src/session_client.h - github/CESNET/libnetconf2 - Gitiles

 /**
  * \file session_client.h
  * \author Michal Vasko <mvasko@cesnet.cz>
  * \brief libnetconf2 session client manipulation
  *
  * Copyright (c) 2015 CESNET, z.s.p.o.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in
  *    the documentation and/or other materials provided with the
  *    distribution.
  * 3. Neither the name of the Company nor the names of its contributors
  *    may be used to endorse or promote products derived from this
  *    software without specific prior written permission.
  *
  */

 #ifndef NC_SESSION_CLIENT_H_
 #define NC_SESSION_CLIENT_H_

 #include <libyang/libyang.h>

 #ifdef ENABLE_SSH

 #include <libssh/libssh.h>

 #endif

 #ifdef ENABLE_TLS

 #include <openssl/ssl.h>

 #endif

 #include "session.h"
 #include "netconf.h"
 #include "messages.h"
 #include "messages_client.h"

 /**
  * @brief Set location where libnetconf tries to search for YANG/YIN schemas.
  *
  * The location is search when connecting to a NETCONF server and building
  * YANG context for further processing of the NETCONF messages and data.
  *
  * Function is provided only via nc_client.h header file.
  *
  * @param[in] path Directory where to search for YANG/YIN schemas.
  * @return 0 on success, 1 on (memory allocation) failure.
  */
 int nc_schema_searchpath(const char *path);

 /**
  * @brief Connect to the NETCONF server via proviaded input/output file descriptors.
  *
  * Transport layer is supposed to be already set. Function do not cover authentication
  * or any other manipulation with the transport layer, it only establish NETCONF session
  * by sending and processing NETCONF \<hello\> messages.
  *
  * Function is provided only via nc_client.h header file.
  *
  * @param[in] fdin Input file descriptor for reading (clear) data from NETCONF server.
  * @param[in] fdout Output file descriptor for writing (clear) data for NETCONF server.
  * @param[in] ctx Optional parameter. If set, provides strict YANG context for the session
  *                (ignoring what is actually supported by the server side). If not set,
  *                YANG context is created for the session using \<get-schema\> (if supported
  *                by the server side) or/and by searching for YANG schemas in the searchpath
  *                (see nc_schema_searchpath()). In every case except not providing context
  *                to connect to a server supporting \<get-schema\> it is possible that
  *                the session context will not include all the models supported by the server.
  * @return Created NETCONF session object or NULL in case of error.
  */
 struct nc_session *nc_connect_inout(int fdin, int fdout, struct ly_ctx *ctx);

 #ifdef ENABLE_SSH

 /**
  * @brief Destroy any dynamically allocated SSH-specific client context.
  *
  * Function is provided only via nc_client.h header file and only when libnetconf2 is compiled with libssh support.
  */
 void nc_ssh_client_destroy(void);

 /**
  * @brief Connect to the NETCONF server using SSH transport (via libssh).
  *
  * SSH session is created with default options. If the caller needs to use specific SSH session properties,
  * they are supposed to use nc_connect_libssh().
  *
  * Function is provided only via nc_client.h header file and only when libnetconf2 is compiled with libssh support.
  *
  * @param[in] host Hostname or address (both Ipv4 and IPv6 are accepted) of the target server.
  *                 'localhost' is used by default if NULL is specified.
  * @param[in] port Port number of the target server. Default value 830 is used if 0 is specified.
  * @param[in] username Name of the user to login to the server. The user running the application (detected from the
  *                     effective UID) is used if NULL is specified.
  * @param[in] ctx Optional parameter. If set, provides strict YANG context for the session
  *                (ignoring what is actually supported by the server side). If not set,
  *                YANG context is created for the session using \<get-schema\> (if supported
  *                by the server side) or/and by searching for YANG schemas in the searchpath
  *                (see nc_schema_searchpath()). In every case except not providing context
  *                to connect to a server supporting \<get-schema\> it is possible that
  *                the session context will not include all the models supported by the server.
  * @return Created NETCONF session object or NULL on error.
  */
 struct nc_session *nc_connect_ssh(const char *host, uint16_t port, const char* username, struct ly_ctx *ctx);

