/**
* @mainpage About
*
* libnetconf2 is a NETCONF library in C handling NETCONF authentication and all NETCONF
* RPC communication both server and client-side. Note that NETCONF datastore implementation
* is not a part of this library. The library supports both NETCONF 1.0
* ([RFC 4741](https://tools.ietf.org/html/rfc4741)) as well as NETCONF 1.1
* ([RFC 6241](https://tools.ietf.org/html/rfc6241)).
*
* @section about-features Main Features
*
* - Creating SSH ([RFC 4742](https://tools.ietf.org/html/rfc4742), [RFC 6242](https://tools.ietf.org/html/rfc6242)),
* using [libssh](https://www.libssh.org/), or TLS ([RFC 7589](https://tools.ietf.org/html/rfc7589)),
* using [OpenSSL](https://www.openssl.org/), authenticated NETCONF sessions.
* - Creating NETCONF sessions with a pre-established transport protocol
* (using this mechanism the communication can be tunneled through sshd(8), for instance).
* - Creating NETCONF Call Home sessions ([RFC 8071](https://tools.ietf.org/html/rfc8071)).
* - Creating, sending, receiving, and replying to RPCs ([RFC 4741](https://tools.ietf.org/html/rfc4741),
* [RFC 6241](https://tools.ietf.org/html/rfc6241)).
* - Creating, sending and receiving NETCONF Event Notifications ([RFC 5277](https://tools.ietf.org/html/rfc5277)).
* - Configuring the NETCONF server based on the [ietf-netconf-server](https://datatracker.ietf.org/doc/html/draft-ietf-netconf-netconf-client-server-29) YANG module
*
* @section about-license License
*
* Copyright (c) 2015-2021 CESNET, z.s.p.o.
*
* (The BSD 3-Clause License)
*
* 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.
*/
/**
* @page howto How To ...
*
* - @subpage howtoinit
* - @subpage howtoclient
* - @subpage howtoserver
* - @subpage howtoclientcomm
* - @subpage howtoservercomm
* - @subpage howtotimeouts
*/
/**
* @page howtoinit Init and Thread-safety Information
*
* Before working with the library, it must be initialized using ::nc_client_init()
* and/or ::nc_server_init(). To prevent any reachable memory at the end of your
* application, there are complementary destroy functions
* (::nc_server_destroy() and ::nc_client_destroy() available). If your
* application is multi-threaded, call the destroy functions in the main thread,
* after all the other threads have ended.
*
* If _libnetconf2_ is used in accordance with this information, there should
* not be memory leaks of any kind at program exit. For thread-safety details
* of _libssh_, _libssl_, and _libcrypto_, please refer to the corresponding project
* documentation. _libnetconf2_ thread-safety information is below.
*
* Client
* ------
*
* Optionally, a client can specify two alternative ways to get schemas needed when connecting
* with a server. The primary way is to read local files in searchpath (and its subdirectories)
* specified via ::nc_client_set_schema_searchpath(). Alternatively, _libnetconf2_ can use callback
* provided via ::nc_client_set_schema_callback(). If these ways do not succeed and the server
* implements NETCONF \<get-schema\> operation, the schema is retrieved from the server and stored
* locally into the searchpath (if specified) for a future use. If none of these methods succeed to
* load particular schema, the data from this schema are ignored during the communication with the
* server.
*
* Besides the mentioned setters, there are many other @ref howtoclientssh "SSH", @ref howtoclienttls "TLS"
* and @ref howtoclientch "Call Home" getter/setter functions to manipulate with various settings. All these
* settings are internally placed in a thread-specific context so they are independent and
* initialized to the default values within each new thread. However, the context can be shared among
* the threads using ::nc_client_get_thread_context() and ::nc_client_set_thread_context() functions. In such
* a case, be careful and avoid concurrent execution of the mentioned setters/getters and functions
* creating connection (no matter if it is a standard NETCONF connection or Call Home).
*
* In the client, it is always thread-safe to work with a NETCONF session in a single thread since the client
* settings are thread-specific as described above. Generally, one can access a session in several threads
* as well but there is little incentive to do so.
*
* Server
* ------
*
* Server is __FULLY__ thread-safe meaning you can set all the (thread-shared in contrast to
* client) options simultaneously while listening for or accepting new sessions or
* polling the existing ones. It is even safe to poll one session in several
* pollsession structures or one pollsession structure in several threads. Generally,
* servers can use more threads without any problems as long as they keep their workflow sane
* (behavior such as freeing sessions only after no thread uses them or similar).
