cfg80211: advertise possible interface combinations

Add the ability to advertise interface combinations in nl80211.
This allows the driver to indicate what the combinations are
that it supports. "Combinations" of just a single interface are
implicit, as previously. Note that cfg80211 will enforce that
the restrictions are met, but not for all drivers yet (once all
drivers are updated, we can remove the flag and enforce for all).

When no combinations are actually supported, an empty list will
be exported so that userspace can know if the kernel exported
this info or not (although it isn't clear to me what tools using
the info should do if the kernel didn't export it).

Since some interface types are purely virtual/software and don't
fit the restrictions, those are exposed in a new list of pure SW
types, not subject to restrictions. This mainly exists to handle
AP-VLAN and monitor interfaces in mac80211.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

4 files changed, 251 insertions, 14 deletions

diff --git a/net/wireless/core.c b/net/wireless/core.c
index 18b002f..c22ef34 100644
--- a/net/wireless/core.c
+++ b/net/wireless/core.c
@@ -416,6 +416,67 @@ struct wiphy *wiphy_new(const struct cfg80211_ops *ops, int sizeof_priv)
 }
 EXPORT_SYMBOL(wiphy_new);
 
+static int wiphy_verify_combinations(struct wiphy *wiphy)
+{
+	const struct ieee80211_iface_combination *c;
+	int i, j;
+
+	/* If we have combinations enforce them */
+	if (wiphy->n_iface_combinations)
+		wiphy->flags |= WIPHY_FLAG_ENFORCE_COMBINATIONS;
+
+	for (i = 0; i < wiphy->n_iface_combinations; i++) {
+		u32 cnt = 0;
+		u16 all_iftypes = 0;
+
+		c = &wiphy->iface_combinations[i];
+
+		/* Combinations with just one interface aren't real */
+		if (WARN_ON(c->max_interfaces < 2))
+			return -EINVAL;
+
+		/* Need at least one channel */
+		if (WARN_ON(!c->num_different_channels))
+			return -EINVAL;
+
+		if (WARN_ON(!c->n_limits))
+			return -EINVAL;
+
+		for (j = 0; j < c->n_limits; j++) {
+			u16 types = c->limits[j].types;
+
+			/*
+			 * interface types shouldn't overlap, this is
+			 * used in cfg80211_can_change_interface()
+			 */
+			if (WARN_ON(types & all_iftypes))
+				return -EINVAL;
+			all_iftypes |= types;
+
+			if (WARN_ON(!c->limits[j].max))
+				return -EINVAL;
+
+			/* Shouldn't list software iftypes in combinations! */
+			if (WARN_ON(wiphy->software_iftypes & types))
+				return -EINVAL;
+
+			cnt += c->limits[j].max;
+			/*
+			 * Don't advertise an unsupported type
+			 * in a combination.
+			 */
+			if (WARN_ON((wiphy->interface_modes & types) != types))
+				return -EINVAL;
+		}
+
+		/* You can't even choose that many! */
+		if (WARN_ON(cnt < c->max_interfaces))
+			return -EINVAL;
+	}
+
+	return 0;
+}
+
 int wiphy_register(struct wiphy *wiphy)
 {
 	struct cfg80211_registered_device *rdev = wiphy_to_dev(wiphy);
@@ -444,6 +505,10 @@ int wiphy_register(struct wiphy *wiphy)
 	if (WARN_ON(ifmodes != wiphy->interface_modes))
 		wiphy->interface_modes = ifmodes;
 
+	res = wiphy_verify_combinations(wiphy);
+	if (res)
+		return res;
+
 	/* sanity check supported bands/channels */
 	for (band = 0; band < IEEE80211_NUM_BANDS; band++) {
 		sband = wiphy->bands[band];
@@ -698,6 +763,7 @@ static int cfg80211_netdev_notifier_call(struct notifier_block * nb,
 	struct net_device *dev = ndev;
 	struct wireless_dev *wdev = dev->ieee80211_ptr;
 	struct cfg80211_registered_device *rdev;
+	int ret;
 
 	if (!wdev)
 		return NOTIFY_DONE;
@@ -893,6 +959,9 @@ static int cfg80211_netdev_notifier_call(struct notifier_block * nb,
 			return notifier_from_errno(-EOPNOTSUPP);
 		if (rfkill_blocked(rdev->rfkill))
 			return notifier_from_errno(-ERFKILL);
+		ret = cfg80211_can_add_interface(rdev, wdev->iftype);
+		if (ret)
+			return notifier_from_errno(ret);
 		break;
 	}
 
diff --git a/net/wireless/core.h b/net/wireless/core.h
index d4b8f4c..bf0fb40 100644
--- a/net/wireless/core.h
+++ b/net/wireless/core.h
@@ -422,6 +422,17 @@ int cfg80211_change_iface(struct cfg80211_registered_device *rdev,
 			  u32 *flags, struct vif_params *params);
 void cfg80211_process_rdev_events(struct cfg80211_registered_device *rdev);
 
