cfg80211/mac80211: better channel handling

Currently (all tested with hwsim) you can do stupid
things like setting up an AP on a certain channel,
then adding another virtual interface and making
that associate on another channel -- this will make
the beaconing to move channel but obviously without
the necessary IEs data update.

In order to improve this situation, first make the
configuration APIs (cfg80211 and nl80211) aware of
multi-channel operation -- we'll eventually need
that in the future anyway. There's one userland API
change and one API addition. The API change is that
now SET_WIPHY must be called with virtual interface
index rather than only wiphy index in order to take
effect for that interface -- luckily all current
users (hostapd) do that. For monitor interfaces, the
old setting is preserved, but monitors are always
slaved to other devices anyway so no guarantees.

The second userland API change is the introduction
of a per virtual interface SET_CHANNEL command, that
hostapd should use going forward to make it easier
to understand what's going on (it can automatically
detect a kernel with this command).

Other than mac80211, no existing cfg80211 drivers
are affected by this change because they only allow
a single virtual interface.

mac80211, however, now needs to be aware that the
channel settings are per interface now, and needs
to disallow (for now) real multi-channel operation,
which is another important part of this patch.

One of the immediate benefits is that you can now
start hostapd to operate on a hardware that already
has a connection on another virtual interface, as
long as you specify the same channel.

Note that two things are left unhandled (this is an
improvement -- not a complete fix):

 * different HT/no-HT modes

   currently you could start an HT AP and then
   connect to a non-HT network on the same channel
   which would configure the hardware for no HT;
   that can be fixed fairly easily

 * CSA

   An AP we're connected to on a virtual interface
   might indicate switching channels, and in that
   case we would follow it, regardless of how many
   other interfaces are operating; this requires
   more effort to fix but is pretty rare after all

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

7 files changed, 163 insertions, 103 deletions

diff --git a/net/wireless/chan.c b/net/wireless/chan.c
index bf1737f..d92d088 100644
--- a/net/wireless/chan.c
+++ b/net/wireless/chan.c
@@ -10,38 +10,6 @@
 #include "core.h"
 
 struct ieee80211_channel *
-rdev_fixed_channel(struct cfg80211_registered_device *rdev,
-		   struct wireless_dev *for_wdev)
-{
-	struct wireless_dev *wdev;
-	struct ieee80211_channel *result = NULL;
-
-	WARN_ON(!mutex_is_locked(&rdev->devlist_mtx));
-
-	list_for_each_entry(wdev, &rdev->netdev_list, list) {
-		if (wdev == for_wdev)
-			continue;
-
-		/*
-		 * Lock manually to tell lockdep about allowed
-		 * nesting here if for_wdev->mtx is held already.
-		 * This is ok as it's all under the rdev devlist
-		 * mutex and as such can only be done once at any
-		 * given time.
-		 */
-		mutex_lock_nested(&wdev->mtx, SINGLE_DEPTH_NESTING);
-		if (wdev->current_bss)
-			result = wdev->current_bss->pub.channel;
-		wdev_unlock(wdev);
-
-		if (result)
-			break;
-	}
-
-	return result;
-}
-
-struct ieee80211_channel *
 rdev_freq_to_chan(struct cfg80211_registered_device *rdev,
 		  int freq, enum nl80211_channel_type channel_type)
 {
@@ -75,15 +43,22 @@ rdev_freq_to_chan(struct cfg80211_registered_device *rdev,
 	return chan;
 }
 
-int rdev_set_freq(struct cfg80211_registered_device *rdev,
-		  struct wireless_dev *for_wdev,
-		  int freq, enum nl80211_channel_type channel_type)
+int cfg80211_set_freq(struct cfg80211_registered_device *rdev,
+		      struct wireless_dev *wdev, int freq,
+		      enum nl80211_channel_type channel_type)
 {
 	struct ieee80211_channel *chan;
 	int result;
 
-	if (rdev_fixed_channel(rdev, for_wdev))
-		return -EBUSY;
+	if (wdev->iftype == NL80211_IFTYPE_MONITOR)
+		wdev = NULL;
+
+	if (wdev) {
+		ASSERT_WDEV_LOCK(wdev);
+
+		if (!netif_running(wdev->netdev))
+			return -ENETDOWN;
+	}
 
 	if (!rdev->ops->set_channel)
 		return -EOPNOTSUPP;
@@ -92,11 +67,14 @@ int rdev_set_freq(struct cfg80211_registered_device *rdev,
 	if (!chan)
 		return -EINVAL;
 
