hnsd

SPV resolver daemon for the Handshake network. Written in C for speed/size/embedability.

Architecture

hnsd exists as a 4-layer architecture:

1. An SPV node which syncs headers and requests name proofs and data from peers over the HNS P2P network.
2. An authoritative root server which translates the HNS name data to DNS responses. These responses appear as if they came from a root zone.
3. A recursive name server pointed at the authoritative server, which serves . as a stub zone
4. A hardcoded fallback for ICANN's root zone, residing in the authoritative layer.

A standard stub resolver can hit the recursive server with a request. The flow looks something like this.

stub resolver
  -> +rd request
  -> recursive server
  -> libunbound
  -> +nord request
  -> authoritative server
  -> spv node
  -> proof request
  -> peer

Coming back, a response will look like:

peer
  -> proof response
  -> spv node
  -> authoritative server
  -> translated dns response
  -> libunbound
  -> recursive server
  -> dns response
  -> stub resolver

---

This daemon currently stores no data, and uses about 12mb of memory when operating with a full DNS cache.

This architecture works well, given that there's two layers of caching between the final resolution and the p2p layer (which entails the production of slightly expensive-to-compute proofs).

The recursive resolver leverages libunbound's built-in cache: there is, however, also a cache for the authoritative server. This is atypical when compared to a standard RFC 1035 nameserver which simply holds a zonefile in memory and serves it. All current ICANN-based root zone servers are RFC 1035 nameservers. We differ in that our root zonefile is a blockchain. With caching for the root server, new proofs only need to be requested every 6 hours (the duration of name tree update interval at the consensus layer). This substantially reduces load for full nodes who are willing to serve proofs as a public service.

Dependencies

Build

• libuv >= 1.19.2 (included)

Build/Runtime

• libunbound >= 1.6.0

hnsd will recursively build and statically link to uv, which is included in the source repo.

Installing Dependencies

OSX

$ brew install git automake autoconf libtool unbound

Linux

You're a Linux user so you probably already know what to do. Make sure you have git, autotools, libtool, and unbound installed via whatever package manager your OS uses.

Cloning

$ git clone git://github.com/handshake-org/hnsd.git
$ cd hnsd

Building

$ ./autogen.sh && ./configure && make

Setup

Currently, hnsd will setup a recursive name server listening locally. If you want to resolve names through the handshake network, this requires you to change your resolv.conf to 127.0.0.1, as well as configure the daemon to listen on port 53 -- this requires root access on OSX, and some hackery on Linux.

OSX

1. Open "System Preferences" on the panel/dock.
2. Select "Network".
3. Select "Advanced".
4. Select "DNS".
5. Here, you can add and remove nameservers. Remove all nameservers and add a single server: "127.0.0.1". You can change this back to google's servers (8.8.8.8 and 8.8.4.4) later if you want.
6. Run hnsd with $ sudo ./hnsd -p 4 -r 127.0.0.1:53.

Linux

First we need to alter our resolv.conf:

echo 'nameserver 127.0.0.1' | sudo tee /etc/resolv.conf > /dev/null

Secondly, we need to allow our daemon to listen on low ports, without root access (much safer than running as root directly).

$ sudo setcap 'cap_net_bind_service=+ep' /path/to/hnsd

Now run with:

$ ./hnsd -p 4 -r 127.0.0.1:53

Using a static resolv.conf

On Linux, there are a few services which may try to automatically overwrite your resolv.conf. resolvconf, dhcpcd, and NetworkManager are usually the culprits here.

resolvconf

If you're using resolvconf, /etc/resolvconf.conf must be modified:

$ sudo vi /etc/resolvconf.conf

The name_servers field must be altered in order to truly alter your resolv.conf:

name_servers="127.0.0.1"

dhcpcd

dhcpcd may try to overwrite your resolv.conf with whatever nameservers are advertised by your router (usually your ISP's nameservers). To prevent this, /etc/dhcpcd.conf must be modified:

$ sudo vi /etc/dhcpcd.conf

In the default config, you may see a line which looks like:

option domain_name_servers, domain_name, domain_search, host_name

We want to remove domain_name_servers, domain_name, and domain_search.

option host_name

NetworkManager

Likewise, NetworkManager has similar behavior to dhcpcd. To prevent it from tainting your resolv.conf, /etc/NetworkManager/NetworkManager.conf must be altered:

$ sudo vi /etc/NetworkManager/NetworkManager.conf

The default NetworkManager.conf is usually empty, but we need to add a dns option under the [main] section, resulting in a configuration like:

[main]
dns=none

Note that NetworkManager will also check connectivity by resolving a domain. This can cause issues with hnsd. Disable with:

[connectivity]
interval=604800

Usage

$ hnsd [options]

Options

-c, --config <config>
  Path to config file.

-n, --ns-host <ip[:port]>
  IP address and port for root nameserver, e.g. 127.0.0.1:5369.

-r, --rs-host <ip[:port]>
  IP address and port for recursive nameserver, e.g. 127.0.0.1:53.

-i, --ns-ip <ip>
  Public IP for NS records in the root zone.

-u, --rs-config <config>
  Path to unbound config file.

-p, --pool-size <size>
  Size of peer pool.

-k, --identity-key <hex-string>
  Identity key for signing DNS responses as well as P2P messages.

-s, --seeds <seed1,seed2,...>
  Extra seeds to connect to on P2P network.
  Example:
    -s aorsxa4ylaacshipyjkfbvzfkh3jhh4yowtoqdt64nzemqtiw2whk@127.0.0.1

-l, --log-file <filename>
  Redirect output to a log file.

-d, --daemon
  Fork and background the process.

-h, --help
  Help message.

License

• Copyright (c) 2018, Christopher Jeffrey (MIT License).

See LICENSE for more info.