[PATCH v5 1/4] mac80211: remove unnecessary num_mcast_sta user

[PATCH v5 1/4] mac80211: remove unnecessary num_mcast_sta user

[Michael Braun]

Checking for num_mcast_sta in __ieee80211_request_smps_ap() is unnecessary,
as sta list will be empty in this case anyway, so list_for_each_entry(sta,
...) will exit immediately.

Signed-off-by: Michael Braun <michael-dev@fami-braun.de>
---
 net/mac80211/cfg.c | 7 -------
 1 file changed, 7 deletions(-)

diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c
index 543b1d4..24133f5 100644
--- a/net/mac80211/cfg.c
+++ b/net/mac80211/cfg.c
@@ -2313,13 +2313,6 @@ int __ieee80211_request_smps_ap(struct ieee80211_sub_if_data *sdata,
 	    smps_mode == IEEE80211_SMPS_AUTOMATIC)
 		return 0;
 
-	 /* If no associated stations, there's no need to do anything */
-	if (!atomic_read(&sdata->u.ap.num_mcast_sta)) {
-		sdata->smps_mode = smps_mode;
-		ieee80211_queue_work(&sdata->local->hw, &sdata->recalc_smps);
-		return 0;
-	}
-
 	ht_dbg(sdata,
 	       "SMPS %d requested in AP mode, sending Action frame to %d stations\n",
 	       smps_mode, atomic_read(&sdata->u.ap.num_mcast_sta));
-- 
2.1.4

[PATCH v5 2/4] mac80211: filter multicast data packets on AP / AP_VLAN

[Michael Braun]

This patch adds filtering for multicast data packets on AP_VLAN interfaces
that have no authorized station connected and changes filtering on AP
interfaces to not count stations assigned to AP_VLAN interfaces.

This saves airtime and avoids waking up other stations currently authorized
in this BSS. When using WPA, the packets dropped could not be decrypted by
any station.

The behaviour when there are no AP_VLAN interfaces is left unchanged.
When there are AP_VLAN interfaces, this patch
1. adds filtering multicast data packets sent on AP_VLAN interfaces that
   have no authorized station connected.
   No filtering happens on 4addr AP_VLAN interfaces.
2. makes filtering of multicast data packets sent on AP interfaces depend
   on the number of authorized stations in this bss not assigned to an
   AP_VLAN interface.

Therefore, a new num_mcast_sta counter is added for AP_VLAN interfaces.
The existing one for AP interfaces is altered to not track stations
assigned to an AP_VLAN interface.

The new counter is exposed in debugfs.

Signed-off-by: Michael Braun <michael-dev@fami-braun.de>

--
v4:
 - update description
v3:
 - reuse existing num_mcast_sta
v2:
 - use separate function to inc/dec mcast_sta counters
 - do not filter in 4addr mode
 - change description
 - change filtering on AP interface (do not count AP_VLAN sta)
 - use new counters regardless of 4addr or not
 - simplify cfg.c:change_station
 - remove no-op change in __cleanup_single_sta
---
 net/mac80211/cfg.c            | 20 ++++++--------------
 net/mac80211/debugfs_netdev.c | 11 +++++++++++
 net/mac80211/ieee80211_i.h    | 33 +++++++++++++++++++++++++++++++++
 net/mac80211/rx.c             |  5 +++--
 net/mac80211/sta_info.c       | 10 ++--------
 net/mac80211/tx.c             |  5 ++---
 6 files changed, 57 insertions(+), 27 deletions(-)

diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c
index 24133f5..1edb017 100644
--- a/net/mac80211/cfg.c
+++ b/net/mac80211/cfg.c
@@ -1357,9 +1357,6 @@ static int ieee80211_change_station(struct wiphy *wiphy,
 		goto out_err;
 
 	if (params->vlan && params->vlan != sta->sdata->dev) {
-		bool prev_4addr = false;
-		bool new_4addr = false;
-
 		vlansdata = IEEE80211_DEV_TO_SUB_IF(params->vlan);
 
 		if (params->vlan->ieee80211_ptr->use_4addr) {
@@ -1369,26 +1366,21 @@ static int ieee80211_change_station(struct wiphy *wiphy,
 			}
 
 			rcu_assign_pointer(vlansdata->u.vlan.sta, sta);
-			new_4addr = true;
 			__ieee80211_check_fast_rx_iface(vlansdata);
 		}
 
