dns_cache.js

var dns = require("dns");

// cache reverse DNS lookups for the life of the program. No TTL checking. No tricks.

function DNSCache() {
 this.cache = {};
 this.requests = {};
}

DNSCache.prototype.ptr = function (ip) {
 if (this.cache[ip]) {
 return this.cache[ip];
 }

 if (this.requests[ip] === undefined) {
 this.requests[ip] = true;
 var self = this;
 dns.reverse(ip, function (err, domains) {
 self.on_ptr(err, ip, domains);
 });
 }

 return ip;
};

DNSCache.prototype.on_ptr = function (err, ip, domains) {
 // TODO - check for network and broadcast addrs, since we have iface info
 if (err) {
 this.cache[ip] = ip;
 } else {
 this.cache[ip] = domains[0];
 }
};

module.exports = DNSCache;