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>

1 files changed, 121 insertions, 1 deletions

diff --git a/include/linux/nl80211.h b/include/linux/nl80211.h
index 281a2bb6a6e..0ea497cb607 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 */