 		if (sta->sdata->vif.type == NL80211_IFTYPE_AP_VLAN &&
-		    sta->sdata->u.vlan.sta) {
+		    sta->sdata->u.vlan.sta)
 			RCU_INIT_POINTER(sta->sdata->u.vlan.sta, NULL);
-			prev_4addr = true;
-		}
+
+		if (test_sta_flag(sta, WLAN_STA_AUTHORIZED))
+			ieee80211_vif_dec_num_mcast(sta->sdata);
 
 		sta->sdata = vlansdata;
 		ieee80211_check_fast_xmit(sta);
 
-		if (sta->sta_state == IEEE80211_STA_AUTHORIZED &&
-		    prev_4addr != new_4addr) {
-			if (new_4addr)
-				atomic_dec(&sta->sdata->bss->num_mcast_sta);
-			else
-				atomic_inc(&sta->sdata->bss->num_mcast_sta);
-		}
+		if (test_sta_flag(sta, WLAN_STA_AUTHORIZED))
+			ieee80211_vif_inc_num_mcast(sta->sdata);
 
 		ieee80211_send_layer2_update(sta);
 	}
diff --git a/net/mac80211/debugfs_netdev.c b/net/mac80211/debugfs_netdev.c
index a5ba739..ed7bff4 100644
--- a/net/mac80211/debugfs_netdev.c
+++ b/net/mac80211/debugfs_netdev.c
@@ -477,6 +477,7 @@ IEEE80211_IF_FILE_RW(tdls_wider_bw);
 IEEE80211_IF_FILE(num_mcast_sta, u.ap.num_mcast_sta, ATOMIC);
 IEEE80211_IF_FILE(num_sta_ps, u.ap.ps.num_sta_ps, ATOMIC);
 IEEE80211_IF_FILE(dtim_count, u.ap.ps.dtim_count, DEC);
+IEEE80211_IF_FILE(num_mcast_sta_vlan, u.vlan.num_mcast_sta, ATOMIC);
 
 static ssize_t ieee80211_if_fmt_num_buffered_multicast(
 	const struct ieee80211_sub_if_data *sdata, char *buf, int buflen)
@@ -643,6 +644,13 @@ static void add_ap_files(struct ieee80211_sub_if_data *sdata)
 	DEBUGFS_ADD_MODE(tkip_mic_test, 0200);
 }
 
+static void add_vlan_files(struct ieee80211_sub_if_data *sdata)
+{
+	/* add num_mcast_sta_vlan using name num_mcast_sta */
+	debugfs_create_file("num_mcast_sta", 0400, sdata->vif.debugfs_dir,
+			    sdata, &num_mcast_sta_vlan_ops);
+}
+
 static void add_ibss_files(struct ieee80211_sub_if_data *sdata)
 {
 	DEBUGFS_ADD_MODE(tsf, 0600);
@@ -746,6 +754,9 @@ static void add_files(struct ieee80211_sub_if_data *sdata)
 	case NL80211_IFTYPE_AP:
 		add_ap_files(sdata);
 		break;
+	case NL80211_IFTYPE_AP_VLAN:
+		add_vlan_files(sdata);
+		break;
 	case NL80211_IFTYPE_WDS:
 		add_wds_files(sdata);
 		break;
diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index f56d342..70c0963 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -305,6 +305,7 @@ struct ieee80211_if_vlan {
 
 	/* used for all tx if the VLAN is configured to 4-addr mode */
 	struct sta_info __rcu *sta;
+	atomic_t num_mcast_sta; /* number of stations receiving multicast */
 };
 
 struct mesh_stats {
@@ -1496,6 +1497,38 @@ ieee80211_have_rx_timestamp(struct ieee80211_rx_status *status)
 	return false;
 }
 
