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doc: add hotspot documentation

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James Prestwood 2019-06-26 12:20:36 -07:00 committed by Denis Kenzior
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Hotspot 2.0 networks are common in airports/airplanes (e.g. Boingo) and are also
found in various other locations implemented by cable/cellular providers. These
networks allow you to use a secure 8021x access point using the account
credentials for your e.g. cable/cellular provider, or via a dedicated account
like Boingo. Lots of these services also allow you to roam between networks.
The underlying authentication is standard WPA2-Enterprise but Hotspot 2.0 adds a
'discovery' stage to identifiying networks. This discovery is done using ANQP,
which queries the network for additional information to determine if the client
has the credentials to connect.
Because of this network identification capability the hotspot network must be
provisioned before hand as you would with 8021x, though the provisioning file
requires at least one additional value in addition to the regular 8021x EAP
information. Under the Hotspot group NAIRealmNames and HESSID have
been added. NAIRealmNames is a required field. HESSID is optional but, if
provided, may allow IWD to skip the ANQP step and directly connect (assuming
the network advertised HESSID matches).
NAIRealmNames is a comma separated list of realms e.g.
[Hotspot]
NAIRealmNames=realm.example.com,another.realm.com
HESSID is simply a MAC address e.g.
[Hotspot]
HESSID=ab:cd:ef:01:23:67
A side note:
Since hotspot's use of ANQP is done before we are connected, it is done via
public action frames. This requires the WiFi hardware go offchannel, similar
to scans. Because of this scans and ANQP are done on a first come first serve
basis in the kernel, which can result in delays. To mitigate this IWD will
suspend any scanning until ANQP finishes. There is also a new feature in the
5.3 kernel which notifies userspace when a 'remain-on-channel' action has
completed. This feature is only available on mac80211 based driver and is
required for IWD to do ANQP reliably.
Since not all kernels will have this option right away an option was added to
IWD which allows the user to disable ANQP. As a result, this will also disable
any hotspot 2.0 network connections unless the HESSID is provided in the
configuration file. By default ANQP will be disabled. It can be enabled with:
disable_anqp=0