7 files changed, 472 insertions, 19 deletions

diff --git a/include/linux/nl80211.h b/include/linux/nl80211.h
index 281a2bb6a6ec..0ea497cb607c 100644
--- a/include/linux/nl80211.h
+++ b/include/linux/nl80211.h
@@ -77,6 +77,39 @@
  */
 
 /**
+ * DOC: Virtual interface / concurrency capabilities
+ *
+ * Some devices are able to operate with virtual MACs, they can have
+ * more than one virtual interface. The capability handling for this
+ * is a bit complex though, as there may be a number of restrictions
+ * on the types of concurrency that are supported.
+ *
+ * To start with, each device supports the interface types listed in
+ * the %NL80211_ATTR_SUPPORTED_IFTYPES attribute, but by listing the
+ * types there no concurrency is implied.
+ *
+ * Once concurrency is desired, more attributes must be observed:
+ * To start with, since some interface types are purely managed in
+ * software, like the AP-VLAN type in mac80211 for example, there's
+ * an additional list of these, they can be added at any time and
+ * are only restricted by some semantic restrictions (e.g. AP-VLAN
+ * cannot be added without a corresponding AP interface). This list
+ * is exported in the %NL80211_ATTR_SOFTWARE_IFTYPES attribute.
+ *
+ * Further, the list of supported combinations is exported. This is
+ * in the %NL80211_ATTR_INTERFACE_COMBINATIONS attribute. Basically,
+ * it exports a list of "groups", and at any point in time the
+ * interfaces that are currently active must fall into any one of
+ * the advertised groups. Within each group, there are restrictions
+ * on the number of interfaces of different types that are supported
+ * and also the number of different channels, along with potentially
+ * some other restrictions. See &enum nl80211_if_combination_attrs.
+ *
+ * All together, these attributes define the concurrency of virtual
+ * interfaces that a given device supports.
+ */
+
+/**
  * enum nl80211_commands - supported nl80211 commands
  *
  * @NL80211_CMD_UNSPEC: unspecified command to catch errors
@@ -954,6 +987,14 @@ enum nl80211_commands {
  * @NL80211_ATTR_SCHED_SCAN_INTERVAL: Interval between scheduled scan
  *      cycles, in msecs.
  *
+ * @NL80211_ATTR_INTERFACE_COMBINATIONS: Nested attribute listing the supported
+ *      interface combinations. In each nested item, it contains attributes
+ *      defined in &enum nl80211_if_combination_attrs.
+ * @NL80211_ATTR_SOFTWARE_IFTYPES: Nested attribute (just like
+ *      %NL80211_ATTR_SUPPORTED_IFTYPES) containing the interface types that
+ *      are managed in software: interfaces of these types aren't subject to
+ *      any restrictions in their number or combinations.
+ *
  * @NL80211_ATTR_MAX: highest attribute number currently defined
  * @__NL80211_ATTR_AFTER_LAST: internal use
  */
@@ -1149,6 +1190,9 @@ enum nl80211_attrs {
 
         NL80211_ATTR_SCHED_SCAN_INTERVAL,
 
+        NL80211_ATTR_INTERFACE_COMBINATIONS,
+        NL80211_ATTR_SOFTWARE_IFTYPES,
+
         /* add attributes here, update the policy in nl80211.c */
 
         __NL80211_ATTR_AFTER_LAST,
@@ -1201,7 +1245,9 @@ enum nl80211_attrs {
  * @NL80211_IFTYPE_ADHOC: independent BSS member
  * @NL80211_IFTYPE_STATION: managed BSS member
  * @NL80211_IFTYPE_AP: access point
- * @NL80211_IFTYPE_AP_VLAN: VLAN interface for access points
+ * @NL80211_IFTYPE_AP_VLAN: VLAN interface for access points; VLAN interfaces
+ *      are a bit special in that they must always be tied to a pre-existing
+ *      AP type interface.
  * @NL80211_IFTYPE_WDS: wireless distribution interface
  * @NL80211_IFTYPE_MONITOR: monitor interface receiving all frames
  * @NL80211_IFTYPE_MESH_POINT: mesh point
@@ -2206,4 +2252,78 @@ enum nl80211_wowlan_triggers {
         MAX_NL80211_WOWLAN_TRIG = NUM_NL80211_WOWLAN_TRIG - 1
 };
 
