(big patch) Added top-level pjnath project and moved STUN related files to this new project

git-svn-id: http://svn.pjsip.org/repos/pjproject/trunk@1062 74dad513-b988-da41-8d7b-12977e46ad98

7 files changed, 2752 insertions, 0 deletions

diff --git a/pjnath/include/pjnath/stun_auth.h b/pjnath/include/pjnath/stun_auth.h
new file mode 100644
index 00000000..49b2acbb
--- /dev/null
+++ b/pjnath/include/pjnath/stun_auth.h
@@ -0,0 +1,275 @@
+/* $Id$ */
+/* 
+ * Copyright (C) 2003-2005 Benny Prijono <benny@prijono.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA 
+ */
+#ifndef __PJLIB_UTIL_STUN_AUTH_H__
+#define __PJLIB_UTIL_STUN_AUTH_H__
+
+/**
+ * @file stun_auth.h
+ * @brief STUN authentication.
+ */
+
+#include <pjlib-util/stun_msg.h>
+
+
+PJ_BEGIN_DECL
+
+
+/* **************************************************************************/
+/**
+ * @defgroup PJLIB_UTIL_STUN_AUTH STUN Authentication
+ * @ingroup PJLIB_UTIL_STUN
+ * @{
+ */
+
+/**
+ * Type of authentication data in the credential.
+ */
+typedef enum pj_stun_auth_cred_type
+{
+    /**
+     * The credential data contains a static credential to be matched 
+     * against the credential in the message. A static credential can be 
+     * used as both client side or server side authentication.
+     */
+    PJ_STUN_AUTH_CRED_STATIC,
+
+    /**
+     * The credential data contains callbacks to be called to verify the 
+     * credential in the message. A dynamic credential is suitable when 
+     * performing server side authentication where server does not know
+     * in advance the identity of the user requesting authentication.
+     */
+    PJ_STUN_AUTH_CRED_DYNAMIC
+
+} pj_stun_auth_cred_type;
+
+
+/**
+ * This structure contains the descriptions needed to perform server side
+ * authentication. Depending on the \a type set in the structure, application
+ * may specify a static username/password combination, or to have callbacks
+ * called by the function to authenticate the credential dynamically.
+ */
+typedef struct pj_stun_auth_cred
+{
+    /**
+     * The type of authentication information in this structure.
+     */
+    pj_stun_auth_cred_type	type;
+
+    /**
+     * This union contains the authentication data.
+     */
+    union 
+    {
+	/**
+	 * This structure contains static data for performing authentication.
+	 * A non-empty realm indicates whether short term or long term
+	 * credential is used.
+	 */
+	struct
+	{
+	    /** 
+	     * If not-empty, it indicates that this is a long term credential.
+	     */
+	    pj_str_t	  realm;
+
+	    /** 
+	     * The username of the credential.
+	     */
+	    pj_str_t	  username;
+
+	    /**
+	     * Data type to indicate the type of password in the \a data field.
+	     * Value zero indicates that the data contains a plaintext
+	     * password.
+	     */
+	    int		  data_type;
+
+	    /** 
+	     * The data, which depends depends on the value of \a data_type
+	     * field. When \a data_type is zero, this field will contain the
+	     * plaintext password.
+	     */
+	    pj_str_t	  data;
+
+	    /** 
+	     * Optional NONCE.
+	     */
+	    pj_str_t	  nonce;
+
+	} static_cred;
+
+	/**
+	 * This structure contains callback to be called by the framework
+	 * to authenticate the incoming message.
+	 */
+	struct
+	{
+	    /**
+	     * User data which will be passed back to callback functions.
+	     */
+	    void *user_data;
+
+	    /**
+	     * This callback is called by pj_stun_verify_credential() when
+	     * server needs to challenge the request with 401 response.
+	     *
+	     * @param user_data	The user data as specified in the credential.
+	     * @param pool	Pool to allocate memory.
+	     * @param realm	On return, the function should fill in with
+	     *			realm if application wants to use long term
+	     *			credential. Otherwise application should set
+	     *			empty string for the realm.
+	     * @param nonce	On return, if application wants to use long
+	     *			term credential, it MUST fill in the nonce
+	     *			with some value. Otherwise  if short term 
+	     *			credential is wanted, it MAY set this value.
+	     *			If short term credential is wanted and the
+	     *			application doesn't want to include NONCE,
+	     *			then it must set this to empty string.
+	     *
+	     * @return		The callback should return PJ_SUCCESS, or
+	     *			otherwise response message will not be 
+	     *			created.
+	     */
+	    pj_status_t (*get_auth)(void *user_data,
+				    pj_pool_t *pool,
+				    pj_str_t *realm,
+				    pj_str_t *nonce);
+
+	    /**
+	     * Get the password for the specified username. This function 
+	     * is also used to check whether the username is valid.
+	     *
+	     * @param user_data	The user data as specified in the credential.
+	     * @param realm	The realm as specified in the message.
+	     * @param username	The username as specified in the message.
+	     * @param pool	Pool to allocate memory when necessary.
+	     * @param data_type On return, application should fill up this
+	     *			argument with the type of data (which should
+	     *			be zero if data is a plaintext password).
+	     * @param data	On return, application should fill up this
+	     *			argument with the password according to
+	     *			data_type.
+	     *
+	     * @return		The callback should return PJ_SUCCESS if
+	     *			username has been successfully verified
+	     *			and password was obtained. If non-PJ_SUCCESS
+	     *			is returned, it is assumed that the
+	     *			username is not valid.
+	     */
+	    pj_status_t	(*get_password)(void *user_data, 
+				        const pj_str_t *realm,
+				        const pj_str_t *username,
+					pj_pool_t *pool,
+					int *data_type,
+					pj_str_t *data);
+
+	    /**
+	     * This callback will be called to verify that the NONCE given
+	     * in the message can be accepted. If this callback returns
+	     * PJ_FALSE, 438 (Stale Nonce) response will be created.
+	     *
+	     * @param user_data	The user data as specified in the credential.
+	     * @param realm	The realm as specified in the message.
+	     * @param username	The username as specified in the message.
+	     * @param nonce	The nonce to be verified.
+	     *
+	     * @return		The callback MUST return non-zero if the 
+	     *			NONCE can be accepted.
+	     */
+	    pj_bool_t	(*verify_nonce)(void *user_data,
+					const pj_str_t *realm,
+					const pj_str_t *username,
+					const pj_str_t *nonce);
+
+	} dyn_cred;
+
+    } data;
+
+} pj_stun_auth_cred;
+
+
+/**
+ * Duplicate authentication credential.
+ *
+ * @param pool		Pool to be used to allocate memory.
+ * @param dst		Destination credential.
+ * @param src		Source credential.
+ */
+PJ_DECL(void) pj_stun_auth_cred_dup(pj_pool_t *pool,
+				      pj_stun_auth_cred *dst,
+				      const pj_stun_auth_cred *src);
+
+
+/**
+ * Verify credential in the STUN message. Note that before calling this
+ * function, application must have checked that the message contains
+ * PJ_STUN_ATTR_MESSAGE_INTEGRITY attribute by calling pj_stun_msg_find_attr()
+ * function, because this function will reject the message with 401 error
+ * if it doesn't contain PJ_STUN_ATTR_MESSAGE_INTEGRITY attribute.
+ *
+ * @param pkt		The original packet which has been parsed into
+ *			the message. This packet MUST NOT have been modified
+ *			after the parsing.
+ * @param pkt_len	The length of the packet.
+ * @param msg		The parsed message to be verified.
+ * @param cred		Pointer to credential to be used to authenticate
+ *			the message.
+ * @param pool		If response is to be created, then memory will
+ *			be allocated from this pool.
+ * @param p_response	Optional pointer to receive the response message
+ *			then the credential in the request fails to
+ *			authenticate.
+ *
+ * @return		PJ_SUCCESS if credential is verified successfully.
+ *			If the verification fails and \a p_response is not
+ *			NULL, an appropriate response will be returned in
+ *			\a p_response.
+ */
+PJ_DECL(pj_status_t) pj_stun_verify_credential(const pj_uint8_t *pkt,
+					       unsigned pkt_len,
+					       const pj_stun_msg *msg,
+					       pj_stun_auth_cred *cred,
+					       pj_pool_t *pool,
+					       pj_stun_msg **p_response);
+
+
+
+
+/**
+ * @}
+ */
+
+
+/* Calculate HMAC-SHA1 key for long term credential, by getting
+ * MD5 digest of username, realm, and password. 
+ */
+void pj_stun_calc_md5_key(pj_uint8_t digest[16],
+			  const pj_str_t *realm,
+			  const pj_str_t *username,
+			  const pj_str_t *passwd);
+
+
+PJ_END_DECL
+
+
+#endif	/* __PJLIB_UTIL_STUN_AUTH_H__ */
+
diff --git a/pjnath/include/pjnath/stun_doc.h b/pjnath/include/pjnath/stun_doc.h
new file mode 100644
index 00000000..612bf1a7
--- /dev/null
+++ b/pjnath/include/pjnath/stun_doc.h
@@ -0,0 +1,100 @@
+/* $Id$ */
+/* 
+ * Copyright (C) 2003-2005 Benny Prijono <benny@prijono.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA 
+ */
+#ifndef __PJ_STUN_SERVER_H__
+#define __PJ_STUN_SERVER_H__
+
+/*
+ * STUN documentation. There is no code here.
+ */
+
+/**
+ * @defgroup PJLIB_UTIL_STUN STUN and TURN
+ * @ingroup PJLIB_UTIL
+
+ This is the implementation of STUN/TURN in PJLIB-UTIL library.
+
+ The STUN/TURN implementation in PJLIB-UTIL has the following objectives:
+ - standard based (of course)
+ - supports both client and server side STUN/TURN services
+ - independent (that is, only dependent to pjlib), and general purpose
+   enough to be used not only by pjsip applications but also by other 
+   types of applications
+ - must be able to support ICE.
+
+ The STUN/TURN implementation is based on the following standards:
+ - <A HREF="http://www.ietf.org/internet-drafts/draft-ietf-behave-rfc3489bis-05.txt">
+   draft-ietf-behave-rfc3489bis-05.txt</A>
+ - <A HREF="http://www.ietf.org/internet-drafts/draft-ietf-behave-turn-02.txt">
+   draft-ietf-behave-turn-02.txt</A>
+
+ But as STUN standards are currently defined as work in progress at IETF,
+ the implementation will be updated as these standards are updated.
+
+  
+
+ @section stun_org_sec Organization
+
+ The implementation consists of the following components.
+
+ @subsection stun_msg_sec Messaging and Parsing
+
+ The lowest layer of the STUN implementation is the @ref PJLIB_UTIL_STUN_MSG
+ component. This part is responsible for encoding and decoding STUN messages.
+
+ This layer only implements message representation and parsing. In particular,
+ it does not provide any transport functionalities, therefore it can be used
+ by different types of applications.
+
+
+
+ @subsection stun_endpt_sec Endpoint
+
+ The @ref PJLIB_UTIL_STUN_ENDPOINT is used by the library to put together
+ common settings for all STUN objects. For example, the STUN endpoint has a
+ reference of timer heap to poll all STUN timers, reference to ioqueue to
+ poll network events for STUN servers, and some common settings used by
+ various STUN objects.
+
+
+ @subsection stun_clt_tsx_sec Client Transaction
+
+ The @ref PJLIB_UTIL_STUN_TRANSACTION is used to manage outgoing STUN request,
+ for example to retransmit the request and to notify application about the
+ completion of the request.
+
+ The @ref PJLIB_UTIL_STUN_TRANSACTION does not use any networking operations,
+ but instead application must supply the transaction with a callback to
+ be used by the transaction to send outgoing requests. This way the STUN
+ transaction is made more generic and can work with different types of
+ networking codes in application.
+
+
+
+ @subsection stun_srv_sec Server Components
+
+ The @ref PJLIB_UTIL_STUN_SERVER is used for:
+ - implementing STUN servers, and/or
+ - implementing server side STUN handling (for example for ICE).
