cfg80211: introduce capability for 4addr mode

It's very likely that not many devices will support
four-address mode in station or AP mode so introduce
capability bits for both modes, set them in mac80211
and check them when userspace tries to use the mode.
Also, keep track of 4addr in cfg80211 (wireless_dev)
and not in mac80211 any more. mac80211 can also be
improved for the VLAN case by not looking at the
4addr flag but maintaining the station pointer for
it correctly. However, keep track of use_4addr for
station mode in mac80211 to avoid all the derefs.

Signed-off-by: Johannes Berg <[e-mail]>
Signed-off-by: John W. Linville <[e-mail]>

include/net/cfg80211.h

···
  *	by default -- this flag will be set depending on the kernel's default
  *	on wiphy_new(), but can be changed by the driver if it has a good
  *	reason to override the default
+ * @WIPHY_FLAG_4ADDR_AP: supports 4addr mode even on AP (with a single station
+ *	on a VLAN interface)
+ * @WIPHY_FLAG_4ADDR_STATION: supports 4addr mode even as a station
  */
 enum wiphy_flags {
 	WIPHY_FLAG_CUSTOM_REGULATORY	= BIT(0),
···
 	WIPHY_FLAG_DISABLE_BEACON_HINTS	= BIT(2),
 	WIPHY_FLAG_NETNS_OK		= BIT(3),
 	WIPHY_FLAG_PS_ON_BY_DEFAULT	= BIT(4),
+	WIPHY_FLAG_4ADDR_AP		= BIT(5),
+	WIPHY_FLAG_4ADDR_STATION	= BIT(6),
 };
 
 /**
···
  * @ssid_len: (private) Used by the internal configuration code
  * @wext: (private) Used by the internal wireless extensions compat code
  * @wext_bssid: (private) Used by the internal wireless extensions compat code
+ * @use_4addr: indicates 4addr mode is used on this interface, must be
+ *	set by driver (if supported) on add_interface BEFORE registering the
+ *	netdev and may otherwise be used by driver read-only, will be update
+ *	by cfg80211 on change_interface
  */
 struct wireless_dev {
 	struct wiphy *wiphy;
···
 	struct mutex mtx;
 
 	struct work_struct cleanup_work;
+
+	bool use_4addr;
 
 	/* currently used for IBSS and SME - might be rearranged later */
 	u8 ssid[IEEE80211_MAX_SSID_LEN];

net/mac80211/cfg.c

···
 	if (!nl80211_type_check(type))
 		return false;
 
-	if (params->use_4addr > 0) {
-		switch(type) {
-		case NL80211_IFTYPE_AP_VLAN:
-		case NL80211_IFTYPE_STATION:
-			break;
-		default:
-			return false;
-		}
-	}
 	return true;
 }
 
···
 					    params->mesh_id_len,
 					    params->mesh_id);
 
-	if (params->use_4addr >= 0)
-		sdata->use_4addr = !!params->use_4addr;
-
 	if (sdata->vif.type != NL80211_IFTYPE_MONITOR || !flags)
 		return 0;
+
+	if (type == NL80211_IFTYPE_AP_VLAN &&
+	    params && params->use_4addr == 0)
+		rcu_assign_pointer(sdata->u.vlan.sta, NULL);
+	else if (type == NL80211_IFTYPE_STATION &&
+		 params && params->use_4addr >= 0)
+		sdata->u.mgd.use_4addr = params->use_4addr;
 
 	sdata->u.mntr_flags = *flags;
 	return 0;
···
 			return -EINVAL;
 		}
 
-		if (vlansdata->use_4addr) {
+		if (params->vlan->ieee80211_ptr->use_4addr) {
 			if (vlansdata->u.vlan.sta)
 				return -EBUSY;
 

net/mac80211/ieee80211_i.h

···
 	} mfp; /* management frame protection */
 
 	int wmm_last_param_set;
+
+	u8 use_4addr;
 };
 
 enum ieee80211_ibss_request {
···
 
 	int force_unicast_rateidx; /* forced TX rateidx for unicast frames */
 	int max_ratectrl_rateidx; /* max TX rateidx for rate control */
-
-	bool use_4addr; /* use 4-address frames */
 
 	union {
 		struct ieee80211_if_ap ap;

net/mac80211/iface.c

···
 		ieee80211_mandatory_rates(sdata->local,
 			sdata->local->hw.conf.channel->band);
 	sdata->drop_unencrypted = 0;
-	sdata->use_4addr = 0;
+	if (type == NL80211_IFTYPE_STATION)
+		sdata->u.mgd.use_4addr = false;
 
 	return 0;
 }
···
 	/* setup type-dependent data */
 	ieee80211_setup_sdata(sdata, type);
 