+static inline void
+ieee80211_vif_inc_num_mcast(struct ieee80211_sub_if_data *sdata)
+{
+	if (sdata->vif.type == NL80211_IFTYPE_AP)
+		atomic_inc(&sdata->u.ap.num_mcast_sta);
+	else if (sdata->vif.type == NL80211_IFTYPE_AP_VLAN)
+		atomic_inc(&sdata->u.vlan.num_mcast_sta);
+}
+
+static inline void
+ieee80211_vif_dec_num_mcast(struct ieee80211_sub_if_data *sdata)
+{
+	if (sdata->vif.type == NL80211_IFTYPE_AP)
+		atomic_dec(&sdata->u.ap.num_mcast_sta);
+	else if (sdata->vif.type == NL80211_IFTYPE_AP_VLAN)
+		atomic_dec(&sdata->u.vlan.num_mcast_sta);
+}
+
+/* This function returns the number of multicast stations connected to this
+ * interface. It returns -1 if that number is not tracked, that is for netdevs
+ * not in AP or AP_VLAN mode or when using 4addr.
+ */
+static inline int
+ieee80211_vif_get_num_mcast_if(struct ieee80211_sub_if_data *sdata)
+{
+	if (sdata->vif.type == NL80211_IFTYPE_AP)
+		return atomic_read(&sdata->u.ap.num_mcast_sta);
+	if (sdata->vif.type == NL80211_IFTYPE_AP_VLAN && !sdata->u.vlan.sta)
+		return atomic_read(&sdata->u.vlan.num_mcast_sta);
+	return -1;
+}
+
 u64 ieee80211_calculate_rx_timestamp(struct ieee80211_local *local,
 				     struct ieee80211_rx_status *status,
 				     unsigned int mpdu_len,
diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
index 9617f93..252d922 100644
--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c
@@ -2160,7 +2160,8 @@ ieee80211_deliver_skb(struct ieee80211_rx_data *rx)
 	     sdata->vif.type == NL80211_IFTYPE_AP_VLAN) &&
 	    !(sdata->flags & IEEE80211_SDATA_DONT_BRIDGE_PACKETS) &&
 	    (sdata->vif.type != NL80211_IFTYPE_AP_VLAN || !sdata->u.vlan.sta)) {
-		if (is_multicast_ether_addr(ehdr->h_dest)) {
+		if (is_multicast_ether_addr(ehdr->h_dest) &&
+		    ieee80211_vif_get_num_mcast_if(sdata) != 0) {
 			/*
 			 * send multicast frames both to higher layers in
 			 * local net stack and back to the wireless medium
@@ -2169,7 +2170,7 @@ ieee80211_deliver_skb(struct ieee80211_rx_data *rx)
 			if (!xmit_skb)
 				net_info_ratelimited("%s: failed to clone multicast frame\n",
 						    dev->name);
-		} else {
+		} else if (!is_multicast_ether_addr(ehdr->h_dest)) {
 			dsta = sta_info_get(sdata, skb->data);
 			if (dsta) {
 				/*
diff --git a/net/mac80211/sta_info.c b/net/mac80211/sta_info.c
index 76b737d..216ef65 100644
--- a/net/mac80211/sta_info.c
+++ b/net/mac80211/sta_info.c
@@ -1882,10 +1882,7 @@ int sta_info_move_state(struct sta_info *sta,
 			if (!sta->sta.support_p2p_ps)
 				ieee80211_recalc_p2p_go_ps_allowed(sta->sdata);
 		} else if (sta->sta_state == IEEE80211_STA_AUTHORIZED) {
-			if (sta->sdata->vif.type == NL80211_IFTYPE_AP ||
-			    (sta->sdata->vif.type == NL80211_IFTYPE_AP_VLAN &&
-			     !sta->sdata->u.vlan.sta))
-				atomic_dec(&sta->sdata->bss->num_mcast_sta);
+			ieee80211_vif_dec_num_mcast(sta->sdata);
 			clear_bit(WLAN_STA_AUTHORIZED, &sta->_flags);
 			ieee80211_clear_fast_xmit(sta);
 			ieee80211_clear_fast_rx(sta);
@@ -1893,10 +1890,7 @@ int sta_info_move_state(struct sta_info *sta,
 		break;
 	case IEEE80211_STA_AUTHORIZED:
 		if (sta->sta_state == IEEE80211_STA_ASSOC) {
-			if (sta->sdata->vif.type == NL80211_IFTYPE_AP ||
-			    (sta->sdata->vif.type == NL80211_IFTYPE_AP_VLAN &&
-			     !sta->sdata->u.vlan.sta))
-				atomic_inc(&sta->sdata->bss->num_mcast_sta);
+			ieee80211_vif_inc_num_mcast(sta->sdata);
 			set_bit(WLAN_STA_AUTHORIZED, &sta->_flags);
 			ieee80211_check_fast_xmit(sta);
 			ieee80211_check_fast_rx(sta);
diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index 5023966..c3ce86e 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -331,9 +331,8 @@ ieee80211_tx_h_check_assoc(struct ieee80211_tx_data *tx)
 			I802_DEBUG_INC(tx->local->tx_handlers_drop_not_assoc);
 			return TX_DROP;
 		}
-	} else if (unlikely(tx->sdata->vif.type == NL80211_IFTYPE_AP &&
-			    ieee80211_is_data(hdr->frame_control) &&
-			    !atomic_read(&tx->sdata->u.ap.num_mcast_sta))) {
+	} else if (unlikely(ieee80211_is_data(hdr->frame_control) &&
+			    ieee80211_vif_get_num_mcast_if(tx->sdata) == 0)) {
 		/*
 		 * No associated STAs - no need to send multicast
 		 * frames.
-- 
2.1.4