 /**
  * @brief Connect to the NETCONF server using the provided SSH (libssh) session.
  *
  * SSH session can have any options set, they will not be modified. If no options were set,
  * host 'localhost', port 22, and the username detected from the EUID is used. If socket is
  * set and connected only the host and the username must be set/is detected. Or the \p ssh_session
  * can already be authenticated in which case it is used directly.
  *
  * Function is provided only via nc_client.h header file and only when libnetconf2 is compiled with libssh support.
  *
  * @param[in] ssh_session libssh structure representing SSH session object. After passing it
  *                        to libnetconf2 this way, it is fully managed by it (including freeing!).
  * @param[in] ctx Optional parameter. If set, provides strict YANG context for the session
  *                (ignoring what is actually supported by the server side). If not set,
  *                YANG context is created for the session using \<get-schema\> (if supported
  *                by the server side) or/and by searching for YANG schemas in the searchpath
  *                (see nc_schema_searchpath()). In every case except not providing context
  *                to connect to a server supporting \<get-schema\> it is possible that
  *                the session context will not include all the models supported by the server.
  * @return Created NETCONF session object or NULL on error.
  */
 struct nc_session *nc_connect_libssh(ssh_session ssh_session, struct ly_ctx *ctx);

 /**
  * @brief Create another NETCONF session on existing SSH session using separated SSH channel.
  *
  * Function is provided only via nc_client.h header file and only when libnetconf2 is compiled with libssh support.
  *
  * @param[in] session Existing NETCONF session. The session has to be created on SSH transport layer using libssh -
  *                    it has to be created by nc_connect_ssh(), nc_connect_libssh() or nc_connect_ssh_channel().
  * @param[in] ctx Optional parameter. If set, provides strict YANG context for the session
  *                (ignoring what is actually supported by the server side). If not set,
  *                YANG context is created for the session using \<get-schema\> (if supported
  *                by the server side) or/and by searching for YANG schemas in the searchpath
  *                (see nc_schema_searchpath()). In every case except not providing context
  *                to connect to a server supporting \<get-schema\> it is possible that
  *                the session context will not include all the models supported by the server.
  * @return Created NETCONF session object or NULL on error.
  */
 struct nc_session *nc_connect_ssh_channel(struct nc_session *session, struct ly_ctx *ctx);

 /**
  * @brief Accept a Call Home SSH connection from a NETCONF server.
  *
  * Function is provided only via nc_client.h header file and only when libnetconf2 is compiled with libssh support.
  *
  * @param[in] port Port the NETCONF client will listen on.
  * @param[in] username Name of the user to login to the server. The user running the application (detected from the
  *                     effective UID) is used if NULL is specified.
  * @param[in] timeout Timeout for reading in milliseconds. Use negative value for infinite
  *                    waiting and 0 for immediate return if data are not available on wire.
  * @param[in] ctx Optional parameter. If set, provides strict YANG context for the session
  *                (ignoring what is actually supported by the server side). If not set,
  *                YANG context is created for the session using \<get-schema\> (if supported
  *                by the server side) or/and by searching for YANG schemas in the searchpath
  *                (see nc_schema_searchpath()). In every case except not providing context
  *                to connect to a server supporting \<get-schema\> it is possible that
  *                the session context will not include all the models supported by the server.
  * @return Created NETCONF session object or NULL on error.
  */
 struct nc_session *nc_callhome_accept_ssh(uint16_t port, const char *username, int timeout, struct ly_ctx *ctx);

 /**
  * @brief Add an SSH public and private key pair to be used for client authentication.
  *
  * Private key can be encrypted, the passphrase will be asked for before using it.
  *
  * Function is provided only via nc_client.h header file and only when libnetconf2 is compiled with libssh support.
  *
  * @param[in] pub_key Path to the public key.
  * @param[in] priv_key Path to the private key.
  *
  * @return EXIT_SUCCESS on success, EXIT_FAILURE otherwise.
  */
 int nc_ssh_client_add_keypair(const char *pub_key, const char *priv_key);

 /**
  * @brief Remove an SSH public and private key pair that was used for client authentication.
  *
  * Function is provided only via nc_client.h header file and only when libnetconf2 is compiled with libssh support.
  *
  * @param[in] idx Index of the keypair starting with 0.
  *
  * @return EXIT_SUCCESS on success, EXIT_FAILURE otherwise.
  */
 int nc_ssh_client_del_keypair(int idx);

 /**
  * @brief Get the number of public an private key pairs set to be used for client authentication.
  *
  * @return Set keypair count.
  */
 int nc_ssh_client_get_keypair_count(void);

