nng_zerotier(7)
===============
:doctype: manpage
:manmanual: nng
:mansource: nng
:manvolnum: 7
:icons: font
:source-highlighter: pygments
:copyright: Copyright 2017 Garrett D'Amore <garrett@damore.org> \
            Copyright 2017 Capitar IT Group BV <info@capitar.com> \
            This software 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_zerotier - ZeroTier transport for nng

SYNOPSIS
--------

*#include <nn/transports/zt.h>*

*int nng_zt_register(void);*

DESCRIPTION
-----------

The _nng_zerotier_ transport provides communication support for
_nng_ applications over a http://www.zerotier.com[ZeroTier] network,
using a Virtual Layer 2 packet facility.

CAUTION: This transport is very experimental.  To utilize it at
present, the library must be built with support, and the
ZeroTierOne `dev` branch must be included; this will require
linking against a suitable `libzerotiercore` static library.         

NOTE: The `libzerotiercore` library at present is covered under different
license terms than the rest of _nng_.  Please be careful to review
and adhere to the licensing terms.

While ZeroTier makes use of the host's IP stack (and UDP in particular),
this transport does not use or require an IP stack on the virtual
network; thereby mitigating any considerations about IP address management.

This service uses Ethernet type 901 to transport packets.  Network rules
must permit this Ethernet type to pass in order to have a functional
network.

NOTE: This document assumes that the reader is familiar with ZeroTier
concepts and administration.

Registration
~~~~~~~~~~~~

Depending upon how the library was built, it may be necessary to
register the transport by calling `nng_zt_register`.  This function
returns zero on success, or an nng error value if the transport
cannot be initialized for any reason.

URI Format
~~~~~~~~~~

This transport uses URIs using the scheme `zt://`, followed by a network
address (ten hexadecimal digits), followed by a `/` delimiter,
followed by the node number (sixteen hexadecimal digits) of the listening
node, followed by a service or port number (decimal value, up to 24-bits).
For example, the URI `zt://123456789a/0123456789abcdef:934` indicates
that node 0123456789abcdef on network 123456789a listening on port 934.

Listening nodes may use port 0, or `*`, to indicate that a suitable port
number be selected automatically. Applications using this must get the
selected port address using the `nng_listener_getopt` function.

Listening nodes may also elide their own node number, as well as the
delimiter seperating the node number.

Socket Address
~~~~~~~~~~~~~~

When using an `nng_sockaddr` structure, the actual structure is of type
`struct nng_sockaddr_zt`.  This type has the following definition:

[source,c]
--------
#define NNG_AF_ZT 5

struct nng_sockaddr_zt {
    uint16_t sa_family;  // must be NNG_AF_ZT
    uint64_t sa_nwid;    // 40-bit network ID
    uint64_t sa_nodeid;  // 64-bit node ID
    uint32_t sa_port;    // 24-bit application port
}
--------

The `sa_family` member will have the value `NNG_AF_ZT` (5).  The remaining
members are, unlike TCP socket address, in native byte order.  Only the
lower 24-bits of the `sa_port` may be used.  Likewise only the lower 40-bits
of the `sa_nwid` may be used.

Node Presence
~~~~~~~~~~~~~

By default this transport creates an "ephemeral" node, and used the
same ephemeral node for any additional endpoints created.  As this node
is ephemeral, the keys associated with it and all associated data are
located in memory and are discarded upon application termination.  If
a persistent node is desired, please see the `NNG_OPT_ZT_HOME` option
below.

It is possible for a single application to join multiple networks
using the same node, or using separate nodes.


Transport Options
~~~~~~~~~~~~~~~~~

The following transport options are available:

*NNG_OPT_ZT_HOME*::

  This is a string representing the "home directory", where the transport
  can store (and reuse) persistent state, such as key materials, node
  identity, and federation membership.  This option must be set before the
  ZeroTier transport is first used.  If this value is empty, then an ephermal
  ZeroTier node is created, and no persistent state is used.  The default
  is to use an ephemeral node.
+ 
NOTE: If this option is set to different values on different sockets,
dialers, or listeners, then separate nodes will be created.  It
is perfectly valid for an application to have multiple node identities
in this fashion.

*NNG_OPT_ZT_NWID*::

  This is a read-only option for listeners, dialers, and pipes, and
  provides a `uint64_t` in native byte order representing the 64-bit ZeroTier
  network number.

*NNG_OPT_ZT_NODE*::

  This is a read-only option for listeners, dialers, and pipes, and
  provides a `uint64_t` in native byte order representing the ZeroTier
  40-bit node address.

*NNG_OPT_ZT_NETWORK_STATUS*::

  This is a read-ony integer, representing the ZeroTier network status.
  Valid values for this are:
+
[cols="1,2"]
|===

| *nng_zt_network_status_configuring*
| The ZeroTier node is still configuring, network services are not available.

| *nng_zt_network_status_ok*
| The ZeroTier network is up.

| *nng_zt_network_status_denied*
| The node does not have permission to join the ZeroTier network.

| *nng_zt_network_status_notfound*
| The ZeroTier network is not found.

| *nng_zt_network_status_error*
| Some other ZeroTier error has occurred; the network is not available.

| *nng_zt_network_status_obsolete*
| The node is running obsolete software; the network is not available.

|===


*NNG_OPT_ZT_NETWORK_NAME*::

  This is a read-only ASCIIZ string containing the name of the network
  as established by the ZeroTier network administrator.

*NNG_OPT_ZT_PING_TIME*::

   If no traffic has been received from the ZeroTier peer after this
   period of time, then a "ping" message is sent to check if the peer
   is still alive.  This is an `nng_duration` (msec).

*NNG_OPT_ZT_PING_COUNT*::

   If this number (`int`) of consecutive "ping" requests are sent to the
   peer with no response (and no other intervening traffic), then the
   peer is assumed to be dead and the connection is closed.  Note that
   if any traffic is received from the peer, then the underlying counter
   is reset to zero.

*NNG_OPT_ZT_MTU*::

   This is a read-only size (`size_t`) representing the ZeroTier virtual
   network MTU; this is the Virtual Layer 2 MTU.  The headers used by
   this transport and the protocols consume some of this for each message
   sent over the network.  (The transport uses 20-bytes of this, and each
   protocol may consume additional space, typically not more than 16-bytes.)

*NNG_OPT_ZT_ORBIT*::

   This is a write-only option that takes an array of two `uint64_t` values,
   indicating the ID of a ZeroTier "moon", and the node ID of the root server
   for that moon.  (The ID may be zero if the moon ID is the same as it's
   root server ID, which is conventional.)

*NNG_OPT_ZT_DEORBIT*::

   This write-only option takes a single `uint64_t` indicating the moon
   ID to "deorbit".  If the node is not already orbiting the moon, then
   this has no effect.
    
AUTHORS
-------
link:mailto:garrett@damore.org[Garrett D'Amore]

SEE ALSO
--------
<<nng.adoc#,nng(7)>>

COPYRIGHT
---------

Copyright 2017 mailto:garrett@damore.org[Garrett D'Amore] +
Copyright 2017 mailto:info@capitar.com[Capitar IT Group BV]

This document is supplied under the terms of the
https://opensource.org/licenses/LICENSE.txt[MIT License].
