tree a2c5feec8a10025d9bc3850ae7b600b8c5bcc09c
parent 237e6a0d655df300b59b98b8a809f95bacb7206f
author Amaury Denoyelle <adenoyelle@haproxy.com> 1678184307 +0100
committer Amaury Denoyelle <adenoyelle@haproxy.com> 1678200718 +0100

BUG/MEDIUM: dns: ensure ring offset is properly reajusted to head

Since the below patch, ring offset calculation for readers has changed.
  commit d9c718863384e32307f65a9ce319dc362b73feb6
  MEDIUM: ring: make the offset relative to the head/tail instead of absolute

For readers, this requires to adjust their offsets to be relative to the
ring head each time read is resumed. Indeed, buffer head can change any
time a ring_write() is performed after older entries were purged.
This operation was not performed on the DNS code which causes the offset
to become invalid. In most cases, the following BUG_ON() was triggered :

  FATAL: bug condition "msg_len + ofs + cnt + 1 > b_data(buf)" matched
  at src/dns.c:522

Fix this by adjusting DNS reader offsets when entering
dns_session_io_handler() and dns_process_req().

This bug was reproduced by using a backend with 10 servers using SRV
record resolution on a single resolvers section. A BUG_ON() crash would
occur after less than 5 minutes of process execution.

This does not need to be backported as the above patch is not.

This should fix github issue #2068.