 /**
  * @brief Get a specific keypair set to be used for client authentication.
  *
  * @param[in] idx Index of the specific keypair.
  * @param[out] pub_key Path to the public key.
  * @param[out] priv_key Path to the private key.
  *
  * @return EXIT_SUCCESS on success, EXIT_FAILURE otherwise.
  */
 int nc_ssh_client_get_keypair(int idx, const char **pub_key, const char **priv_key);

 /**
  * @brief Set SSH authentication method preference.
  *
  * Function is provided only via nc_client.h header file and only when libnetconf2 is compiled with libssh support.
  *
  * @param[in] auth_type Authentication method to modify the prefrence of.
  * @param[in] pref Preference of \p auth_type. Negative values disable the method.
  */
 void nc_ssh_client_set_auth_pref(NC_SSH_AUTH_TYPE auth_type, short int pref);

 /**
  * @brief Get SSH authentication method preference.
  *
  * Function is provided only via nc_client.h header file and only when libnetconf2 is compiled with libssh support.
  *
  * @param[in] auth_type Authentication method to retrieve the prefrence of.
  *
  * @return Preference of the \p auth_type.
  */
 short int nc_ssh_client_get_auth_pref(NC_SSH_AUTH_TYPE auth_type);

 #endif /* ENABLE_SSH */

 #ifdef ENABLE_TLS

 /**
  * @brief Initialize libssl context with certificates.
  *
  * Must be called before calling nc_connect_tls() or nc_connect_libssl()! This also initializes libssl, if your application
  * uses it, do not initialize it again.
  *
  * Function is provided only via nc_client.h header file and only when libnetconf2 is compiled with TLS support.
  *
  * @param[in] client_cert Path to the file containing the client certificate. If NULL, only initializes libssl/libcrypto.
  * @param[in] client_key Path to the file containing the private key for the \p client_cert.
  *                       If NULL, key is expected to be stored with \p client_cert.
  * @param[in] ca_file Location of the CA certificate file used to verify server certificates.
  *                    For more info, see the documentation for SSL_CTX_load_verify_locations() from OpenSSL.
  * @param[in] ca_dir Location of the CA certificates directory used to verify the server certificates.
  *                   For more info, see the documentation for SSL_CTX_load_verify_locations() from OpenSSL.
  * @param[in] crl_file Location of the CRL certificate file used to check for revocated certificates.
  * @param[in] crl_dir Location of the CRL certificate directory used to check for revocated certificates.
  *
  * @return EXIT_SUCCESS on success, EXIT_FAILURE otherwise.
  */
 int nc_tls_client_init(const char *client_cert, const char *client_key, const char *ca_file, const char *ca_dir,
                        const char *crl_file, const char *crl_dir);

 /**
  * @brief Destroy any dynamically allocated TLS-specific and libssl/librypto context.
  *
  * nc_connect_tls(), nc_connect_libssl() or any libssl/librypto functions cannnot be called after this.
  *
  * Function is provided only via nc_client.h header file and only when libnetconf2 is compiled with TLS support.
  */
 void nc_tls_client_destroy(void);

 /**
  * @brief Connect to the NETCONF server using TLS transport (via libssl)
  *
  * TLS session is created with the certificates set using nc_client_init_tls(), which must be called beforehand!
  * If the caller needs to use specific TLS session properties, they are supposed to use nc_connect_libssl().
  *
  * Function is provided only via nc_client.h header file and only when libnetconf2 is compiled with TLS support.
  *
  * @param[in] host Hostname or address (both Ipv4 and IPv6 are accepted) of the target server.
  *                 'localhost' is used by default if NULL is specified.
  * @param[in] port Port number of the target server. Default value 6513 is used if 0 is specified.
  * @param[in] ctx Optional parameter. If set, provides strict YANG context for the session
  *                (ignoring what is actually supported by the server side). If not set,
  *                YANG context is created for the session using \<get-schema\> (if supported
  *                by the server side) or/and by searching for YANG schemas in the searchpath
  *                (see nc_schema_searchpath()). In every case except not providing context
  *                to connect to a server supporting \<get-schema\> it is possible that
  *                the session context will not include all the models supported by the server.
  * @return Created NETCONF session object or NULL on error.
  */
 struct nc_session *nc_connect_tls(const char *host, uint16_t port, struct ly_ctx *ctx);

