LittleChest/dns-packet-polyfill
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Implement QU bit support in question encoder/decoder

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This commit fix current QU bit implementation that may be used in mDNS
protocol. Indeed, until now, if a packet with QU bit set is received,
it is decoded as:

{

  ...

  questions: [
    {
      name: '...',
      type: 'PTR',
      class: 'UNKNOWN_32769'
    },
    {
      name: '...',
      type: 'PTR',
      class: 'UNKNOWN_32769'
    }
  ],

  ...

}

Instead of :

{

  ...

  questions: [
    {
      name: '...',
      type: 'PTR',
      class: 'IN'
    },
    {
      name: '...',
      type: 'PTR',
      class: 'IN'
    }
  ],

  ...

}

This commit adds a proper QU bit support via the qu_bit field.
It enables:

- The encoder to parse properly both the class and the QU bit
- THe decoder to encode a DNS packet with the QU bit set
This commit is contained in:
vulcainman 2023-10-09 17:07:30 +02:00 committed by LittleChest
parent 5b155e76d9
commit dfe5e3f86b
1 changed files with 3 additions and 5 deletions
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8
index.js
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@ -1600,7 +1600,7 @@ question.encode = function (q, buf, offset) {
buf.writeUInt16BE(types.toType(q.type), offset)
offset += 2
buf.writeUInt16BE(classes.toClass(q.class === undefined ? 'IN' : q.class), offset)
buf.writeUInt16BE(((q.qu_bit === undefined || !q.qu_bit) ? 0 : QU_MASK) | classes.toClass(q.class === undefined ? 'IN' : q.class), offset)
offset += 2
question.encode.bytes = offset - oldOffset
@ -1621,12 +1621,10 @@ question.decode = function (buf, offset) {
q.type = types.toString(buf.readUInt16BE(offset))
offset += 2
q.class = classes.toString(buf.readUInt16BE(offset))
q.qu_bit = (buf.readUInt16BE(offset) & QU_MASK) != 0;
q.class = q.qu_bit ? classes.toString(buf.readUInt16BE(offset) - QU_MASK) : classes.toString(buf.readUInt16BE(offset));
offset += 2
const qu = !!(q.class & QU_MASK)
if (qu) q.class &= NOT_QU_MASK
question.decode.bytes = offset - oldOffset
return q
}