Merge pull request #17 from pusateri/rcode

Add support for RCODE and other header flag decoding.

index.js

@@ -1,4 +1,6 @@
 var types = require('./types')
+var rcodes = require('./rcodes')
+var opcodes = require('./opcodes')
 var ip = require('ip')
 var Buffer = require('safe-buffer').Buffer
 
@@ -126,6 +128,16 @@ header.decode = function (buf, offset) {
     id: buf.readUInt16BE(offset),
     type: flags & RESPONSE_FLAG ? 'response' : 'query',
     flags: flags & 32767,
+    flag_qr: ((flags >> 15) & 0x1) === 1,
+    opcode: opcodes.toString((flags >> 11) & 0xf),
+    flag_auth: ((flags >> 10) & 0x1) === 1,
+    flag_trunc: ((flags >> 9) & 0x1) === 1,
+    flag_rd: ((flags >> 8) & 0x1) === 1,
+    flag_ra: ((flags >> 7) & 0x1) === 1,
+    flag_z: ((flags >> 6) & 0x1) === 1,
+    flag_ad: ((flags >> 5) & 0x1) === 1,
+    flag_cd: ((flags >> 4) & 0x1) === 1,
+    rcode: rcodes.toString(flags & 0xf),
     questions: new Array(buf.readUInt16BE(offset + 4)),
     answers: new Array(buf.readUInt16BE(offset + 6)),
     authorities: new Array(buf.readUInt16BE(offset + 8)),

opcodes.js

@@ -0,0 +1,48 @@
+/*
+ * Traditional DNS header OPCODEs (4-bits) defined by IANA in
+ * https://www.iana.org/assignments/dns-parameters/dns-parameters.xhtml#dns-parameters-5
+ */
+
+exports.toString = function (opcode) {
+  switch (opcode) {
+    case 0: return 'QUERY'
+    case 1: return 'IQUERY'
+    case 2: return 'STATUS'
+    case 3: return 'OPCODE_3'
+    case 4: return 'NOTIFY'
+    case 5: return 'UPDATE'
+    case 6: return 'OPCODE_6'
+    case 7: return 'OPCODE_7'
+    case 8: return 'OPCODE_8'
+    case 9: return 'OPCODE_9'
+    case 10: return 'OPCODE_10'
+    case 11: return 'OPCODE_11'
+    case 12: return 'OPCODE_12'
+    case 13: return 'OPCODE_13'
+    case 14: return 'OPCODE_14'
+    case 15: return 'OPCODE_15'
+  }
+  return 'OPCODE_' + opcode
+}
+
+exports.toOpcode = function (code) {
+  switch (code.toUpperCase()) {
+    case 'QUERY': return 0
+    case 'IQUERY': return 1
+    case 'STATUS': return 2
+    case 'OPCODE_3': return 3
+    case 'NOTIFY': return 4
+    case 'UPDATE': return 5
+    case 'OPCODE_6': return 6
+    case 'OPCODE_7': return 7
+    case 'OPCODE_8': return 8
+    case 'OPCODE_9': return 9
+    case 'OPCODE_10': return 10
+    case 'OPCODE_11': return 11
+    case 'OPCODE_12': return 12
+    case 'OPCODE_13': return 13
+    case 'OPCODE_14': return 14
+    case 'OPCODE_15': return 15
+  }
+  return 0
+}

package.json

@@ -32,7 +32,9 @@
   ],
   "files": [
     "index.js",
-    "types.js"
+    "types.js",
+    "rcodes.js",
+    "opcodes.js"
   ],
   "author": "Mathias Buus",
   "license": "MIT"