+/**
+ * enum nl80211_iface_limit_attrs - limit attributes
+ * @NL80211_IFACE_LIMIT_UNSPEC: (reserved)
+ * @NL80211_IFACE_LIMIT_MAX: maximum number of interfaces that
+ *      can be chosen from this set of interface types (u32)
+ * @NL80211_IFACE_LIMIT_TYPES: nested attribute containing a
+ *      flag attribute for each interface type in this set
+ * @NUM_NL80211_IFACE_LIMIT: number of attributes
+ * @MAX_NL80211_IFACE_LIMIT: highest attribute number
+ */
+enum nl80211_iface_limit_attrs {
+        NL80211_IFACE_LIMIT_UNSPEC,
+        NL80211_IFACE_LIMIT_MAX,
+        NL80211_IFACE_LIMIT_TYPES,
+
+        /* keep last */
+        NUM_NL80211_IFACE_LIMIT,
+        MAX_NL80211_IFACE_LIMIT = NUM_NL80211_IFACE_LIMIT - 1
+};
+
+/**
+ * enum nl80211_if_combination_attrs -- interface combination attributes
+ *
+ * @NL80211_IFACE_COMB_UNSPEC: (reserved)
+ * @NL80211_IFACE_COMB_LIMITS: Nested attributes containing the limits
+ *      for given interface types, see &enum nl80211_iface_limit_attrs.
+ * @NL80211_IFACE_COMB_MAXNUM: u32 attribute giving the total number of
+ *      interfaces that can be created in this group. This number doesn't
+ *      apply to interfaces purely managed in software, which are listed
+ *      in a separate attribute %NL80211_ATTR_INTERFACES_SOFTWARE.
+ * @NL80211_IFACE_COMB_STA_AP_BI_MATCH: flag attribute specifying that
+ *      beacon intervals within this group must be all the same even for
+ *      infrastructure and AP/GO combinations, i.e. the GO(s) must adopt
+ *      the infrastructure network's beacon interval.
+ * @NL80211_IFACE_COMB_NUM_CHANNELS: u32 attribute specifying how many
+ *      different channels may be used within this group.
+ * @NUM_NL80211_IFACE_COMB: number of attributes
+ * @MAX_NL80211_IFACE_COMB: highest attribute number
+ *
+ * Examples:
+ *      limits = [ #{STA} <= 1, #{AP} <= 1 ], matching BI, channels = 1, max = 2
+ *      => allows an AP and a STA that must match BIs
+ *
+ *      numbers = [ #{AP, P2P-GO} <= 8 ], channels = 1, max = 8
+ *      => allows 8 of AP/GO
+ *
+ *      numbers = [ #{STA} <= 2 ], channels = 2, max = 2
+ *      => allows two STAs on different channels
+ *
+ *      numbers = [ #{STA} <= 1, #{P2P-client,P2P-GO} <= 3 ], max = 4
+ *      => allows a STA plus three P2P interfaces
+ *
+ * The list of these four possiblities could completely be contained
+ * within the %NL80211_ATTR_INTERFACE_COMBINATIONS attribute to indicate
+ * that any of these groups must match.
+ *
+ * "Combinations" of just a single interface will not be listed here,
+ * a single interface of any valid interface type is assumed to always
+ * be possible by itself. This means that implicitly, for each valid
+ * interface type, the following group always exists:
+ *      numbers = [ #{<type>} <= 1 ], channels = 1, max = 1
+ */
+enum nl80211_if_combination_attrs {
+        NL80211_IFACE_COMB_UNSPEC,
+        NL80211_IFACE_COMB_LIMITS,
+        NL80211_IFACE_COMB_MAXNUM,
+        NL80211_IFACE_COMB_STA_AP_BI_MATCH,
+        NL80211_IFACE_COMB_NUM_CHANNELS,
+
+        /* keep last */
+        NUM_NL80211_IFACE_COMB,
+        MAX_NL80211_IFACE_COMB = NUM_NL80211_IFACE_COMB - 1
+};
+
 #endif /* __LINUX_NL80211_H */
diff --git a/include/net/cfg80211.h b/include/net/cfg80211.h
index e1f1b41f7b13..04afcfb9eaf4 100644
--- a/include/net/cfg80211.h
+++ b/include/net/cfg80211.h
@@ -1547,6 +1547,10 @@ struct cfg80211_ops {