*
* Functions List
* --------------
*
* Available in __nc_client.h__.
*
* - ::nc_client_init()
* - ::nc_client_destroy()
*
* - ::nc_client_set_schema_searchpath()
* - ::nc_client_get_schema_searchpath()
* - ::nc_client_set_schema_callback()
* - ::nc_client_get_schema_callback()
*
* - ::nc_client_set_thread_context()
* - ::nc_client_get_thread_context()
*
* Available in __nc_server.h__.
*
* - ::nc_server_init()
* - ::nc_server_destroy()
*/
/**
* @page howtoclient Client sessions
*
* To connect to a NETCONF server, a NETCONF session must be established,
* which requires a working transport session. It is possible to create
* NETCONF sessions with SSH (using _libssh_) or TLS (using _libssl/libcrypto_)
* as the underlying transport protocol. It is also possible to establish
* the transport protocol outside _libnetconf2_ and then provide these file
* descriptors (FD) for full NETCONF session creation.
*
* There are a lot of options for both an SSH and a TLS client. All of them
* have setters and getters so that there is no need to duplicate them in
* a client.
*
* @anchor howtoclientssh
* SSH
* ===
*
* Connecting to a server using SSH does not strictly require to set any
* options, there are sensible default values for all the basic ones.
* Except all the SSH options, optionally some authetication callbacks can be set,
* which are particulary useful in automated clients (passwords cannot be
* asked a user) or simply if any additional information is retrieved some
* other way than from standard terminal input.
*
* Having the default options or changing any unsuitable ones, there are 2 functions
* to use for a new server connection. ::nc_connect_ssh() is the standard function
* that creates sessions using the set options. If there are some options, which
* cannot be changed with the provided API, there is ::nc_connect_libssh() available.
* It requires a _libssh_ session, in which all the SSH options can be modified
* and even the connection established. This allows for full customization and
* should fit any specific situation.
*
* New NETCONF sessions can also be created on existing authenticated SSH sessions.
* There is a new SSH channel needed, on which the NETCONF session is then created.
* Use ::nc_connect_ssh_channel() for this purpose.
*
* Functions List
* --------------
*
* Available in __nc_client.h__.
*
* - ::nc_client_ssh_set_auth_password_clb()
* - ::nc_client_ssh_get_auth_password_clb()
* - ::nc_client_ssh_set_auth_interactive_clb()
* - ::nc_client_ssh_get_auth_interactive_clb()
* - ::nc_client_ssh_set_auth_privkey_passphrase_clb()
* - ::nc_client_ssh_get_auth_privkey_passphrase_clb()
* - ::nc_client_ssh_add_keypair()
* - ::nc_client_ssh_del_keypair()
* - ::nc_client_ssh_get_keypair_count()
* - ::nc_client_ssh_get_keypair()
* - ::nc_client_ssh_set_auth_pref()
* - ::nc_client_ssh_get_auth_pref()
* - ::nc_client_ssh_set_username()
* - ::nc_client_ssh_get_username()
*
* - ::nc_connect_ssh()
* - ::nc_connect_libssh()
* - ::nc_connect_ssh_channel()
*
* @anchor howtoclienttls
* TLS
* ===
*
* To connect to a server using TLS, there must be some client identification
* options set. Client must specify its certificate with a private key using
* ::nc_client_tls_set_cert_key_paths(). Also, the Certificate Authority of
* a server certificate must be considered trusted. Paths to all the trusted
* CA certificates can be set by ::nc_client_tls_set_trusted_ca_paths().
*
* Then there are again 2 functions for connecting, ::nc_connect_tls() being
* the standard way of connecting. ::nc_connect_libssl() again enables
* to customize the TLS session in every way _libssl_ allows.
*
* Functions List
* --------------
*
* Available in __nc_client.h__.
*
* - ::nc_client_tls_set_cert_key_paths()
* - ::nc_client_tls_get_cert_key_paths()
* - ::nc_client_tls_set_trusted_ca_paths()
* - ::nc_client_tls_get_trusted_ca_paths()
*
* - ::nc_connect_tls()
* - ::nc_connect_libssl()
*
*
* FD and UNIX socket
* ==================
*
* If you authenticated the connection using some tunneling software, you
* can pass its file descriptors to _libnetconf2_ using ::nc_connect_inout(),
* which will continue to establish a full NETCONF session. To connect locally
* on a UNIX socket avoiding all cryptography use ::nc_connect_unix().
