Block local connections from hyperswarm

[gmaclennan]

One way to avoid duplicate connections from both hyperswarm and mdns is to block local connections with hyperswarm (and block non-local connections on the hyperswarm socket see #68)

We can do this with opts.firewall once holepunchto/hyperswarm#131 is merged. E.g.

const { isPrivate } = require('bogon')

const swarm = new Hyperswarm({
  firewall: (remotePublicKey, payload, clientAddress) => !!clientAddress && isPrivate(clientAddress.host)
})