[Bug 1804487] [NEW] systemd-resolved has issues when the answer is over 512 bytes with EDNS disabled

[Victor Tapia]

Public bug reported:

Querying a domain name that has >512 bytes in records (e.g. 30+ A
records), the number of results depends on the DNS client used:

- If the client supports EDNS:

$ dig +noall +answer testing.irongiantdesign.com @127.0.0.53 | wc -l
30 

- If the client does not support EDNS:

$ dig +noedns +noall +answer testing.irongiantdesign.com @127.0.0.53 | wc -l
29

Normally a client that doesn't support EDNS would receive a truncated
reply from the initial UDP connection (limited by the spec to 512 bytes)
and a second query would be established via TCP to receive the complete
results. In this case, the number of results is the same regardless of
the protocol used (29).

Upstream bug: https://github.com/systemd/systemd/issues/10816

** Affects: systemd (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: sts

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Title:
  systemd-resolved has issues when the answer is over 512 bytes with
  EDNS disabled

Status in systemd package in Ubuntu:
  New

Bug description:
  Querying a domain name that has >512 bytes in records (e.g. 30+ A
  records), the number of results depends on the DNS client used:

  - If the client supports EDNS:

  $ dig +noall +answer testing.irongiantdesign.com @127.0.0.53 | wc -l
  30 

  - If the client does not support EDNS:

  $ dig +noedns +noall +answer testing.irongiantdesign.com @127.0.0.53 | wc -l
  29

  Normally a client that doesn't support EDNS would receive a truncated
  reply from the initial UDP connection (limited by the spec to 512
  bytes) and a second query would be established via TCP to receive the
  complete results. In this case, the number of results is the same
  regardless of the protocol used (29).

  Upstream bug: https://github.com/systemd/systemd/issues/10816

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