From: Linus Lüssing linus.luessing@c0d3.blue
commit 3236d215ad38a3f5372e65cd1e0a52cf93d3c6a2 upstream.
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: 1d8ab8d3c176 ("batman-adv: Modified forwarding behaviour for multicast packets") Signed-off-by: Linus Lüssing linus.luessing@c0d3.blue Signed-off-by: Simon Wunderlich sw@simonwunderlich.de [ bp: 4.19 backport: drop usage in non-existing batadv_mcast_forw*, correct fixes line ] Signed-off-by: Sven Eckelmann sven@narfation.org --- net/batman-adv/multicast.c | 31 +++++++++++++++++++++++++++++++ net/batman-adv/multicast.h | 15 +++++++++++++++ net/batman-adv/soft-interface.c | 5 ++--- 3 files changed, 48 insertions(+), 3 deletions(-)
diff --git a/net/batman-adv/multicast.c b/net/batman-adv/multicast.c index b90fe25d6b0b..9b3311dae2e4 100644 --- a/net/batman-adv/multicast.c +++ b/net/batman-adv/multicast.c @@ -62,10 +62,12 @@ #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" #include "netlink.h" +#include "send.h" #include "soft-interface.h" #include "translation-table.h" #include "tvlv.h" @@ -1024,6 +1026,35 @@ batadv_mcast_forw_mode(struct batadv_priv *bat_priv, struct sk_buff *skb, } }
+/** + * 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_want_unsnoop_update() - update unsnoop counter and list * @bat_priv: the bat priv with all the soft interface information diff --git a/net/batman-adv/multicast.h b/net/batman-adv/multicast.h index 3b04ab13f0eb..6f9f3813fc59 100644 --- a/net/batman-adv/multicast.h +++ b/net/batman-adv/multicast.h @@ -51,6 +51,11 @@ 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); + void batadv_mcast_init(struct batadv_priv *bat_priv);
int batadv_mcast_flags_seq_print_text(struct seq_file *seq, void *offset); @@ -78,6 +83,16 @@ static inline int batadv_mcast_init(struct batadv_priv *bat_priv) return 0; }
+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_mesh_info_put(struct sk_buff *msg, struct batadv_priv *bat_priv) { diff --git a/net/batman-adv/soft-interface.c b/net/batman-adv/soft-interface.c index 6ff78080ec7f..1003abb8cc35 100644 --- a/net/batman-adv/soft-interface.c +++ b/net/batman-adv/soft-interface.c @@ -367,9 +367,8 @@ static netdev_tx_t batadv_interface_tx(struct sk_buff *skb, 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 (batadv_dat_snoop_outgoing_arp_request(bat_priv, skb))