ee:ff
Then, the address 12:34:56:78:90:ab might be deleted instead of
ee:ff:12:34:56:78, the original mac address of eth0.

Address this issue by introducing a new flag, added_by_user, to struct
net_bridge_fdb_entry.

Note that br_fdb_delete_by_port() has to set added_by_user to 0 in cases
like:
  ip link set eth0 address 12:34:56:78:90:ab
  ip link set eth1 address aa:bb:cc:dd:ee:ff
  brctl addif br0 eth0
  bridge fdb add aa:bb:cc:dd:ee:ff dev eth0 master
  brctl addif br0 eth1
  brctl delif br0 eth0
In this case, kernel should delete the user-added entry aa:bb:cc:dd:ee:ff,
but it also should have been added by "brctl addif br0 eth1" originally,
so we don't delete it and treat it a new kernel-created entry.

Signed-off-by: Toshiaki Makita <makita.toshiaki@lab.ntt.co.jp>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 16 insertions, 7 deletions

diff --git a/net/bridge/br_fdb.c b/net/bridge/br_fdb.c
index c5f5a4a933f4..ce5411995a63 100644
--- a/net/bridge/br_fdb.c
+++ b/net/bridge/br_fdb.c
@@ -104,7 +104,7 @@ void br_fdb_changeaddr(struct net_bridge_port *p, const unsigned char *newaddr)
                         struct net_bridge_fdb_entry *f;
 
                         f = hlist_entry(h, struct net_bridge_fdb_entry, hlist);
-                        if (f->dst == p && f->is_local) {
+                        if (f->dst == p && f->is_local && !f->added_by_user) {
                                 /* maybe another port has same hw addr? */
                                 struct net_bridge_port *op;
                                 u16 vid = f->vlan_id;
@@ -247,6 +247,7 @@ void br_fdb_delete_by_port(struct net_bridge *br,
                                             ether_addr_equal(op->dev->dev_addr,
                                                              f->addr.addr)) {
                                                 f->dst = op;
+                                                f->added_by_user = 0;
                                                 goto skip_delete;
                                         }
                                 }
@@ -397,6 +398,7 @@ static struct net_bridge_fdb_entry *fdb_create(struct hlist_head *head,
                 fdb->vlan_id = vid;
                 fdb->is_local = 0;
                 fdb->is_static = 0;
+                fdb->added_by_user = 0;
                 fdb->updated = fdb->used = jiffies;
                 hlist_add_head_rcu(&fdb->hlist, head);
         }
@@ -447,7 +449,7 @@ int br_fdb_insert(struct net_bridge *br, struct net_bridge_port *source,
 }
 
 void br_fdb_update(struct net_bridge *br, struct net_bridge_port *source,
-                   const unsigned char *addr, u16 vid)
+                   const unsigned char *addr, u16 vid, bool added_by_user)
 {
         struct hlist_head *head = &br->hash[br_mac_hash(addr, vid)];
         struct net_bridge_fdb_entry *fdb;
@@ -473,13 +475,18 @@ void br_fdb_update(struct net_bridge *br, struct net_bridge_port *source,
                         /* fastpath: update of existing entry */
                         fdb->dst = source;
                         fdb->updated = jiffies;
+                        if (unlikely(added_by_user))
+                                fdb->added_by_user = 1;
                 }
         } else {
                 spin_lock(&br->hash_lock);
                 if (likely(!fdb_find(head, addr, vid))) {
                         fdb = fdb_create(head, source, addr, vid);
-                        if (fdb)
+                        if (fdb) {
+                                if (unlikely(added_by_user))
+                                        fdb->added_by_user = 1;
                                 fdb_notify(br, fdb, RTM_NEWNEIGH);
+                        }
                 }
                 /* else  we lose race and someone else inserts
                  * it first, don't bother updating
@@ -647,6 +654,7 @@ static int fdb_add_entry(struct net_bridge_port *source, const __u8 *addr,
 
                 modified = true;
         }
+        fdb->added_by_user = 1;
 
         fdb->used = jiffies;
         if (modified) {
@@ -664,7 +672,7 @@ static int __br_fdb_add(struct ndmsg *ndm, struct net_bridge_port *p,
 
         if (ndm->ndm_flags & NTF_USE) {
                 rcu_read_lock();
-                br_fdb_update(p->br, p, addr, vid);
+                br_fdb_update(p->br, p, addr, vid, true);
                 rcu_read_unlock();
         } else {
                 spin_lock_bh(&p->br->hash_lock);
diff --git a/net/bridge/br_input.c b/net/bridge/br_input.c
index bf8dc7d308d6..28d544627422 100644
--- a/net/bridge/br_input.c
+++ b/net/bridge/br_input.c
@@ -77,7 +77,7 @@ int br_handle_frame_finish(struct sk_buff *skb)
         /* insert into forwarding database after filtering to avoid spoofing */
         br = p->br;
         if (p->flags & BR_LEARNING)
-                br_fdb_update(br, p, eth_hdr(skb)->h_source, vid);
+                br_fdb_update(br, p, eth_hdr(skb)->h_source, vid, false);
 
         if (!is_broadcast_ether_addr(dest) && is_multicast_ether_addr(dest) &&
             br_multicast_rcv(br, p, skb, vid))
@@ -148,7 +148,7 @@ static int br_handle_local_finish(struct sk_buff *skb)
 
         br_vlan_get_tag(skb, &vid);
         if (p->flags & BR_LEARNING)
-                br_fdb_update(p->br, p, eth_hdr(skb)->h_source, vid);
+                br_fdb_update(p->br, p, eth_hdr(skb)->h_source, vid, false);
         return 0;        /* process further */
 }
 
diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
index fcd12333c59b..939a59e15036 100644
--- a/net/bridge/br_private.h
+++ b/net/bridge/br_private.h
@@ -104,6 +104,7 @@ struct net_bridge_fdb_entry
         mac_addr                        addr;
         unsigned char                   is_local;
         unsigned char                   is_static;
+        unsigned char                   added_by_user;
         __u16                           vlan_id;
 };
 
@@ -383,7 +384,7 @@ int br_fdb_fillbuf(struct net_bridge *br, void *buf, unsigned long count,
 int br_fdb_insert(struct net_bridge *br, struct net_bridge_port *source,
                   const unsigned char *addr, u16 vid);
 void br_fdb_update(struct net_bridge *br, struct net_bridge_port *source,
-                   const unsigned char *addr, u16 vid);
+                   const unsigned char *addr, u16 vid, bool added_by_user);
 int fdb_delete_by_addr(struct net_bridge *br, const u8 *addr, u16 vid);
 
 int br_fdb_delete(struct ndmsg *ndm, struct nlattr *tb[],