+
+ */
+
+
+
+#endif	/* __PJ_STUN_SERVER_H__ */
+
diff --git a/pjnath/include/pjnath/stun_endpoint.h b/pjnath/include/pjnath/stun_endpoint.h
new file mode 100644
index 00000000..b341309a
--- /dev/null
+++ b/pjnath/include/pjnath/stun_endpoint.h
@@ -0,0 +1,117 @@
+/* $Id$ */
+/* 
+ * Copyright (C) 2003-2005 Benny Prijono <benny@prijono.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA 
+ */
+#ifndef __PJLIB_UTIL_STUN_ENDPOINT_H__
+#define __PJLIB_UTIL_STUN_ENDPOINT_H__
+
+/**
+ * @file stun_endpoint.h
+ * @brief STUN endpoint.
+ */
+
+#include <pjlib-util/stun_msg.h>
+
+
+PJ_BEGIN_DECL
+
+
+/* **************************************************************************/
+/**
+ * @defgroup PJLIB_UTIL_STUN_ENDPOINT STUN Endpoint
+ * @brief Management of incoming and outgoing STUN transactions.
+ * @ingroup PJLIB_UTIL_STUN
+ * @{
+ */
+
+/**
+ * Opaque declaration for STUN endpoint. STUN endpoint manages client and
+ * server STUN transactions, and it needs to be initialized before application
+ * can send or receive STUN messages.
+ */
+typedef struct pj_stun_endpoint
+{
+    /**
+     * Pool factory to be used by the STUN endpoint and all objects created
+     * that use this STUN endpoint.
+     */
+    pj_pool_factory	*pf;
+
+    /**
+     * Ioqueue used by this endpoint.
+     */
+    pj_ioqueue_t	*ioqueue;
+
+    /**
+     * Timer heap instance used by this endpoint.
+     */
+    pj_timer_heap_t	*timer_heap;
+
+    /**
+     * Internal pool used by this endpoint. This shouldn't be used by
+     * application.
+     */
+    pj_pool_t		*pool;
+
+    /**
+     * Options.
+     */
+    unsigned		 options;
+
+    /**
+     * The default initial STUN round-trip time estimation in msecs.
+     * The value normally is PJ_STUN_RTO_VALUE.
+     */
+    unsigned		 rto_msec;
+
+    /**
+     * The interval to cache outgoing  STUN response in the STUN session,
+     * in miliseconds. 
+     *
+     * Default 10000 (10 seconds).
+     */
+    unsigned		 res_cache_msec;
+
+} pj_stun_endpoint;
+
+
+
+/**
+ * Create a STUN endpoint instance.
+ */
+PJ_DECL(pj_status_t) pj_stun_endpoint_create(pj_pool_factory *factory,
+					     unsigned options,
+					     pj_ioqueue_t *ioqueue,
+					     pj_timer_heap_t *timer_heap,
+					     pj_stun_endpoint **p_endpt);
+
+/**
+ * Destroy STUN endpoint instance.
+ */
+PJ_DECL(pj_status_t) pj_stun_endpoint_destroy(pj_stun_endpoint *endpt);
+
+
+/**
+ * @}
+ */
+
+
+PJ_END_DECL
+
+
+#endif	/* __PJLIB_UTIL_STUN_ENDPOINT_H__ */
+
diff --git a/pjnath/include/pjnath/stun_msg.h b/pjnath/include/pjnath/stun_msg.h
new file mode 100644
index 00000000..ae66c2d1
--- /dev/null
+++ b/pjnath/include/pjnath/stun_msg.h
@@ -0,0 +1,1539 @@
+/* $Id$ */
+/* 
+ * Copyright (C) 2003-2005 Benny Prijono <benny@prijono.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA 
+ */
+#ifndef __PJLIB_UTIL_STUN_MSG_H__
+#define __PJLIB_UTIL_STUN_MSG_H__
+
+/**
+ * @file stun_msg.h
+ * @brief STUN message components.
+ */
+
+#include <pjlib-util/types.h>
+#include <pj/sock.h>
+
+
+PJ_BEGIN_DECL
+
+
+/* **************************************************************************/
+/**
+ * @defgroup PJLIB_UTIL_STUN_MSG STUN Message Representation and Parsing
+ * @brief Low-level representation and parsing of STUN messages.
+ * @ingroup PJLIB_UTIL_STUN
+ * @{
+ */
+
+
+/**
+ * The default initial STUN round-trip time estimation (the RTO value
+ * in RFC 3489-bis), in miliseconds. 
+ * This value is used to control the STUN request 
+ * retransmit time. The initial value of retransmission interval 
+ * would be set to this value, and will be doubled after each
+ * retransmission.
+ */
+#ifndef PJ_STUN_RTO_VALUE
+#   define PJ_STUN_RTO_VALUE		    100
+#endif
+
+
+/**
+ * The STUN transaction timeout value, in miliseconds.
+ * After the last retransmission is sent and if no response is received 
+ * after this time, the STUN transaction will be considered to have failed.
+ *
+ * The default value is 1600 miliseconds (as per RFC 3489-bis).
+ */
+#ifndef PJ_STUN_TIMEOUT_VALUE
+#   define PJ_STUN_TIMEOUT_VALUE	    1600
+#endif
+
+
+/**
+ * Maximum number of STUN retransmission count.
+ *
+ * Default: 7 (as per RFC 3489-bis)
+ */
+#ifndef PJ_STUN_MAX_RETRANSMIT_COUNT
+#   define PJ_STUN_MAX_RETRANSMIT_COUNT	    7
+#endif
+
+
+/**
+ * Maximum size of STUN message.
+ */
+#ifndef PJ_STUN_MAX_PKT_LEN
+#   define PJ_STUN_MAX_PKT_LEN		    512
+#endif
+
+
+/**
+ * Default STUN port as defined by RFC 3489.
+ */
+#define PJ_STUN_PORT			    3478
+
+/**
+ * STUN magic cookie.
+ */
+#define PJ_STUN_MAGIC			    0x2112A442
+
+
+/**
+ * STUN method constants.
+ */
+enum pj_stun_method_e
+{
+    /**
+     * STUN Binding method as defined by RFC 3489-bis.
+     */
+    PJ_STUN_BINDING_METHOD		    = 1,
+
+    /**
+     * STUN Shared Secret method as defined by RFC 3489-bis.
+     */
+    PJ_STUN_SHARED_SECRET_METHOD	    = 2,
+
+    /**
+     * STUN/TURN Allocate method as defined by draft-ietf-behave-turn
+     */
+    PJ_STUN_ALLOCATE_METHOD		    = 3,
+
+    /**
+     * STUN/TURN Send Indication as defined by draft-ietf-behave-turn
+     */
+    PJ_STUN_SEND_INDICATION_METHOD	    = 4,
+
+    /**
+     * STUN/TURN Data Indication as defined by draft-ietf-behave-turn
+     */
+    PJ_STUN_DATA_INDICATION_METHOD	    = 5,
+
+    /**
+     * STUN/TURN Set Active Destination as defined by draft-ietf-behave-turn
+     */
+    PJ_STUN_SET_ACTIVE_DESTINATION_METHOD   = 6,
+
+    /**
+     * STUN/TURN Connect method as defined by draft-ietf-behave-turn
+     */
+    PJ_STUN_CONNECT_METHOD		    = 7,
+
+    /**
+     * STUN/TURN Connect Status indication method.
+     */
+    PJ_STUN_CONNECT_STATUS_METHOD	    = 8
+};
+
+
+/**
+ * Retrieve the STUN method from the message-type field of the STUN
+ * message.
+ */
+#define PJ_STUN_GET_METHOD(msg_type)	((msg_type) & 0xFEEF)
+
+
+/**
+ * STUN message classes constants.
+ */
+enum pj_stun_msg_class_e
+{
+    /**
+     * This specifies that the message type is a STUN request message.
+     */
+    PJ_STUN_REQUEST_CLASS	    = 0,
+
+    /**
+     * This specifies that the message type is a STUN indication message.
+     */
+    PJ_STUN_INDICATION_CLASS	    = 1,
+
+    /**
+     * This specifies that the message type is a STUN successful response.
+     */
+    PJ_STUN_SUCCESS_CLASS	    = 2,
+
+    /**
+     * This specifies that the message type is a STUN error response.
+     */
+    PJ_STUN_ERROR_CLASS		    = 3
+};
+
+
+/**
+ * Determine if the message type is a request.
+ */
+#define PJ_STUN_IS_REQUEST(msg_type)	(((msg_type) & 0x0110) == 0x0000)
+
+
+/**
+ * Determine if the message type is a response.
+ */
+#define PJ_STUN_IS_RESPONSE(msg_type)	(((msg_type) & 0x0110) == 0x0100)
+
+
+/**
+ * The response bit in the message type.
+ */
+#define PJ_STUN_RESPONSE_BIT		(0x0100)
+
+/**
+ * Determine if the message type is an error response.
+ */
+#define PJ_STUN_IS_ERROR_RESPONSE(msg_type) (((msg_type) & 0x0110) == 0x0110)
+
+
+/**
+ * The error response bit in the message type.
+ */
+#define PJ_STUN_ERROR_RESPONSE_BIT	(0x0110)
+
+
+/**
+ * Determine if the message type is an indication message.
+ */
+#define PJ_STUN_IS_INDICATION(msg_type)	(((msg_type) & 0x0110) == 0x0010)
+
+
+/**
+ * The error response bit in the message type.
+ */
+#define PJ_STUN_INDICATION_BIT		(0x0010)
+
+
+/**
+ * This enumeration describes STUN message types.
+ */
+typedef enum pj_stun_msg_type
+{
+    /**
+     * STUN BINDING request.
+     */
+    PJ_STUN_BINDING_REQUEST		    = 0x0001,
+
+    /**
+     * Successful response to STUN BINDING-REQUEST.
+     */
+    PJ_STUN_BINDING_RESPONSE		    = 0x0101,
+
+    /**
+     * Error response to STUN BINDING-REQUEST.
+     */
+    PJ_STUN_BINDING_ERROR_RESPONSE	    = 0x0111,
+
+    /**
+     * STUN SHARED-SECRET reqeust.
+     */
+    PJ_STUN_SHARED_SECRET_REQUEST	    = 0x0002,
+
+    /**
+     * Successful response to STUN SHARED-SECRET reqeust.
+     */
+    PJ_STUN_SHARED_SECRET_RESPONSE	    = 0x0102,
+
+    /**
+     * Error response to STUN SHARED-SECRET reqeust.
+     */
+    PJ_STUN_SHARED_SECRET_ERROR_RESPONSE    = 0x0112,
+
+    /**
+     * STUN/TURN Allocate Request
+     */
+    PJ_STUN_ALLOCATE_REQUEST		    = 0x0003,
+
+    /**
+     * Successful response to STUN/TURN Allocate Request
+     */
+    PJ_STUN_ALLOCATE_RESPONSE		    = 0x0103,
+
+    /**
+     * Failure response to STUN/TURN Allocate Request
+     */
+    PJ_STUN_ALLOCATE_ERROR_RESPONSE	    = 0x0113,
+
+    /**
+     * STUN/TURN Send Indication
+     */
+    PJ_STUN_SEND_INDICATION		    = 0x0014,
+
+    /**
+     * STUN/TURN Data Indication
+     */
+    PJ_STUN_DATA_INDICATION		    = 0x0015,
+
+    /**
+     * STUN/TURN Set Active Destination Request
+     */
+    PJ_STUN_SET_ACTIVE_DESTINATION_REQUEST  = 0x0006,
+
+    /** 
+     * STUN/TURN Set Active Destination Response
+     */
+    PJ_STUN_SET_ACTIVE_DESTINATION_RESPONSE = 0x0106,
+
+    /**
+     * STUN/TURN Set Active Destination Error Response
+     */
+    PJ_STUN_SET_ACTIVE_DESTINATION_ERROR_RESPONSE = 0x0116,
+
+    /**
+     * STUN/TURN Connect Request
+     */
+    PJ_STUN_CONNECT_REQUEST		    = 0x0007,
+
+    /**
+     * STUN/TURN Connect Response
+     */
+    PJ_STUN_CONNECT_RESPONSE		    = 0x0107,
+
+    /**
+     * STUN/TURN Connect Error Response
+     */
+    PJ_STUN_CONNECT_ERROR_RESPONSE	    = 0x0117,
+
+    /**
+     * STUN/TURN Connect Status Indication
+     */
+    PJ_STUN_CONNECT_STATUS_INDICATION	    = 0x0018
+
+
+} pj_stun_msg_type;
+
+
+
+/**
+ * This enumeration describes STUN attribute types.
