dns: add getServers and setServers

getServers returns an array of ips that are currently being used for
resolution

setServers takes an array of ips that are to be used for resolution,
this will throw if there's invalid input but preserve the original
configuration

1 files changed, 49 insertions, 0 deletions

diff --git a/lib/dns.js b/lib/dns.js
index 10214790de..e9611a3a71 100644
--- a/lib/dns.js
+++ b/lib/dns.js
@@ -192,6 +192,55 @@ exports.resolve = function(domain, type_, callback_) {
 };
 
 
+exports.getServers = function() {
+  return cares.getServers();
+};
+
+
+exports.setServers = function(servers) {
+  // cache the original servers because in the event of an error setting the
+  // servers cares won't have any servers available for resolution
+  var orig = cares.getServers();
+
+  var newSet = [];
+
+  servers.forEach(function(serv) {
+    var ver = isIp(serv);
+
+    if (ver)
+      return newSet.push([ver, serv]);
+
+    var match = serv.match(/\[(.*)\](:\d+)?/);
+
+    // we have an IPv6 in brackets
+    if (match) {
+      ver = isIp(match[1]);
+      if (ver)
+        return newSet.push([ver, match[1]]);
+    }
+
+    var s = serv.split(/:\d+$/)[0];
+    ver = isIp(s);
+
+    if (ver)
+      return newSet.push([ver, s]);
+
+    throw new Error('IP address is not properly formatted: ' + serv);
+  });
+
+  var r = cares.setServers(newSet);
+
+  if (r) {
+    // reset the servers to the old servers, because ares probably unset them
+    cares.setServers(orig.join(','));
+
+    var err = cares.strerror(r);
+    throw new Error('c-ares failed to set servers: "' + err +
+                    '" [' + servers + ']');
+  }
+};
+
+
 // ERROR CODES
 exports.NODATA = 'ENODATA';
 exports.FORMERR = 'EFORMERR';