[PATCH v5 3/4] cfg80211: configure multicast to unicast for AP interfaces

[Michael Braun]

This add a userspace toggle to configure multicast to unicast.

Signed-off-by: Michael Braun <michael-dev-1SGGS//iJ+Y38rf8aCqVIw@public.gmane.org>
---
 include/net/cfg80211.h       |  6 ++++++
 include/uapi/linux/nl80211.h | 10 ++++++++++
 net/wireless/nl80211.c       | 36 ++++++++++++++++++++++++++++++++++++
 net/wireless/rdev-ops.h      | 12 ++++++++++++
 net/wireless/trace.h         | 19 +++++++++++++++++++
 5 files changed, 83 insertions(+)

diff --git a/include/net/cfg80211.h b/include/net/cfg80211.h
index 7ce6223..7b0941d 100644
--- a/include/net/cfg80211.h
+++ b/include/net/cfg80211.h
@@ -2460,6 +2460,8 @@ struct cfg80211_qos_map {
  *
  * @set_wds_peer: set the WDS peer for a WDS interface
  *
+ * @set_multicast_to_unicast: configure multicast to unicast conversion for BSS
+ *
  * @rfkill_poll: polls the hw rfkill line, use cfg80211 reporting
  *	functions to adjust rfkill hw state
  *
@@ -2722,6 +2724,10 @@ struct cfg80211_ops {
 	int	(*set_wds_peer)(struct wiphy *wiphy, struct net_device *dev,
 				const u8 *addr);
 
+	int	(*set_multicast_to_unicast)(struct wiphy *wiphy,
+					    struct net_device *dev,
+					    const bool enabled);
+
 	void	(*rfkill_poll)(struct wiphy *wiphy);
 
 #ifdef CONFIG_NL80211_TESTMODE
diff --git a/include/uapi/linux/nl80211.h b/include/uapi/linux/nl80211.h
index 2206941..1b9e87b 100644
--- a/include/uapi/linux/nl80211.h
+++ b/include/uapi/linux/nl80211.h
@@ -599,6 +599,9 @@
  *
  * @NL80211_CMD_SET_WDS_PEER: Set the MAC address of the peer on a WDS interface.
  *
+ * @NL80211_CMD_SET_MULTICAST_TO_UNICAST: Configure if AP interface should
+ *      perform multicast to unicast conversion (per-BSS).
+ *
  * @NL80211_CMD_JOIN_MESH: Join a mesh. The mesh ID must be given, and initial
  *	mesh config parameters may be given.
  * @NL80211_CMD_LEAVE_MESH: Leave the mesh network -- no special arguments, the
@@ -1026,6 +1029,8 @@ enum nl80211_commands {
 
 	NL80211_CMD_ABORT_SCAN,
 
+	NL80211_CMD_SET_MULTICAST_TO_UNICAST,
+
 	/* add new commands above here */
 
 	/* used to define NL80211_CMD_MAX below */
@@ -1867,6 +1872,9 @@ enum nl80211_commands {
  * @NL80211_ATTR_MESH_PEER_AID: Association ID for the mesh peer (u16). This is
  *	used to pull the stored data for mesh peer in power save state.
  *
+ * @NL80211_ATTR_MULTICAST_TO_UNICAST_ENABLED: Multicast packets should be
+ *      send out as unicast to all stations.
+ *
  * @NUM_NL80211_ATTR: total number of nl80211_attrs available
  * @NL80211_ATTR_MAX: highest attribute number currently defined
  * @__NL80211_ATTR_AFTER_LAST: internal use
@@ -2261,6 +2269,8 @@ enum nl80211_attrs {
 