+ */
+typedef enum pj_stun_attr_type
+{
+    PJ_STUN_ATTR_MAPPED_ADDR	    = 0x0001,/**< MAPPED-ADDRESS.	    */
+    PJ_STUN_ATTR_RESPONSE_ADDR	    = 0x0002,/**< RESPONSE-ADDRESS (deprcatd)*/
+    PJ_STUN_ATTR_CHANGE_REQUEST	    = 0x0003,/**< CHANGE-REQUEST (deprecated)*/
+    PJ_STUN_ATTR_SOURCE_ADDR	    = 0x0004,/**< SOURCE-ADDRESS (deprecated)*/
+    PJ_STUN_ATTR_CHANGED_ADDR	    = 0x0005,/**< CHANGED-ADDRESS (deprecatd)*/
+    PJ_STUN_ATTR_USERNAME	    = 0x0006,/**< USERNAME attribute.	    */
+    PJ_STUN_ATTR_PASSWORD	    = 0x0007,/**< PASSWORD attribute.	    */
+    PJ_STUN_ATTR_MESSAGE_INTEGRITY  = 0x0008,/**< MESSAGE-INTEGRITY.	    */
+    PJ_STUN_ATTR_ERROR_CODE	    = 0x0009,/**< ERROR-CODE.		    */
+    PJ_STUN_ATTR_UNKNOWN_ATTRIBUTES = 0x000A,/**< UNKNOWN-ATTRIBUTES.	    */
+    PJ_STUN_ATTR_REFLECTED_FROM	    = 0x000B,/**< REFLECTED-FROM (deprecatd)*/
+    PJ_STUN_ATTR_LIFETIME	    = 0x000D,/**< LIFETIME attribute.	    */
+    PJ_STUN_ATTR_BANDWIDTH	    = 0x0010,/**< BANDWIDTH attribute	    */
+    PJ_STUN_ATTR_REMOTE_ADDR	    = 0x0012,/**< REMOTE-ADDRESS attribute  */
+    PJ_STUN_ATTR_DATA		    = 0x0013,/**< DATA attribute.	    */
+    PJ_STUN_ATTR_REALM		    = 0x0014,/**< REALM attribute.	    */
+    PJ_STUN_ATTR_NONCE		    = 0x0015,/**< NONCE attribute.	    */
+    PJ_STUN_ATTR_RELAY_ADDR	    = 0x0016,/**< RELAY-ADDRESS attribute.  */
+    PJ_STUN_ATTR_REQ_ADDR_TYPE	    = 0x0017,/**< REQUESTED-ADDRESS-TYPE    */
+    PJ_STUN_ATTR_REQ_PORT_PROPS	    = 0x0018,/**< REQUESTED-PORT-PROPS	    */
+    PJ_STUN_ATTR_REQ_TRANSPORT	    = 0x0019,/**< REQUESTED-TRANSPORT	    */
+    PJ_STUN_ATTR_XOR_MAPPED_ADDR    = 0x0020,/**< XOR-MAPPED-ADDRESS	    */
+    PJ_STUN_ATTR_TIMER_VAL	    = 0x0021,/**< TIMER-VAL attribute.	    */
+    PJ_STUN_ATTR_REQ_IP		    = 0x0022,/**< REQUESTED-IP attribute    */
+    PJ_STUN_ATTR_XOR_REFLECTED_FROM = 0x0023,/**< XOR-REFLECTED-FROM	    */
+    PJ_STUN_ATTR_PRIORITY	    = 0x0024,/**< PRIORITY		    */
+    PJ_STUN_ATTR_USE_CANDIDATE	    = 0x0025,/**< USE-CANDIDATE		    */
+    PJ_STUN_ATTR_XOR_INTERNAL_ADDR  = 0x0026,/**< XOR-INTERNAL-ADDRESS	    */
+
+    PJ_STUN_ATTR_END_MANDATORY_ATTR,
+
+    PJ_STUN_ATTR_START_EXTENDED_ATTR= 0x8021,
+
+    PJ_STUN_ATTR_SERVER		    = 0x8022,/**< SERVER attribute.	    */
+    PJ_STUN_ATTR_ALTERNATE_SERVER   = 0x8023,/**< ALTERNATE-SERVER.	    */
+    PJ_STUN_ATTR_REFRESH_INTERVAL   = 0x8024,/**< REFRESH-INTERVAL.	    */
+    PJ_STUN_ATTR_FINGERPRINT	    = 0x8028,/**< FINGERPRINT attribute.    */
+
+    PJ_STUN_ATTR_END_EXTENDED_ATTR
+
+} pj_stun_attr_type;
+
+
+/**
+ * STUN error codes, which goes into STUN ERROR-CODE attribute.
+ */
+typedef enum pj_stun_status
+{
+    PJ_STUN_SC_TRY_ALTERNATE		= 300,  /**< Try Alternate	    */
+    PJ_STUN_SC_BAD_REQUEST		= 400,  /**< Bad Request	    */
+    PJ_STUN_SC_UNAUTHORIZED	        = 401,  /**< Unauthorized	    */
+    PJ_STUN_SC_UNKNOWN_ATTRIBUTE        = 420,  /**< Unknown Attribute	    */
+    PJ_STUN_SC_STALE_CREDENTIALS        = 430,  /**< Stale Credentials	    */
+    PJ_STUN_SC_INTEGRITY_CHECK_FAILURE  = 431,  /**< Integrity Chk Fail	    */
+    PJ_STUN_SC_MISSING_USERNAME		= 432,  /**< Missing Username	    */
+    PJ_STUN_SC_USE_TLS			= 433,  /**< Use TLS		    */
+    PJ_STUN_SC_MISSING_REALM		= 434,  /**< Missing Realm	    */
+    PJ_STUN_SC_MISSING_NONCE		= 435,  /**< Missing Nonce	    */
+    PJ_STUN_SC_UNKNOWN_USERNAME		= 436,  /**< Unknown Username	    */
+    PJ_STUN_SC_NO_BINDING	        = 437,  /**< No Binding.	    */
+    PJ_STUN_SC_STALE_NONCE	        = 438,  /**< Stale Nonce	    */
+    PJ_STUN_SC_TRANSITIONING		= 439,  /**< Transitioning.	    */
+    PJ_STUN_SC_WRONG_USERNAME	        = 441,  /**< Wrong Username.	    */
+    PJ_STUN_SC_UNSUPP_TRANSPORT_PROTO   = 442,  /**< Unsupported Transport or
+						     Protocol */
+    PJ_STUN_SC_INVALID_IP_ADDR		= 443,  /**< Invalid IP Address	    */
+    PJ_STUN_SC_INVALID_PORT	        = 444,  /**< Invalid Port	    */
+    PJ_STUN_SC_OPER_TCP_ONLY		= 445,  /**< Operation for TCP Only */
+    PJ_STUN_SC_CONNECTION_FAILURE       = 446,  /**< Connection Failure	    */
+    PJ_STUN_SC_CONNECTION_TIMEOUT       = 447,  /**< Connection Timeout	    */
+    PJ_STUN_SC_ALLOCATION_QUOTA_REACHED = 486,  /**< Allocation Quota Reached
+						     (TURN) */
+    PJ_STUN_SC_SERVER_ERROR	        = 500,  /**< Server Error	    */
+    PJ_STUN_SC_INSUFFICIENT_CAPACITY    = 507,  /**< Insufficient Capacity 
+						     (TURN) */
+    PJ_STUN_SC_GLOBAL_FAILURE	        = 600   /**< Global Failure	    */
+} pj_stun_status;
+
+
+/**
+ * This structure describes STUN message header. A STUN message has the 
+ * following format:
+ *
+ * \verbatim
+
+        0                   1                   2                   3
+        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+       |0 0|     STUN Message Type     |         Message Length        |
+       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+       |                         Magic Cookie                          |
+       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+       |
+       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+                                Transaction ID
+       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+                                                                       |
+       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+   \endverbatim
+ */
+typedef struct pj_stun_msg_hdr
+{
+    /**
+     * STUN message type, which the first two bits must be zeroes.
+     */
+    pj_uint16_t		type;
+
+    /**
+     * The message length is the size, in bytes, of the message not
+     * including the 20 byte STUN header.
+     */
+    pj_uint16_t		length;
+
+    /**
+     * The magic cookie is a fixed value, 0x2112A442 (PJ_STUN_MAGIC constant).
+     * In the previous version of this specification [15] this field was part 
+     * of the transaction ID.
+     */
+    pj_uint32_t		magic;
+
+    /**
+     * The transaction ID is a 96 bit identifier.  STUN transactions are
+     * identified by their unique 96-bit transaction ID.  For request/
+     * response transactions, the transaction ID is chosen by the STUN
+     * client and MUST be unique for each new STUN transaction generated by
+     * that STUN client.  The transaction ID MUST be uniformly and randomly
+     * distributed between 0 and 2**96 - 1. 
+     */
+    pj_uint8_t		tsx_id[12];
+
+} pj_stun_msg_hdr;
+
+
+/**
+ * This structre describes STUN attribute header. Each attribute is
+ * TLV encoded, with a 16 bit type, 16 bit length, and variable value.
+ * Each STUN attribute ends on a 32 bit boundary:
+ *
+ * \verbatim
+
+        0                   1                   2                   3
+        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+       |         Type                  |            Length             |
+       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+       |                             Value                 ....        |
+       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+   \endverbatim
+ */
+typedef struct pj_stun_attr_hdr
+{
+    /**
+     * STUN attribute type.
+     */
+    pj_uint16_t		type;
+
+    /**
+     * The Length refers to the length of the actual useful content of the
+     * Value portion of the attribute, measured in bytes. The value
+     * in the Length field refers to the length of the Value part of the
+     * attribute prior to padding - i.e., the useful content.
+     */
+    pj_uint16_t		length;
+
+} pj_stun_attr_hdr;
+
+
+/**
+ * This structure describes STUN generic IP address attribute, used for
+ * example to represent STUN MAPPED-ADDRESS attribute.
+ *
+ * The generic IP address attribute indicates the transport address.
+ * It consists of an eight bit address family, and a sixteen bit port,
+ * followed by a fixed length value representing the IP address.  If the
+ * address family is IPv4, the address is 32 bits, in network byte
+ * order.  If the address family is IPv6, the address is 128 bits in
+ * network byte order.
+ *
+ * The format of the generic IP address attribute is:
+ *
+ * \verbatim
+
+        0                   1                   2                   3
+        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+       |x x x x x x x x|    Family     |           Port                |
+       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+       |                   Address  (variable)
+       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+   \endverbatim
+ */
+typedef struct pj_stun_sockaddr_attr
+{
+    /**
+     * Standard STUN attribute header.
+     */
+    pj_stun_attr_hdr	hdr;
+
+    /**
+     * Flag to indicate whether this attribute should be sent in XOR-ed
+     * format, or has been received in XOR-ed format.
+     */
+    pj_bool_t		xor_ed;
+
+    /**
+     * The socket address (as a union)
+     */
+    union {
+	pj_sockaddr	    addr;   /**< Generic socket address.    */
+	pj_sockaddr_in	    ipv4;   /**< IPv4 socket address.	    */
+	pj_sockaddr_in6	    ipv6;   /**< IPv6 socket address.	    */
+    } addr;
+
+} pj_stun_sockaddr_attr;
+
+
+/**
+ * This structure represents a generic STUN attributes with no payload,
+ * and it is used for example by ICE USE-CANDIDATE attribute.
+ */
+typedef struct pj_stun_empty_attr
+{
+    /**
+     * Standard STUN attribute header.