 /**
  * @brief Connect to the NETCONF server using the provided TLS (libssl) session.
  *
  * The TLS session supplied is expected to be fully connected and authenticated!
  *
  * Function is provided only via nc_client.h header file and only when libnetconf2 is compiled with TLS support.
  *
  * @param[in] tls libssl structure representing the TLS session object.
  * @param[in] ctx Optional parameter. If set, provides strict YANG context for the session
  *                (ignoring what is actually supported by the server side). If not set,
  *                YANG context is created for the session using \<get-schema\> (if supported
  *                by the server side) or/and by searching for YANG schemas in the searchpath
  *                (see nc_schema_searchpath()). In every case except not providing context
  *                to connect to a server supporting \<get-schema\> it is possible that
  *                the session context will not include all the models supported by the server.
  * @return Created NETCONF session object or NULL on error.
  */
 struct nc_session *nc_connect_libssl(SSL *tls, struct ly_ctx *ctx);

 /**
  * @brief Accept a Call Home TLS connection from a NETCONF server.
  *
  * Function is provided only via nc_client.h header file and only when libnetconf2 is compiled with TLS support.
  *
  * @param[in] port Port the NETCONF client will listen on.
  * @param[in] timeout Timeout for reading in milliseconds. Use negative value for infinite
  *                    waiting and 0 for immediate return if data are not available on wire.
  * @param[in] ctx Optional parameter. If set, provides strict YANG context for the session
  *                (ignoring what is actually supported by the server side). If not set,
  *                YANG context is created for the session using \<get-schema\> (if supported
  *                by the server side) or/and by searching for YANG schemas in the searchpath
  *                (see nc_schema_searchpath()). In every case except not providing context
  *                to connect to a server supporting \<get-schema\> it is possible that
  *                the session context will not include all the models supported by the server.
  * @return Created NETCONF session object or NULL on error.
  */
 struct nc_session *nc_callhome_accept_tls(uint16_t port, int32_t timeout, struct ly_ctx *ctx);

 #endif /* ENABLE_TLS */

 /**
  * @brief Receive NETCONF RPC reply.
  *
  * If a reply to \<get\> or \<get-config\> RPCs is received, the data are the whole configuration
  * parsed (usually results in more top-level nodes), not just a single 'data' anyxml node with
  * the configuration unparsed inside (which would strictly be according to the model).
  *
  * @param[in] session NETCONF session from which the function gets data. It must be the
  *            client side session object.
  * @param[in] rpc Original RPC this should be the reply to.
  * @param[in] msgid Expected message ID of the reply.
  * @param[in] timeout Timeout for reading in milliseconds. Use negative value for infinite
  *            waiting and 0 for immediate return if data are not available on wire.
  * @param[out] reply Resulting object of NETCONF RPC reply.
  * @return NC_MSG_REPLY for success, NC_MSG_WOULDBLOCK if timeout reached and NC_MSG_ERROR
  *         when reading has failed.
  */
 NC_MSG_TYPE nc_recv_reply(struct nc_session *session, struct nc_rpc *rpc, uint64_t msgid, int32_t timeout,
                           struct nc_reply **reply);

 /**
  * @brief Receive NETCONF Notification.
  *
  * @param[in] session NETCONF session from which the function gets data. It must be the
  *            client side session object.
  * @param[in] timeout Timeout for reading in milliseconds. Use negative value for infinite
  *            waiting and 0 for immediate return if data are not available on wire.
  * @param[out] notif Resulting object of NETCONF Notification.
  * @return NC_MSG_NOTIF for success, NC_MSG_WOULDBLOCK if timeout reached and NC_MSG_ERROR
  *         when reading has failed.
  */
 NC_MSG_TYPE nc_recv_notif(struct nc_session* session, int32_t timeout, struct nc_notif **notif);

 /**
  * @brief Send NETCONF RPC message via the session.
  *
  * @param[in] session NETCONF session where the RPC will be written.
  * @param[in] rpc NETCOFN RPC object to send via specified session. Object can be created by
  *            nc_rpc_lock(), nc_rpc_unlock() and nc_rpc_generic() functions.
  * @param[in] timeout Timeout for writing in milliseconds. Use negative value for infinite
  *            waiting and 0 for return if data cannot be sent immediately.
  * @param[out] msgid If RPC was successfully sent, this is it's message ID.
  * @return #NC_MSG_RPC on success, #NC_MSG_WOULDBLOCK in case of busy session
  *         and #NC_MSG_ERROR on error.
  */
 NC_MSG_TYPE nc_send_rpc(struct nc_session *session, struct nc_rpc *rpc, int32_t timeout, uint64_t *msgid);