+	if (params) {
+		ndev->ieee80211_ptr->use_4addr = params->use_4addr;
+		if (type == NL80211_IFTYPE_STATION)
+			sdata->u.mgd.use_4addr = params->use_4addr;
+	}
+
 	ret = register_netdevice(ndev);
 	if (ret)
 		goto fail;
···
 		ieee80211_sdata_set_mesh_id(sdata,
 					    params->mesh_id_len,
 					    params->mesh_id);
-
-	if (params && params->use_4addr >= 0)
-		sdata->use_4addr = !!params->use_4addr;
 
 	mutex_lock(&local->iflist_mtx);
 	list_add_tail_rcu(&sdata->list, &local->interfaces);

net/mac80211/main.c

···
 	if (!wiphy)
 		return NULL;
 
-	wiphy->flags |= WIPHY_FLAG_NETNS_OK;
+	wiphy->flags |= WIPHY_FLAG_NETNS_OK |
+			WIPHY_FLAG_4ADDR_AP |
+			WIPHY_FLAG_4ADDR_STATION;
 	wiphy->privid = mac80211_wiphy_privid;
 
 	/* Yes, putting cfg80211_bss into ieee80211_bss is a hack */

net/mac80211/rx.c

···
 	struct net_device *dev = sdata->dev;
 	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)rx->skb->data;
 
-	if (sdata->vif.type == NL80211_IFTYPE_AP_VLAN && !sdata->use_4addr &&
-	    ieee80211_has_a4(hdr->frame_control))
+	if (ieee80211_has_a4(hdr->frame_control) &&
+	    sdata->vif.type == NL80211_IFTYPE_AP_VLAN && !sdata->u.vlan.sta)
 		return -1;
-	if (sdata->use_4addr && is_multicast_ether_addr(hdr->addr1))
+
+	if (is_multicast_ether_addr(hdr->addr1) &&
+	    ((sdata->vif.type == NL80211_IFTYPE_AP_VLAN && sdata->u.vlan.sta) ||
+	     (sdata->vif.type == NL80211_IFTYPE_STATION && sdata->u.mgd.use_4addr)))
 		return -1;
 
 	return ieee80211_data_to_8023(rx->skb, dev->dev_addr, sdata->vif.type);
···
 	if ((sdata->vif.type == NL80211_IFTYPE_AP ||
 	     sdata->vif.type == NL80211_IFTYPE_AP_VLAN) &&
 	    !(sdata->flags & IEEE80211_SDATA_DONT_BRIDGE_PACKETS) &&
-	    (rx->flags & IEEE80211_RX_RA_MATCH) && !rx->sdata->use_4addr) {
+	    (rx->flags & IEEE80211_RX_RA_MATCH) &&
+	    (sdata->vif.type != NL80211_IFTYPE_AP_VLAN || !sdata->u.vlan.sta)) {
 		if (is_multicast_ether_addr(ehdr->h_dest)) {
 			/*
 			 * send multicast frames both to higher layers in
···
 
 	switch (sdata->vif.type) {
 	case NL80211_IFTYPE_STATION:
-		if (!bssid && !sdata->use_4addr)
+		if (!bssid && !sdata->u.mgd.use_4addr)
 			return 0;
 		if (!multicast &&
 		    compare_ether_addr(sdata->dev->dev_addr, hdr->addr1) != 0) {

net/mac80211/tx.c

···
 
 	hdr = (struct ieee80211_hdr *) skb->data;
 
