@node Yggdrasil
@cindex yggdrasil
@unnumbered Yggdrasil support

NNCP is able to act as a node of
@url{https://yggdrasil-network.github.io/, Yggdrasil} overlay network.
Current IPv6 adoption for @strong{home} users is relatively bad in many
countries. That is why Yggdrasil overlay network uses dynamic spanning
tree mesh network for packets routing, making it useful for gaining
hosts high reachability without complex manual manipulations. By default
it creates 200::/7 IPv6 network, where each host's address is derived
from its public key.

NNCP reuses Yggdrasil's source code, but instead of relying on operating
system's network stack, that would require use of some kind
full-featured TUN network interface, there is pure Go built-in stack,
responsible for IPv6 and TCP protocols support. You do not need to think
about network interfaces, addressing and firewall setup at all:
@command{@ref{nncp-daemon}} acts as Yggdrasil IPv6 reachable host,
listening on single TCP port. You can reach it using ordinary
non-Yggdrasil capable version of @command{@ref{nncp-call}}, calling
corresponding 200::/7 IPv6 address through native Yggdrasil daemon
created TUN interface. @command{@ref{nncp-daemon}},
@command{@ref{nncp-call}}* can freely peer with Yggdrasil nodes, reusing
existing infrastructure.

Only minor modifications were done to current NNCP's tools:

@itemize

@cindex yggdrasils schema
@item @command{@ref{nncp-daemon}} has @option{-yggdrasil yggdrasils://}
option, making it also as a Yggdrasil listener network node. It can
automatically connect to other peers and participate in routing. It does
not have to answer NNCP's online protocol requests at all and just can
be some intermediate routing point in the whole mesh network.

@cindex yggdrasilc schema
@item @command{@ref{nncp-call}}/@command{@ref{nncp-caller}} commands understand
@code{yggdrasilc://} addresses, pointing to the desired Yggdrasil's
public key (that also acts as the destination host's address). Yggdrasil
background goroutine is automatically started, connecting to the
specified Yggdrasil entrypoints, calling remote NNCP node and initiating
NNCP's native @ref{Sync, online protocol} handshake on top of that.

@item @command{@ref{nncp-cfgnew}} is able to generate ed25519 keypair.

@item @ref{CfgYggdrasilAliases, Configuration file} optionally contains
@code{yggdrasil-aliases} map.

@end itemize

How to start using NNCP through that overlay network?

@enumerate

@item
Generate ed25519 keypair, that will be used for identification and
authentication of your node in Yggdrasil network:

@example
$ nncp-cfgnew -yggdrasil
Public: 4fd64130e23cf7abdbc0fabdf2ae12bbc2ab7179861efa296d2beb0181ae07ea
Private: 571fb05c81e62a572096566fd48e87ad47e706b1f600dd625ebbf86d310332624fd64130e23cf7abdbc0fabdf2ae12bbc2ab7179861efa296d2beb0181ae07ea
@end example

You should share that public key with other NNCP peers.

@item
Start @command{@ref{nncp-daemon}} listening on Yggdrasil's incoming connections.
You have to specify:

@itemize

@vindex PrivateKey
@item
Your private key (generated above). Yggdrasil's @code{PrivateKey} analogue.

@item
Optional non-default port you will listen on Yggdrasil's IPv6 address.

@vindex Listen
@item
Optional list of bind addresses, used for peering between the nodes.
Yggdrasil's @code{Listen} analogue.

@vindex Peers
@item
Optional list of peer addresses you should connect to.
Yggdrasil's @code{Peers} analogue.

@vindex AllowedPublicKeys
@item
Optional list of allowed peer public keys, allowed for incoming peering
connections from. Yggdrasil's @code{AllowedPublicKeys} analogue.

@item
Optional list of multicast-related regular expressions to match desired
network interfaces where Yggdrasil multicasting must be enabled. Beacon
and listening are always enabled on them, but optionally you can specify
port you forcefully want to listen on.

@end itemize

@example
$ nncp-daemon -yggdrasil "yggdrasils://571f...07ea:6789"\
"?bind=tcp://[::1]:1234"\
"&bind=tcp://[2001::1]:1234"\
"&pub=c6b7...9469"\
"&pub=eb2d...ca07"\
"&peer=tcp://example.com:2345"\
"&peer=tcp://another.peer:3456%3Fkey=f879...2e9b"
"&mcast=.*:5400"
"&mcast=lo0"
@end example

That @code{yggdrasils://} is transformed to following Yggdrasil's
configuration analogue:

@verbatim
{
  PrivateKey: 571f...07ea
  Listen: ["tcp://[::1]:1234", "tcp://[2001::1]:1234"]
  AllowedPublicKeys: ["c6b7...9469", "eb2d...ca07"]
  Peers: [
    tcp://some.peer.be:2345
    tcp://some.peer.ru:3456?key=f879...2e9b
  ]
  MulticastInterfaces: [
    {
        Regex: .*
        Beacon: true
        Listen: true
        Port: 5400
    }, {
        Regex: lo0
        Beacon: true
        Listen: true
        Port: 0
    }
  ]
}
@end verbatim

Basically you have to specify only private key and either @code{bind} or
@code{peer} address. Look for Yggdrasil's documentation for more
description of each option and related behaviour.

As you can see, private key is in command line arguments, that could be
treated as a security issue. That is why it is preferred to specify them
in @ref{CfgYggdrasilAliases, configuration}'s @code{yggdrasil-aliases}
section, where you can alias all of entities and reference them in
@option{-yggdrasil} or @code{yggdrasilc://}-addresses:

@verbatim
yggdrasil-aliases: {
  myprv: 571f...07ea
  bindPublic: tcp://[2001::1]:1234
  bindLocalhost: tcp://[::1]:2345
  peerBE: tcp://some.peer.be:2345
  peerRU: tcp://some.peer.ru:3456?key=f879...2e9b
  somePeerPub1: c6b7...9469
  somePeerPub2: eb2d...ca07
  remoteAlicePub: 52be...3c14
  mcastAll: .*:5400
}
@end verbatim

And now you can more conveniently and safely specify:

@example
$ nncp-daemon -yggdrasil "yggdrasils://myprv:6789"\
"?bind=bindPublic&bind=bindLocalhost"\
"&peer=peerBE&peer=peerRU"\
"&pub=somePeerPub1&pub=somePeerPub2"\
"&mcast=mcastAll&mcast=lo0"
@end example

@item
Make calls to that node from another ones, by using
@code{yggdrasilc://}-address, similarly:

@example
yggdrasilc://PUB[:PORT]?prv=PRV[&peer=PEER][&mcast=REGEX[:PORT]]
@end example

where @code{PUB} is remote node's public key.

@example
$ nncp-call alice "yggdrasilc://remoteAlicePub?prv=myprv&mcast=mcastAll"
@end example

@end enumerate

Per private key Yggdrasil core goroutine is started when first call is
initiated and stays until program is finished. You can have multiple
Yggdrasil-related private keys and multiple (Yggdrasil) cores will work
simultaneously. But running multiple cores for one private key with
varying configuration (except for destination public key of course) is
not supported.