 #endif /* NC_SESSION_CLIENT_H_ */
	/**
	* \file session_client.h
	* \author Michal Vasko <mvasko@cesnet.cz>
	* \brief libnetconf2 session client manipulation
	*
	* Copyright (c) 2015 CESNET, z.s.p.o.
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions
	* are met:
	* 1. Redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer.
	* 2. Redistributions in binary form must reproduce the above copyright
	* notice, this list of conditions and the following disclaimer in
	* the documentation and/or other materials provided with the
	* distribution.
	* 3. Neither the name of the Company nor the names of its contributors
	* may be used to endorse or promote products derived from this
	* software without specific prior written permission.
	*
	*/

	#ifndef NC_SESSION_CLIENT_H_
	#define NC_SESSION_CLIENT_H_

	#include <libyang/libyang.h>

	#ifdef ENABLE_SSH

	#include <libssh/libssh.h>

	#endif

	#ifdef ENABLE_TLS

	#include <openssl/ssl.h>

	#endif

	#include "session.h"
	#include "netconf.h"
	#include "messages.h"
	#include "messages_client.h"

	/**
	* @brief Set location where libnetconf tries to search for YANG/YIN schemas.
	*
	* The location is search when connecting to a NETCONF server and building
	* YANG context for further processing of the NETCONF messages and data.
	*
	* Function is provided only via nc_client.h header file.
	*
	* @param[in] path Directory where to search for YANG/YIN schemas.
	* @return 0 on success, 1 on (memory allocation) failure.
	*/
	int nc_schema_searchpath(const char *path);

	/**
	* @brief Connect to the NETCONF server via proviaded input/output file descriptors.
	*
	* Transport layer is supposed to be already set. Function do not cover authentication
	* or any other manipulation with the transport layer, it only establish NETCONF session
	* by sending and processing NETCONF \<hello\> messages.
	*
	* Function is provided only via nc_client.h header file.
	*
	* @param[in] fdin Input file descriptor for reading (clear) data from NETCONF server.
	* @param[in] fdout Output file descriptor for writing (clear) data for NETCONF server.
	* @param[in] ctx Optional parameter. If set, provides strict YANG context for the session
	* (ignoring what is actually supported by the server side). If not set,
	* YANG context is created for the session using \<get-schema\> (if supported
	* by the server side) or/and by searching for YANG schemas in the searchpath
	* (see nc_schema_searchpath()). In every case except not providing context
	* to connect to a server supporting \<get-schema\> it is possible that
	* the session context will not include all the models supported by the server.
	* @return Created NETCONF session object or NULL in case of error.
	*/
	struct nc_session nc_connect_inout(int fdin, int fdout, struct ly_ctx ctx);

	#ifdef ENABLE_SSH

	/**
	* @brief Destroy any dynamically allocated SSH-specific client context.
	*
	* Function is provided only via nc_client.h header file and only when libnetconf2 is compiled with libssh support.
	*/
	void nc_ssh_client_destroy(void);

	/**
	* @brief Connect to the NETCONF server using SSH transport (via libssh).
	*
	* SSH session is created with default options. If the caller needs to use specific SSH session properties,
	* they are supposed to use nc_connect_libssh().
	*
	* Function is provided only via nc_client.h header file and only when libnetconf2 is compiled with libssh support.
	*
	* @param[in] host Hostname or address (both Ipv4 and IPv6 are accepted) of the target server.
	* 'localhost' is used by default if NULL is specified.
	* @param[in] port Port number of the target server. Default value 830 is used if 0 is specified.
	* @param[in] username Name of the user to login to the server. The user running the application (detected from the
	* effective UID) is used if NULL is specified.
	* @param[in] ctx Optional parameter. If set, provides strict YANG context for the session
	* (ignoring what is actually supported by the server side). If not set,
	* YANG context is created for the session using \<get-schema\> (if supported
	* by the server side) or/and by searching for YANG schemas in the searchpath
	* (see nc_schema_searchpath()). In every case except not providing context
	* to connect to a server supporting \<get-schema\> it is possible that
	* the session context will not include all the models supported by the server.
	* @return Created NETCONF session object or NULL on error.
	*/
	struct nc_session nc_connect_ssh(const char host, uint16_t port, const char* username, struct ly_ctx *ctx);