*
* Funtions List
* -------------
*
* Available in __nc_client.h__.
*
* - ::nc_connect_inout()
* - ::nc_connect_unix()
*
*
* @anchor howtoclientch
* Call Home
* =========
*
* Call Home needs the same options set as standard SSH or TLS and the functions
* reflect it exactly. However, to accept a connection, the client must first
* specify addresses and ports, which to listen on by ::nc_client_ssh_ch_add_bind_listen()
* and ::nc_client_tls_ch_add_bind_listen(). Then connections can be
* accepted using ::nc_accept_callhome().
*
* Functions List
* --------------
*
* Available in __nc_client.h__.
*
* - ::nc_client_ssh_ch_set_auth_password_clb()
* - ::nc_client_ssh_ch_set_auth_interactive_clb()
* - ::nc_client_ssh_ch_set_auth_privkey_passphrase_clb()
* - ::nc_client_ssh_ch_add_bind_listen()
* - ::nc_client_ssh_ch_del_bind()
* - ::nc_client_ssh_ch_add_keypair()
* - ::nc_client_ssh_ch_del_keypair()
* - ::nc_client_ssh_ch_get_keypair_count()
* - ::nc_client_ssh_ch_get_keypair()
* - ::nc_client_ssh_ch_set_auth_pref()
* - ::nc_client_ssh_ch_get_auth_pref()
* - ::nc_client_ssh_ch_set_username()
* - ::nc_client_ssh_ch_get_username()
*
* - ::nc_client_tls_ch_add_bind_listen()
* - ::nc_client_tls_ch_del_bind()
* - ::nc_client_tls_ch_set_cert_key_paths()
* - ::nc_client_tls_ch_get_cert_key_paths()
* - ::nc_client_tls_ch_set_trusted_ca_paths()
* - ::nc_client_tls_ch_get_trusted_ca_paths()
*
* - ::nc_accept_callhome()
*
*
* Cleanup
* =======
*
* These options and the schema searchpath are stored in dynamically
* allocated memory. They are freed as a part of [destroying the client](@ref howtoinit).
*/
/**
* @page howtoserver Server sessions
*
* Init
* ====
*
* Server must start with [initialization](@ref howtoinit). Its capabilities are
* determined by the context used when accepting new NETCONF sessions. Few capabilities that
* cannot be learnt from the context are set with separate functions
* ::nc_server_set_capab_withdefaults() and generally ::nc_server_set_capability().
*
* Context does not only determine server modules, but its overall
* functionality as well. For every RPC the server should support,
* an nc_rpc_clb callback should be set on that node in the context using ::nc_set_rpc_callback().
* Server then calls these as appropriate [during poll](@ref howtoservercomm).
*
* Just like in the [client](@ref howtoclient), you can let _libnetconf2_
* establish SSH or TLS transport or do it yourself and only provide the file
* descriptors of the connection.
*
* To be able to accept any connections, the server must first be configured.
*
* Functions List
* --------------
*
* Available in __nc_server.h__.
*
* - ::nc_server_set_capab_withdefaults()
* - ::nc_server_set_capability()
* - ::nc_server_endpt_count()
* - ::nc_server_add_endpt_unix_socket_listen()
* - ::nc_server_del_endpt_unix_socket()
*
* Server Configuration
* ===
*
* To successfully accept connections on a server, you first need to configure it.
* The *libnetconf2* server natively supports the *ietf-netconf-server YANG* module.
* This allows for a bigger scaling and flexibility of the *NETCONF* server.
* By using *ietf-netconf-server YANG* data you can express network configurations
* in a standardized and hierarchical format, enabling you to define complex network
* structures with greater ease.
*
* The process of configuring a server is comprised of two steps. The first step is creating the
* configuration data and the second is applying it. The server supports two forms of the configuration
* data - *YANG data* and *YANG diff*.
*
* YANG data
* ---
* Configuring the server using YANG data simplifies the management of network services.
* With YANG data, you build a structured configuration tree and apply it as a whole.
* This approach is user-friendly, allowing you to modify the configuration by adding or deleting nodes,
* and then deploying the updated configuration tree in its entirety, providing a way to manage your server's settings.