 	NL80211_ATTR_MESH_PEER_AID,
 
+	NL80211_ATTR_MULTICAST_TO_UNICAST_ENABLED,
+
 	/* add attributes here, update the policy in nl80211.c */
 
 	__NL80211_ATTR_AFTER_LAST,
diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index f02653a..57b5d70 100644
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -409,6 +409,7 @@ static const struct nla_policy nl80211_policy[NUM_NL80211_ATTR] = {
 		.len = VHT_MUMIMO_GROUPS_DATA_LEN
 	},
 	[NL80211_ATTR_MU_MIMO_FOLLOW_MAC_ADDR] = { .len = ETH_ALEN },
+	[NL80211_ATTR_MULTICAST_TO_UNICAST_ENABLED] = { .type = NLA_U8, },
 };
 
 /* policy for the key attributes */
@@ -1538,6 +1539,7 @@ static int nl80211_send_wiphy(struct cfg80211_registered_device *rdev,
 				goto nla_put_failure;
 		}
 		CMD(set_wds_peer, SET_WDS_PEER);
+		CMD(set_multicast_to_unicast, SET_MULTICAST_TO_UNICAST);
 		if (rdev->wiphy.flags & WIPHY_FLAG_SUPPORTS_TDLS) {
 			CMD(tdls_mgmt, TDLS_MGMT);
 			CMD(tdls_oper, TDLS_OPER);
@@ -2164,6 +2166,32 @@ static int nl80211_set_wds_peer(struct sk_buff *skb, struct genl_info *info)
 	return rdev_set_wds_peer(rdev, dev, bssid);
 }
 
+static int nl80211_set_multicast_to_unicast(struct sk_buff *skb,
+					    struct genl_info *info)
+{
+	struct cfg80211_registered_device *rdev = info->user_ptr[0];
+	struct net_device *dev = info->user_ptr[1];
+	struct wireless_dev *wdev = dev->ieee80211_ptr;
+	const struct nlattr *nla;
+	bool enabled;
+
+	if (!info->attrs[NL80211_ATTR_MULTICAST_TO_UNICAST_ENABLED])
+		return -EINVAL;
+
+	if (netif_running(dev))
+		return -EBUSY;
+
+	if (!rdev->ops->set_multicast_to_unicast)
+		return -EOPNOTSUPP;
+
+	if (wdev->iftype != NL80211_IFTYPE_AP)
+		return -EOPNOTSUPP;
+
+	nla = info->attrs[NL80211_ATTR_MULTICAST_TO_UNICAST_ENABLED];
+	enabled = nla_get_flag(nla);
+	return rdev_set_multicast_to_unicast(rdev, dev, enabled);
+}
+
 static int nl80211_set_wiphy(struct sk_buff *skb, struct genl_info *info)
 {
 	struct cfg80211_registered_device *rdev;
@@ -11574,6 +11602,14 @@ static const struct genl_ops nl80211_ops[] = {
 				  NL80211_FLAG_NEED_RTNL,
 	},
 	{
+		.cmd = NL80211_CMD_SET_MULTICAST_TO_UNICAST,
+		.doit = nl80211_set_multicast_to_unicast,
+		.policy = nl80211_policy,
+		.flags = GENL_UNS_ADMIN_PERM,
+		.internal_flags = NL80211_FLAG_NEED_NETDEV |
+				  NL80211_FLAG_NEED_RTNL,
+	},
+	{
 		.cmd = NL80211_CMD_JOIN_MESH,
 		.doit = nl80211_join_mesh,
 		.policy = nl80211_policy,
diff --git a/net/wireless/rdev-ops.h b/net/wireless/rdev-ops.h
index 85ff30b..7d93c3d 100644
--- a/net/wireless/rdev-ops.h
+++ b/net/wireless/rdev-ops.h
@@ -562,6 +562,18 @@ static inline int rdev_set_wds_peer(struct cfg80211_registered_device *rdev,
 	return ret;
 }
 
