batman-adv: mcast: fix duplicate mcast packets from BLA backbone to mesh

Scenario:
* Multicast frame send from BLA backbone gateways (multiple nodes
  with their bat0 bridged together, with BLA enabled) sharing the same
  LAN to nodes in the mesh

Issue:
* Nodes receive the frame multiple times on bat0 from the mesh,
  once from each foreign BLA backbone gateway which shares the same LAN
  with another

For multicast frames via batman-adv broadcast packets coming from the
same BLA backbone but from different backbone gateways duplicates are
currently detected via a CRC history of previously received packets.

However this CRC so far was not performed for multicast frames received
via batman-adv unicast packets. Fixing this by appyling the same check
for such packets, too.

Room for improvements in the future: Ideally we would introduce the
possibility to not only claim a client, but a complete originator, too.
This would allow us to only send a multicast-in-unicast packet from a BLA
backbone gateway claiming the node and by that avoid potential redundant
transmissions in the first place.

Fixes: 279e89b2281a ("batman-adv: add broadcast duplicate check")
Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>

diff --git a/net/batman-adv/bridge_loop_avoidance.c b/net/batman-adv/bridge_loop_avoidance.c
index 6871578..c350ab6 100644 (file)
--- a/net/batman-adv/bridge_loop_avoidance.c
+++ b/net/batman-adv/bridge_loop_avoidance.c
@@ -1581,13 +1581,16 @@ int batadv_bla_init(struct batadv_priv *bat_priv)
 }
 
 /**
- * batadv_bla_check_bcast_duplist() - Check if a frame is in the broadcast dup.
+ * batadv_bla_check_duplist() - Check if a frame is in the broadcast dup.
  * @bat_priv: the bat priv with all the soft interface information
- * @skb: contains the bcast_packet to be checked
+ * @skb: contains the multicast packet to be checked
+ * @payload_ptr: pointer to position inside the head buffer of the skb
+ *  marking the start of the data to be CRC'ed
+ * @orig: originator mac address, NULL if unknown
  *
- * check if it is on our broadcast list. Another gateway might
- * have sent the same packet because it is connected to the same backbone,
- * so we have to remove this duplicate.
+ * Check if it is on our broadcast list. Another gateway might have sent the
+ * same packet because it is connected to the same backbone, so we have to
+ * remove this duplicate.
  *
  * This is performed by checking the CRC, which will tell us
  * with a good chance that it is the same packet. If it is furthermore
@@ -1596,19 +1599,17 @@ int batadv_bla_init(struct batadv_priv *bat_priv)
  *
  * Return: true if a packet is in the duplicate list, false otherwise.
  */
-bool batadv_bla_check_bcast_duplist(struct batadv_priv *bat_priv,
-                                   struct sk_buff *skb)
+static bool batadv_bla_check_duplist(struct batadv_priv *bat_priv,
+                                    struct sk_buff *skb, u8 *payload_ptr,
+                                    const u8 *orig)
 {
-       int i, curr;
-       __be32 crc;
-       struct batadv_bcast_packet *bcast_packet;
        struct batadv_bcast_duplist_entry *entry;
        bool ret = false;
-
-       bcast_packet = (struct batadv_bcast_packet *)skb->data;
+       int i, curr;
+       __be32 crc;
 
        /* calculate the crc ... */
-       crc = batadv_skb_crc32(skb, (u8 *)(bcast_packet + 1));
+       crc = batadv_skb_crc32(skb, payload_ptr);
 
        spin_lock_bh(&bat_priv->bla.bcast_duplist_lock);
 
@@ -1627,8 +1628,21 @@ bool batadv_bla_check_bcast_duplist(struct batadv_priv *bat_priv,
                if (entry->crc != crc)
                        continue;
 
