batman-adv: mcast: fix duplicate mcast packets in BLA backbone from LAN

[ Upstream commit 3236d215ad38a3f5372e65cd1e0a52cf93d3c6a2 ]

Scenario:
* Multicast frame send from a BLA backbone (multiple nodes with
  their bat0 bridged together, with BLA enabled)

Issue:
* BLA backbone nodes receive the frame multiple times on bat0

For multicast frames received via batman-adv broadcast packets the
originator of the broadcast packet is checked before decapsulating and
forwarding the frame to bat0 (batadv_bla_is_backbone_gw()->
batadv_recv_bcast_packet()). If it came from a node which shares the
same BLA backbone with us then it is not forwarded to bat0 to avoid a
loop.

When sending a multicast frame in a non-4-address batman-adv unicast
packet we are currently missing this check - and cannot do so because
the batman-adv unicast packet has no originator address field.

However, we can simply fix this on the sender side by only sending the
multicast frame via unicasts to interested nodes which do not share the
same BLA backbone with us. This also nicely avoids some unnecessary
transmissions on mesh side.

Note that no infinite loop was observed, probably because of dropping
via batadv_interface_tx()->batadv_bla_tx(). However the duplicates still
utterly confuse switches/bridges, ICMPv6 duplicate address detection and
neighbor discovery and therefore leads to long delays before being able
to establish TCP connections, for instance. And it also leads to the Linux
bridge printing messages like:
"br-lan: received packet on eth1 with own address as source address ..."

Fixes: 2d3f6ccc4ea5 ("batman-adv: Modified forwarding behaviour for multicast packets")
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>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/net/batman-adv/multicast.c b/net/batman-adv/multicast.c
index 1d5bdf3a4b65526c7c4b90283d97366e10ba19c3..f5bf931252c4b434e528fc88cfceac9e52913aa3 100644 (file)
--- a/net/batman-adv/multicast.c
+++ b/net/batman-adv/multicast.c
@@ -51,6 +51,7 @@
 #include <uapi/linux/batadv_packet.h>
 #include <uapi/linux/batman_adv.h>
 
+#include "bridge_loop_avoidance.h"
 #include "hard-interface.h"
 #include "hash.h"
 #include "log.h"
@@ -1434,6 +1435,35 @@ batadv_mcast_forw_mode(struct batadv_priv *bat_priv, struct sk_buff *skb,
        return BATADV_FORW_ALL;
 }
 
+/**
+ * batadv_mcast_forw_send_orig() - send a multicast packet to an originator
+ * @bat_priv: the bat priv with all the soft interface information
+ * @skb: the multicast packet to send
+ * @vid: the vlan identifier
+ * @orig_node: the originator to send the packet to
+ *
+ * Return: NET_XMIT_DROP in case of error or NET_XMIT_SUCCESS otherwise.
+ */
+int batadv_mcast_forw_send_orig(struct batadv_priv *bat_priv,
+                               struct sk_buff *skb,
+                               unsigned short vid,
+                               struct batadv_orig_node *orig_node)
+{
+       /* Avoid sending multicast-in-unicast packets to other BLA
+        * gateways - they already got the frame from the LAN side
+        * we share with them.
+        * TODO: Refactor to take BLA into account earlier, to avoid
+        * reducing the mcast_fanout count.
+        */
+       if (batadv_bla_is_backbone_gw_orig(bat_priv, orig_node->orig, vid)) {
+               dev_kfree_skb(skb);
+               return NET_XMIT_SUCCESS;
+       }
+
+       return batadv_send_skb_unicast(bat_priv, skb, BATADV_UNICAST, 0,
+                                      orig_node, vid);
+}
+
 /**
  * batadv_mcast_forw_tt() - forwards a packet to multicast listeners
  * @bat_priv: the bat priv with all the soft interface information
@@ -1471,8 +1501,8 @@ batadv_mcast_forw_tt(struct batadv_priv *bat_priv, struct sk_buff *skb,
                        break;
                }
 
-               batadv_send_skb_unicast(bat_priv, newskb, BATADV_UNICAST, 0,
-                                       orig_entry->orig_node, vid);
+               batadv_mcast_forw_send_orig(bat_priv, newskb, vid,
+                                           orig_entry->orig_node);
        }
        rcu_read_unlock();
 