-	result = rdev->ops->set_channel(&rdev->wiphy, chan, channel_type);
+	result = rdev->ops->set_channel(&rdev->wiphy,
+					wdev ? wdev->netdev : NULL,
+					chan, channel_type);
 	if (result)
 		return result;
 
-	rdev->channel = chan;
+	if (wdev)
+		wdev->channel = chan;
 
 	return 0;
 }
diff --git a/net/wireless/core.h b/net/wireless/core.h
index b2234b4..ae930ac 100644
--- a/net/wireless/core.h
+++ b/net/wireless/core.h
@@ -70,9 +70,6 @@ struct cfg80211_registered_device {
 	struct work_struct conn_work;
 	struct work_struct event_work;
 
-	/* current channel */
-	struct ieee80211_channel *channel;
-
 	/* must be last because of the way we do wiphy_priv(),
 	 * and it should at least be aligned to NETDEV_ALIGN */
 	struct wiphy wiphy __attribute__((__aligned__(NETDEV_ALIGN)));
@@ -388,14 +385,11 @@ int cfg80211_change_iface(struct cfg80211_registered_device *rdev,
 void cfg80211_process_rdev_events(struct cfg80211_registered_device *rdev);
 
 struct ieee80211_channel *
-rdev_fixed_channel(struct cfg80211_registered_device *rdev,
-		   struct wireless_dev *for_wdev);
-struct ieee80211_channel *
 rdev_freq_to_chan(struct cfg80211_registered_device *rdev,
 		  int freq, enum nl80211_channel_type channel_type);
-int rdev_set_freq(struct cfg80211_registered_device *rdev,
-		  struct wireless_dev *for_wdev,
-		  int freq, enum nl80211_channel_type channel_type);
+int cfg80211_set_freq(struct cfg80211_registered_device *rdev,
+		      struct wireless_dev *wdev, int freq,
+		      enum nl80211_channel_type channel_type);
 
 u16 cfg80211_calculate_bitrate(struct rate_info *rate);
 
diff --git a/net/wireless/ibss.c b/net/wireless/ibss.c
index 6ef5a49..9825317 100644
--- a/net/wireless/ibss.c
+++ b/net/wireless/ibss.c
@@ -80,15 +80,10 @@ int __cfg80211_join_ibss(struct cfg80211_registered_device *rdev,
 			 struct cfg80211_cached_keys *connkeys)
 {
 	struct wireless_dev *wdev = dev->ieee80211_ptr;
-	struct ieee80211_channel *chan;
 	int err;
 
 	ASSERT_WDEV_LOCK(wdev);
 
-	chan = rdev_fixed_channel(rdev, wdev);
-	if (chan && chan != params->channel)
-		return -EBUSY;
-
 	if (wdev->ssid_len)
 		return -EALREADY;
 
diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index c27bef8..ec1b4a8 100644
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -588,6 +588,7 @@ static int nl80211_send_wiphy(struct sk_buff *msg, u32 pid, u32 seq, int flags,
 		i++;
 		NLA_PUT_U32(msg, i, NL80211_CMD_SET_WIPHY_NETNS);
 	}
+	CMD(set_channel, SET_CHANNEL);
 
 #undef CMD
 
@@ -688,10 +689,90 @@ static int parse_txq_params(struct nlattr *tb[],
 	return 0;
 }
 
