rif/rif.js

Node.js module to resolve network interfaces.

/* Copyright (c) 2016, Richard Rodger and other contributors, MIT License. */
'use strict'

var Os = require('os')

var Ip = require('ip')


module.exports = function (entries) {
  return function rif (spec) {
    return resolve(spec, merge(Os.networkInterfaces(),entries))
  }
}

module.exports.resolve = resolve

function resolve (spec, netif) {
  var netif  = netif
  var parts  = spec.split('/')
  var ifname = parts[0]
  var ipv    = 6 == parts[1] ? 6 : 4 == parts[1] ? 4 : 0
  var fields = parts[2]

  var all_entries = netif[ifname] ||  []
  if( 0 === all_entries.length && ('*' === ifname || '' === ifname) ) {
    for( var p in netif ) {
      all_entries = all_entries.concat(netif[p])
    }
  }

  var entries = all_entries.filter(function (entry) {
    return 6 === ipv ? 'IPv6' === entry.family : 4 === ipv ? 'IPv4' === entry.family : true
  })

  // If no IP family in entries, ignore IP family
  if( 0 === entries.length ) {
    entries = all_entries
  }

  if( null != fields ) {
    var fexprs = fields.split(',').map(function (fexpr) {
      return (fexpr.match(/^(.*?)([=^$])(.*)$/) || []).slice(1,4)
    }).filter(function (fexpr) {
      return 3 === fexpr.length
    })

    entries = entries.filter(function (entry) {
      for( var i = 0; i < fexprs.length; ++i ) {
        var fvstr = ''+entry[fexprs[i][0]]
        var ftest = fexprs[i][1]        
        var fspec = fexprs[i][2]

        if( '=' === ftest ) {
          if( fvstr !== fspec ) {
            return false
          }
        }
        else if( '^' === ftest ) {
          if( !fvstr.startsWith(fspec) ) {
            return false
          }
        }
        else if( '$' === ftest ) {
          if( !fvstr.endsWith(fspec) ) {
            return false
          }
        }
        else if( '%' === ftest ) {
          if( !fvstr.includes(fspec) ) {
            return false
          }
        }
      }
      return true
    })
  }

  var entry = entries[0]
  var result = entry ? (entry.address || null) : null

  // If unrecognized, maybe it's a vanilla address
  if( Ip.isV4Format(spec) || Ip.isV6Format(spec) ) {
    result = spec
  }

  return result
}


// b wins
function merge (a,b) {
  if( !b ) return a

  var o = {}
  
  for( var p in a ) {
    o[p] = a[p]
  }

  for( var p in b ) {
    o[p] = b[p]
  }

  return o
}