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: e5cf86d30a9b ("batman-adv: add broadcast duplicate check") Signed-off-by: Linus Lüssing linus.luessing@c0d3.blue --- net/batman-adv/bridge_loop_avoidance.c | 109 +++++++++++++++++++++---- 1 file changed, 93 insertions(+), 16 deletions(-)
diff --git a/net/batman-adv/bridge_loop_avoidance.c b/net/batman-adv/bridge_loop_avoidance.c index 3d2a66f2..60ed5293 100644 --- a/net/batman-adv/bridge_loop_avoidance.c +++ b/net/batman-adv/bridge_loop_avoidance.c @@ -1580,14 +1580,17 @@ 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 - * - * 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. + * @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. + * 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 * sent by another host, drop it. We allow equal packets from @@ -1595,23 +1598,23 @@ 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) { + struct batadv_bcast_duplist_entry *entry; + bool ret = false; 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;
/* 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);
for (i = 0; i < BATADV_DUPLIST_SIZE; i++) { + bool is_from_same_orig = false; + curr = (bat_priv->bla.bcast_duplist_curr + i); curr %= BATADV_DUPLIST_SIZE; entry = &bat_priv->bla.bcast_duplist[curr]; @@ -1626,7 +1629,24 @@ 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)) + /* 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 + */ + if (batadv_compare_eth(entry->orig, orig)) + is_from_same_orig = true; + } + + /* 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 (is_from_same_orig) continue;
/* this entry seems to match: same crc, not too old, @@ -1643,7 +1663,14 @@ 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: @@ -1652,6 +1679,48 @@ bool batadv_bla_check_bcast_duplist(struct batadv_priv *bat_priv, return ret; }
+/** + * 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. @@ -1866,6 +1935,14 @@ 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);