+static inline int
+rdev_set_multicast_to_unicast(struct cfg80211_registered_device *rdev,
+			      struct net_device *dev,
+			      const bool enabled)
+{
+	int ret;
+	trace_rdev_set_multicast_to_unicast(&rdev->wiphy, dev, enabled);
+	ret = rdev->ops->set_multicast_to_unicast(&rdev->wiphy, dev, enabled);
+	trace_rdev_return_int(&rdev->wiphy, ret);
+	return ret;
+}
+
 static inline void rdev_rfkill_poll(struct cfg80211_registered_device *rdev)
 {
 	trace_rdev_rfkill_poll(&rdev->wiphy);
diff --git a/net/wireless/trace.h b/net/wireless/trace.h
index 72b5255..8c9aa57 100644
--- a/net/wireless/trace.h
+++ b/net/wireless/trace.h
@@ -2940,6 +2940,25 @@ DEFINE_EVENT(wiphy_wdev_evt, rdev_abort_scan,
 	TP_PROTO(struct wiphy *wiphy, struct wireless_dev *wdev),
 	TP_ARGS(wiphy, wdev)
 );
+
+TRACE_EVENT(rdev_set_multicast_to_unicast,
+	TP_PROTO(struct wiphy *wiphy, struct net_device *netdev,
+		 const bool enabled),
+	TP_ARGS(wiphy, netdev, enabled),
+	TP_STRUCT__entry(
+		WIPHY_ENTRY
+		NETDEV_ENTRY
+		__field(bool, enabled)
+	),
+	TP_fast_assign(
+		WIPHY_ASSIGN;
+		NETDEV_ASSIGN;
+		__entry->enabled = enabled;
+	),
+	TP_printk(WIPHY_PR_FMT ", " NETDEV_PR_FMT ", unicast: %s",
+		  WIPHY_PR_ARG, NETDEV_PR_ARG,
+		  BOOL_TO_STR(__entry->enabled))
+);
 #endif /* !__RDEV_OPS_TRACE || TRACE_HEADER_MULTI_READ */
 
 #undef TRACE_INCLUDE_PATH
-- 
2.1.4

Re: [PATCH v5 3/4] cfg80211: configure multicast to unicast for AP interfaces

[Johannes Berg]

>   *
> + * @NL80211_ATTR_MULTICAST_TO_UNICAST_ENABLED: Multicast packets
> should be
> + *      send out as unicast to all stations.

You should document what type of attribute is expected. You probably
wanted a flag attribute, but ...

> +	[NL80211_ATTR_MULTICAST_TO_UNICAST_ENABLED] = { .type =
> NLA_U8, },

have u8 in the policy, yet

> +	enabled = nla_get_flag(nla);

actually use as a flag :)


In addition to that, I think you should clarify the "per-BSS" comment
in nl80211, and also clarify (at the same place) what kind of
functionality is expected from this.

johannes

[PATCH v5 4/4] mac80211: multicast to unicast conversion

[Michael Braun]

This patch adds support for sending multicast data packets with ARP, IPv4
and IPv6 payload (possible 802.1q tagged) as 802.11 unicast frames to all
stations.

IEEE 802.11 multicast has well known issues, among them:
 1. packets are not acked and hence not retransmitted, resulting in
    decreased reliablity
 2. packets are send at low rate, increasing time required on air

When used with AP_VLAN, there is another disadvantage:
 3. all stations in the BSS are woken up, regardsless of their AP_VLAN
    assignment.

By doing multicast to unicast conversion, all three issus are solved.

IEEE802.11-2012 proposes directed multicast service (DMS) using A-MSDU
frames and a station initiated control protocol. It has the advantage that
the station can recover the destination multicast mac address, but it is
not backward compatible with non QOS stations and does not enable the
administrator of a BSS to force this mode of operation within a BSS.
Additionally, it would require both the ap and the station to implement
the control protocol, which is optional on both ends. Furthermore, I've
seen a few mobile phone stations locally that indicate qos support but
won't complete DHCP if their broadcasts are encapsulated as A-MSDU. Though
they work fine with this series approach.

This patch therefore does not opt to implement DMS but instead just
replicates the packet and changes the destination address. As this works
fine with ARP, IPv4 and IPv6, it is limited to these protocols and normal
802.11 multicast frames are send out for all other payload protocols.