@@ -1513,8 +1543,7 @@ batadv_mcast_forw_want_all_ipv4(struct batadv_priv *bat_priv,
                        break;
                }
 
-               batadv_send_skb_unicast(bat_priv, newskb, BATADV_UNICAST, 0,
-                                       orig_node, vid);
+               batadv_mcast_forw_send_orig(bat_priv, newskb, vid, orig_node);
        }
        rcu_read_unlock();
        return ret;
@@ -1551,8 +1580,7 @@ batadv_mcast_forw_want_all_ipv6(struct batadv_priv *bat_priv,
                        break;
                }
 
-               batadv_send_skb_unicast(bat_priv, newskb, BATADV_UNICAST, 0,
-                                       orig_node, vid);
+               batadv_mcast_forw_send_orig(bat_priv, newskb, vid, orig_node);
        }
        rcu_read_unlock();
        return ret;
@@ -1618,8 +1646,7 @@ batadv_mcast_forw_want_all_rtr4(struct batadv_priv *bat_priv,
                        break;
                }
 
-               batadv_send_skb_unicast(bat_priv, newskb, BATADV_UNICAST, 0,
-                                       orig_node, vid);
+               batadv_mcast_forw_send_orig(bat_priv, newskb, vid, orig_node);
        }
        rcu_read_unlock();
        return ret;
@@ -1656,8 +1683,7 @@ batadv_mcast_forw_want_all_rtr6(struct batadv_priv *bat_priv,
                        break;
                }
 
-               batadv_send_skb_unicast(bat_priv, newskb, BATADV_UNICAST, 0,
-                                       orig_node, vid);
+               batadv_mcast_forw_send_orig(bat_priv, newskb, vid, orig_node);
        }
        rcu_read_unlock();
        return ret;

diff --git a/net/batman-adv/multicast.h b/net/batman-adv/multicast.h
index 5d9e2bb29c9710e22c409629b99c6a4bbbe44d04..403929013ac479e9a53a9820fd2d293b41f06c5b 100644 (file)
--- a/net/batman-adv/multicast.h
+++ b/net/batman-adv/multicast.h
@@ -46,6 +46,11 @@ enum batadv_forw_mode
 batadv_mcast_forw_mode(struct batadv_priv *bat_priv, struct sk_buff *skb,
                       struct batadv_orig_node **mcast_single_orig);
 
+int batadv_mcast_forw_send_orig(struct batadv_priv *bat_priv,
+                               struct sk_buff *skb,
+                               unsigned short vid,
+                               struct batadv_orig_node *orig_node);
+
 int batadv_mcast_forw_send(struct batadv_priv *bat_priv, struct sk_buff *skb,
                           unsigned short vid);
 
@@ -71,6 +76,16 @@ batadv_mcast_forw_mode(struct batadv_priv *bat_priv, struct sk_buff *skb,
        return BATADV_FORW_ALL;
 }
 
+static inline int
+batadv_mcast_forw_send_orig(struct batadv_priv *bat_priv,
+                           struct sk_buff *skb,
+                           unsigned short vid,
+                           struct batadv_orig_node *orig_node)
+{
+       kfree_skb(skb);
+       return NET_XMIT_DROP;
+}
+
 static inline int
 batadv_mcast_forw_send(struct batadv_priv *bat_priv, struct sk_buff *skb,
                       unsigned short vid)

diff --git a/net/batman-adv/soft-interface.c b/net/batman-adv/soft-interface.c
index 5ee8e9a100f903d01fb6799828dfba6ae416ec66..cf1a8ef7464f585cec70b6ef96db6957c312e772 100644 (file)
--- a/net/batman-adv/soft-interface.c
+++ b/net/batman-adv/soft-interface.c
@@ -364,9 +364,8 @@ send:
                                goto dropped;
                        ret = batadv_send_skb_via_gw(bat_priv, skb, vid);
                } else if (mcast_single_orig) {
-                       ret = batadv_send_skb_unicast(bat_priv, skb,
-                                                     BATADV_UNICAST, 0,
-                                                     mcast_single_orig, vid);
+                       ret = batadv_mcast_forw_send_orig(bat_priv, skb, vid,
+                                                         mcast_single_orig);
                } else if (forw_mode == BATADV_FORW_SOME) {
                        ret = batadv_mcast_forw_send(bat_priv, skb, vid);
                } else {