  *      hints read the documenation for regulatory_hint_found_beacon()
  * @WIPHY_FLAG_NETNS_OK: if not set, do not allow changing the netns of this
  *      wiphy at all
+ * @WIPHY_FLAG_ENFORCE_COMBINATIONS: Set this flag to enforce interface
+ *      combinations for this device. This flag is used for backward
+ *      compatibility only until all drivers advertise combinations and
+ *      they will always be enforced.
  * @WIPHY_FLAG_PS_ON_BY_DEFAULT: if set to true, powersave will be enabled
  *      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
@@ -1574,6 +1578,81 @@ enum wiphy_flags {
         WIPHY_FLAG_IBSS_RSN                     = BIT(8),
         WIPHY_FLAG_MESH_AUTH                    = BIT(10),
         WIPHY_FLAG_SUPPORTS_SCHED_SCAN          = BIT(11),
+        WIPHY_FLAG_ENFORCE_COMBINATIONS         = BIT(12),
+};
+
+/**
+ * struct ieee80211_iface_limit - limit on certain interface types
+ * @max: maximum number of interfaces of these types
+ * @types: interface types (bits)
+ */
+struct ieee80211_iface_limit {
+        u16 max;
+        u16 types;
+};
+
+/**
+ * struct ieee80211_iface_combination - possible interface combination
+ * @limits: limits for the given interface types
+ * @n_limits: number of limitations
+ * @num_different_channels: can use up to this many different channels
+ * @max_interfaces: maximum number of interfaces in total allowed in this
+ *      group
+ * @beacon_int_infra_match: In this combination, the beacon intervals
+ *      between infrastructure and AP types must match. This is required
+ *      only in special cases.
+ *
+ * These examples can be expressed as follows:
+ *
+ * Allow #STA <= 1, #AP <= 1, matching BI, channels = 1, 2 total:
+ *
+ *  struct ieee80211_iface_limit limits1[] = {
+ *      { .max = 1, .types = BIT(NL80211_IFTYPE_STATION), },
+ *      { .max = 1, .types = BIT(NL80211_IFTYPE_AP}, },
+ *  };
+ *  struct ieee80211_iface_combination combination1 = {
+ *      .limits = limits1,
+ *      .n_limits = ARRAY_SIZE(limits1),
+ *      .max_interfaces = 2,
+ *      .beacon_int_infra_match = true,
+ *  };
+ *
+ *
+ * Allow #{AP, P2P-GO} <= 8, channels = 1, 8 total:
+ *
+ *  struct ieee80211_iface_limit limits2[] = {
+ *      { .max = 8, .types = BIT(NL80211_IFTYPE_AP) |
+ *                           BIT(NL80211_IFTYPE_P2P_GO), },
+ *  };
+ *  struct ieee80211_iface_combination combination2 = {
+ *      .limits = limits2,
+ *      .n_limits = ARRAY_SIZE(limits2),
+ *      .max_interfaces = 8,
+ *      .num_different_channels = 1,
+ *  };
+ *
+ *
+ * Allow #STA <= 1, #{P2P-client,P2P-GO} <= 3 on two channels, 4 total.
+ * This allows for an infrastructure connection and three P2P connections.
+ *
+ *  struct ieee80211_iface_limit limits3[] = {
+ *      { .max = 1, .types = BIT(NL80211_IFTYPE_STATION), },
+ *      { .max = 3, .types = BIT(NL80211_IFTYPE_P2P_GO) |
+ *                           BIT(NL80211_IFTYPE_P2P_CLIENT), },
+ *  };
+ *  struct ieee80211_iface_combination combination3 = {
+ *      .limits = limits3,
+ *      .n_limits = ARRAY_SIZE(limits3),
+ *      .max_interfaces = 4,
+ *      .num_different_channels = 2,
+ *  };
+ */
+struct ieee80211_iface_combination {
+        const struct ieee80211_iface_limit *limits;
+        u32 num_different_channels;
+        u16 max_interfaces;
+        u8 n_limits;
+        bool beacon_int_infra_match;
 };
 