+     */
+    pj_stun_attr_hdr	hdr;
+
+} pj_stun_empty_attr;
+
+
+/**
+ * This structure represents generic STUN string attributes, such as STUN
+ * USERNAME, PASSWORD, SERVER, REALM, and NONCE attributes. Note that for REALM and
+ * NONCE attributes, the text MUST be quoted with.
+ */
+typedef struct pj_stun_string_attr
+{
+    /**
+     * Standard STUN attribute header.
+     */
+    pj_stun_attr_hdr	hdr;
+
+    /**
+     * The string value.
+     */
+    pj_str_t		value;
+
+} pj_stun_string_attr;
+
+
+/**
+ * This structure represents a generic STUN attributes with 32bit (unsigned)
+ * integer value, such as STUN FINGERPRINT and REFRESH-INTERVAL attributes.
+ */
+typedef struct pj_stun_uint_attr
+{
+    /**
+     * Standard STUN attribute header.
+     */
+    pj_stun_attr_hdr	hdr;
+    
+    /**
+     * The 32bit value.
+     */
+    pj_uint32_t		value;
+
+} pj_stun_uint_attr;
+
+
+/**
+ * This structure represents generic STUN attributes to hold a raw binary
+ * data.
+ */
+typedef struct pj_stun_binary_attr
+{
+    /**
+     * Standard STUN attribute header.
+     */
+    pj_stun_attr_hdr	hdr;
+    
+    /**
+     * Length of the data.
+     */
+    unsigned		length;
+
+    /**
+     * The raw data.
+     */
+    pj_uint8_t	       *data;
+
+} pj_stun_binary_attr;
+
+
+/**
+ * This structure describes STUN MESSAGE-INTEGRITY attribute.
+ * The MESSAGE-INTEGRITY attribute contains an HMAC-SHA1 [10] of the
+ * STUN message.  The MESSAGE-INTEGRITY attribute can be present in any
+ * STUN message type.  Since it uses the SHA1 hash, the HMAC will be 20
+ * bytes.
+ */
+typedef struct pj_stun_msgint_attr
+{
+    /**
+     * Standard STUN attribute header.
+     */
+    pj_stun_attr_hdr	hdr;
+
+    /**
+     * The 20 bytes hmac value.
+     */
+    pj_uint8_t		hmac[20];
+
+} pj_stun_msgint_attr;
+
+
+/**
+ * This structure describes STUN FINGERPRINT attribute. The FINGERPRINT 
+ * attribute can be present in all STUN messages.  It is computed as 
+ * the CRC-32 of the STUN message up to (but excluding) the FINGERPRINT 
+ * attribute itself, xor-d with the 32 bit value 0x5354554e
+ */
+typedef struct pj_stun_uint_attr pj_stun_fingerprint_attr;
+
+
+/**
+ * This structure represents STUN ERROR-CODE attribute. The ERROR-CODE 
+ * attribute is present in the Binding Error Response and Shared Secret 
+ * Error Response.  It is a numeric value in the range of 100 to 699 
+ * plus a textual reason phrase encoded in UTF-8
+ *
+ * \verbatim
+
+        0                   1                   2                   3
+        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+       |                   0                     |Class|     Number    |
+       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+       |      Reason Phrase (variable)                                ..
+       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ \endverbatim
+ */
+typedef struct pj_stun_errcode_attr
+{
+    /**
+     * Standard STUN attribute header.
+     */
+    pj_stun_attr_hdr	hdr;
+
+    /**
+     * The value must be zero.
+     */
+    pj_uint16_t		zero;
+
+    /**
+     * Error class (1-6).
+     */
+    pj_uint8_t		err_class;
+
+    /**
+     * Error number is the error number modulo 100.
+     */
+    pj_uint8_t		number;
+
+    /**
+     * The reason phrase.
+     */
+    pj_str_t		reason;
+
+} pj_stun_errcode_attr;
+
+
+/**
+ * This describes STUN REALM attribute.
+ * The REALM attribute is present in requests and responses.  It
+ * contains text which meets the grammar for "realm" as described in RFC
+ * 3261 [11], and will thus contain a quoted string (including the
+ * quotes).
+ */
+typedef struct pj_stun_string_attr pj_stun_realm_attr;
+
+
+/**
+ * This describes STUN NONCE attribute. 
+ * The NONCE attribute is present in requests and in error responses.
+ * It contains a sequence of qdtext or quoted-pair, which are defined in
+ * RFC 3261 [11].  See RFC 2617 [7] for guidance on selection of nonce
+ * values in a server.
+ */
+typedef struct pj_stun_string_attr pj_stun_nonce_attr;
+
+
+/**
+ * This describes STUN UNKNOWN-ATTRIBUTES attribute.
+ * The UNKNOWN-ATTRIBUTES attribute is present only in an error response
+ * when the response code in the ERROR-CODE attribute is 420.
+ * The attribute contains a list of 16 bit values, each of which
+ * represents an attribute type that was not understood by the server.
+ * If the number of unknown attributes is an odd number, one of the
+ * attributes MUST be repeated in the list, so that the total length of
+ * the list is a multiple of 4 bytes.
+ */
+typedef struct pj_stun_unknown_attr
+{
+    /**
+     * Standard STUN attribute header.
+     */
+    pj_stun_attr_hdr	hdr;
+
+    /**
+     * Number of unknown attributes in the array.
+     */
+    unsigned		attr_count;
+
+    /**
+     * Array of unknown attribute IDs.
+     */
+    pj_uint16_t	        attrs[PJ_STUN_MAX_ATTR];
+
+} pj_stun_unknown_attr;
+
+
+/**
+ * This structure describes STUN MAPPED-ADDRESS attribute.
+ * The MAPPED-ADDRESS attribute indicates the mapped transport address.
+ */
+typedef struct pj_stun_sockaddr_attr pj_stun_mapped_addr_attr;
+
+
+/**
+ * This describes STUN XOR-MAPPED-ADDRESS attribute (which has the same
+ * format as STUN MAPPED-ADDRESS attribute).
+ * The XOR-MAPPED-ADDRESS attribute is present in responses.  It
+ * provides the same information that would present in the MAPPED-
+ * ADDRESS attribute but because the NAT's public IP address is
+ * obfuscated through the XOR function, STUN messages are able to pass
+ * through NATs which would otherwise interfere with STUN.
+ */
+typedef struct pj_stun_sockaddr_attr pj_stun_xor_mapped_addr_attr;
+
+
+/**
+ * This describes STUN SERVER attribute.
+ * The server attribute contains a textual description of the software
+ * being used by the server, including manufacturer and version number.
+ * The attribute has no impact on operation of the protocol, and serves
+ * only as a tool for diagnostic and debugging purposes.  The value of
+ * SERVER is variable length.
+ */
+typedef struct pj_stun_string_attr pj_stun_server_attr;
+
+
+/**
+ * This describes STUN ALTERNATE-SERVER attribute.
+ * The alternate server represents an alternate transport address for a
+ * different STUN server to try.  It is encoded in the same way as
+ * MAPPED-ADDRESS.
+ */
+typedef struct pj_stun_sockaddr_attr pj_stun_alt_server_attr;
+
+
+/**
+ * This describes STUN REFRESH-INTERVAL attribute.
+ * The REFRESH-INTERVAL indicates the number of milliseconds that the
+ * server suggests the client should use between refreshes of the NAT
+ * bindings between the client and server.
+ */
+typedef struct pj_stun_uint_attr pj_stun_refresh_interval_attr;
+
+
+/**
+ * This structure describes STUN RESPONSE-ADDRESS attribute.
+ * The RESPONSE-ADDRESS attribute indicates where the response to a
+ * Binding Request should be sent.  Its syntax is identical to MAPPED-
+ * ADDRESS.
+ *
+ * Note that the usage of this attribute has been deprecated by the 
+ * RFC 3489-bis standard.
+ */
+typedef struct pj_stun_sockaddr_attr pj_stun_response_addr_attr;
+
+
+/**
+ * This structure describes STUN CHANGED-ADDRESS attribute.
+ * The CHANGED-ADDRESS attribute indicates the IP address and port where
+ * responses would have been sent from if the "change IP" and "change
+ * port" flags had been set in the CHANGE-REQUEST attribute of the
+ * Binding Request.  The attribute is always present in a Binding
+ * Response, independent of the value of the flags.  Its syntax is
+ * identical to MAPPED-ADDRESS.
+ *
+ * Note that the usage of this attribute has been deprecated by the 
+ * RFC 3489-bis standard.
+ */
+typedef struct pj_stun_sockaddr_attr pj_stun_changed_addr_attr;
+
+
+/**
+ * This structure describes STUN CHANGE-REQUEST attribute.
+ * The CHANGE-REQUEST attribute is used by the client to request that
+ * the server use a different address and/or port when sending the
+ * response. 
+ *
+ * Bit 29 of the value is the "change IP" flag.  If true, it requests 
+ * the server to send the Binding Response with a different IP address 
+ * than the one the Binding Request was received on.
+ *
+ * Bit 30 of the value is the "change port" flag.  If true, it requests 
+ * the server to send the Binding Response with a different port than 
+ * the one the Binding Request was received on.
+ *
+ * Note that the usage of this attribute has been deprecated by the 
+ * RFC 3489-bis standard.
+ */
+typedef struct pj_stun_uint_attr pj_stun_change_request_attr;
+
+/**
+ * This structure describes STUN SOURCE-ADDRESS attribute.
+ * The SOURCE-ADDRESS attribute is present in Binding Responses.  It
+ * indicates the source IP address and port that the server is sending
+ * the response from.  Its syntax is identical to that of MAPPED-
+ * ADDRESS.
+ *
+ * Note that the usage of this attribute has been deprecated by the 
+ * RFC 3489-bis standard.
+ */
+typedef struct pj_stun_sockaddr_attr pj_stun_src_addr_attr;
+
+
+/**
+ * This describes the STUN REFLECTED-FROM attribute.
+ * The REFLECTED-FROM attribute is present only in Binding Responses,
+ * when the Binding Request contained a RESPONSE-ADDRESS attribute.  The
+ * attribute contains the identity (in terms of IP address) of the
+ * source where the request came from.  Its purpose is to provide
+ * traceability, so that a STUN server cannot be used as a reflector for
+ * denial-of-service attacks.
+ */
+typedef struct pj_stun_sockaddr_attr pj_stun_reflected_from_attr;
+
+
+/**
+ * This describes STUN USERNAME attribute.
+ * The USERNAME attribute is used for message integrity.  It identifies
+ * the shared secret used in the message integrity check.  Consequently,
+ * the USERNAME MUST be included in any request that contains the
+ * MESSAGE-INTEGRITY attribute.
+ */
+typedef struct pj_stun_string_attr pj_stun_username_attr;
+
+
+/**
+ * This describes STUN PASSWORD attribute.
+ * If the message type is Shared Secret Response it MUST include the
+ * PASSWORD attribute.
+ */
+typedef struct pj_stun_string_attr pj_stun_password_attr;
+
+
+/**
+ * This describes STUN LIFETIME attribute.
+ * The lifetime attribute represents the duration for which the server
+ * will maintain an allocation in the absence of data traffic either
+ * from or to the client.  It is a 32 bit value representing the number
+ * of seconds remaining until expiration.
+ */
+typedef struct pj_stun_uint_attr pj_stun_lifetime_attr;
+
+
+/**
+ * This describes STUN BANDWIDTH attribute.
+ * The bandwidth attribute represents the peak bandwidth, measured in
+ * kbits per second, that the client expects to use on the binding.  The
+ * value represents the sum in the receive and send directions.
+ */
+typedef struct pj_stun_uint_attr pj_stun_bandwidth_attr;
+
+
+/**
+ * This describes the STUN REMOTE-ADDRESS attribute.
+ * The REMOTE-ADDRESS specifies the address and port of the peer as seen
+ * from the STUN relay server.
+ */
+typedef struct pj_stun_sockaddr_attr pj_stun_remote_addr_attr;
+
+
+/**
+ * This describes the STUN DATA attribute.