+int cfg80211_can_change_interface(struct cfg80211_registered_device *rdev,
+				  struct wireless_dev *wdev,
+				  enum nl80211_iftype iftype);
+
+static inline int
+cfg80211_can_add_interface(struct cfg80211_registered_device *rdev,
+			   enum nl80211_iftype iftype)
+{
+	return cfg80211_can_change_interface(rdev, NULL, iftype);
+}
+
 struct ieee80211_channel *
 rdev_freq_to_chan(struct cfg80211_registered_device *rdev,
 		  int freq, enum nl80211_channel_type channel_type);
diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index 9ef8e28..beac296 100644
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -564,6 +564,88 @@ static int nl80211_key_allowed(struct wireless_dev *wdev)
 	return 0;
 }
 
+static int nl80211_put_iftypes(struct sk_buff *msg, u32 attr, u16 ifmodes)
+{
+	struct nlattr *nl_modes = nla_nest_start(msg, attr);
+	int i;
+
+	if (!nl_modes)
+		goto nla_put_failure;
+
+	i = 0;
+	while (ifmodes) {
+		if (ifmodes & 1)
+			NLA_PUT_FLAG(msg, i);
+		ifmodes >>= 1;
+		i++;
+	}
+
+	nla_nest_end(msg, nl_modes);
+	return 0;
+
+nla_put_failure:
+	return -ENOBUFS;
+}
+
+static int nl80211_put_iface_combinations(struct wiphy *wiphy,
+					  struct sk_buff *msg)
+{
+	struct nlattr *nl_combis;
+	int i, j;
+
+	nl_combis = nla_nest_start(msg,
+				NL80211_ATTR_INTERFACE_COMBINATIONS);
+	if (!nl_combis)
+		goto nla_put_failure;
+
+	for (i = 0; i < wiphy->n_iface_combinations; i++) {
+		const struct ieee80211_iface_combination *c;
+		struct nlattr *nl_combi, *nl_limits;
+
+		c = &wiphy->iface_combinations[i];
+
+		nl_combi = nla_nest_start(msg, i + 1);
+		if (!nl_combi)
+			goto nla_put_failure;
+
+		nl_limits = nla_nest_start(msg, NL80211_IFACE_COMB_LIMITS);
+		if (!nl_limits)
+			goto nla_put_failure;
+
+		for (j = 0; j < c->n_limits; j++) {
+			struct nlattr *nl_limit;
+
+			nl_limit = nla_nest_start(msg, j + 1);
+			if (!nl_limit)
+				goto nla_put_failure;
+			NLA_PUT_U32(msg, NL80211_IFACE_LIMIT_MAX,
+				    c->limits[j].max);
+			if (nl80211_put_iftypes(msg, NL80211_IFACE_LIMIT_TYPES,
+						c->limits[j].types))
+				goto nla_put_failure;
+			nla_nest_end(msg, nl_limit);
+		}
+
+		nla_nest_end(msg, nl_limits);
+
+		if (c->beacon_int_infra_match)
+			NLA_PUT_FLAG(msg,
+				NL80211_IFACE_COMB_STA_AP_BI_MATCH);
+		NLA_PUT_U32(msg, NL80211_IFACE_COMB_NUM_CHANNELS,
+			    c->num_different_channels);
+		NLA_PUT_U32(msg, NL80211_IFACE_COMB_MAXNUM,
+			    c->max_interfaces);
+
+		nla_nest_end(msg, nl_combi);
+	}
+
+	nla_nest_end(msg, nl_combis);
+
+	return 0;
+nla_put_failure:
+	return -ENOBUFS;
+}
+
 static int nl80211_send_wiphy(struct sk_buff *msg, u32 pid, u32 seq, int flags,
 			      struct cfg80211_registered_device *dev)
 {
@@ -571,13 +653,11 @@ static int nl80211_send_wiphy(struct sk_buff *msg, u32 pid, u32 seq, int flags,
 	struct nlattr *nl_bands, *nl_band;
 	struct nlattr *nl_freqs, *nl_freq;
 	struct nlattr *nl_rates, *nl_rate;
-	struct nlattr *nl_modes;
 	struct nlattr *nl_cmds;
 	enum ieee80211_band band;
 	struct ieee80211_channel *chan;
 	struct ieee80211_rate *rate;
 	int i;
-	u16 ifmodes = dev->wiphy.interface_modes;
 	const struct ieee80211_txrx_stypes *mgmt_stypes =
 				dev->wiphy.mgmt_stypes;
 
