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     ieee80211_regdomain — 802.11 regulatory support


     #include <net80211/ieee80211_var.h>
     #include <net80211/ieee80211_regdomain.h>

     ieee80211_init_channels(struct ieee80211com *, const struct ieee80211_regdomain *,
         const uint8_t bands[]);

     ieee80211_sort_channels(struct ieee80211_channel *, int nchans);

     struct ieee80211_appie *
     ieee80211_alloc_countryie(struct ieee80211com *);


     The net80211 software layer provides a support framework for drivers that includes
     comprehensive regulatory support.  net80211 provides mechanisms that enforce regulatory
     policy by privileged user applications.

     Drivers define a device's capabilities and can intercept and control regulatory changes
     requested through net80211.  The initial regulatory state, including the channel list, must
     be filled in by the driver before calling ieee80211_ifattach().  The channel list should
     reflect the set of channels the device is calibrated for use on.  This list may also be
     requested later through the ic_getradiocaps method in the ieee80211com structure.  The
     ieee80211_init_channels() function is provided as a rudimentary fallback for drivers that do
     not (or cannot) fill in a proper channel list.  Default regulatory state is supplied such as
     the regulatory SKU, ISO country code, location (e.g. indoor, outdoor), and a set of
     frequency bands the device is capable of operating on.  net80211 populates the channel table
     in ic_channels with a default set of channels and capabilities.  Note this mechanism should
     be used with care as any mismatch between the channel list created and the device's
     capabilities can result in runtime errors (e.g. a request to operate on a channel the device
     does not support).  The SKU and country information are used for generating 802.11h protocol
     elements and related operation such as for 802.11d; mis-setup by a driver is not fatal, only
     potentially confusing.

     Devices that do not have a fixed/default regulatory state can set the regulatory SKU to
     SKU_DEBUG and country code to CTRY_DEFAULT and leave proper setup to user applications.  If
     default settings are known they can be installed and/or an event can be dispatched to user
     space using ieee80211_notify_country() so that devd(8) will do the appropriate setup work at
     system boot (or device insertion).

     The channel table is sorted to optimize lookups using the ieee80211_sort_channels() routine.
     This should be done whenever the channel table contents are modified.

     The ieee80211_alloc_countryie() function allocates an information element as specified by
     802.11h.  Because this is expensive to generate it is cached in ic_countryie and generated
     only when regulatory state changes.  Drivers that call ieee80211_alloc_countryie() directly
     should not help with this caching; doing so may confuse the net80211 layer.


     Drivers can control regulatory change requests by overriding the ic_setregdomain method that
     checks change requests.  While drivers can reject any request that does not meet its
     requirements it is recommended that one be lenient in what is accepted and, whenever
     possible, instead of rejecting a request, alter it to be correct.  For example, if the
     transmit power cap for a channel is too high the driver can either reject the request or
     (better) reduce the cap to be compliant.  Requests that include unacceptable channels should
     cause the request to be rejected as otherwise a mismatch may be created between application
     state and the state managed by net80211.  The exact rules by which to operate are still
     being codified.


     regdomain(5), ifconfig(8), ieee80211(9)