log rolling limitations

Summary

Log file and dnstap output file rotation is behaving counterintuitively in corner cases. The examples demonstrate behavior with dnstap but logging behavior is the same.

BIND version used

• Affects v9.19: b171cacf
• Affects v9.18: ad6990f0 (not tested, but I believe it ;-))
• Affects v9.16: 5c68a45a

Steps to reproduce

• Build named with dnstap support:

./configure --enable-dnstap

• named.conf:

options {
	dnstap { all query; };
	dnstap-output file "/tmp/test.dnstap" size 1m versions 3 suffix timestamp;
};

Alternative config which demonstrates the same problems with logging:

logging {
      channel an_example_channel {
          file "/tmp/example.log" versions 1 size 1k suffix timestamp;
          print-time yes;
          print-category yes;
	 severity debug 99;
      };
      category default { an_example_channel; };
};

What is the current and expected current behavior?

• rndc dnstap -roll 1 / log file ... versions 1 size 1k suffix timestamp

  • Rolling does not remove old files if filename in named.conf contains a path (e.g. /tmp/) - affects only suffix timestamp variant. All historical files are kept around.

• rndc dnstap -roll 1 / log file ... versions 1 size 1k suffix increment

  • Currently: Does not remove "extra" versions, i.e. versions beyond 0 if they already exist.
  • Expected: Removes older files like .1, .2, etc.

• rndc dnstap -roll 0

  • Currently: Creates new backup files up to versions defined in named.conf
  • Expected: Does not create backup file, just truncates the existing one.

Relevant logs

rm -f /tmp/example.log*

named -f -c named.conf

ls -1 /tmp/example.com*
/tmp/example.log
/tmp/example.log.20230405130407683
/tmp/example.log.20230405130407687
/tmp/example.log.20230405130407690
/tmp/example.log.20230405130407730
/tmp/example.log.20230405130407733