@@ -637,20 +717,10 @@ static int nl80211_send_wiphy(struct sk_buff *msg, u32 pid, u32 seq, int flags,
 		}
 	}
 
-	nl_modes = nla_nest_start(msg, NL80211_ATTR_SUPPORTED_IFTYPES);
-	if (!nl_modes)
+	if (nl80211_put_iftypes(msg, NL80211_ATTR_SUPPORTED_IFTYPES,
+				dev->wiphy.interface_modes))
 		goto nla_put_failure;
 
-	i = 0;
-	while (ifmodes) {
-		if (ifmodes & 1)
-			NLA_PUT_FLAG(msg, i);
-		ifmodes >>= 1;
-		i++;
-	}
-
-	nla_nest_end(msg, nl_modes);
-
 	nl_bands = nla_nest_start(msg, NL80211_ATTR_WIPHY_BANDS);
 	if (!nl_bands)
 		goto nla_put_failure;
@@ -865,6 +935,13 @@ static int nl80211_send_wiphy(struct sk_buff *msg, u32 pid, u32 seq, int flags,
 		nla_nest_end(msg, nl_wowlan);
 	}
 
+	if (nl80211_put_iftypes(msg, NL80211_ATTR_SOFTWARE_IFTYPES,
+				dev->wiphy.software_iftypes))
+		goto nla_put_failure;
+
+	if (nl80211_put_iface_combinations(&dev->wiphy, msg))
+		goto nla_put_failure;
+
 	return genlmsg_end(msg, hdr);
 
  nla_put_failure:
diff --git a/net/wireless/util.c b/net/wireless/util.c
index 414c9f6..95e4e25 100644
--- a/net/wireless/util.c
+++ b/net/wireless/util.c
@@ -803,6 +803,11 @@ int cfg80211_change_iface(struct cfg80211_registered_device *rdev,
 		return -EBUSY;
 
 	if (ntype != otype) {
+		err = cfg80211_can_change_interface(rdev, dev->ieee80211_ptr,
+						    ntype);
+		if (err)
+			return err;
+
 		dev->ieee80211_ptr->use_4addr = false;
 		dev->ieee80211_ptr->mesh_id_up_len = 0;
 
@@ -921,3 +926,78 @@ int cfg80211_validate_beacon_int(struct cfg80211_registered_device *rdev,
 
 	return res;
 }
+
+int cfg80211_can_change_interface(struct cfg80211_registered_device *rdev,
+				  struct wireless_dev *wdev,
+				  enum nl80211_iftype iftype)
+{
+	struct wireless_dev *wdev_iter;
+	int num[NUM_NL80211_IFTYPES];
+	int total = 1;
+	int i, j;
+
+	ASSERT_RTNL();
+
+	/* Always allow software iftypes */
+	if (rdev->wiphy.software_iftypes & BIT(iftype))
+		return 0;
+
+	/*
+	 * Drivers will gradually all set this flag, until all
+	 * have it we only enforce for those that set it.
+	 */
+	if (!(rdev->wiphy.flags & WIPHY_FLAG_ENFORCE_COMBINATIONS))
+		return 0;
+
+	memset(num, 0, sizeof(num));
+
+	num[iftype] = 1;
+
+	mutex_lock(&rdev->devlist_mtx);
+	list_for_each_entry(wdev_iter, &rdev->netdev_list, list) {
+		if (wdev_iter == wdev)
+			continue;
+		if (!netif_running(wdev_iter->netdev))
+			continue;
+
+		if (rdev->wiphy.software_iftypes & BIT(wdev_iter->iftype))
+			continue;
+
+		num[wdev_iter->iftype]++;
+		total++;
+	}
+	mutex_unlock(&rdev->devlist_mtx);
+
+	for (i = 0; i < rdev->wiphy.n_iface_combinations; i++) {
+		const struct ieee80211_iface_combination *c;
+		struct ieee80211_iface_limit *limits;
+
+		c = &rdev->wiphy.iface_combinations[i];
+
+		limits = kmemdup(c->limits, sizeof(limits[0]) * c->n_limits,
+				 GFP_KERNEL);
+		if (!limits)
+			return -ENOMEM;
+		if (total > c->max_interfaces)
+			goto cont;
+
+		for (iftype = 0; iftype < NUM_NL80211_IFTYPES; iftype++) {
+			if (rdev->wiphy.software_iftypes & BIT(iftype))
+				continue;
+			for (j = 0; j < c->n_limits; j++) {
+				if (!(limits[j].types & iftype))
+					continue;
+				if (limits[j].max < num[iftype])
+					goto cont;
+				limits[j].max -= num[iftype];
+			}
+		}
+		/* yay, it fits */
+		kfree(limits);
+		return 0;
+ cont:
+		kfree(limits);
+	}
+
+	return -EBUSY;
+}