* The *libnetconf2* library exports API functions that can help you with creation or deletion of the *YANG* data.
*
* YANG diff
* ---
* YANG diff, enriched with operation attributes, offers advanced configuration control.
* It empowers the user to make precise changes within the configuration tree,
* enabling operations like specific node deletions, additions, and modifications.
* On the other hand, unlike YANG data, YANG diff represents only a subtree of the
* changes expecting the whole configuration to be managed externally.
* For example this is done by the tool [sysrepo](https://www.sysrepo.org/).
*
* Usage
* ---
* To be able to configure the server, the required models first need to be implemented.
* To do this, see ::nc_server_config_load_modules().
* Not all of the *ietf-netconf-server* (and all of its associated modules) features are enabled.
* If you wish to see which features are enabled, extract them from the context after calling the mentioned function.
*
* If you wish not to create the __YANG data__ yourself, you may use the library's functions to do this for you.
* For example ::nc_server_config_add_address_port() creates __YANG data__ corresponding to an SSH/TLS endpoint.
* You can then apply this data by calling ::nc_server_config_setup_data() (or ::nc_server_config_setup_diff() for diff).
* See *examples/server.c* for a simple example.
*
* You may also create entries in the keystore or truststore. For example the asymmetric key and certificate entries
* in the keystore can be then referenced as the SSH hostkeys or TLS server certificates, respectively.
* As for the truststore, you may create public key and certificate entries, which can then be used
* as SSH user's public keys or TLS server's end-entity/trust-anchor certificates, respectively.
*
* Functions List
* --------------
*
* Available in __nc_server.h__.
*
* - ::nc_server_config_load_modules()
* - ::nc_server_config_setup_diff()
* - ::nc_server_config_setup_data()
* - ::nc_server_config_setup_path()
*
* - ::nc_server_config_add_address_port()
* - ::nc_server_config_del_endpt()
* - ::nc_server_config_add_keystore_asym_key()
* - ::nc_server_config_del_keystore_asym_key()
* - ::nc_server_config_add_keystore_cert()
* - ::nc_server_config_del_keystore_cert()
* - ::nc_server_config_add_truststore_pubkey()
* - ::nc_server_config_del_truststore_pubkey()
* - ::nc_server_config_add_truststore_cert()
* - ::nc_server_config_del_truststore_cert()
*
* SSH
* ===
*
* To successfully accept an SSH session you must configure at least one host key.
* You may create this data yourself or by using ::nc_server_config_add_ssh_hostkey().
*
* It is important to decide whether the users that can connect to the SSH server should be obtained from the configuration or from the system.
* If the YANG feature *local-users-supported* is enabled (the default), then the authorized users are derived from the configuration.
* When a client connects to the server, he must be found in the configuration and he must authenticate to **all** of his configured authentication methods.
* If the feature is disabled, then the system will be used to try to authenticate the client via one of the three
* methods - publickey, keyboard-interactive or password (only one of them has to succeed).
*
* If the local users are supported then each SSH endpoint can define it's own authorized clients and their authentication methods.
* For example if you wish to create an SSH user that can authenticate using a password, use ::nc_server_config_add_ssh_user_password().
* Another option for authorized clients is to reference another endpoint's clients, however be careful not to create a cyclic reference
* (see ::nc_server_config_add_ssh_endpoint_client_ref()).
*
* \anchor ln2doc_pubkey
* The Public Key authentication method is supported. If you wish to use this method, you need to specify the given user's
* public keys, which will be compared with the key(s) presented by the SSH client when authenticating. One option is to configure
* the public keys directly in the ietf-netconf-server YANG data (inline-definition). Other option is to configure the keys' data
* in the ietf-trustore module's YANG data and then reference them (truststore-reference). The final option is to set the global
* path to file with public keys. This path may contain special tokens, see ::nc_server_ssh_set_authkey_path_format().
* If the path is set and the use-system-keys container is present in the data for the client wishing to authenticate,
* then the keys from the file will be used for authentication. If the YANG feature *local-users-supported* is disabled,
* then it's neccessary to set the path format using ::nc_server_ssh_set_authkey_path_format().
*
* \anchor ln2doc_kbdint
* The Keyboard Interactive authentication method is also supported. It can be done in three ways.
* If libpam is found, Linux PAM is used to handle the authentication. You need to specify the service name using ::nc_server_ssh_set_pam_conf_filename().
