= 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`.

A URI may be restricted to IPv6 using the scheme `tls+tcp6://`, and may
be restricted to IPv4 using the scheme `tls+tcp4://`.

NOTE: Specifying `tls+tcp6://` may not prevent IPv4 hosts from being used with
IPv4-in-IPv6 addresses, particularly when using a wildcard hostname with
listeners.
The details of this varies across operating systems.

NOTE: Both `tls+tcp6://` and `tls+tcp4://` are _nng_ extensions, and may not
be understood by other implementations.

TIP: We recommend using either numeric IP addresses, or names that are
specific to either IPv4 or IPv6 to prevent confusion and surprises.

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`.

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`))::
(`bool`) Enable TCP keep-alives, defaults to `false`.

((`NNG_OPT_TCP_NODELAY`))::
(`bool`) Disable 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.
Defaults to `true`.

((`NNG_OPT_TLS_CONFIG`))::
(`nng_tls_config *`)
The underlying TLS
configuration object.
A hold is placed on the underlying
configuration object before returning it.
The caller should release the hold with
`<<nng_tls_config_free.3tls#,nng_tls_config_free()>>` when it no
longer needs the TLS configuration object.

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

((`NNG_OPT_TLS_CA_FILE`))::
(string) Write-only option naming a file containing certificates to
use for peer validation.
See `<<nng_tls_config_ca_file.3tls#,nng_tls_config_ca_file()>>` for more
information.

((`NNG_OPT_TLS_CERT_KEY_FILE`))::
(string) Write-only option naming a file containing the local certificate and
associated private key.
The private key used must be unencrypted.
See `<<nng_tls_config_own_cert.3tls#,nng_tls_config_own_cert()>>` for more
information.

((`NNG_OPT_TLS_AUTH_MODE`))::
(`int`) Write-only option used to configure the authentication mode used.
See `<<nng_tls_config_auth_mode.3tls#,nng_tls_config_auth_mode()>>` for
more details.

((`NNG_OPT_TLS_VERIFIED`))::
(`bool`) Whether the remote peer has been properly verified using TLS
authentication.
May return incorrect results if peer authentication is disabled.

== SEE ALSO

[.text-left]
<<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)>>,