+static bool nl80211_can_set_dev_channel(struct wireless_dev *wdev)
+{
+	/*
+	 * You can only set the channel explicitly for AP, mesh
+	 * and WDS type interfaces; all others have their channel
+	 * managed via their respective "establish a connection"
+	 * command (connect, join, ...)
+	 *
+	 * Monitors are special as they are normally slaved to
+	 * whatever else is going on, so they behave as though
+	 * you tried setting the wiphy channel itself.
+	 */
+	return !wdev ||
+		wdev->iftype == NL80211_IFTYPE_AP ||
+		wdev->iftype == NL80211_IFTYPE_WDS ||
+		wdev->iftype == NL80211_IFTYPE_MESH_POINT ||
+		wdev->iftype == NL80211_IFTYPE_MONITOR;
+}
+
+static int __nl80211_set_channel(struct cfg80211_registered_device *rdev,
+				 struct wireless_dev *wdev,
+				 struct genl_info *info)
+{
+	enum nl80211_channel_type channel_type = NL80211_CHAN_NO_HT;
+	u32 freq;
+	int result;
+
+	if (!info->attrs[NL80211_ATTR_WIPHY_FREQ])
+		return -EINVAL;
+
+	if (!nl80211_can_set_dev_channel(wdev))
+		return -EOPNOTSUPP;
+
+	if (info->attrs[NL80211_ATTR_WIPHY_CHANNEL_TYPE]) {
+		channel_type = nla_get_u32(info->attrs[
+				   NL80211_ATTR_WIPHY_CHANNEL_TYPE]);
+		if (channel_type != NL80211_CHAN_NO_HT &&
+		    channel_type != NL80211_CHAN_HT20 &&
+		    channel_type != NL80211_CHAN_HT40PLUS &&
+		    channel_type != NL80211_CHAN_HT40MINUS)
+			return -EINVAL;
+	}
+
+	freq = nla_get_u32(info->attrs[NL80211_ATTR_WIPHY_FREQ]);
+
+	mutex_lock(&rdev->devlist_mtx);
+	if (wdev) {
+		wdev_lock(wdev);
+		result = cfg80211_set_freq(rdev, wdev, freq, channel_type);
+		wdev_unlock(wdev);
+	} else {
+		result = cfg80211_set_freq(rdev, NULL, freq, channel_type);
+	}
+	mutex_unlock(&rdev->devlist_mtx);
+
+	return result;
+}
+
+static int nl80211_set_channel(struct sk_buff *skb, struct genl_info *info)
+{
+	struct cfg80211_registered_device *rdev;
+	struct net_device *netdev;
+	int result;
+
+	rtnl_lock();
+
+	result = get_rdev_dev_by_info_ifindex(info, &rdev, &netdev);
+	if (result)
+		goto unlock;
+
+	result = __nl80211_set_channel(rdev, netdev->ieee80211_ptr, info);
+
+ unlock:
+	rtnl_unlock();
+
+	return result;
+}
+
 static int nl80211_set_wiphy(struct sk_buff *skb, struct genl_info *info)
 {
 	struct cfg80211_registered_device *rdev;
-	int result = 0, rem_txq_params = 0;
+	struct net_device *netdev = NULL;
+	struct wireless_dev *wdev;
+	int result, rem_txq_params = 0;
 	struct nlattr *nl_txq_params;
 	u32 changed;
 	u8 retry_short = 0, retry_long = 0;
@@ -700,16 +781,50 @@ static int nl80211_set_wiphy(struct sk_buff *skb, struct genl_info *info)
 
 	rtnl_lock();
 
+	/*
+	 * Try to find the wiphy and netdev. Normally this
+	 * function shouldn't need the netdev, but this is
+	 * done for backward compatibility -- previously
+	 * setting the channel was done per wiphy, but now
+	 * it is per netdev. Previous userland like hostapd
+	 * also passed a netdev to set_wiphy, so that it is
+	 * possible to let that go to the right netdev!
+	 */
 	mutex_lock(&cfg80211_mutex);
 
-	rdev = __cfg80211_rdev_from_info(info);
-	if (IS_ERR(rdev)) {
-		mutex_unlock(&cfg80211_mutex);
-		result = PTR_ERR(rdev);
-		goto unlock;
+	if (info->attrs[NL80211_ATTR_IFINDEX]) {
+		int ifindex = nla_get_u32(info->attrs[NL80211_ATTR_IFINDEX]);
+
+		netdev = dev_get_by_index(genl_info_net(info), ifindex);
+		if (netdev && netdev->ieee80211_ptr) {
+			rdev = wiphy_to_dev(netdev->ieee80211_ptr->wiphy);
+			mutex_lock(&rdev->mtx);
+		} else
+			netdev = NULL;
 	}
 