	/**
	* @brief Connect to the NETCONF server using the provided SSH (libssh) session.
	*
	* SSH session can have any options set, they will not be modified. If no options were set,
	* host 'localhost', port 22, and the username detected from the EUID is used. If socket is
	* set and connected only the host and the username must be set/is detected. Or the \p ssh_session
	* can already be authenticated in which case it is used directly.
	*
	* Function is provided only via nc_client.h header file and only when libnetconf2 is compiled with libssh support.
	*
	* @param[in] ssh_session libssh structure representing SSH session object. After passing it
	* to libnetconf2 this way, it is fully managed by it (including freeing!).
	* @param[in] ctx Optional parameter. If set, provides strict YANG context for the session
	* (ignoring what is actually supported by the server side). If not set,
	* YANG context is created for the session using \<get-schema\> (if supported
	* by the server side) or/and by searching for YANG schemas in the searchpath
	* (see nc_schema_searchpath()). In every case except not providing context
	* to connect to a server supporting \<get-schema\> it is possible that
	* the session context will not include all the models supported by the server.
	* @return Created NETCONF session object or NULL on error.
	*/
	struct nc_session nc_connect_libssh(ssh_session ssh_session, struct ly_ctx ctx);

	/**
	* @brief Create another NETCONF session on existing SSH session using separated SSH channel.
	*
	* Function is provided only via nc_client.h header file and only when libnetconf2 is compiled with libssh support.
	*
	* @param[in] session Existing NETCONF session. The session has to be created on SSH transport layer using libssh -
	* it has to be created by nc_connect_ssh(), nc_connect_libssh() or nc_connect_ssh_channel().
	* @param[in] ctx Optional parameter. If set, provides strict YANG context for the session
	* (ignoring what is actually supported by the server side). If not set,
	* YANG context is created for the session using \<get-schema\> (if supported
	* by the server side) or/and by searching for YANG schemas in the searchpath
	* (see nc_schema_searchpath()). In every case except not providing context
	* to connect to a server supporting \<get-schema\> it is possible that
	* the session context will not include all the models supported by the server.
	* @return Created NETCONF session object or NULL on error.
	*/
	struct nc_session nc_connect_ssh_channel(struct nc_session session, struct ly_ctx *ctx);

	/**
	* @brief Accept a Call Home SSH connection from a NETCONF server.
	*
	* Function is provided only via nc_client.h header file and only when libnetconf2 is compiled with libssh support.
	*
	* @param[in] port Port the NETCONF client will listen on.
	* @param[in] username Name of the user to login to the server. The user running the application (detected from the
	* effective UID) is used if NULL is specified.
	* @param[in] timeout Timeout for reading in milliseconds. Use negative value for infinite
	* waiting and 0 for immediate return if data are not available on wire.
	* @param[in] ctx Optional parameter. If set, provides strict YANG context for the session
	* (ignoring what is actually supported by the server side). If not set,
	* YANG context is created for the session using \<get-schema\> (if supported
	* by the server side) or/and by searching for YANG schemas in the searchpath
	* (see nc_schema_searchpath()). In every case except not providing context
	* to connect to a server supporting \<get-schema\> it is possible that
	* the session context will not include all the models supported by the server.
	* @return Created NETCONF session object or NULL on error.
	*/
	struct nc_session nc_callhome_accept_ssh(uint16_t port, const char username, int timeout, struct ly_ctx *ctx);

	/**
	* @brief Add an SSH public and private key pair to be used for client authentication.
	*
	* Private key can be encrypted, the passphrase will be asked for before using it.
	*
	* Function is provided only via nc_client.h header file and only when libnetconf2 is compiled with libssh support.
	*
	* @param[in] pub_key Path to the public key.
	* @param[in] priv_key Path to the private key.
	*
	* @return EXIT_SUCCESS on success, EXIT_FAILURE otherwise.
	*/
	int nc_ssh_client_add_keypair(const char pub_key, const char priv_key);

	/**
	* @brief Remove an SSH public and private key pair that was used for client authentication.
	*
	* Function is provided only via nc_client.h header file and only when libnetconf2 is compiled with libssh support.
	*
	* @param[in] idx Index of the keypair starting with 0.
	*
	* @return EXIT_SUCCESS on success, EXIT_FAILURE otherwise.
	*/
	int nc_ssh_client_del_keypair(int idx);

	/**
	* @brief Get the number of public an private key pairs set to be used for client authentication.
	*
	* @return Set keypair count.
	*/
	int nc_ssh_client_get_keypair_count(void);

