= nng_tls(7)
//
// Copyright 2018 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 - TLS transport

== SYNOPSIS

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

int nng_tls_register(void);
----

== DESCRIPTION

(((TLS)))(((Transport Layer Security)))(((transport, _tls_)))
The ((_tls_ transport)) provides communication support between
_nng_ sockets across a TCP/IP network using 
https://tools.ietf.org/html/rfc5246[TLS v1.2] on top of
https://tools.ietf.org/html/rfc793[TCP].
Both IPv4 and IPv6 are supported when the underlying platform also supports it.

The protocol details are documented in
http://nanomsg.org/rfcs/sp-tls-v1.html[TLS Mapping for Scalability Protocols].

=== Registration

Depending upon how the library was built, it may be necessary to
register the transport by calling
<<nng_tls_register.3#,`nng_tls_register()`>>.

=== Availability

The _tls_ transport depends on the use of an external library.
As of this writing, https://tls.mbed.org/[mbedTLS] version 2.0
or later is required.

TIP: Applications may need to add this library (or libraries) to
their link line, particularly when using a statically built
_nng_ library.

NOTE: The mbedTLS library uses different licensing terms than
_nng_ itself; as of this writing it is offered under either
https://opensource.org/licenses/Apache-2.0[Apache License 2.0] or
https://opensource.org/licenses/gpl-license[GNU GPL] terms.
You are responsible for understanding and adhering to the
license terms of any libraries you make use of.

=== URI Format

(((URI, `tls+tcp://`)))
This transport uses URIs using the scheme `tls+tcp://`, followed by
an IP address or hostname, followed by a colon and finally a
TCP port number.
For example, to contact port 4433 on the localhost
either of the following URIs could be used: `tls+tcp://127.0.0.1:4433` or
`tls+tcp://localhost:4433`.

When specifying IPv6 addresses, the address must be enclosed in
square brackets (`[]`) to avoid confusion with the final colon
separating the port.

For example, the same port 4433 on the IPv6 loopback address ('::1') would
be specified as `tls+tcp://[::1]:4433`.

NOTE: When using symbolic names, the name is resolved when the
name is first used. _nng_ won't become aware of changes in the
name resolution until restart,
usually.
(This is a bug and will likely be fixed in the future.)

TIP: Certificate validation generally works when using names
rather than IP addresses.
This transport automatically uses the name supplied in the URL when validating
the certificate supplied by the server.

The special value of 0 (`INADDR_ANY`) can be used for a listener
to indicate that it should listen on all interfaces on the host.
A short-hand for this form is to either omit the address, or specify
the asterisk (`*`) character.
For example, the following three URIs are all equivalent,
and could be used to listen to port 9999 on the host:

  1. `tls+tcp://0.0.0.0:9999`
  2. `tls+tcp://*:9999`
  3. `tls+tcp://:9999`

The entire URI must be less than `NNG_MAXADDRLEN` bytes long.

=== Socket Address

When using an <<nng_sockaddr.5#,`nng_sockaddr`>> structure,
the actual structure is either of type
<<nng_sockaddr_in.5#,`nng_sockaddr_in`>> (for IPv4) or
<<nng_sockaddr_in6.5#,`nng_sockaddr_in6`>> (for IPv6).

=== Transport Options

The following transport options are available.
Note that setting these must be done before the transport is started.

((`NNG_OPT_TCP_KEEPALIVE`))::

This option is used to configure TCP keep-alives.
The value is of type `bool`, and defaults to `false`.

((`NNG_OPT_TCP_NODELAY`))::

This option is used to configure Nagle's algorithm.
When enabled (`false`), the underlying TCP stream will attempt
to buffer and coalesce messages before sending them on, waiting
a short interval to improve buffering and reduce the overhead
caused by sending too-small messages.
This comes at a cost to latency, and is not recommended with modern
high speed networks.
The value is of type `bool` and defaults to `true`.

((`NNG_OPT_TLS_CONFIG`))::

This option is used on an endpoint to access the underlying TLS
configuration object.
The value is of type `nng_tls_config *`.

TIP: Use this option when advanced TLS configuration is required.

((`NNG_OPT_TLS_CA_FILE`))::

This is a write-only option used to load certificates associated
associated private key from a file.
See <<nng_tls_config_ca_file.3tls#,`nng_tls_config_ca_file()`>> for more
information.

((`NNG_OPT_TLS_CERT_KEY_FILE`))::

This is a write-only option used to load the local certificate and
associated private key from a file. The private key used must be
unencrypted. (Use the `NNG_OPT_TLS_CONFIG` option to access the underlying
TLS configuration if more advanced configuration is needed.)
See <<nng_tls_config_own_cert.3tls#,`nng_tls_config_own_cert()`>> for more
information.

((`NNG_OPT_TLS_AUTH_MODE`))::

This is a write-only option used to configure the authentication mode
used.  It can take an integer with value `NNG_TLS_AUTH_MODE_NONE`,
`NNG_TLS_AUTH_MODE_REQUIRED`, or `NNG_TLS_AUTH_MODE_OPTIONAL`.
See <<nng_tls_config_auth_mode.3tls#,`nng_tls_config_auth_mode()`>> for
more details.

((`NNG_OPT_TLS_VERIFIED`))::

This is a read-only option which returns a boolean value (integer 0 or 1).
It will true (1) if the remote peer has been properly verified using TLS
authentication, or false (0) otherwise.
This option may return incorrect
results if peer authentication is disabled with `NNG_TLS_AUTH_MODE_NONE`.

== SEE ALSO

<<nng_tls_config_alloc.3tls#,nng_tls_config_alloc(3tls)>>
<<nng_sockaddr_in.5#,nng_sockaddr_in(5)>>,
<<nng_sockaddr_in6.5#,nng_sockaddr_in6(5)>>,
<<nng.7#,nng(7)>>,
