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Subject[PATCH 5.8 51/99] batman-adv: mcast: fix duplicate mcast packets from BLA backbone to mesh
Date
From: Linus Lüssing <linus.luessing@c0d3.blue>

[ Upstream commit 2369e827046920ef0599e6a36b975ac5c0a359c2 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/batman-adv/bridge_loop_avoidance.c | 103 +++++++++++++++++++++----
1 file changed, 87 insertions(+), 16 deletions(-)

diff --git a/net/batman-adv/bridge_loop_avoidance.c b/net/batman-adv/bridge_loop_avoidance.c
index 164ba5706aa4e..8002a7f8f3fad 100644
--- 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:
@@ -1653,6 +1674,48 @@ 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.
@@ -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);
--
2.25.1


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