youtubebeat/vendor/github.com/elastic/beats/packetbeat/protos/dns/README.md

UDP

Parsing

1. Attempt to decode each UDP packet.
2. If it succeeds, a transaction is sent.

Error management

• Debug information is printed if:

  • A packet fails to decode.

• Error Notes are published if:

  • Never

TCP

Parsing

1. Fetch the first two bytes of a message containing the length of the message (RFC 1035).
2. Fill the buffer DnsStream.rawData with each new Parse.
3. Once the buffer has the expected length (first two bytes), it is decoded and the message is published.

Error management

• Debug information is printed if:

  • A message has an unexpected length at any point of the transmission (Parse, GapInStream, ReceivedFin).
  • A message fails to decode.

• Error Notes are published if:

  • A response following a request (dnsConnectionData.prevRequest) fails to decode.
  • A response following a request (dnsConnectionData.prevRequest) has an unexpected length at any point of the transmission (Parse, GapInStream, ReceivedFin).

When response error Notes are linked to the previous request, the transaction is then published and removed from the cache (see publishResponseError()).

TODO

General

• Publish an event with Notes when a Query or a lone Response cannot be decoded.
• Consider adding ICMP support to
  • correlate ICMP type 3, code 4 (datagram too big) with DNS messages,
  • correlate ICMP type 3, code 13 (administratively prohibited) or ICMP type 3, code 3 (port unreachable) with blocked DNS messages.