wifi: mac80211: select link when transmitting to non-MLO stations

When an MLO AP is transmitting to a non-MLO station, addr2 should be set
to a link address. This should be done before the frame is encrypted as
otherwise aad verification would fail. In case of software encryption
this can't be left for the device to handle, and should be done by
mac80211 when building the frame hdr.
Signed-off-by: Andrei Otcheretianski <andrei.otcheretianski@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

include/net/mac80211.h

@@ -2147,6 +2147,7 @@ struct ieee80211_link_sta {
  * @tdls_initiator: indicates the STA is an initiator of the TDLS link. Only
  *	valid if the STA is a TDLS peer in the first place.
  * @mfp: indicates whether the STA uses management frame protection or not.
+ * @mlo: indicates whether the STA is MLO station.
  * @max_amsdu_subframes: indicates the maximal number of MSDUs in a single
  *	A-MSDU. Taken from the Extended Capabilities element. 0 means
  *	unlimited.
@@ -2180,6 +2181,7 @@ struct ieee80211_sta {
 	bool tdls;
 	bool tdls_initiator;
 	bool mfp;
+	bool mlo;
 	u8 max_amsdu_subframes;
 
 	/**

net/mac80211/cfg.c

@@ -1818,6 +1818,10 @@ static int sta_apply_parameters(struct ieee80211_local *local,
 			return ret;
 	}
 
+	/* Mark the STA as MLO if MLD MAC address is available */
+	if (params->link_sta_params.mld_mac)
+		sta->sta.mlo = true;
+
 	return 0;
 }
 

net/mac80211/tx.c

@@ -2570,6 +2570,7 @@ static struct sk_buff *ieee80211_build_hdr(struct ieee80211_sub_if_data *sdata,
 	struct ieee80211_chanctx_conf *chanctx_conf = NULL;
 	enum nl80211_band band;
 	int ret;
+	u8 link_id = IEEE80211_LINK_UNSPECIFIED;
 
 	if (IS_ERR(sta))
 		sta = NULL;
@@ -2618,7 +2619,21 @@ static struct sk_buff *ieee80211_build_hdr(struct ieee80211_sub_if_data *sdata,
 		fc |= cpu_to_le16(IEEE80211_FCTL_FROMDS);
 		/* DA BSSID SA */
 		memcpy(hdr.addr1, skb->data, ETH_ALEN);
-		memcpy(hdr.addr2, sdata->vif.addr, ETH_ALEN);
+
+		if (sdata->vif.valid_links && sta && !sta->sta.mlo) {
+			struct ieee80211_link_data *link;
+
+			link_id = sta->deflink.link_id;
+			link = rcu_dereference(sdata->link[link_id]);
+			if (WARN_ON(!link)) {
+				ret = -ENOLINK;
+				goto free;
+			}
+			memcpy(hdr.addr2, link->conf->addr, ETH_ALEN);
+		} else {
+			memcpy(hdr.addr2, sdata->vif.addr, ETH_ALEN);
+		}
+
 		memcpy(hdr.addr3, skb->data + ETH_ALEN, ETH_ALEN);
 		hdrlen = 24;
 		break;
@@ -2882,7 +2897,7 @@ static struct sk_buff *ieee80211_build_hdr(struct ieee80211_sub_if_data *sdata,
 	info->ack_frame_id = info_id;
 	info->band = band;
 	info->control.flags = ctrl_flags |
-			      u32_encode_bits(IEEE80211_LINK_UNSPECIFIED,
+			      u32_encode_bits(link_id,
 					      IEEE80211_TX_CTRL_MLO_LINK);
 
 	return skb;