There is a runtime toggle to enable multicast conversion in a per-bss
fashion.

When there is only a single station assigned to the AP_VLAN interface, no
packet replication will occur. 4addr mode of operation is unchanged.

This change opts for iterating all BSS stations for finding the stations
assigned to this AP/AP_VLAN interface, as there currently is no per
AP_VLAN list to iterate and multicast packets are expected to be few.
If needed, such a list could be added later.

Signed-off-by: Michael Braun <michael-dev@fami-braun.de>

--
v5:
  - rename bss->unicast to bss->multicast_to_unicast
  - access sdata->bss only after checking iftype
v4:
  - rename MULTICAST_TO_UNICAST to MULTICAST_TO_UNICAST
v3: fix compile error for trace.h
v2: add nl80211 toggle
    rename tx_dnat to change_da
    change int to bool unicast
---
 net/mac80211/cfg.c            |  15 +++++++
 net/mac80211/debugfs_netdev.c |   3 ++
 net/mac80211/ieee80211_i.h    |   1 +
 net/mac80211/tx.c             | 101 ++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 120 insertions(+)

diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c
index 1edb017..1db4c3e 100644
--- a/net/mac80211/cfg.c
+++ b/net/mac80211/cfg.c
@@ -2242,6 +2242,20 @@ static int ieee80211_set_wds_peer(struct wiphy *wiphy, struct net_device *dev,
 	return 0;
 }
 
+static int ieee80211_set_multicast_to_unicast(struct wiphy *wiphy,
+					      struct net_device *dev,
+					      const bool enabled)
+{
+	struct ieee80211_sub_if_data *sdata = IEEE80211_DEV_TO_SUB_IF(dev);
+
+	if (sdata->vif.type != NL80211_IFTYPE_AP)
+		return -1;
+
+	sdata->u.ap.multicast_to_unicast = enabled;
+
+	return 0;
+}
+
 static void ieee80211_rfkill_poll(struct wiphy *wiphy)
 {
 	struct ieee80211_local *local = wiphy_priv(wiphy);
@@ -3400,6 +3414,7 @@ const struct cfg80211_ops mac80211_config_ops = {
 	.set_tx_power = ieee80211_set_tx_power,
 	.get_tx_power = ieee80211_get_tx_power,
 	.set_wds_peer = ieee80211_set_wds_peer,
+	.set_multicast_to_unicast = ieee80211_set_multicast_to_unicast,
 	.rfkill_poll = ieee80211_rfkill_poll,
 	CFG80211_TESTMODE_CMD(ieee80211_testmode_cmd)
 	CFG80211_TESTMODE_DUMP(ieee80211_testmode_dump)
diff --git a/net/mac80211/debugfs_netdev.c b/net/mac80211/debugfs_netdev.c
index ed7bff4..509c6c3 100644
--- a/net/mac80211/debugfs_netdev.c
+++ b/net/mac80211/debugfs_netdev.c
@@ -487,6 +487,8 @@ static ssize_t ieee80211_if_fmt_num_buffered_multicast(
 }
 IEEE80211_IF_FILE_R(num_buffered_multicast);
 
+IEEE80211_IF_FILE(multicast_to_unicast, u.ap.multicast_to_unicast, HEX);
+
 /* IBSS attributes */
 static ssize_t ieee80211_if_fmt_tsf(
 	const struct ieee80211_sub_if_data *sdata, char *buf, int buflen)
@@ -642,6 +644,7 @@ static void add_ap_files(struct ieee80211_sub_if_data *sdata)
 	DEBUGFS_ADD(dtim_count);
 	DEBUGFS_ADD(num_buffered_multicast);
 	DEBUGFS_ADD_MODE(tkip_mic_test, 0200);
+	DEBUGFS_ADD_MODE(multicast_to_unicast, 0600);
 }
 
 static void add_vlan_files(struct ieee80211_sub_if_data *sdata)
diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index 70c0963..84374ed 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -293,6 +293,7 @@ struct ieee80211_if_ap {
 			 driver_smps_mode; /* smps mode request */
 
 	struct work_struct request_smps_work;
+	bool multicast_to_unicast;
 };
 
 struct ieee80211_if_wds {
diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index c3ce86e..142201d 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -16,6 +16,7 @@
 #include <linux/kernel.h>
 #include <linux/slab.h>
 #include <linux/skbuff.h>
+#include <linux/if_vlan.h>
 #include <linux/etherdevice.h>
 #include <linux/bitmap.h>
 #include <linux/rcupdate.h>
@@ -1770,6 +1771,102 @@ bool ieee80211_tx_prepare_skb(struct ieee80211_hw *hw,
 }
 EXPORT_SYMBOL(ieee80211_tx_prepare_skb);
 