	/**
	* @brief Get a specific keypair set to be used for client authentication.
	*
	* @param[in] idx Index of the specific keypair.
	* @param[out] pub_key Path to the public key.
	* @param[out] priv_key Path to the private key.
	*
	* @return EXIT_SUCCESS on success, EXIT_FAILURE otherwise.
	*/
	int nc_ssh_client_get_keypair(int idx, const char pub_key, const char priv_key);

	/**
	* @brief Set SSH authentication method preference.
	*
	* Function is provided only via nc_client.h header file and only when libnetconf2 is compiled with libssh support.
	*
	* @param[in] auth_type Authentication method to modify the prefrence of.
	* @param[in] pref Preference of \p auth_type. Negative values disable the method.
	*/
	void nc_ssh_client_set_auth_pref(NC_SSH_AUTH_TYPE auth_type, short int pref);

	/**
	* @brief Get SSH authentication method preference.
	*
	* Function is provided only via nc_client.h header file and only when libnetconf2 is compiled with libssh support.
	*
	* @param[in] auth_type Authentication method to retrieve the prefrence of.
	*
	* @return Preference of the \p auth_type.
	*/
	short int nc_ssh_client_get_auth_pref(NC_SSH_AUTH_TYPE auth_type);

	#endif /* ENABLE_SSH */

	#ifdef ENABLE_TLS

	/**
	* @brief Initialize libssl context with certificates.
	*
	* Must be called before calling nc_connect_tls() or nc_connect_libssl()! This also initializes libssl, if your application
	* uses it, do not initialize it again.
	*
	* Function is provided only via nc_client.h header file and only when libnetconf2 is compiled with TLS support.
	*
	* @param[in] client_cert Path to the file containing the client certificate. If NULL, only initializes libssl/libcrypto.
	* @param[in] client_key Path to the file containing the private key for the \p client_cert.
	* If NULL, key is expected to be stored with \p client_cert.
	* @param[in] ca_file Location of the CA certificate file used to verify server certificates.
	* For more info, see the documentation for SSL_CTX_load_verify_locations() from OpenSSL.
	* @param[in] ca_dir Location of the CA certificates directory used to verify the server certificates.
	* For more info, see the documentation for SSL_CTX_load_verify_locations() from OpenSSL.
	* @param[in] crl_file Location of the CRL certificate file used to check for revocated certificates.
	* @param[in] crl_dir Location of the CRL certificate directory used to check for revocated certificates.
	*
	* @return EXIT_SUCCESS on success, EXIT_FAILURE otherwise.
	*/
	int nc_tls_client_init(const char client_cert, const char client_key, const char ca_file, const char ca_dir,
	const char crl_file, const char crl_dir);

	/**
	* @brief Destroy any dynamically allocated TLS-specific and libssl/librypto context.
	*
	* nc_connect_tls(), nc_connect_libssl() or any libssl/librypto functions cannnot be called after this.
	*
	* Function is provided only via nc_client.h header file and only when libnetconf2 is compiled with TLS support.
	*/
	void nc_tls_client_destroy(void);

	/**
	* @brief Connect to the NETCONF server using TLS transport (via libssl)
	*
	* TLS session is created with the certificates set using nc_client_init_tls(), which must be called beforehand!
	* If the caller needs to use specific TLS session properties, they are supposed to use nc_connect_libssl().
	*
	* Function is provided only via nc_client.h header file and only when libnetconf2 is compiled with TLS support.
	*
	* @param[in] host Hostname or address (both Ipv4 and IPv6 are accepted) of the target server.
	* 'localhost' is used by default if NULL is specified.
	* @param[in] port Port number of the target server. Default value 6513 is used if 0 is specified.
	* @param[in] ctx Optional parameter. If set, provides strict YANG context for the session
	* (ignoring what is actually supported by the server side). If not set,
	* YANG context is created for the session using \<get-schema\> (if supported
	* by the server side) or/and by searching for YANG schemas in the searchpath
	* (see nc_schema_searchpath()). In every case except not providing context
	* to connect to a server supporting \<get-schema\> it is possible that
	* the session context will not include all the models supported by the server.
	* @return Created NETCONF session object or NULL on error.
	*/
	struct nc_session nc_connect_tls(const char host, uint16_t port, struct ly_ctx *ctx);