-	mutex_lock(&rdev->mtx);
+	if (!netdev) {
+		rdev = __cfg80211_rdev_from_info(info);
+		if (IS_ERR(rdev)) {
+			mutex_unlock(&cfg80211_mutex);
+			result = PTR_ERR(rdev);
+			goto unlock;
+		}
+		wdev = NULL;
+		netdev = NULL;
+		result = 0;
+
+		mutex_lock(&rdev->mtx);
+	} else if (netif_running(netdev) &&
+		   nl80211_can_set_dev_channel(netdev->ieee80211_ptr))
+		wdev = netdev->ieee80211_ptr;
+	else
+		wdev = NULL;
+
+	/*
+	 * end workaround code, by now the rdev is available
+	 * and locked, and wdev may or may not be NULL.
+	 */
 
 	if (info->attrs[NL80211_ATTR_WIPHY_NAME])
 		result = cfg80211_dev_rename(
@@ -748,26 +863,7 @@ static int nl80211_set_wiphy(struct sk_buff *skb, struct genl_info *info)
 	}
 
 	if (info->attrs[NL80211_ATTR_WIPHY_FREQ]) {
-		enum nl80211_channel_type channel_type = NL80211_CHAN_NO_HT;
-		u32 freq;
-
-		result = -EINVAL;
-
-		if (info->attrs[NL80211_ATTR_WIPHY_CHANNEL_TYPE]) {
-			channel_type = nla_get_u32(info->attrs[
-					   NL80211_ATTR_WIPHY_CHANNEL_TYPE]);
-			if (channel_type != NL80211_CHAN_NO_HT &&
-			    channel_type != NL80211_CHAN_HT20 &&
-			    channel_type != NL80211_CHAN_HT40PLUS &&
-			    channel_type != NL80211_CHAN_HT40MINUS)
-				goto bad_res;
-		}
-
-		freq = nla_get_u32(info->attrs[NL80211_ATTR_WIPHY_FREQ]);
-
-		mutex_lock(&rdev->devlist_mtx);
-		result = rdev_set_freq(rdev, NULL, freq, channel_type);
-		mutex_unlock(&rdev->devlist_mtx);
+		result = __nl80211_set_channel(rdev, wdev, info);
 		if (result)
 			goto bad_res;
 	}
@@ -864,6 +960,8 @@ static int nl80211_set_wiphy(struct sk_buff *skb, struct genl_info *info)
 
  bad_res:
 	mutex_unlock(&rdev->mtx);
+	if (netdev)
+		dev_put(netdev);
  unlock:
 	rtnl_unlock();
 	return result;
@@ -3561,9 +3659,8 @@ static int nl80211_associate(struct sk_buff *skb, struct genl_info *info)
 {
 	struct cfg80211_registered_device *rdev;
 	struct net_device *dev;
-	struct wireless_dev *wdev;
 	struct cfg80211_crypto_settings crypto;
-	struct ieee80211_channel *chan, *fixedchan;
+	struct ieee80211_channel *chan;
 	const u8 *bssid, *ssid, *ie = NULL, *prev_bssid = NULL;
 	int err, ssid_len, ie_len = 0;
 	bool use_mfp = false;
@@ -3606,16 +3703,6 @@ static int nl80211_associate(struct sk_buff *skb, struct genl_info *info)
 		goto out;
 	}
 
-	mutex_lock(&rdev->devlist_mtx);
-	wdev = dev->ieee80211_ptr;
-	fixedchan = rdev_fixed_channel(rdev, wdev);
-	if (fixedchan && chan != fixedchan) {
-		err = -EBUSY;
-		mutex_unlock(&rdev->devlist_mtx);
-		goto out;
-	}
-	mutex_unlock(&rdev->devlist_mtx);
-
 	ssid = nla_data(info->attrs[NL80211_ATTR_SSID]);
 	ssid_len = nla_len(info->attrs[NL80211_ATTR_SSID]);
 