 struct mac_address {
@@ -1653,6 +1732,11 @@ struct wiphy_wowlan_support {
  * @priv: driver private data (sized according to wiphy_new() parameter)
  * @interface_modes: bitmask of interfaces types valid for this wiphy,
  *      must be set by driver
+ * @iface_combinations: Valid interface combinations array, should not
+ *      list single interface types.
+ * @n_iface_combinations: number of entries in @iface_combinations array.
+ * @software_iftypes: bitmask of software interface types, these are not
+ *      subject to any restrictions since they are purely managed in SW.
  * @flags: wiphy flags, see &enum wiphy_flags
  * @bss_priv_size: each BSS struct has private data allocated with it,
  *      this variable determines its size
@@ -1697,6 +1781,10 @@ struct wiphy {
 
         const struct ieee80211_txrx_stypes *mgmt_stypes;
 
+        const struct ieee80211_iface_combination *iface_combinations;
+        int n_iface_combinations;
+        u16 software_iftypes;
+
         u16 n_addresses;
 
         /* Supported interface modes, OR together BIT(NL80211_IFTYPE_...) */
diff --git a/net/mac80211/main.c b/net/mac80211/main.c
index 7f89011fa22d..79a2281678bf 100644
--- a/net/mac80211/main.c
+++ b/net/mac80211/main.c
@@ -685,7 +685,7 @@ EXPORT_SYMBOL(ieee80211_alloc_hw);
 int ieee80211_register_hw(struct ieee80211_hw *hw)
 {
         struct ieee80211_local *local = hw_to_local(hw);
-        int result;
+        int result, i;
         enum ieee80211_band band;
         int channels, max_bitrates;
         bool supp_ht;
@@ -743,11 +743,19 @@ int ieee80211_register_hw(struct ieee80211_hw *hw)
                 return -ENOMEM;
 
         /* if low-level driver supports AP, we also support VLAN */
-        if (local->hw.wiphy->interface_modes & BIT(NL80211_IFTYPE_AP))
-                local->hw.wiphy->interface_modes |= BIT(NL80211_IFTYPE_AP_VLAN);
+        if (local->hw.wiphy->interface_modes & BIT(NL80211_IFTYPE_AP)) {
+                hw->wiphy->interface_modes |= BIT(NL80211_IFTYPE_AP_VLAN);
+                hw->wiphy->software_iftypes |= BIT(NL80211_IFTYPE_AP_VLAN);
+        }
 
         /* mac80211 always supports monitor */
-        local->hw.wiphy->interface_modes |= BIT(NL80211_IFTYPE_MONITOR);
+        hw->wiphy->interface_modes |= BIT(NL80211_IFTYPE_MONITOR);
+        hw->wiphy->software_iftypes |= BIT(NL80211_IFTYPE_MONITOR);
+
+        /* mac80211 doesn't support more than 1 channel */
+        for (i = 0; i < hw->wiphy->n_iface_combinations; i++)
+                if (hw->wiphy->iface_combinations[i].num_different_channels > 1)
+                        return -EINVAL;
 
 #ifndef CONFIG_MAC80211_MESH
         /* mesh depends on Kconfig, but drivers should set it if they want */
diff --git a/net/wireless/core.c b/net/wireless/core.c
index 18b002f16860..c22ef3492ee6 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 d4b8f4c0bbbb..bf0fb40e3c8b 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 9ef8e287d61b..beac296b1fde 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 414c9f604df6..95e4e254da0a 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;
+}