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+\page eap_peer_module EAP peer implementation
+Extensible Authentication Protocol (EAP) is an authentication framework
+defined in RFC 3748. %wpa_supplicant uses a separate code module for EAP
+peer implementation. This module was designed to use only a minimal set
+of direct function calls (mainly, to debug/event functions) in order for
+it to be usable in other programs. The design of the EAP
+implementation is based loosely on RFC 4137. The state machine is
+defined in this RFC and so is the interface between the peer state
+machine and methods. As such, this RFC provides useful information for
+understanding the EAP peer implementation in %wpa_supplicant.
+Some of the terminology used in EAP state machine is referring to
+EAPOL (IEEE 802.1X), but there is no strict requirement on the lower
+layer being IEEE 802.1X if EAP module is built for other programs than
+%wpa_supplicant. These terms should be understood to refer to the
+lower layer as defined in RFC 4137.
+\section adding_eap_methods Adding EAP methods
+Each EAP method is implemented as a separate module, usually as one C
+file named eap_<name of the method>.c, e.g., eap_md5.c. All EAP
+methods use the same interface between the peer state machine and
+method specific functions. This allows new EAP methods to be added
+without modifying the core EAP state machine implementation.
+New EAP methods need to be registered by adding them into the build
+(Makefile) and the EAP method registration list in the
+eap_peer_register_methods() function of eap_methods.c. Each EAP
+method should use a build-time configuration option, e.g., EAP_TLS, in
+order to make it possible to select which of the methods are included
+in the build.
+EAP methods must implement the interface defined in eap_i.h. struct
+eap_method defines the needed function pointers that each EAP method
+must provide. In addition, the EAP type and name are registered using
+this structure. This interface is based on section 4.4 of RFC 4137.
+It is recommended that the EAP methods would use generic helper
+functions, eap_msg_alloc() and eap_hdr_validate() when processing
+messages. This allows code sharing and can avoid missing some of the
+needed validation steps for received packets. In addition, these
+functions make it easier to change between expanded and legacy EAP
+header, if needed.
+When adding an EAP method that uses a vendor specific EAP type
+(Expanded Type as defined in RFC 3748, Chapter 5.7), the new method
+must be registered by passing vendor id instead of EAP_VENDOR_IETF to
+eap_peer_method_alloc(). These methods must not try to emulate
+expanded types by registering a legacy EAP method for type 254. See
+eap_vendor_test.c for an example of an EAP method implementation that
+is implemented as an expanded type.
+\section used_eap_library Using EAP implementation as a library
+The Git repository has an eap_example directory that contains an
+example showing how EAP peer and server code from %wpa_supplicant and
+hostapd can be used as a library. The example program initializes both
+an EAP server and an EAP peer entities and then runs through an
+EAP-PEAP/MSCHAPv2 authentication.
+eap_example_peer.c shows the initialization and glue code needed to
+control the EAP peer implementation. eap_example_server.c does the
+same for EAP server. eap_example.c is an example that ties in both the
+EAP server and client parts to allow an EAP authentication to be
+In this example, the EAP messages are passed between the server and
+the peer are passed by direct function calls within the same process.
+In practice, server and peer functionalities would likely reside in
+separate devices and the EAP messages would be transmitted between the
+devices based on an external protocol. For example, in IEEE 802.11
+uses IEEE 802.1X EAPOL state machines to control the transmission of
+EAP messages and WiMax supports optional PMK EAP authentication
+mechanism that transmits EAP messages as defined in IEEE 802.16e.
+The EAP library links in number of helper functions from src/utils and
+src/crypto directories. Most of these are suitable as-is, but it may
+be desirable to replace the debug output code in src/utils/wpa_debug.c
+by dropping this file from the library and re-implementing the
+functions there in a way that better fits in with the main