@@ -5185,6 +5272,12 @@ static struct genl_ops nl80211_ops[] = {
 		.policy = nl80211_policy,
 		.flags = GENL_ADMIN_PERM,
 	},
+	{
+		.cmd = NL80211_CMD_SET_CHANNEL,
+		.doit = nl80211_set_channel,
+		.policy = nl80211_policy,
+		.flags = GENL_ADMIN_PERM,
+	},
 };
 
 static struct genl_multicast_group nl80211_mlme_mcgrp = {
diff --git a/net/wireless/sme.c b/net/wireless/sme.c
index dcd7685..14cf8163 100644
--- a/net/wireless/sme.c
+++ b/net/wireless/sme.c
@@ -740,7 +740,6 @@ int __cfg80211_connect(struct cfg80211_registered_device *rdev,
 		       const u8 *prev_bssid)
 {
 	struct wireless_dev *wdev = dev->ieee80211_ptr;
-	struct ieee80211_channel *chan;
 	struct cfg80211_bss *bss = NULL;
 	int err;
 
@@ -749,10 +748,6 @@ int __cfg80211_connect(struct cfg80211_registered_device *rdev,
 	if (wdev->sme_state != CFG80211_SME_IDLE)
 		return -EALREADY;
 
-	chan = rdev_fixed_channel(rdev, wdev);
-	if (chan && chan != connect->channel)
-		return -EBUSY;
-
 	if (WARN_ON(wdev->connect_keys)) {
 		kfree(wdev->connect_keys);
 		wdev->connect_keys = NULL;
diff --git a/net/wireless/wext-compat.c b/net/wireless/wext-compat.c
index 9ab5183..75848c6 100644
--- a/net/wireless/wext-compat.c
+++ b/net/wireless/wext-compat.c
@@ -781,16 +781,22 @@ int cfg80211_wext_siwfreq(struct net_device *dev,
 		return cfg80211_mgd_wext_siwfreq(dev, info, wextfreq, extra);
 	case NL80211_IFTYPE_ADHOC:
 		return cfg80211_ibss_wext_siwfreq(dev, info, wextfreq, extra);
-	default:
+	case NL80211_IFTYPE_MONITOR:
+	case NL80211_IFTYPE_WDS:
+	case NL80211_IFTYPE_MESH_POINT:
 		freq = cfg80211_wext_freq(wdev->wiphy, wextfreq);
 		if (freq < 0)
 			return freq;
 		if (freq == 0)
 			return -EINVAL;
+		wdev_lock(wdev);
 		mutex_lock(&rdev->devlist_mtx);
-		err = rdev_set_freq(rdev, NULL, freq, NL80211_CHAN_NO_HT);
+		err = cfg80211_set_freq(rdev, wdev, freq, NL80211_CHAN_NO_HT);
 		mutex_unlock(&rdev->devlist_mtx);
+		wdev_unlock(wdev);
 		return err;
+	default:
+		return -EOPNOTSUPP;
 	}
 }
 EXPORT_SYMBOL_GPL(cfg80211_wext_siwfreq);
@@ -800,7 +806,6 @@ int cfg80211_wext_giwfreq(struct net_device *dev,
 			  struct iw_freq *freq, char *extra)
 {
 	struct wireless_dev *wdev = dev->ieee80211_ptr;
-	struct cfg80211_registered_device *rdev = wiphy_to_dev(wdev->wiphy);
 
 	switch (wdev->iftype) {
 	case NL80211_IFTYPE_STATION:
@@ -808,9 +813,9 @@ int cfg80211_wext_giwfreq(struct net_device *dev,
 	case NL80211_IFTYPE_ADHOC:
 		return cfg80211_ibss_wext_giwfreq(dev, info, freq, extra);
 	default:
-		if (!rdev->channel)
+		if (!wdev->channel)
 			return -EINVAL;
-		freq->m = rdev->channel->center_freq;
+		freq->m = wdev->channel->center_freq;
 		freq->e = 6;
 		return 0;
 	}
diff --git a/net/wireless/wext-sme.c b/net/wireless/wext-sme.c
index 5615a88..8e5ab4f 100644
--- a/net/wireless/wext-sme.c
+++ b/net/wireless/wext-sme.c
@@ -107,7 +107,7 @@ int cfg80211_mgd_wext_siwfreq(struct net_device *dev,
 
 	/* SSID is not set, we just want to switch channel */
 	if (chan && !wdev->wext.connect.ssid_len) {
-		err = rdev_set_freq(rdev, wdev, freq, NL80211_CHAN_NO_HT);
+		err = cfg80211_set_freq(rdev, wdev, freq, NL80211_CHAN_NO_HT);
 		goto out;
 	}