* Else if the standard functions for accessing local users are found on the system, they are used. The only Keyboard Interactive challenge will be the given
* user's password (that is if he's found on the system).
* Either way, you can always define your own callback to perform the authentication, see ::nc_server_ssh_set_interactive_auth_clb().
* The callback has a higher priority than the other two methods.
*
* There are also some other optional settings.
*
* Functions List
* --------------
*
* Available in __nc_server.h__.
*
* - ::nc_server_config_add_ssh_hostkey()
* - ::nc_server_config_del_ssh_hostkey()
* - ::nc_server_config_add_ssh_keystore_ref()
* - ::nc_server_config_del_ssh_keystore_ref()
*
* - ::nc_server_config_add_ssh_user_pubkey()
* - ::nc_server_config_del_ssh_user_pubkey()
* - ::nc_server_config_add_ssh_user_password()
* - ::nc_server_config_del_ssh_user_password()
* - ::nc_server_config_add_ssh_user_interactive()
* - ::nc_server_config_del_ssh_user_interactive()
* - ::nc_server_config_del_ssh_user()
* - ::nc_server_config_add_ssh_truststore_ref()
* - ::nc_server_config_del_ssh_truststore_ref()
* - ::nc_server_config_add_ssh_endpoint_client_ref()
* - ::nc_server_config_del_ssh_endpoint_client_ref()
*
* - ::nc_server_ssh_set_authkey_path_format()
* - ::nc_server_ssh_set_pam_conf_filename()
* - ::nc_server_ssh_set_interactive_auth_clb()
*
* TLS
* ===
*
* TLS works with endpoints too, but its options differ
* significantly from the SSH ones, especially in the _cert-to-name_
* options that TLS uses to derive usernames from client certificates.
*
* If you wish to listen on a TLS endpoint, you need to configure the endpoint's
* server certificate (see ::nc_server_config_add_tls_server_cert()).
*
* To accept client certificates, they must first be considered trusted.
* For each TLS endpoint you may configure two types of client certificates.
* The first type are end-entity (client) certificates. These are certificates that belong
* to given clients. These certificates need to be trusted.
* The second type are trust-anchor (certificate authority) certificates,
* which carry over the trust (a chain of trust).
* Another option is to reference another TLS endpoint's end-entity certificates, however be careful not to create a cyclic reference
* (see ::nc_server_config_add_tls_endpoint_client_ref()).
*
* Then, from each trusted client certificate a username must be derived
* for the NETCONF session. This is accomplished by finding a matching
* _cert-to-name_ entry.
*
* There are some further options. For example you can configure the TLS
* version and ciphers to be used.
*
* You may also choose to use a Certificate Revocation List. These lists
* are downloaded from the URIs specified in the x509 CRLDistributionPoints extensions.
* Be mindful that if any CRL is successfully downloaded and set, then at least one of them has to belong
* to the peer (e.g. the client) certificate (in other words it has to be issued by peer's CA).
*
* Functions List
* --------------
*
* Available in __nc_server.h__.
*
* - ::nc_server_config_add_tls_server_cert()
* - ::nc_server_config_del_tls_server_cert()
* - ::nc_server_config_add_tls_keystore_ref()
* - ::nc_server_config_del_tls_keystore_ref()
*
* - ::nc_server_config_add_tls_client_cert()
* - ::nc_server_config_del_tls_client_cert()
* - ::nc_server_config_add_tls_client_cert_truststore_ref()
* - ::nc_server_config_del_tls_client_cert_truststore_ref()
* - ::nc_server_config_add_tls_ca_cert()
* - ::nc_server_config_del_tls_ca_cert()
* - ::nc_server_config_add_tls_ca_cert_truststore_ref()
* - ::nc_server_config_del_tls_ca_cert_truststore_ref()
* - ::nc_server_config_add_tls_endpoint_client_ref()
* - ::nc_server_config_del_tls_endpoint_client_ref()
* - ::nc_server_config_add_tls_ctn()
* - ::nc_server_config_del_tls_ctn()
*
* FD
* ==
*
* If you used a tunneling software, which does its own authentication,
* you can accept a NETCONF session on its file descriptors with
* ::nc_accept_inout().
*
* Functions List
* --------------
*
* Available in __nc_server.h__.
*
* - ::nc_accept_inout()
*
*
* Call Home
* =========
*
* _Call Home_ works with endpoints just like standard sessions, but
* the options are organized a bit differently and endpoints are added
* for CH clients.
