The hash table rework MRs (!3865, !3871) increased the default RBT hash
table size from 64 to 65,536 entries (for 64-bit architectures, that is
512 bytes before vs. 524,288 bytes after). This works fine for RBTs
used for cache databases, but since three separate RBT databases are
created for every zone loaded (RRs, NSEC, NSEC3), memory usage would
skyrocket when BIND 9 is used as an authoritative DNS server with many
zones.
The default RBT hash table size before the rework was 64 entries, this
commit reduces it to 16 entries because our educated guess is that most
zones are just couple of entries (SOA, NS, A, AAAA, MX) and rehashing
small hash tables is actually cheap. The rework we did in the previous
MRs tries to avoid growing the hash tables for big-to-huge caches where
growing the hash table comes at a price because the whole cache needs to
be locked.
(cherry picked from commit 1e043a011b)
When pk11_numbits() is passed a user provided input that contains all
zeroes (via crafted DNS message), it would crash with assertion
failure. Fix that by properly handling such input.
QNAME minimization is normally disabled when forwarding. if, in the
course of processing a fetch, we switch back to normal recursion at
some point, we can't safely start minimizing because we may have
been left in an inconsistent state.
Each worker has a receive buffer with space for 20 DNS messages of up
to 2^16 bytes each, and the allocator function passed to uv_read_start()
or uv_udp_recv_start() will reserve a portion of it for use by sockets.
UDP can use recvmmsg() and so it needs that entire space, but TCP reads
one message at a time.
This commit introduces separate allocator functions for TCP and UDP
setting different buffer size limits, so that libuv will provide the
correct buffer sizes to each of them.
The only arm64 runner we have at our disposal is suffering from
intermittent connectivity issues which make it unusable for extended
periods of time. Remove arm64 jobs from GitLab CI until we manage to
set up an arm64 runner with more reliable connectivity.
The named configuration files used in the "geoip2" system test cause a
rather large number of views (6-8) to be set up in each tested named
instance. Each view has its own cache.
Commit e24bc324b4 caused the RBT hash
table to be pre-allocated to a size derived from "max-cache-size", so
that it never needs to be rehashed. The size of that hash table is not
expected to be significant enough to cause memory use issues in typical
conditions even for large "max-cache-size" settings.
However, these two factors combined can cause memory exhaustion issues
in GitLab CI, where we run multiple "instances" of the test suite in
parallel on the same runner, each test suite executes multiple system
tests concurrently, and each system test may potentially start multiple
named instances at the same time. In practice, this problem currently
only seems to be affecting the "geoip2" system test, which is failing
intermittently due to named instances used by that test getting killed
by oom-killer.
Prevent the "geoip2" system test from failing intermittently by setting
"max-cache-size" in named configuration files used in that test to a low
value in order to keep memory usage at bay even with a large number of
views configured.
Resolve "BIND ARM incorrectly documents the processing of forwarders (still has the pre 9.3.0 explanation)"
Closes#2030
See merge request isc-projects/bind9!3881
Now that the log message has been printed set the result code to
DNS_R_FORMERR. We don't do this via dns_result_torcode() as we
don't want upstream errors to produce FORMERR if that processing
end with DNS_R_BADTSIG.
When a received RRSet has TTL 0, they would be preserved for
serve-stale (default `max-stale-cache` is 12 hours) rather than expiring
them quickly from the cache database.
This commit makes sure the RRSet didn't have TTL 0 before marking the
entry in the database as "stale".
The current serve-stale implementation in BIND 9 stores all received
records in the cache for a max-stale-ttl interval (default 12 hours).
This allows DNS operators to turn the serve-stale answers in an event of
large authoritative DNS outage. The caching of the stale answers needs
to be enabled before the outage happens or the feature would be
otherwise useless.
The negative consequence of the default setting is the inevitable
cache-bloat that happens for every and each DNS operator running named.
In this MR, a new configuration option `stale-cache-enable` is
introduced that allows the operators to selectively enable or disable
the serve-stale feature of BIND 9 based on their decision.
The newly introduced option has been disabled by default,
e.g. serve-stale is disabled in the default configuration and has to be
enabled if required.