+ * The DATA attribute is present in Send Indications and Data
+ * Indications.  It contains raw payload data that is to be sent (in the
+ * case of a Send Request) or was received (in the case of a Data
+ * Indication)..
+ */
+typedef struct pj_stun_binary_attr pj_stun_data_attr;
+
+
+/**
+ * This describes the STUN RELAY-ADDRESS attribute.
+ * The RELAY-ADDRESS is present in Allocate responses.  It specifies the
+ * address and port that the server allocated to the client.
+ */
+typedef struct pj_stun_sockaddr_attr pj_stun_relay_addr_attr;
+
+
+/**
+ * This describes the REQUESTED-ADDRESS-TYPE attribute.
+ * The REQUESTED-ADDRESS-TYPE attribute is used by clients to request
+ * the allocation of a specific address type from a server.  The
+ * following is the format of the REQUESTED-ADDRESS-TYPE attribute.
+
+ \verbatim
+
+      0                   1                   2                   3
+      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+     |        Family                 |           Reserved            |
+     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ \endverbatim
+ */
+typedef struct pj_stun_uint_attr pj_stun_req_addr_type;
+
+/**
+ * This describes the STUN REQUESTED-PORT-PROPS attribute.
+ * This attribute allows the client to request certain properties for
+ * the port that is allocated by the server.  The attribute can be used
+ * with any transport protocol that has the notion of a 16 bit port
+ * space (including TCP and UDP).  The attribute is 32 bits long.  Its
+ * format is:
+
+ \verbatim
+
+    0                   1                   2                   3
+    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+   |                           Reserved = 0                  |B| A |
+   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ \endverbatim  
+ */
+typedef struct pj_stun_uint_attr pj_stun_req_port_props_attr;
+
+
+/**
+ * This describes the STUN REQUESTED-TRANSPORT attribute.
+ * This attribute is used by the client to request a specific transport
+ * protocol for the allocated transport address.  It is a 32 bit
+ * unsigned integer.  Its values are: 0x0000 for UDP and 0x0000 for TCP.
+ */
+typedef struct pj_stun_uint_attr pj_stun_req_transport_attr;
+
+
+/**
+ * This describes the STUN REQUESTED-IP attribute.
+ * The REQUESTED-IP attribute is used by the client to request that a
+ * specific IP address be allocated to it.
+ */
+typedef struct pj_stun_sockaddr_attr pj_stun_req_ip_attr;
+
+/**
+ * This describes the XOR-REFLECTED-FROM attribute, as described by
+ * draft-macdonald-behave-nat-behavior-discovery-00.
+ * The XOR-REFLECTED-FROM attribute is used in place of the REFLECTED-
+ * FROM attribute.  It provides the same information, but because the
+ * NAT's public address is obfuscated through the XOR function, It can
+ * pass through a NAT that would otherwise attempt to translate it to
+ * the private network address.  XOR-REFLECTED-FROM has identical syntax
+ * to XOR-MAPPED-ADDRESS.
+ */
+typedef struct pj_stun_sockaddr_attr pj_stun_xor_reflected_from_attr;
+
+/**
+ * This describes the PRIORITY attribute from draft-ietf-mmusic-ice-13.
+ * The PRIORITY attribute indicates the priority that is to be
+ * associated with a peer reflexive candidate, should one be discovered
+ * by this check.  It is a 32 bit unsigned integer, and has an attribute
+ * type of 0x0024.
+ */
+typedef struct pj_stun_uint_attr pj_stun_priority_attr;
+
+/**
+ * This describes the USE-CANDIDATE attribute from draft-ietf-mmusic-ice-13.
+ * The USE-CANDIDATE attribute indicates that the candidate pair
+ * resulting from this check should be used for transmission of media.
+ * The attribute has no content (the Length field of the attribute is
+ * zero); it serves as a flag.
+ */
+typedef struct pj_stun_empty_attr pj_stun_use_candidate_attr;
+
+/**
+ * This structure describes STUN XOR-INTERNAL-ADDRESS attribute from
+ * draft-wing-behave-nat-control-stun-usage-00.
+ * This attribute MUST be present in a Binding Response and may be used
+ * in other responses as well.  This attribute is necessary to allow a
+ * STUN client to 'walk backwards' and communicate directly with all of
+ * the STUN-aware NATs along the path.
+ */
+typedef pj_stun_sockaddr_attr pj_stun_xor_internal_addr_attr;
+
+/**
+ * This describes the STUN TIMER-VAL attribute.
+ * The TIMER-VAL attribute is used only in conjunction with the Set
+ * Active Destination response.  It conveys from the server, to the
+ * client, the value of the timer used in the server state machine.
+ */
+typedef struct pj_stun_uint_attr pj_stun_timer_val_attr;
+
+
+/**
+ * This structure describes a parsed STUN message. All integral fields
+ * in this structure (including IP addresses) will be in the host
+ * byte order.
+ */
+typedef struct pj_stun_msg
+{
+    /**
+     * STUN message header.
+     */
+    pj_stun_msg_hdr     hdr;
+
+    /**
+     * Number of attributes in the STUN message.
+     */
+    unsigned		attr_count;
+
+    /**
+     * Array of STUN attributes.
+     */
+    pj_stun_attr_hdr   *attr[PJ_STUN_MAX_ATTR];
+
+} pj_stun_msg;
+
+
+/** STUN decoding options */
+enum pj_stun_decode_options
+{
+    /** 
+     * Tell the decoder that the message was received from datagram
+     * oriented transport (such as UDP).
+     */
+    PJ_STUN_IS_DATAGRAM	    = 1,
+
+    /**
+     * Tell pj_stun_msg_decode() to check the validity of the STUN
+     * message by calling pj_stun_msg_check() before starting to
+     * decode the packet.
+     */
+    PJ_STUN_CHECK_PACKET    = 2
+};
+
+
+/**
+ * Get STUN message method name.
+ *
+ * @param msg_type	The STUN message type (in host byte order)
+ *
+ * @return		The STUN message method name string.
+ */
+PJ_DECL(const char*) pj_stun_get_method_name(unsigned msg_type);
+
+
+/**
+ * Get STUN message class name.
+ *
+ * @param msg_type	The STUN message type (in host byte order)
+ *
+ * @return		The STUN message class name string.
+ */
+PJ_DECL(const char*) pj_stun_get_class_name(unsigned msg_type);
+
+
+/**
+ * Get STUN attribute name.
+ *
+ * @return attr_type	The STUN attribute type (in host byte order).
+ *
+ * @return		The STUN attribute type name string.
+ */
+PJ_DECL(const char*) pj_stun_get_attr_name(unsigned attr_type);
+
+
+/**
+ * Get STUN standard reason phrase for the specified error code.
+ *
+ * @param err_code	The STUN error code.
+ *
+ * @return		The STUN error reason phrase.
+ */
+PJ_DECL(pj_str_t) pj_stun_get_err_reason(int err_code);
+
+
+/**
+ * Create a generic STUN message.
+ *
+ * @param pool		Pool to create the STUN message.
+ * @param msg_type	The 14bit message type.
+ * @param magic		Magic value to be put to the mesage; for requests,
+ *			the value should be PJ_STUN_MAGIC.
+ * @param tsx_id	Optional transaction ID, or NULL to let the
+ *			function generates a random transaction ID.
+ * @param p_msg		Pointer to receive the message.
+ *
+ * @return		PJ_SUCCESS on success.
+ */
+PJ_DECL(pj_status_t) pj_stun_msg_create(pj_pool_t *pool,
+					unsigned msg_type,
+					pj_uint32_t magic,
+					const pj_uint8_t tsx_id[12],
+					pj_stun_msg **p_msg);
+
+/**
+ * Create STUN response message. 
+ *
+ * @param pool		Pool to create the mesage.
+ * @param req_msg	The request message.
+ * @param err_code	STUN error code. If this value is not zero,
+ *			then error response will be created, otherwise
+ *			successful response will be created.
+ * @param err_msg	Optional error message to explain err_code.
+ *			If this value is NULL and err_code is not zero,
+ *			the error string will be taken from the default
+ *			STUN error message.
+ * @param p_response	Pointer to receive the response.
+ *
+ * @return		PJ_SUCCESS on success, or the appropriate error.
+ */
+PJ_DECL(pj_status_t) pj_stun_msg_create_response(pj_pool_t *pool,
+						 const pj_stun_msg *req_msg,
+						 unsigned err_code,
+						 const pj_str_t *err_msg,
+						 pj_stun_msg **p_response);
+
+
+/**
+ * Add STUN attribute to STUN message.
+ *
+ * @param msg		The STUN message.
+ * @param attr		The STUN attribute to be added to the message.
+ *
+ * @return		PJ_SUCCESS on success, or PJ_ETOOMANY if there are
+ *			already too many attributes in the message.
+ */
+PJ_DECL(pj_status_t) pj_stun_msg_add_attr(pj_stun_msg *msg,
+					  pj_stun_attr_hdr *attr);
+
+
+/**
+ * Print the STUN message structure to a packet buffer, ready to be 
+ * sent to remote destination. This function will take care about 
+ * calculating the MESSAGE-INTEGRITY digest as well as FINGERPRINT
+ * value.
+ *
+ * If MESSAGE-INTEGRITY attribute is present, the function assumes
+ * that application wants to include credential (short or long term)
+ * in the message, and this function will calculate the HMAC digest
+ * from the message using the supplied password in the parameter. 
+ * If REALM attribute is present, the HMAC digest is calculated as
+ * long term credential, otherwise as short term credential.
+ *
+ * If FINGERPRINT attribute is present, this function will calculate
+ * the FINGERPRINT CRC attribute for the message.
+ *
+ * @param msg		The STUN message to be printed. Upon return,
+ *			some fields in the header (such as message
+ *			length) will be updated.
+ * @param pkt_buf	The buffer to be filled with the packet.
+ * @param buf_size	Size of the buffer.
+ * @param options	Options, which currently must be zero.
+ * @param password	Password to be used when credential is to be
+ *			included. This parameter MUST be specified when
+ *			the message contains MESSAGE-INTEGRITY attribute.
+ * @param p_msg_len	Upon return, it will be filed with the size of 
+ *			the packet in bytes, or negative value on error.
+ *
+ * @return		PJ_SUCCESS on success or the appropriate error code.
+ */
+PJ_DECL(pj_status_t) pj_stun_msg_encode(pj_stun_msg *msg,
+				        pj_uint8_t *pkt_buf,
+				        unsigned buf_size,
+				        unsigned options,
+					const pj_str_t *password,
+				        unsigned *p_msg_len);
+
+/**
+ * Check that the PDU is potentially a valid STUN message. This function
+ * is useful when application needs to multiplex STUN packets with other
+ * application traffic. When this function returns PJ_SUCCESS, there is a
+ * big chance that the packet is a STUN packet.
+ *
+ * Note that we cannot be sure that the PDU is a really valid STUN message 
+ * until we actually parse the PDU.
+ *
+ * @param pdu		The packet buffer.
+ * @param pdu_len	The length of the packet buffer.
+ * @param options	Additional options to be applied in the checking,
+ *			which can be taken from pj_stun_decode_options. One 
+ *			of the useful option is PJ_STUN_IS_DATAGRAM which 
+ *			means that the pdu represents a whole STUN packet.
+ *
+ * @return		PJ_SUCCESS if the PDU is a potentially valid STUN
+ *			message.
+ */
+PJ_DECL(pj_status_t) pj_stun_msg_check(const pj_uint8_t *pdu, 
+				       unsigned pdu_len, unsigned options);
+
+
+/**
+ * Decode incoming packet into STUN message.
+ *
+ * @param pool		Pool to allocate the message.
+ * @param pdu		The incoming packet to be parsed.
+ * @param pdu_len	The length of the incoming packet.
+ * @param options	Parsing flags, according to pj_stun_decode_options.
+ * @param p_msg		Pointer to receive the parsed message.
+ * @param p_parsed_len	Optional pointer to receive how many bytes have
+ *			been parsed for the STUN message. This is useful
+ *			when the packet is received over stream oriented
+ *			transport.
