= nng_tls_config_alloc(3tls)
//
// Copyright 2019 Staysail Systems, Inc. <info@staysail.tech>
// Copyright 2018 Capitar IT Group BV <info@capitar.com>
//
// This document is supplied under the terms of the MIT License, a
// copy of which should be located in the distribution where this
// file was obtained (LICENSE.txt).  A copy of the license may also be
// found online at https://opensource.org/licenses/MIT.
//

== NAME

nng_tls_config_alloc - allocate TLS configuration object

== SYNOPSIS

[source, c]
----
#include <nng/nng.h>
#include <nng/supplemental/tls/tls.h>

typedef enum nng_tls_mode {
    NNG_TLS_MODE_CLIENT,
    NNG_TLS_MODE_SERVER
} nng_tls_mode;

int nng_tls_config_alloc(nng_tls_config **cfgp, nng_tls_mode mode);
----

== DESCRIPTION

The `nng_tls_config_alloc()` function creates a newly initialized
https://tools.ietf.org/html/rfc5246[Transport Layer Security])
configuration object, and stores a pointer to it in the value pointed
to by _cfgp_.

This object is initialized for use when acting as either a
client (`NNG_TLS_MODE_CLIENT`) or as a server (`NNG_TLS_MODE_SERVER`),
depending on the value of _mode_.

A TLS object can be further modified by functions that set the security
keys used, peer certificates, protocol policies, and so forth.

A single TLS configuration object can be used with multiple TLS streams
or services.
The underlying system uses reference counting to ensure
that object is not inadvertently freed while in use.

A configuration object created with `nng_tls_config_alloc()` starts
with a reference count of one.
The reference count may be incremented using
xref:nng_tls_config_hold.3tls.adoc[`nng_tls_config_hold()`] and may be
decremented with
xref:nng_tls_config_free.3tls.adoc[`nng_tls_config_free()`].

Also note that a TLS configuration object becomes "`read-only`" after it
is first used with a service.
After this points, attempts to apply
further changes to the configuration will result in `NNG_EBUSY`.


== RETURN VALUES

This function returns 0 on success, and non-zero otherwise.

== ERRORS

[horizontal]
`NNG_ENOMEM`:: Insufficient memory is available.
`NNG_EINVAL`:: An invalid _mode_ was specified.

== SEE ALSO

[.text-left]
xref:nng_strerror.3.adoc[nng_strerror(3)],
xref:nng_tls_config_auth_mode.3tls.adoc[nng_tls_config_auth_mode(3tls)],
xref:nng_tls_config_ca_chain.3tls.adoc[nng_tls_config_ca_chain(3tls)],
xref:nng_tls_config_own_cert.3tls.adoc[nng_tls_config_own_cert(3tls)],
xref:nng_tls_config_free.3tls.adoc[nng_tls_config_free(3tls)],
xref:nng_tls_config_hold.3tls.adoc[nng_tls_config_hold(3tls)],
xref:nng_tls_config_server_name.3tls.adoc[nng_tls_config_server_name(3tls)],
xref:nng_tls_config.5.adoc[nng_tls_config(5)],
xref:nng.7.adoc[nng(7)]