+/* rewrite destination mac address */
+static int ieee80211_change_da(struct sk_buff *skb, struct sta_info *sta)
+{
+	struct ethhdr *eth;
+	int err;
+
+	err = skb_ensure_writable(skb, ETH_HLEN);
+	if (unlikely(err))
+		return err;
+
+	eth = (void *)skb->data;
+	ether_addr_copy(eth->h_dest, sta->sta.addr);
+
+	return 0;
+}
+
+/* Check if multicast to unicast conversion is needed and do it.
+ * Returns 1 if skb was freed and should not be send out.
+ */
+static int
+ieee80211_tx_multicast_to_unicast(struct ieee80211_sub_if_data *sdata,
+				  struct sk_buff *skb, u32  info_flags)
+{
+	struct ieee80211_local *local = sdata->local;
+	const struct ethhdr *eth = (void *)skb->data;
+	const struct vlan_ethhdr *ethvlan = (void *)skb->data;
+	struct sta_info *sta, *prev = NULL;
+	struct sk_buff *cloned_skb;
+	u16 ethertype;
+
+	/* check if this is a multicast frame */
+	if (!is_multicast_ether_addr(eth->h_dest))
+		return 0;
+
+	/* multicast to unicast conversion only for AP interfaces */
+	switch (sdata->vif.type) {
+	case NL80211_IFTYPE_AP_VLAN:
+		sta = rcu_dereference(sdata->u.vlan.sta);
+		if (sta) /* 4addr */
+			return 0;
+		/* fall through */
+	case NL80211_IFTYPE_AP:
+		/* check runtime toggle for this bss */
+		if (!sdata->bss->multicast_to_unicast)
+			return 0;
+		break;
+	default:
+		return 0;
+	}
+
+	/* info_flags would not get preserved, used only by TLDS */
+	if (info_flags)
+		return 0;
+
+	/* multicast to unicast conversion only for some payload */
+	ethertype = ntohs(eth->h_proto);
+	if (ethertype == ETH_P_8021Q && skb->len >= VLAN_ETH_HLEN)
+		ethertype = ntohs(ethvlan->h_vlan_encapsulated_proto);
+	switch (ethertype) {
+	case ETH_P_ARP:
+	case ETH_P_IP:
+	case ETH_P_IPV6:
+		break;
+	default:
+		return 0;
+	}
+
+	/* clone packets and update destination mac */
+	list_for_each_entry_rcu(sta, &local->sta_list, list) {
+		if (sdata != sta->sdata)
+			continue;
+		if (unlikely(!ether_addr_equal(eth->h_source, sta->sta.addr)))
+			/* do not send back to source */
+			continue;
+		if (!prev) {
+			prev = sta;
+			continue;
+		}
+		cloned_skb = skb_clone(skb, GFP_ATOMIC);
+		if (unlikely(ieee80211_change_da(cloned_skb, prev))) {
+			dev_kfree_skb(cloned_skb);
+			continue;
+		}
+		__ieee80211_subif_start_xmit(cloned_skb, cloned_skb->dev, 0);
+		prev = sta;
+	}
+
+	if (likely(prev)) {
+		ieee80211_change_da(skb, prev);
+		return 0;
+	}
+
+	/* no STA connected, drop */
+	return 1;
+}
+
 /*
  * Returns false if the frame couldn't be transmitted but was queued instead.
  */
@@ -3353,6 +3450,10 @@ void __ieee80211_subif_start_xmit(struct sk_buff *skb,
 
 	rcu_read_lock();
 
+	/* AP multicast to unicast conversion */
+	if (ieee80211_tx_multicast_to_unicast(sdata, skb, info_flags))
+		goto out_free;
+
 	if (ieee80211_lookup_ra_sta(sdata, skb, &sta))
 		goto out_free;
 
-- 
2.1.4