* You may choose one of two approaches for creating a new Call Home
* session (or in other words making a server connect to a client).
* The first is to set all the required callbacks
* by calling ::nc_server_ch_set_dispatch_data(). By setting the callbacks,
* the server will automatically start connecting to a client, whenever
* a new Call Home client is created.
* The second approach is to create the Call Home thread manually.
* To do this, you need to call ::nc_connect_ch_client_dispatch(),
* which then creates a new thread and the server will start to connect.
* Unix socket _Call Home_ sessions are not supported.
*
* Functions List
* --------------
*
* Available in __nc_server.h__.
*
* - ::nc_server_config_add_ch_address_port()
* - ::nc_server_config_del_ch_client()
* - ::nc_server_config_del_ch_endpt()
* - ::nc_server_config_add_ch_persistent()
* - ::nc_server_config_add_ch_period()
* - ::nc_server_config_del_ch_period()
* - ::nc_server_config_add_ch_anchor_time()
* - ::nc_server_config_del_ch_anchor_time()
* - ::nc_server_config_add_ch_idle_timeout()
* - ::nc_server_config_del_ch_idle_timeout()
* - ::nc_server_config_add_ch_reconnect_strategy()
* - ::nc_server_config_del_ch_reconnect_strategy()
*
* - ::nc_server_config_add_ch_ssh_hostkey()
* - ::nc_server_config_del_ch_ssh_hostkey()
* - ::nc_server_config_add_ch_ssh_keystore_ref()
* - ::nc_server_config_del_ch_ssh_keystore_ref()
* - ::nc_server_config_add_ch_ssh_user_pubkey()
* - ::nc_server_config_del_ch_ssh_user_pubkey()
* - ::nc_server_config_add_ch_ssh_user_password()
* - ::nc_server_config_del_ch_ssh_user_password()
* - ::nc_server_config_add_ch_ssh_user_interactive()
* - ::nc_server_config_del_ch_ssh_user_interactive()
* - ::nc_server_config_del_ch_ssh_user()
* - ::nc_server_config_add_ch_ssh_truststore_ref()
* - ::nc_server_config_del_ch_ssh_truststore_ref()
*
* - ::nc_server_config_add_ch_tls_server_cert()
* - ::nc_server_config_del_ch_tls_server_cert()
* - ::nc_server_config_add_ch_tls_keystore_ref()
* - ::nc_server_config_del_ch_tls_keystore_ref()
* - ::nc_server_config_add_ch_tls_client_cert()
* - ::nc_server_config_del_ch_tls_client_cert()
* - ::nc_server_config_add_ch_tls_client_cert_truststore_ref()
* - ::nc_server_config_del_ch_tls_client_cert_truststore_ref()
* - ::nc_server_config_add_ch_tls_ca_cert()
* - ::nc_server_config_del_ch_tls_ca_cert()
* - ::nc_server_config_add_ch_tls_ca_cert_truststore_ref()
* - ::nc_server_config_del_ch_tls_ca_cert_truststore_ref()
* - ::nc_server_config_add_ch_tls_ctn()
* - ::nc_server_config_del_ch_tls_ctn()
*
* Connecting And Cleanup
* ======================
*
* When accepting connections with ::nc_accept(), all the endpoints are examined
* and the first with a pending connection is used. To remove all CH clients,
* endpoints, and free any used dynamic memory, [destroy](@ref howtoinit) the server.
*
* Functions List
* --------------
*
* Available in __nc_server.h__.
*
* - ::nc_accept()
*/
/**
* @page howtoclientcomm Client communication
*
* To send RPCs on a session, you simply create an RPC, send it using ::nc_send_rpc(),
* and then wait for a reply using ::nc_recv_reply(). If you are subscribed, there are 2 ways
* of receiving notifications. Either you wait for them the same way
* as for standard replies with ::nc_recv_notif() or you create a dispatcher
* with ::nc_recv_notif_dispatch() that asynchronously (in a separate thread)
* reads notifications and passes them to your callback.
*
* Functions List
* --------------
*
* Available in __nc_client.h__.