+ * @param p_response	Optional pointer to receive an instance of response
+ *			message, if one can be created. If the packet being
+ *			decoded is a request message, and it contains error,
+ *			and a response can be created, then the STUN 
+ *			response message will be returned on this argument.
+ *
+ * @return		PJ_SUCCESS if a STUN message has been successfully
+ *			decoded.
+ */
+PJ_DECL(pj_status_t) pj_stun_msg_decode(pj_pool_t *pool,
+				        const pj_uint8_t *pdu,
+				        unsigned pdu_len,
+				        unsigned options,
+				        pj_stun_msg **p_msg,
+					unsigned *p_parsed_len,
+				        pj_stun_msg **p_response);
+
+/**
+ * Dump STUN message to a printable string output.
+ *
+ * @param msg		The STUN message
+ * @param buffer	Buffer where the printable string output will
+ *			be printed on.
+ * @param length	Specify the maximum length of the buffer.
+ * @param printed_len	Optional pointer, which on output will be filled
+ *			up with the actual length of the output string.
+ *
+ * @return		The message string output.
+ */
+PJ_DECL(char*) pj_stun_msg_dump(const pj_stun_msg *msg,
+			        char *buffer,
+			        unsigned length,
+				unsigned *printed_len);
+
+
+/**
+ * Find STUN attribute in the STUN message, starting from the specified
+ * index.
+ *
+ * @param msg		The STUN message.
+ * @param attr_type	The attribute type to be found, from pj_stun_attr_type.
+ * @param start_index	The start index of the attribute in the message.
+ *			Specify zero to start searching from the first
+ *			attribute.
+ *
+ * @return		The attribute instance, or NULL if it cannot be
+ *			found.
+ */
+PJ_DECL(pj_stun_attr_hdr*) pj_stun_msg_find_attr(const pj_stun_msg *msg,
+						 int attr_type,
+						 unsigned start_index);
+
+
+/**
+ * Create a generic STUN IP address attribute. The \a addr_len and
+ * \a addr parameters specify whether the address is IPv4 or IPv4
+ * address.
+ *
+ * @param pool		The pool to allocate memory from.
+ * @param attr_type	Attribute type, from #pj_stun_attr_type.
+ * @param xor_ed	If non-zero, the port and address will be XOR-ed
+ *			with magic, to make the XOR-MAPPED-ADDRESS attribute.
+ * @param addr		A pj_sockaddr_in or pj_sockaddr_in6 structure.
+ * @param addr_len	Length of \a addr parameter.
+ * @param p_attr	Pointer to receive the attribute.
+ *
+ * @return		PJ_SUCCESS on success or the appropriate error code.
+ */
+PJ_DECL(pj_status_t) pj_stun_sockaddr_attr_create(pj_pool_t *pool,
+						int attr_type, 
+						pj_bool_t xor_ed,
+						const pj_sockaddr_t *addr,
+						unsigned addr_len,
+						pj_stun_sockaddr_attr **p_attr);
+
+
+/**
+ * Create and add generic STUN IP address attribute to a STUN message.
+ * The \a addr_len and \a addr parameters specify whether the address is 
+ * IPv4 or IPv4 address.
+ *
+ * @param pool		The pool to allocate memory from.
+ * @param msg		The STUN message.
+ * @param attr_type	Attribute type, from #pj_stun_attr_type.
+ * @param xor_ed	If non-zero, the port and address will be XOR-ed
+ *			with magic, to make the XOR-MAPPED-ADDRESS attribute.
+ * @param addr		A pj_sockaddr_in or pj_sockaddr_in6 structure.
+ * @param addr_len	Length of \a addr parameter.
+ *
+ * @return		PJ_SUCCESS on success or the appropriate error code.
+ */
+PJ_DECL(pj_status_t) pj_stun_msg_add_sockaddr_attr(pj_pool_t *pool,
+						  pj_stun_msg *msg,
+						  int attr_type, 
+						  pj_bool_t xor_ed,
+						  const pj_sockaddr_t *addr,
+						  unsigned addr_len);
+
+/**
+ * Create a STUN generic string attribute.
+ *
+ * @param pool		The pool to allocate memory from.
+ * @param attr_type	Attribute type, from #pj_stun_attr_type.
+ * @param value		The string value to be assigned to the attribute.
+ * @param p_attr	Pointer to receive the attribute.
+ *
+ * @return		PJ_SUCCESS on success or the appropriate error code.
+ */
+PJ_DECL(pj_status_t) pj_stun_string_attr_create(pj_pool_t *pool,
+					        int attr_type,
+					        const pj_str_t *value,
+					        pj_stun_string_attr **p_attr);
+
+/**
+ * Create and add STUN generic string attribute to the message.
+ *
+ * @param pool		The pool to allocate memory from.
+ * @param msg		The STUN message.
+ * @param attr_type	Attribute type, from #pj_stun_attr_type.
+ * @param value		The string value to be assigned to the attribute.
+ *
+ * @return		PJ_SUCCESS on success or the appropriate error code.
+ */
+PJ_DECL(pj_status_t) pj_stun_msg_add_string_attr(pj_pool_t *pool,
+						 pj_stun_msg *msg,
+						 int attr_type,
+						 const pj_str_t *value);
+
+/**
+ * Create a STUN generic 32bit value attribute.
+ *
+ * @param pool		The pool to allocate memory from.
+ * @param attr_type	Attribute type, from #pj_stun_attr_type.
+ * @param value		The 32bit value to be assigned to the attribute.
+ * @param p_attr	Pointer to receive the attribute.
+ *
+ * @return		PJ_SUCCESS on success or the appropriate error code.
+ */
+PJ_DECL(pj_status_t) pj_stun_uint_attr_create(pj_pool_t *pool,
+					      int attr_type,
+					      pj_uint32_t value,
+					      pj_stun_uint_attr **p_attr);
+
+/**
+ * Create and add STUN generic 32bit value attribute to the message.
+ *
+ * @param pool		The pool to allocate memory from.
+ * @param msg		The STUN message
+ * @param attr_type	Attribute type, from #pj_stun_attr_type.
+ * @param value		The 32bit value to be assigned to the attribute.
+ *
+ * @return		PJ_SUCCESS on success or the appropriate error code.
+ */
+PJ_DECL(pj_status_t) pj_stun_msg_add_uint_attr(pj_pool_t *pool,
+					       pj_stun_msg *msg,
+					       int attr_type,
+					       pj_uint32_t value);
+
+
+/**
+ * Create a STUN MESSAGE-INTEGRITY attribute.
+ *
+ * @param pool		The pool to allocate memory from.
+ * @param p_attr	Pointer to receive the attribute.
+ *
+ * @return		PJ_SUCCESS on success or the appropriate error code.
+ */
+PJ_DECL(pj_status_t) pj_stun_msgint_attr_create(pj_pool_t *pool,
+						pj_stun_msgint_attr **p_attr);
+
+/** 
+ * Create and add STUN MESSAGE-INTEGRITY attribute.
+ *
+ * @param pool		The pool to allocate memory from.
+ * @param msg		The STUN message
+ *
+ * @return		PJ_SUCCESS on success or the appropriate error code.
+ */
+PJ_DECL(pj_status_t) pj_stun_msg_add_msgint_attr(pj_pool_t *pool,
+						 pj_stun_msg *msg);
+
+/**
+ * Create a STUN ERROR-CODE attribute.
+ *
+ * @param pool		The pool to allocate memory from.
+ * @param err_code	STUN error code.
+ * @param err_reason	Optional STUN error reason. If NULL is given, the
+ *			standard error reason will be given.
+ * @param p_attr	Pointer to receive the attribute.
+ *
+ * @return		PJ_SUCCESS on success or the appropriate error code.
+ */
+PJ_DECL(pj_status_t) pj_stun_errcode_attr_create(pj_pool_t *pool,
+						int err_code,
+						const pj_str_t *err_reason,
+						pj_stun_errcode_attr **p_attr);
+
+
+/**
+ * Create and add STUN ERROR-CODE attribute to the message.
+ *
+ * @param pool		The pool to allocate memory from.
+ * @param msg		The STUN mesage.
+ * @param err_code	STUN error code.
+ * @param err_reason	Optional STUN error reason. If NULL is given, the
+ *			standard error reason will be given.
+ *
+ * @return		PJ_SUCCESS on success or the appropriate error code.
+ */
+PJ_DECL(pj_status_t) pj_stun_msg_add_errcode_attr(pj_pool_t *pool,
+						  pj_stun_msg *msg,
+						  int err_code,
+						  const pj_str_t *err_reason);
+
+/**
+ * Create instance of STUN UNKNOWN-ATTRIBUTES attribute and copy the
+ * unknown attribute array to the attribute.
+ *
+ * @param pool		The pool to allocate memory from.
+ * @param attr_cnt	Number of attributes in the array (can be zero).
+ * @param attr		Optional array of attributes.
+ * @param p_attr	Pointer to receive the attribute.
+ *
+ * @return		PJ_SUCCESS on success or the appropriate error code.
+ */
+PJ_DECL(pj_status_t) pj_stun_unknown_attr_create(pj_pool_t *pool,
+						unsigned attr_cnt,
+						const pj_uint16_t attr[],
+						pj_stun_unknown_attr **p_attr);
+
+/**
+ * Create and add STUN UNKNOWN-ATTRIBUTES attribute to the message.
+ *
+ * @param pool		The pool to allocate memory from.
+ * @param msg		The STUN message.
+ * @param attr_cnt	Number of attributes in the array (can be zero).
+ * @param attr		Optional array of attributes.
+ *
+ * @return		PJ_SUCCESS on success or the appropriate error code.
+ */
+PJ_DECL(pj_status_t) pj_stun_msg_add_unknown_attr(pj_pool_t *pool,
+						  pj_stun_msg *msg,
+						  unsigned attr_cnt,
+						  const pj_uint16_t attr[]);
+
+/**
+ * Create STUN binary attribute.
+ *
+ * @param pool		The pool to allocate memory from.
+ * @param attr_type	The attribute type, from #pj_stun_attr_type.
+ * @param data		Data to be coped to the attribute, or NULL
+ *			if no data to be copied now.
+ * @param length	Length of data, or zero if no data is to be
+ *			copied now.
+ * @param p_attr	Pointer to receive the attribute.
+ *
+ * @return		PJ_SUCCESS on success or the appropriate error code.
+ */
+PJ_DECL(pj_status_t) pj_stun_binary_attr_create(pj_pool_t *pool,
+					        int attr_type,
+					        const pj_uint8_t *data,
+					        unsigned length,
+					        pj_stun_binary_attr **p_attr);
+
+/**
+ * Create STUN binary attribute and add the attribute to the message.
+ *
+ * @param pool		The pool to allocate memory from.
+ * @param msg		The STUN message.
+ * @param attr_type	The attribute type, from #pj_stun_attr_type.
+ * @param data		Data to be coped to the attribute, or NULL
+ *			if no data to be copied now.
+ * @param length	Length of data, or zero if no data is to be
+ *			copied now.
+ * @param p_attr	Pointer to receive the attribute.
+ *
+ * @return		PJ_SUCCESS on success or the appropriate error code.