-               if (batadv_compare_eth(entry->orig, bcast_packet->orig))
-                       continue;
+               /* are the originators both known and not anonymous? */
+               if (orig && !is_zero_ether_addr(orig) &&
+                   !is_zero_ether_addr(entry->orig)) {
+                       /* If known, check if the new frame came from
+                        * the same originator:
+                        * We are safe to take identical frames from the
+                        * same orig, if known, as multiplications in
+                        * the mesh are detected via the (orig, seqno) pair.
+                        * So we can be a bit more liberal here and allow
+                        * identical frames from the same orig which the source
+                        * host might have sent multiple times on purpose.
+                        */
+                       if (batadv_compare_eth(entry->orig, orig))
+                               continue;
+               }
 
                /* this entry seems to match: same crc, not too old,
                 * and from another gw. therefore return true to forbid it.
@@ -1644,7 +1658,14 @@ bool batadv_bla_check_bcast_duplist(struct batadv_priv *bat_priv,
        entry = &bat_priv->bla.bcast_duplist[curr];
        entry->crc = crc;
        entry->entrytime = jiffies;
-       ether_addr_copy(entry->orig, bcast_packet->orig);
+
+       /* known originator */
+       if (orig)
+               ether_addr_copy(entry->orig, orig);
+       /* anonymous originator */
+       else
+               eth_zero_addr(entry->orig);
+
        bat_priv->bla.bcast_duplist_curr = curr;
 
 out:
@@ -1654,6 +1675,48 @@ out:
 }
 
 /**
+ * batadv_bla_check_ucast_duplist() - Check if a frame is in the broadcast dup.
+ * @bat_priv: the bat priv with all the soft interface information
+ * @skb: contains the multicast packet to be checked, decapsulated from a
+ *  unicast_packet
+ *
+ * Check if it is on our broadcast list. Another gateway might have sent the
+ * same packet because it is connected to the same backbone, so we have to
+ * remove this duplicate.
+ *
+ * Return: true if a packet is in the duplicate list, false otherwise.
+ */
+static bool batadv_bla_check_ucast_duplist(struct batadv_priv *bat_priv,
+                                          struct sk_buff *skb)
+{
+       return batadv_bla_check_duplist(bat_priv, skb, (u8 *)skb->data, NULL);
+}
+
+/**
+ * batadv_bla_check_bcast_duplist() - Check if a frame is in the broadcast dup.
+ * @bat_priv: the bat priv with all the soft interface information
+ * @skb: contains the bcast_packet to be checked
+ *
+ * Check if it is on our broadcast list. Another gateway might have sent the
+ * same packet because it is connected to the same backbone, so we have to
+ * remove this duplicate.
+ *
+ * Return: true if a packet is in the duplicate list, false otherwise.
+ */
+bool batadv_bla_check_bcast_duplist(struct batadv_priv *bat_priv,
+                                   struct sk_buff *skb)
+{
+       struct batadv_bcast_packet *bcast_packet;
+       u8 *payload_ptr;
+
+       bcast_packet = (struct batadv_bcast_packet *)skb->data;
+       payload_ptr = (u8 *)(bcast_packet + 1);
+
+       return batadv_bla_check_duplist(bat_priv, skb, payload_ptr,
+                                       bcast_packet->orig);
+}
+
+/**
  * batadv_bla_is_backbone_gw_orig() - Check if the originator is a gateway for
  *  the VLAN identified by vid.
  * @bat_priv: the bat priv with all the soft interface information
@@ -1867,6 +1930,14 @@ bool batadv_bla_rx(struct batadv_priv *bat_priv, struct sk_buff *skb,
                            packet_type == BATADV_UNICAST)
                                goto handled;
 
+       /* potential duplicates from foreign BLA backbone gateways via
+        * multicast-in-unicast packets
+        */
+       if (is_multicast_ether_addr(ethhdr->h_dest) &&
+           packet_type == BATADV_UNICAST &&
+           batadv_bla_check_ucast_duplist(bat_priv, skb))
+               goto handled;
+
        ether_addr_copy(search_claim.addr, ethhdr->h_source);
        search_claim.vid = vid;
        claim = batadv_claim_hash_find(bat_priv, &search_claim);