	/**
	* @brief Connect to the NETCONF server using the provided TLS (libssl) session.
	*
	* The TLS session supplied is expected to be fully connected and authenticated!
	*
	* Function is provided only via nc_client.h header file and only when libnetconf2 is compiled with TLS support.
	*
	* @param[in] tls libssl structure representing the TLS session object.
	* @param[in] ctx Optional parameter. If set, provides strict YANG context for the session
	* (ignoring what is actually supported by the server side). If not set,
	* YANG context is created for the session using \<get-schema\> (if supported
	* by the server side) or/and by searching for YANG schemas in the searchpath
	* (see nc_schema_searchpath()). In every case except not providing context
	* to connect to a server supporting \<get-schema\> it is possible that
	* the session context will not include all the models supported by the server.
	* @return Created NETCONF session object or NULL on error.
	*/
	struct nc_session nc_connect_libssl(SSL tls, struct ly_ctx *ctx);

	/**
	* @brief Accept a Call Home TLS connection from a NETCONF server.
	*
	* Function is provided only via nc_client.h header file and only when libnetconf2 is compiled with TLS support.
	*
	* @param[in] port Port the NETCONF client will listen on.
	* @param[in] timeout Timeout for reading in milliseconds. Use negative value for infinite
	* waiting and 0 for immediate return if data are not available on wire.
	* @param[in] ctx Optional parameter. If set, provides strict YANG context for the session
	* (ignoring what is actually supported by the server side). If not set,
	* YANG context is created for the session using \<get-schema\> (if supported
	* by the server side) or/and by searching for YANG schemas in the searchpath
	* (see nc_schema_searchpath()). In every case except not providing context
	* to connect to a server supporting \<get-schema\> it is possible that
	* the session context will not include all the models supported by the server.
	* @return Created NETCONF session object or NULL on error.
	*/
	struct nc_session nc_callhome_accept_tls(uint16_t port, int32_t timeout, struct ly_ctx ctx);

	#endif /* ENABLE_TLS */

	/**
	* @brief Receive NETCONF RPC reply.
	*
	* If a reply to \<get\> or \<get-config\> RPCs is received, the data are the whole configuration
	* parsed (usually results in more top-level nodes), not just a single 'data' anyxml node with
	* the configuration unparsed inside (which would strictly be according to the model).
	*
	* @param[in] session NETCONF session from which the function gets data. It must be the
	* client side session object.
	* @param[in] rpc Original RPC this should be the reply to.
	* @param[in] msgid Expected message ID of the reply.
	* @param[in] timeout Timeout for reading in milliseconds. Use negative value for infinite
	* waiting and 0 for immediate return if data are not available on wire.
	* @param[out] reply Resulting object of NETCONF RPC reply.
	* @return NC_MSG_REPLY for success, NC_MSG_WOULDBLOCK if timeout reached and NC_MSG_ERROR
	* when reading has failed.
	*/
	NC_MSG_TYPE nc_recv_reply(struct nc_session session, struct nc_rpc rpc, uint64_t msgid, int32_t timeout,
	struct nc_reply **reply);

	/**
	* @brief Receive NETCONF Notification.
	*
	* @param[in] session NETCONF session from which the function gets data. It must be the
	* client side session object.
	* @param[in] timeout Timeout for reading in milliseconds. Use negative value for infinite
	* waiting and 0 for immediate return if data are not available on wire.
	* @param[out] notif Resulting object of NETCONF Notification.
	* @return NC_MSG_NOTIF for success, NC_MSG_WOULDBLOCK if timeout reached and NC_MSG_ERROR
	* when reading has failed.
	*/
	NC_MSG_TYPE nc_recv_notif(struct nc_session* session, int32_t timeout, struct nc_notif **notif);

	/**
	* @brief Send NETCONF RPC message via the session.
	*
	* @param[in] session NETCONF session where the RPC will be written.
	* @param[in] rpc NETCOFN RPC object to send via specified session. Object can be created by
	* nc_rpc_lock(), nc_rpc_unlock() and nc_rpc_generic() functions.
	* @param[in] timeout Timeout for writing in milliseconds. Use negative value for infinite
	* waiting and 0 for return if data cannot be sent immediately.
	* @param[out] msgid If RPC was successfully sent, this is it's message ID.
	* @return #NC_MSG_RPC on success, #NC_MSG_WOULDBLOCK in case of busy session
	* and #NC_MSG_ERROR on error.
	*/
	NC_MSG_TYPE nc_send_rpc(struct nc_session session, struct nc_rpc rpc, int32_t timeout, uint64_t *msgid);

	#endif /* NC_SESSION_CLIENT_H_ */