+ */
+PJ_DECL(pj_status_t) pj_stun_msg_add_binary_attr(pj_pool_t *pool,
+						 pj_stun_msg *msg,
+						 int attr_type,
+						 const pj_uint8_t *data,
+						 unsigned length);
+
+
+/**
+ * @}
+ */
+
+
+PJ_END_DECL
+
+
+#endif	/* __PJLIB_UTIL_STUN_MSG_H__ */
+
diff --git a/pjnath/include/pjnath/stun_session.h b/pjnath/include/pjnath/stun_session.h
new file mode 100644
index 00000000..fa18dc3a
--- /dev/null
+++ b/pjnath/include/pjnath/stun_session.h
@@ -0,0 +1,372 @@
+/* $Id$ */
+/* 
+ * Copyright (C) 2003-2005 Benny Prijono <benny@prijono.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA 
+ */
+#ifndef __PJLIB_UTIL_STUN_SESSION_H__
+#define __PJLIB_UTIL_STUN_SESSION_H__
+
+#include <pjlib-util/stun_msg.h>
+#include <pjlib-util/stun_auth.h>
+#include <pjlib-util/stun_endpoint.h>
+#include <pjlib-util/stun_transaction.h>
+#include <pj/list.h>
+#include <pj/timer.h>
+
+PJ_BEGIN_DECL
+
+
+/* **************************************************************************/
+/**
+ * @defgroup PJLIB_UTIL_STUN_SESSION STUN Client/Server Session
+ * @brief STUN client and server session
+ * @ingroup PJLIB_UTIL_STUN
+ * @{
+ */
+
+
+/** Forward declaration for pj_stun_tx_data */
+typedef struct pj_stun_tx_data pj_stun_tx_data;
+
+/** Forward declaration for pj_stun_session */
+typedef struct pj_stun_session pj_stun_session;
+
+
+/**
+ * This is the callback to be registered to pj_stun_session, to send
+ * outgoing message and to receive various notifications from the STUN
+ * session.
+ */
+typedef struct pj_stun_session_cb
+{
+    /**
+     * Callback to be called by the STUN session to send outgoing message.
+     *
+     * @param sess	    The STUN session.
+     * @param pkt	    Packet to be sent.
+     * @param pkt_size	    Size of the packet to be sent.
+     * @param dst_addr	    The destination address.
+     * @param addr_len	    Length of destination address.
+     *
+     * @return		    The callback should return the status of the
+     *			    packet sending.
+     */
+    pj_status_t (*on_send_msg)(pj_stun_session *sess,
+			       const void *pkt,
+			       pj_size_t pkt_size,
+			       const pj_sockaddr_t *dst_addr,
+			       unsigned addr_len);
+
+    /** 
+     * Callback to be called on incoming STUN request message. In the 
+     * callback processing, application MUST create a response by calling
+     * pj_stun_session_create_response() function and send the response
+     * with pj_stun_session_send_msg() function, before returning from
+     * the callback.
+     *
+     * @param sess	    The STUN session.
+     * @param pkt	    Pointer to the original STUN packet.
+     * @param pkt_len	    Length of the STUN packet.
+     * @param msg	    The parsed STUN request.
+     * @param src_addr	    Source address of the packet.
+     * @param src_addr_len  Length of the source address.
+     *
+     * @return		    The return value of this callback will be
+     *			    returned back to pj_stun_session_on_rx_pkt()
+     *			    function.
+     */
+    pj_status_t (*on_rx_request)(pj_stun_session *sess,
+				 const pj_uint8_t *pkt,
+				 unsigned pkt_len,
+				 const pj_stun_msg *msg,
+				 const pj_sockaddr_t *src_addr,
+				 unsigned src_addr_len);
+
+    /**
+     * Callback to be called when response is received or the transaction 
+     * has timed out.
+     *
+     * @param sess	    The STUN session.
+     * @param status	    Status of the request. If the value if not
+     *			    PJ_SUCCESS, the transaction has timed-out
+     *			    or other error has occurred, and the response
+     *			    argument may be NULL.
+     * @param request	    The original STUN request.
+     * @param response	    The response message, on successful transaction.
+     */
+    void (*on_request_complete)(pj_stun_session *sess,
+			        pj_status_t status,
+			        pj_stun_tx_data *tdata,
+			        const pj_stun_msg *response);
+
+
+    /**
+     * Type of callback to be called on incoming STUN indication.
+     */
+    pj_status_t (*on_rx_indication)(pj_stun_session *sess,
+				    const pj_uint8_t *pkt,
+				    unsigned pkt_len,
+				    const pj_stun_msg *msg,
+				    const pj_sockaddr_t *src_addr,
+				    unsigned src_addr_len);
+
+} pj_stun_session_cb;
+
+
+/**
+ * This structure describe the outgoing STUN transmit data to carry the
+ * message to be sent.
+ */
+struct pj_stun_tx_data
+{
+    PJ_DECL_LIST_MEMBER(struct pj_stun_tx_data);
+
+    pj_pool_t		*pool;		/**< Pool.			    */
+    pj_stun_session	*sess;		/**< The STUN session.		    */
+    pj_stun_msg		*msg;		/**< The STUN message.		    */
+
+    pj_stun_client_tsx	*client_tsx;	/**< Client STUN transaction.	    */
+    pj_uint32_t		 msg_magic;	/**< Message magic.		    */
+    pj_uint8_t		 msg_key[12];	/**< Message/transaction key.	    */
+
+    void		*pkt;		/**< The STUN packet.		    */
+    unsigned		 max_len;	/**< Length of packet buffer.	    */
+    unsigned		 pkt_size;	/**< The actual length of STUN pkt. */
+
+    unsigned		 addr_len;	/**< Length of destination address. */
+    const pj_sockaddr_t	*dst_addr;	/**< Destination address.	    */
+
+    pj_timer_entry	 res_timer;	/**< Response cache timer.	    */
+};
+
+
+/**
+ * Create a STUN session.
+ *
+ * @param endpt		The STUN endpoint, to be used to register timers etc.
+ * @param name		Optional name to be associated with this instance. The
+ *			name will be used for example for logging purpose.
+ * @param cb		Session callback.
+ * @param fingerprint	Enable message fingerprint for outgoing messages.
+ * @param p_sess	Pointer to receive STUN session instance.
+ *
+ * @return	    PJ_SUCCESS on success, or the appropriate error code.
+ */
+PJ_DECL(pj_status_t) pj_stun_session_create(pj_stun_endpoint *endpt,
+					    const char *name,
+					    const pj_stun_session_cb *cb,
+					    pj_bool_t fingerprint,
+					    pj_stun_session **p_sess);
+
+/**
+ * Destroy the STUN session.
+ *
+ * @param sess	    The STUN session instance.
+ *
+ * @return	    PJ_SUCCESS on success, or the appropriate error code.
+ */
+PJ_DECL(pj_status_t) pj_stun_session_destroy(pj_stun_session *sess);
+
+/**
+ * Associated an arbitrary data with this STUN session. The user data may
+ * be retrieved later with pj_stun_session_get_user_data() function.
+ *
+ * @param sess	    The STUN session instance.
+ *
+ * @return	    PJ_SUCCESS on success, or the appropriate error code.
+ */
+PJ_DECL(pj_status_t) pj_stun_session_set_user_data(pj_stun_session *sess,
+						   void *user_data);
+
+/**
+ * Retrieve the user data previously associated to this STUN session with
+ * pj_stun_session_set_user_data().
+ *
+ * @param sess	    The STUN session instance.
+ *
+ * @return	    The user data associated with this STUN session.
+ */
+PJ_DECL(void*) pj_stun_session_get_user_data(pj_stun_session *sess);
+
+/**
+ * Set server name to be included in all response.
+ *
+ * @param sess	    The STUN session instance.
+ * @param srv_name  Server name string.
+ *
+ * @return	    The user data associated with this STUN session.
+ */
+PJ_DECL(pj_status_t) pj_stun_session_set_server_name(pj_stun_session *sess,
+						     const pj_str_t *srv_name);
+
+/**
+ * Set credential to be used by this session. Once credential is set, all
+ * outgoing messages will include MESSAGE-INTEGRITY, and all incoming
+ * message will be authenticated against this credential.
+ *
+ * To disable authentication after it has been set, call this function
+ * again with NULL as the argument.
+ *
+ * @param sess	    The STUN session instance.
+ * @param cred	    The credential to be used by this session. If NULL
+ *		    is specified, authentication will be disabled.
+ *
+ * @return	    PJ_SUCCESS on success, or the appropriate error code.
+ */
+PJ_DECL(void) pj_stun_session_set_credential(pj_stun_session *sess,
+					     const pj_stun_auth_cred *cred);
+
+/**
+ * Create a STUN request message. After the message has been successfully
+ * created, application can send the message by calling 
+ * pj_stun_session_send_msg().
+ *
+ * @param sess	    The STUN session instance.
+ * @param msg_type  The STUN request message type, from pj_stun_method_e or
+ *		    from pj_stun_msg_type.
+ * @param p_tdata   Pointer to receive STUN transmit data instance containing
+ *		    the request.
+ *
+ * @return	    PJ_SUCCESS on success, or the appropriate error code.
+ */
+PJ_DECL(pj_status_t) pj_stun_session_create_req(pj_stun_session *sess,
+						int msg_type,
+						pj_stun_tx_data **p_tdata);
+
+/**
+ * Create a STUN Indication message. After the message  has been successfully
+ * created, application can send the message by calling 
+ * pj_stun_session_send_msg().
+ *
+ * @param sess	    The STUN session instance.
+ * @param msg_type  The STUN request message type, from pj_stun_method_e or
+ *		    from pj_stun_msg_type. This function will add the
+ *		    indication bit as necessary.
+ * @param p_tdata   Pointer to receive STUN transmit data instance containing
+ *		    the message.
+ *
+ * @return	    PJ_SUCCESS on success, or the appropriate error code.
+ */
+PJ_DECL(pj_status_t) pj_stun_session_create_ind(pj_stun_session *sess,
+						int msg_type,
+					        pj_stun_tx_data **p_tdata);
+
+/**
+ * Create a STUN response message. After the message has been 
+ * successfully created, application can send the message by calling 
+ * pj_stun_session_send_msg().
+ *
+ * @param sess	    The STUN session instance.
+ * @param req	    The STUN request where the response is to be created.
+ * @param err_code  Error code to be set in the response, if error response
+ *		    is to be created, according to pj_stun_status enumeration.
+ *		    This argument MUST be zero if successful response is
+ *		    to be created.
+ * @param err_msg   Optional pointer for the error message string, when
+ *		    creating error response. If the value is NULL and the
+ *		    \a err_code is non-zero, then default error message will
+ *		    be used.
+ * @param p_tdata   Pointer to receive the response message created.
+ *
+ * @return	    PJ_SUCCESS on success, or the appropriate error code.
+ */
+PJ_DECL(pj_status_t) pj_stun_session_create_response(pj_stun_session *sess,
+						     const pj_stun_msg *req,
+						     unsigned err_code,
+						     const pj_str_t *err_msg,
+						     pj_stun_tx_data **p_tdata);
+
+
+/**
+ * Send STUN message to the specified destination. This function will encode
+ * the pj_stun_msg instance to a packet buffer, and add credential or
+ * fingerprint if necessary. If the message is a request, the session will
+ * also create and manage a STUN client transaction to be used to manage the
+ * retransmission of the request. After the message has been encoded and
+ * transaction is setup, the \a on_send_msg() callback of pj_stun_session_cb
+ * (which is registered when the STUN session is created) will be called
+ * to actually send the message to the wire.
+ *
+ * @param sess	    The STUN session instance.
+ * @param cache_res If PJ_TRUE then response will be cached.
+ * @param dst_addr  The destination socket address.
+ * @param addr_len  Length of destination address.
+ * @param tdata	    The STUN transmit data containing the STUN message to
+ *		    be sent.
+ *
+ * @return	    PJ_SUCCESS on success, or the appropriate error code.
+ */
+PJ_DECL(pj_status_t) pj_stun_session_send_msg(pj_stun_session *sess,
+					      pj_bool_t cache_res,
+					      const pj_sockaddr_t *dst_addr,
+					      unsigned addr_len,
+					      pj_stun_tx_data *tdata);
+
+/**
+ * Application must call this function to notify the STUN session about
+ * the arrival of STUN packet. The STUN packet MUST have been checked
+ * first with #pj_stun_msg_check() to verify that this is indeed a valid
+ * STUN packet.
+ *
+ * The STUN session will decode the packet into pj_stun_msg, and process
+ * the message accordingly. If the message is a response, it will search
+ * through the outstanding STUN client transactions for a matching
+ * transaction ID and hand over the response to the transaction.
+ *
+ * On successful message processing, application will be notified about
+ * the message via one of the pj_stun_session_cb callback.
+ *
+ * @param sess	     The STUN session instance.
+ * @param packet     The packet containing STUN message.
