From 27ddd5f1bfd812d3a1e89a06056805d21de38e1e Mon Sep 17 00:00:00 2001
From: Drew Warren <drew.warren@daplie.com>
Date: Fri, 17 Feb 2017 15:37:07 -0700
Subject: [PATCH] Add MX Test

---
 dns.packer.type.cname.js  |  2 +-
 dns.packer.type.mx.js     | 41 +++++++++++++++++++++++++++++++++++++++
 test/packer.type.cname.js |  2 +-
 test/packer.type.mx.js    | 21 ++++++++++++++++++++
 4 files changed, 64 insertions(+), 2 deletions(-)
 create mode 100644 dns.packer.type.mx.js
 create mode 100644 test/packer.type.mx.js

diff --git a/dns.packer.type.cname.js b/dns.packer.type.cname.js
index 70cd22c..3ca92fe 100644
--- a/dns.packer.type.cname.js
+++ b/dns.packer.type.cname.js
@@ -13,7 +13,7 @@ exports.DNS_PACKER_TYPE_CNAME = function (ab, dv, total, record) {
   total += 2;
 
   // RDATA
-  // i.e. 127.0.0.1 => 0x7F, 0x00, 0x00, 0x01
+  // a sequence of labels
   record.data.split('.').forEach(function (label) {
     cnameLen += 1 + label.length;
     
diff --git a/dns.packer.type.mx.js b/dns.packer.type.mx.js
new file mode 100644
index 0000000..910e47c
--- /dev/null
+++ b/dns.packer.type.mx.js
@@ -0,0 +1,41 @@
+(function (exports) {
+'use strict';
+
+// An 'MX' record is a 32-bit value representing the IP address
+
+exports.DNS_PACKER_TYPE_MX = function (ab, dv, total, record) {
+  if (!record.exchange) {
+    throw new Error("no exchange for MX record");
+  }
+  if (!record.priority) {
+    // TODO: Check that number is in range 1-64k
+    throw new Error("no priority for MX record");
+  }
+
+  var mxLen = 2; // 16-bit priority plus label sequence
+  var rdLenIndex = total;
+  total += 2; // The space for RDLENGTH is reserved now and set below
+  dv.setUint16(total, parseInt(record.priority, 10), false);
+  total += 2;
+
+  // RDATA
+  // 16-bit priority and a sequence of labels as the exchange
+  record.exchange.split('.').forEach(function (label) {
+    mxLen += 1 + label.length;
+    
+    dv.setUint8(total, label.length, false);
+    total += 1;
+
+    label.split('').forEach(function (ch) {
+      dv.setUint8(total, ch.charCodeAt(0), false);
+      total += 1;
+    });
+  });
+
+  // RDLENGTH
+  dv.setUint16(rdLenIndex, mxLen, false);
+  
+  return total;
+};
+
+}('undefined' !== typeof window ? window : exports));
diff --git a/test/packer.type.cname.js b/test/packer.type.cname.js
index d18d8ee..c69355f 100644
--- a/test/packer.type.cname.js
+++ b/test/packer.type.cname.js
@@ -1,7 +1,7 @@
 'use strict';
 
 var packer = require('../dns.packer.type.cname.js').DNS_PACKER_TYPE_CNAME;
-var ab = new ArrayBuffer(255); // max len per label is 63, max label sequence is 254 + null terminator
+var ab = new ArrayBuffer(254); // max len per label is 63, max label sequence is 254
 var dv = new DataView(ab);
 var total = 0;
 
diff --git a/test/packer.type.mx.js b/test/packer.type.mx.js
new file mode 100644
index 0000000..34ee983
--- /dev/null
+++ b/test/packer.type.mx.js
@@ -0,0 +1,21 @@
+'use strict';
+
+var packer = require('../dns.packer.type.mx.js').DNS_PACKER_TYPE_MX;
+var ab = new ArrayBuffer(256); // priority + max len per label is 63, max label sequence is 254
+var dv = new DataView(ab);
+var total = 0;
+
+[ [ '10:www.example.com'
+  , [ 0x00, 0x12, 0x00, 0x0A, 0x03, 119, 119, 119, 0x07, 101, 120, 97, 109, 112, 108, 101, 0x03, 99, 111, 109 ].join(' ') ]
+].forEach(function (mx) {
+  total = packer(ab, dv, total, { priority: mx[0].split(':')[0], exchange: mx[0].split(':')[1] });
+  ab = ab.slice(0, total);
+  // TODO: Check that total increments appropriately
+  if (mx[1] !== new Uint8Array(ab).join(' ')) {
+    console.error("expected: ", mx[1]);
+    console.error("actual: ", new Uint8Array(ab).join(' '));
+    process.exit(1);
+  }
+});
+
+console.log('PASS');