-	if ((sdata->vif.type == NL80211_IFTYPE_AP_VLAN) && sdata->use_4addr)
+	if (sdata->vif.type == NL80211_IFTYPE_AP_VLAN)
 		tx->sta = rcu_dereference(sdata->u.vlan.sta);
 	if (!tx->sta)
 		tx->sta = sta_info_get(local, hdr->addr1);
···
 	switch (sdata->vif.type) {
 	case NL80211_IFTYPE_AP_VLAN:
 		rcu_read_lock();
-		if (sdata->use_4addr)
-			sta = rcu_dereference(sdata->u.vlan.sta);
+		sta = rcu_dereference(sdata->u.vlan.sta);
 		if (sta) {
 			fc |= cpu_to_le16(IEEE80211_FCTL_FROMDS | IEEE80211_FCTL_TODS);
 			/* RA TA DA SA */
···
 #endif
 	case NL80211_IFTYPE_STATION:
 		memcpy(hdr.addr1, sdata->u.mgd.bssid, ETH_ALEN);
-		if (sdata->use_4addr && ethertype != ETH_P_PAE) {
+		if (sdata->u.mgd.use_4addr && ethertype != ETH_P_PAE) {
 			fc |= cpu_to_le16(IEEE80211_FCTL_FROMDS | IEEE80211_FCTL_TODS);
 			/* RA TA DA SA */
 			memcpy(hdr.addr2, dev->dev_addr, ETH_ALEN);

net/wireless/nl80211.c

···
 	return 0;
 }
 
+static int nl80211_valid_4addr(struct cfg80211_registered_device *rdev,
+			       u8 use_4addr, enum nl80211_iftype iftype)
+{
+	if (!use_4addr)
+		return 0;
+
+	switch (iftype) {
+	case NL80211_IFTYPE_AP_VLAN:
+		if (rdev->wiphy.flags & WIPHY_FLAG_4ADDR_AP)
+			return 0;
+		break;
+	case NL80211_IFTYPE_STATION:
+		if (rdev->wiphy.flags & WIPHY_FLAG_4ADDR_STATION)
+			return 0;
+		break;
+	default:
+		break;
+	}
+
+	return -EOPNOTSUPP;
+}
+
 static int nl80211_set_interface(struct sk_buff *skb, struct genl_info *info)
 {
 	struct cfg80211_registered_device *rdev;
···
 	if (info->attrs[NL80211_ATTR_4ADDR]) {
 		params.use_4addr = !!nla_get_u8(info->attrs[NL80211_ATTR_4ADDR]);
 		change = true;
+		err = nl80211_valid_4addr(rdev, params.use_4addr, ntype);
+		if (err)
+			goto unlock;
 	} else {
 		params.use_4addr = -1;
 	}
···
 		err = cfg80211_change_iface(rdev, dev, ntype, flags, &params);
 	else
 		err = 0;
+
+	if (!err && params.use_4addr != -1)
+		dev->ieee80211_ptr->use_4addr = params.use_4addr;
 
  unlock:
 	dev_put(dev);
···
 		params.mesh_id_len = nla_len(info->attrs[NL80211_ATTR_MESH_ID]);
 	}
 
-	if (info->attrs[NL80211_ATTR_4ADDR])
+	if (info->attrs[NL80211_ATTR_4ADDR]) {
 		params.use_4addr = !!nla_get_u8(info->attrs[NL80211_ATTR_4ADDR]);
+		err = nl80211_valid_4addr(rdev, params.use_4addr, type);
+		if (err)
+			goto unlock;
+	}
 
 	err = parse_monitor_flags(type == NL80211_IFTYPE_MONITOR ?
 				  info->attrs[NL80211_ATTR_MNTR_FLAGS] : NULL,

net/wireless/util.c

···
 		return -EOPNOTSUPP;
 
 	if (ntype != otype) {
+		dev->ieee80211_ptr->use_4addr = false;
+
 		switch (otype) {
 		case NL80211_IFTYPE_ADHOC:
 			cfg80211_leave_ibss(rdev, dev, false);
···
 					     ntype, flags, params);
 
 	WARN_ON(!err && dev->ieee80211_ptr->iftype != ntype);
+
+	if (!err && params && params->use_4addr != -1)
+		dev->ieee80211_ptr->use_4addr = params->use_4addr;
 
 	return err;
 }