+ * @param pkt_size   Size of the packet.
+ * @param options    Options, from #pj_stun_decode_options.
+ * @param parsed_len Optional pointer to receive the size of the parsed
+ *		     STUN message (useful if packet is received via a
+ *		     stream oriented protocol).
+ *
+ * @return	     PJ_SUCCESS on success, or the appropriate error code.
+ */
+PJ_DECL(pj_status_t) pj_stun_session_on_rx_pkt(pj_stun_session *sess,
+					       const void *packet,
+					       pj_size_t pkt_size,
+					       unsigned options,
+					       unsigned *parsed_len,
+					       const pj_sockaddr_t *src_addr,
+					       unsigned src_addr_len);
+
+/**
+ * Destroy the transmit data. Call this function only when tdata has been
+ * created but application doesn't want to send the message (perhaps
+ * because of other error).
+ *
+ * @param sess	    The STUN session.
+ * @param tdata	    The transmit data.
+ *
+ * @return	    PJ_SUCCESS on success, or the appropriate error code.
+ */
+PJ_DECL(void) pj_stun_msg_destroy_tdata(pj_stun_session *sess,
+					pj_stun_tx_data *tdata);
+
+
+/**
+ * @}
+ */
+
+
+PJ_END_DECL
+
+#endif	/* __PJLIB_UTIL_STUN_SESSION_H__ */
+
diff --git a/pjnath/include/pjnath/stun_transaction.h b/pjnath/include/pjnath/stun_transaction.h
new file mode 100644
index 00000000..c7a5bf93
--- /dev/null
+++ b/pjnath/include/pjnath/stun_transaction.h
@@ -0,0 +1,217 @@
+/* $Id$ */
+/* 
+ * Copyright (C) 2003-2005 Benny Prijono <benny@prijono.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA 
+ */
+#ifndef __PJLIB_UTIL_STUN_TRANSACTION_H__
+#define __PJLIB_UTIL_STUN_TRANSACTION_H__
+
+/**
+ * @file stun_transaction.h
+ * @brief STUN transaction
+ */
+
+#include <pjlib-util/stun_msg.h>
+#include <pjlib-util/stun_endpoint.h>
+
+
+PJ_BEGIN_DECL
+
+
+/* **************************************************************************/
+/**
+ * @defgroup PJLIB_UTIL_STUN_TRANSACTION STUN Client Transaction
+ * @brief STUN client transaction
+ * @ingroup PJLIB_UTIL_STUN
+ * @{
+ *
+ The @ref PJLIB_UTIL_STUN_TRANSACTION is used to manage outgoing STUN request,
+ for example to retransmit the request and to notify application about the
+ completion of the request.
+
+ The @ref PJLIB_UTIL_STUN_TRANSACTION does not use any networking operations,
+ but instead application must supply the transaction with a callback to
+ be used by the transaction to send outgoing requests. This way the STUN
+ transaction is made more generic and can work with different types of
+ networking codes in application.
+
+
+ */
+
+/**
+ * Opaque declaration of STUN client transaction.
+ */
+typedef struct pj_stun_client_tsx pj_stun_client_tsx;
+
+/**
+ * STUN client transaction callback.
+ */
+typedef struct pj_stun_tsx_cb
+{
+    /**
+     * This callback is called when the STUN transaction completed.
+     *
+     * @param tsx	    The STUN transaction.
+     * @param status	    Status of the transaction. Status PJ_SUCCESS
+     *			    means that the request has received a successful
+     *			    response.
+     * @param response	    The STUN response, which value may be NULL if
+     *			    \a status is not PJ_SUCCESS.
+     */
+    void	(*on_complete)(pj_stun_client_tsx *tsx,
+			       pj_status_t status, 
+			       const pj_stun_msg *response);
+
+    /**
+     * This callback is called by the STUN transaction when it wants to send
+     * outgoing message.
+     *
+     * @param tsx	    The STUN transaction instance.
+     * @param stun_pkt	    The STUN packet to be sent.
+     * @param pkt_size	    Size of the STUN packet.
+     *
+     * @return		    If return value of the callback is not PJ_SUCCESS,
+     *			    the transaction will fail.
+     */
+    pj_status_t (*on_send_msg)(pj_stun_client_tsx *tsx,
+			       const void *stun_pkt,
+			       pj_size_t pkt_size);
+
+} pj_stun_tsx_cb;
+
+
+
+/**
+ * Create an instance of STUN client transaction. The STUN client 
+ * transaction is used to transmit outgoing STUN request and to 
+ * ensure the reliability of the request by periodically retransmitting
+ * the request, if necessary.
+ *
+ * @param endpt		The STUN endpoint, which will be used to retrieve
+ *			various settings for the transaction.
+ * @param pool		Pool to be used to allocate memory from.
+ * @param cb		Callback structure, to be used by the transaction
+ *			to send message and to notify the application about
+ *			the completion of the transaction.
+ * @param p_tsx		Pointer to receive the transaction instance.
+ *
+ * @return		PJ_SUCCESS on success, or the appropriate error code.
+ */
+PJ_DECL(pj_status_t) pj_stun_client_tsx_create(	pj_stun_endpoint *endpt,
+					        pj_pool_t *pool,
+						const pj_stun_tsx_cb *cb,
+						pj_stun_client_tsx **p_tsx);
+
+/**
+ * Destroy a STUN client transaction.
+ *
+ * @param tsx		The STUN transaction.
+ *
+ * @return		PJ_SUCCESS on success, or the appropriate error code.
+ */
+PJ_DECL(pj_status_t) pj_stun_client_tsx_destroy(pj_stun_client_tsx *tsx);
+
+
+/**
+ * Check if transaction has completed.
+ *
+ * @param tsx		The STUN transaction.
+ *
+ * @return		Non-zero if transaction has completed.
+ */
+PJ_DECL(pj_bool_t) pj_stun_client_tsx_is_complete(pj_stun_client_tsx *tsx);
+
+
+/**
+ * Associate an arbitrary data with the STUN transaction. This data
+ * can be then retrieved later from the transaction, by using
+ * pj_stun_client_tsx_get_data() function.
+ *
+ * @param tsx		The STUN client transaction.
+ * @param data		Application data to be associated with the
+ *			STUN transaction.
+ *
+ * @return		PJ_SUCCESS on success.
+ */
+PJ_DECL(pj_status_t) pj_stun_client_tsx_set_data(pj_stun_client_tsx *tsx,
+						 void *data);
+
+
+/**
+ * Get the user data that was previously associated with the STUN 
+ * transaction.
+ *
+ * @param tsx		The STUN client transaction.
+ *
+ * @return		The user data.
+ */
+PJ_DECL(void*) pj_stun_client_tsx_get_data(pj_stun_client_tsx *tsx);
+
+
+/**
+ * Start the STUN client transaction by sending STUN request using
+ * this transaction. If reliable transport such as TCP or TLS is used,
+ * the retransmit flag should be set to PJ_FALSE because reliablity
+ * will be assured by the transport layer.
+ *
+ * @param tsx		The STUN client transaction.
+ * @param retransmit	Should this message be retransmitted by the
+ *			STUN transaction.
+ * @param pkt		The STUN packet to send.
+ * @param pkt_len	Length of STUN packet.
+ *
+ * @return		PJ_SUCCESS on success or the appropriate error code.
+ */
+PJ_DECL(pj_status_t) pj_stun_client_tsx_send_msg(pj_stun_client_tsx *tsx,
+						 pj_bool_t retransmit,
+						 void *pkt,
+						 unsigned pkt_len);
+
+
+
+/**
+ * Notify the STUN transaction about the arrival of STUN response.
+ * If the STUN response contains a final error (300 and greater), the
+ * transaction will be terminated and callback will be called. If the
+ * STUN response contains response code 100-299, retransmission
+ * will  cease, but application must still call this function again
+ * with a final response later to allow the transaction to complete.
+ *
+ * @param tsx		The STUN client transaction instance.
+ * @param packet	The incoming packet.
+ * @param pkt_size	Size of the incoming packet.
+ * @param parsed_len	Optional pointer to receive the number of bytes
+ *			that have been parsed from the incoming packet
+ *			for the STUN message. This is useful if the
+ *			STUN transaction is running over stream oriented
+ *			socket such as TCP or TLS.
+ *
+ * @return		PJ_SUCCESS on success or the appropriate error code.
+ */
+PJ_DECL(pj_status_t) pj_stun_client_tsx_on_rx_msg(pj_stun_client_tsx *tsx,
+						  const pj_stun_msg *msg);
+
+
+/**
+ * @}
+ */
+
+
+PJ_END_DECL
+
+
+#endif	/* __PJLIB_UTIL_STUN_TRANSACTION_H__ */
+
diff --git a/pjnath/include/pjnath/turn_client.h b/pjnath/include/pjnath/turn_client.h
new file mode 100644
index 00000000..83d8d2d6
--- /dev/null
+++ b/pjnath/include/pjnath/turn_client.h
@@ -0,0 +1,132 @@
+/* $Id$ */
+/* 
+ * Copyright (C) 2003-2005 Benny Prijono <benny@prijono.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA 
+ */
+#ifndef __PJLIB_UTIL_TURN_CLIENT_H__
+#define __PJLIB_UTIL_TURN_CLIENT_H__
+
+/**
+ * @file turn_client.h
+ * @brief TURN client session.
+ */
+
+#include <pjlib-util/stun_msg.h>
+
+
+PJ_BEGIN_DECL
+
+
+/**
+ * @defgroup PJLIB_UTIL_TURN_CLIENT TURN Client Session
+ * @brief Management of STUN/TURN client session
+ * @ingroup PJLIB_UTIL_STUN
+ * @{
+ */
+
+typedef struct pj_turn_client pj_turn_client;
+
+/**
+ * This describes TURN client config.
+ */
+typedef struct pj_turn_client_cb
+{
+    /**
+     * Callback to be called by the TURN session to send outgoing message.
+     *
+     * @param client	    The TURN client session.
+     * @param pkt	    Packet to be sent.
+     * @param pkt_size	    Size of the packet to be sent.
+     * @param dst_addr	    The destination address.
+     * @param addr_len	    Length of destination address.
+     *
+     * @return		    The callback should return the status of the
+     *			    packet sending.
+     */
+    pj_status_t (*on_send_msg)(pj_turn_client *client,
+			       const void *pkt,
+			       pj_size_t pkt_size,
+			       const pj_sockaddr_t *dst_addr,
+			       unsigned addr_len);
+
+    /**
+     * Callback to be called by TURN session when its state has changed.
+     */
+    pj_status_t (*on_state_changed)(pj_turn_client *client);
+
+} pj_turn_client_cb;
+
+
+/**
+ * Options
+ */
+typedef struct pj_turn_client_config
+{
+    int	    bandwidth;
+    int	    lifetime;
+    int	    sock_type;
+    int	    port;
+} pj_turn_client_config;
+
+
+PJ_INLINE(void) pj_turn_client_config_default(pj_turn_client_config *cfg)
+{
+    pj_bzero(cfg, sizeof(*cfg));
+    cfg->bandwidth = -1;
+    cfg->lifetime = -1;
+    cfg->sock_type = -1;
+    cfg->port = -1;
+}
+
+
+/**
+ * This describes the TURN client session.
+ */
+struct pj_turn_client
+{
+    pj_pool_t	    *pool;
+    pj_stun_session *session;
+    pj_timer_entry   alloc_timer;
+    pj_sockaddr_in   mapped_addr;
+    pj_sockaddr_in   relay_addr;
+};
+
+
+
+
+/**
+ * Create the TURN client session.
+ */
+PJ_DECL(pj_status_t) pj_turn_client_create(pj_stun_endpoint *endpt,
+					   const pj_turn_client_config *cfg,
+					   const pj_turn_client_cb *cb,
+					   pj_turn_client **p_client);
+
+/**
+ * Start the TURN client session by sending Allocate request to the server.
+ */
+
+
+/**
+ * @}
+ */
+
+
+PJ_END_DECL
+
+
+#endif	/* __PJLIB_UTIL_TURN_CLIENT_H__ */
+