hostap/hostapd/developer.txt

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Developer notes for hostapd
===========================
hostapd daemon setup, operations, and shutdown
----------------------------------------------
Files: hostapd.[ch]
Externally called functions:
hostapd_new_assoc_sta() is called when a station associates with the AP
Event loop functions:
handle_term() is called on SIGINT and SIGTERM to terminate hostapd process
handle_reload() is called on SIGHUP to reload configuration
handle_dump_state() is called on SIGUSR1 to dump station state data to a
text file
hostapd_rotate_wep() is called to periodically change WEP keys
Configuration parsing
---------------------
Configuration file parsing and data structure definition.
Files: config.[ch]
Externally called functions:
hostapd_config_read() is called to read and parse a configuration file;
allocates and returns configuration data structure
hostapd_config_free() is called to free configuration data structure
hostapd_maclist_found() is called to check whether a given address is found
in a list of MAC addresses
Kernel driver access
--------------------
Helper functions for configuring the Host AP kernel driver and
accessing data from it.
Files: driver.[ch]
IEEE 802.11 frame handling (netdevice wlan#ap)
----------------------------------------------
Receive all incoming IEEE 802.11 frames from the kernel driver via
wlan#ap interface.
Files: receive.c
Externally called functions:
hostapd_init_sockets() is called to initialize sockets for receiving and
sending IEEE 802.11 frames via wlan#ap interface
Event loop functions:
handle_read() is called for each incoming packet from wlan#ap net device
Station table
-------------
Files: sta_info.[ch], ap.h
Event loop functions:
ap_handle_timer() is called to check station activity and to remove
inactive stations
IEEE 802.11 management
----------------------
IEEE 802.11 management frame sending and processing (mainly,
authentication and association). IEEE 802.11 station functionality
(authenticate and associate with another AP as an station).
Files: ieee802_11.[ch]
Externally called functions:
ieee802_11_mgmt() is called for each received IEEE 802.11 management frame
(from handle_frame() in hostapd.c)
ieee802_11_mgmt_cb() is called for each received TX callback of IEEE 802.11
management frame (from handle_tx_callback() in hostapd.c)
ieee802_11_send_deauth() is called to send deauthentication frame
ieee802_11_send_disassoc() is called to send disassociation frame
ieee802_11_parse_elems() is used to parse information elements in
IEEE 802.11 management frames
Event loop functions:
ieee802_11_sta_authenticate() called to retry authentication (with another
AP)
ieee802_11_sta_associate() called to retry association (with another AP)
IEEE 802.11 authentication
--------------------------
Access control list for IEEE 802.11 authentication. Uses staticly
configured ACL from configuration files or an external RADIUS
server. Results from external RADIUS queries are cached to allow
faster authentication frame processing.
Files: ieee802_11_auth.[ch]
Externally called functions:
hostapd_acl_init() called once during hostapd startup
hostapd_acl_deinit() called once during hostapd shutdown
hostapd_acl_recv_radius() called by IEEE 802.1X code for incoming RADIUS
Authentication messages (returns 0 if message was processed)
hostapd_allowed_address() called to check whether a specified station can be
authenticated
Event loop functions:
hostapd_acl_expire() is called to expire ACL cache entries
IEEE 802.1X Authenticator
-------------------------
Files: ieee802_1x.[ch]
Externally called functions:
ieee802_1x_receive() is called for each incoming EAPOL frame from the
wireless interface
ieee802_1x_new_station() is called to start IEEE 802.1X authentication when
a new station completes IEEE 802.11 association
Event loop functions:
ieee802_1x_receive_auth() called for each incoming RADIUS Authentication
message
EAPOL state machine
-------------------
IEEE 802.1X state machine for EAPOL.
Files: eapol_sm.[ch]
Externally called functions:
eapol_sm_step() is called to advance EAPOL state machines after any change
that could affect their state
Event loop functions:
eapol_port_timers_tick() called once per second to advance Port Timers state
machine
IEEE 802.11f (IAPP)
-------------------
Files: iapp.[ch]
Externally called functions:
iapp_new_station() is called to start accounting session when a new station
completes IEEE 802.11 association or IEEE 802.1X authentication
Event loop functions:
iapp_receive_udp() is called for incoming IAPP frames over UDP
Per station accounting
----------------------
Send RADIUS Accounting start and stop messages to a RADIUS Accounting
server. Process incoming RADIUS Accounting messages.
Files: accounting.[ch]
Externally called functions:
accounting_init() called once during hostapd startup
accounting_deinit() called once during hostapd shutdown
accounting_sta_start() called when a station starts new session
accounting_sta_stop() called when a station session is terminated
Event loop functions:
accounting_receive() called for each incoming RADIUS Accounting message
accounting_list_timer() called to retransmit accounting messages and to
remove expired entries
RADIUS messages
---------------
RADIUS message generation and parsing functions.
Files: radius.[ch]
Event loop
----------
Event loop for registering timeout calls, signal handlers, and socket
read events.
Files: eloop.[ch]
RC4
---
RC4 encryption
Files: rc4.[ch]
MD5
---
MD5 hash and HMAC-MD5.
Files: md5.[ch]
Miscellaneous helper functions
------------------------------
Files: common.[ch]