*
* - ::nc_rpc_act_generic()
* - ::nc_rpc_act_generic_xml()
* - ::nc_rpc_getconfig()
* - ::nc_rpc_edit()
* - ::nc_rpc_copy()
* - ::nc_rpc_delete()
* - ::nc_rpc_lock()
* - ::nc_rpc_unlock()
* - ::nc_rpc_get()
* - ::nc_rpc_kill()
* - ::nc_rpc_commit()
* - ::nc_rpc_discard()
* - ::nc_rpc_cancel()
* - ::nc_rpc_validate()
* - ::nc_rpc_getschema()
* - ::nc_rpc_subscribe()
* - ::nc_rpc_getdata()
* - ::nc_rpc_editdata()
* - ::nc_rpc_establishsub()
* - ::nc_rpc_modifysub()
* - ::nc_rpc_deletesub()
* - ::nc_rpc_killsub()
* - ::nc_rpc_establishpush_periodic()
* - ::nc_rpc_establishpush_onchange()
* - ::nc_rpc_modifypush_periodic()
* - ::nc_rpc_modifypush_onchange()
* - ::nc_rpc_resyncsub()
*
* - ::nc_send_rpc()
* - ::nc_recv_reply()
* - ::nc_recv_notif()
* - ::nc_recv_notif_dispatch()
*/
/**
* @page howtoservercomm Server communication
*
* Once at least one session is established, an nc_pollsession structure
* should be created with ::nc_ps_new(), filled with the session using
* ::nc_ps_add_session() and finally polled with ::nc_ps_poll(). Based on
* the return value from the poll, further actions can be taken. More
* sessions can be polled at the same time and any requests received on
* the sessions are [handled internally](@ref howtoserver).
*
* If an SSH NETCONF session asks for a new channel, you can accept
* this request with ::nc_ps_accept_ssh_channel() or ::nc_session_accept_ssh_channel()
* depending on the structure you want to use as the argument.
*
* The server-side notifications are also supported. You can create a new notification
* with ::nc_server_notif_new() and send it via ::nc_server_notif_send() to subscribed clients.
* Keep in mind that the session you wish to send a notification on has to have at least one
* subscriber, see ::nc_session_inc_notif_status().
* Currently, only notifications about certificate expiration are implemented,
* see ::nc_server_notif_cert_expiration_thread_start().
*
* Functions List
* --------------
*
* Available in __nc_server.h__.
*
* - ::nc_ps_new()
* - ::nc_ps_add_session()
* - ::nc_ps_del_session()
* - ::nc_ps_session_count()
* - ::nc_ps_free()
*
* - ::nc_ps_poll()
* - ::nc_ps_clear()
* - ::nc_ps_accept_ssh_channel()
* - ::nc_session_accept_ssh_channel()
*
* - ::nc_server_notif_new()
* - ::nc_server_notif_send()
* - ::nc_server_notif_free()
* - ::nc_server_notif_get_time()
* - ::nc_session_inc_notif_status()
* - ::nc_session_dec_notif_status()
* - ::nc_session_get_notif_status()
* - ::nc_server_notif_cert_expiration_thread_start()
* - ::nc_server_notif_cert_expiration_thread_stop()
*/
/**
* @page howtotimeouts Timeouts
*
* There are several timeouts which are used throughout _libnetconf2_ to
* assure that it will never indefinitely hang on any operation. Normally,
* you should not need to worry about them much because they are set by
* default to reasonable values for common systems. However, if your
* platform is not common (embedded, ...), adjusting these timeouts may
* save a lot of debugging and time.
*
* Compile Options
* ---------------
*
* You can adjust active and inactive read timeout using `cmake` variables.
* For details look into `README.md`.
*
* Configurable timeouts
* ---------------------
*
* Once a new connection is established including transport protocol negotiations,
* _hello_ message is exchanged. You can set how long will the server wait for
* receiving this message from a client before dropping it.
*
* Having a NETCONF session working, it may not communicate for a longer time.
* To free up some resources, it is possible to adjust the maximum idle period
* of a session before it is disconnected. In _Call Home_, for both a persistent
* and periodic connection can this idle timeout be specified separately for each
* client. Lastly, SSH user authentication timeout can be also modified. It is the time
* a client has to successfully authenticate after connecting before it is disconnected.
*
* These timeouts can be toggled by applying corresponding configuration data.
*/
/**
* @defgroup misc Miscellaneous
* @brief Miscellaneous macros, types, structure and functions for a generic use by both server and client applications.
*/
/**
* @defgroup client Client
* @brief NETCONF client functionality.
*/
/**
* @defgroup server Server
* @brief NETCONF server functionality.
* @{
* @} Server
*/