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wifi: mt76: mt7996: use own MAC as BSS BSSID for mesh interfaces

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mac80211 deliberately leaves bss_conf.bssid as zero_addr for mesh
interfaces, because an MBSS has no BSSID in the infrastructure sense:

  net/mac80211/mesh.c:  sdata->vif.bss_conf.bssid = zero_addr;

mt7996_mcu_bss_basic_tlv() copies that value into the hardware BSS entry,
and the hardware stamps the programmed BSS BSSID into Address 3 of the
management frames it transmits. Every Mesh Peering Management frame
(Self-Protected Action, category 15) therefore leaves the radio with
addr3 = 00:00:00:00:00:00.

That value is wrong for the wire. mac80211's own kernel MPM puts the
transmitter's MAC in addr3 (net/mac80211/mesh_plink.c: memcpy(mgmt->bssid,
sdata->vif.addr, ETH_ALEN)), and hostapd does the same for user-space MPM.
bss_conf.bssid == zero is a "no associated BSS" marker, not a value to
transmit.

This breaks 802.11s interoperability with peers that filter received
management frames on BSSID. Measured against an ath11k (QCN9074) peer over
a 35 s window: 217 Mesh Peering Open and 194 Peering Confirm frames were
transmitted and ACKed at the MAC layer, and none were delivered to the
peer's host, while 108 of 400 SAE Authentication frames from the same
radio -- which carry a correct addr3 -- were delivered normally. SAE
therefore completes and MPM never does; the peer closes with reason 56
(MESH_MAX_RETRIES) reporting our link ID as 0.

Instrumenting mt7996_tx() confirms the header is correct on entry to the
driver and zeroed on air (same 25 s window: 1035 frames with
addr3 = own MAC at mt7996_tx(), 915 frames with addr3 = 0 on air,
captured by an independent monitor-mode station). mld=0 on every sample,
so the MLD address rewrite in mt7996_tx() is not involved.

With this change addr3 is correct on air and a BPI-R4 joins a three-node
ath11k 802.11s/batman-adv mesh: all four nodes reach plink ESTAB and
exchange batman-adv originators.

Signed-off-by: outbackdingo <[email protected]>
This commit is contained in:
gitops
2026-09-11 13:50:25 +07:00
parent be5ce79105
commit f5f3418279
1 changed files with 9 additions and 1 deletions
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mt7996/mcu.c
+8
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@@ -1260,6 +1260,14 @@ mt7996_mcu_bss_basic_tlv(struct sk_buff *skb,
return 0;
}
/* mac80211 sets bss_conf.bssid = zero_addr for mesh interfaces, and the
* HW stamps the programmed BSS BSSID into addr3 of TXed mgmt frames.
* That would send mesh peering frames with addr3 = 00:00:00:00:00:00,
* which peers filtering on BSSID (e.g. ath11k) silently drop.
*/
if (vif->type == NL80211_IFTYPE_MESH_POINT)
memcpy(bss->bssid, link_conf->addr, ETH_ALEN);
else
memcpy(bss->bssid, link_conf->bssid, ETH_ALEN);
bss->bcn_interval = cpu_to_le16(link_conf->beacon_int);
bss->dtim_period = link_conf->dtim_period;