rcodes.js

@@ -0,0 +1,48 @@
+/*
+ * Traditional DNS header RCODEs (4-bits) defined by IANA in
+ * https://www.iana.org/assignments/dns-parameters/dns-parameters.xhtml
+ */
+
+exports.toString = function (rcode) {
+  switch (rcode) {
+    case 0: return 'NOERROR'
+    case 1: return 'FORMERR'
+    case 2: return 'SERVFAIL'
+    case 3: return 'NXDOMAIN'
+    case 4: return 'NOTIMP'
+    case 5: return 'REFUSED'
+    case 6: return 'YXDOMAIN'
+    case 7: return 'YXRRSET'
+    case 8: return 'NXRRSET'
+    case 9: return 'NOTAUTH'
+    case 10: return 'NOTZONE'
+    case 11: return 'RCODE_11'
+    case 12: return 'RCODE_12'
+    case 13: return 'RCODE_13'
+    case 14: return 'RCODE_14'
+    case 15: return 'RCODE_15'
+  }
+  return 'RCODE_' + rcode
+}
+
+exports.toRcode = function (code) {
+  switch (code.toUpperCase()) {
+    case 'NOERROR': return 0
+    case 'FORMERR': return 1
+    case 'SERVFAIL': return 2
+    case 'NXDOMAIN': return 3
+    case 'NOTIMP': return 4
+    case 'REFUSED': return 5
+    case 'YXDOMAIN': return 6
+    case 'YXRRSET': return 7
+    case 'NXRRSET': return 8
+    case 'NOTAUTH': return 9
+    case 'NOTZONE': return 10
+    case 'RCODE_11': return 11
+    case 'RCODE_12': return 12
+    case 'RCODE_13': return 13
+    case 'RCODE_14': return 14
+    case 'RCODE_15': return 15
+  }
+  return 0
+}

test.js

@@ -1,5 +1,7 @@
 var tape = require('tape')
 var packet = require('./')
+var rcodes = require('./rcodes')
+var opcodes = require('./opcodes')
 var Buffer = require('safe-buffer').Buffer
 
 tape('unknown', function (t) {
@@ -173,6 +175,44 @@ tape('response', function (t) {
   t.end()
 })
 
+tape('rcode', function (t) {
+  const errors = ['NOERROR', 'FORMERR', 'SERVFAIL', 'NXDOMAIN', 'NOTIMP', 'REFUSED', 'YXDOMAIN', 'YXRRSET', 'NXRRSET', 'NOTAUTH', 'NOTZONE', 'RCODE_11', 'RCODE_12', 'RCODE_13', 'RCODE_14', 'RCODE_15']
+  for (var i in errors) {
+    var code = rcodes.toRcode(errors[i])
+    t.ok(errors[i] === rcodes.toString(code), 'rcode conversion from/to string matches: ' + rcodes.toString(code))
+  }
+
+  const ops = ['QUERY', 'IQUERY', 'STATUS', 'OPCODE_3', 'NOTIFY', 'UPDATE', 'OPCODE_6', 'OPCODE_7', 'OPCODE_8', 'OPCODE_9', 'OPCODE_10', 'OPCODE_11', 'OPCODE_12', 'OPCODE_13', 'OPCODE_14', 'OPCODE_15']
+  for (i in ops) {
+    code = opcodes.toOpcode(ops[i])
+    t.ok(ops[i] === opcodes.toString(code), 'opcode conversion from/to string matches: ' + opcodes.toString(code))
+  }
+
+  var buf = packet.encode({
+    type: 'response',
+    id: 45632,
+    flags: 0x8480,
+    answers: [{
+      type: 'A',
+      name: 'hello.example.net',
+      data: '127.0.0.1'
+    }]
+  })
+  var val = packet.decode(buf)
+  t.ok(val.type === 'response', 'decode type')
+  t.ok(val.opcode === 'QUERY', 'decode opcode')
+  t.ok(val.flag_qr === true, 'decode flag_auth')
+  t.ok(val.flag_auth === true, 'decode flag_auth')
+  t.ok(val.flag_trunc === false, 'decode flag_trunc')
+  t.ok(val.flag_rd === false, 'decode flag_rd')
+  t.ok(val.flag_ra === true, 'decode flag_ra')
+  t.ok(val.flag_z === false, 'decode flag_z')
+  t.ok(val.flag_ad === false, 'decode flag_ad')
+  t.ok(val.flag_cd === false, 'decode flag_cd')
+  t.ok(val.rcode === 'NOERROR', 'decode rcode')
+  t.end()
+})
+
 function testEncoder (t, packet, val) {
   var buf = packet.encode(val)
   var val2 = packet.decode(buf)