The dns_cache_flush() drops the old database and creates a new one, but
it forgets to pass the loop that runs the node pruning and cleaning
the rbtdb when flushing it next time. This causes the cleaning to skip
cleaning the parent nodes (with .down == NULL) leading to increased
memory usage over time until the database is unable to keep up and just
stays overmem all the time.
Reconstruct the variant of the prune_tree() parent cleaning to consider
all elibible parents in a single loop as we were doing before all the
changes that led to this commit.
Update code comments so that they more precisely describe what the
relevant bits of code actually do.
by default, QPDB is the database used by named and all tools and
unit tests. the old default of RBTDB can now be restored by using
"configure --with-zonedb=rbt --with-cachedb=rbt".
some tests have been fixed so they will work correctly with either
database.
CHANGES and release notes have been updated to reflect this change.
When running resolver benchmark pipeline, a crash occurred:
https://gitlab.isc.org/isc-projects/bind9-shotgun-ci/-/pipelines/163946
In the code we are doing a lookup, it fails (meaning there is no node
with lookup name), we create the node and insert it and it fails.
But dns_qp_insert can only return ISC_R_SUCCESS or ISC_R_EXISTS.
So it must have been inserted in between. This is a race condition bug.
The first lookup only requires a write lock and if the lookup failed
the lock gets upgraded to a write lock and we insert the missing data.
To fix the race condition bug, we need to do a lookup again after we
have upgraded the lock to make sure it wasn't inserted in the mean
time.
the dyndb test requires a mechanism to retrieve the name associated
with a database node, and since the database no longer uses RBT for
its underlying storage, dns_rbt_fullnamefromnode() doesn't work.
addressed this by adding dns_db_nodefullname() to the database API.
If the iterator is paused, the tree is unlocked and may change.
In an RBT tree it's always possible to resume iteration as long
as a valid node pointer was still held, but now that the underlying
database structure is a QP trie, the iterator needs to be initialized
based on the existing structure of the trie or it will return
inconsistent results. We now call dns_qp_lookup() to reinitialize
the QP iterator whenever dbiterator_next() or dbiterator_prev() is
called on a paused iterator.
QP database node data is not reference counted the same way RBT nodes
were: in the RBT, node->references could be zero if the node was in the
tree but was not in use by any caller, whereas in the QP trie, the
database itself uses reference counting of nodes internally.
this caused some subtle errors. in RBTDB, when the newref() function is
called and the node reference count was zero, the node lock reference
counter would also be incremented. in the QP trie, this can never
happen - because as long as the node is in the database its reference
count cannot be zero - and so the node lock reference counter was never
incremented.
reference counting will probably need to be refactored in more detail
later; the node lock reference count may not be needed at all. but
for now, as a temporary measure, we add a third reference counter,
'erefs' (external references), to the dns_qpdata structure. this is
counted separately from the main reference counter, and should match
the node reference count as it would have been in RBTDB.
this change revealed a number of places where the node reference counter
was being incremented on behalf of a caller without newref() being
called; those were cleaned up as well.
This is an adaptation of commit 3dd686261d2c4bcd15a96ebfea10baffa277732b
Fix reference counting: unreference nodes that are succesfully inserted
in the tree, detach created nodes, and cleanup the interior data in
dns_qpdata_destroy().
The name will be stored inside the node now so we can just copy it.
These are leftovers, most of the namefromnode code has been replaced
already in previous commits.
The qp approach pulled apart the chain and iterator into two separate
things. Replace the rbtnodechain with qpchain and qpiter. Most of the
times we are interested in the iterator only, the rbtnodechain was
mainly used as an an iterator to get the previous and next name in the
DNS canonical order.
Since dns_qpiter_prev() and dns_qpiter_next() store the name, origin,
and node in the provided parameters, often there is no need to call
a current() function anymore.
Getting the first or last item from the iterator is done by
re-initializing the iterator and then call dns_qpiter_next() or
dns_qpiter_prev() respectively.
The dbiterator no longer needs to maintain a chain, only an iterator.
All dns_qp_lookup() calls assume it is okay to find empty data, so
we don't need to do anything special for the DNS_RBTFIND_EMPTYDATA.
You can pass a callback function to dns_rbt_findnode(), something that
qp does not support. Instead, call the function afterwards. This has
the drawback that we do more lookup work if there was a zonecut.
With dns_qp_lookup() we also don't pass any options. In this case,
when DNS_RBTFIND_NOEXACT was set, we adapt the result after the lookup.
Replace dns_rbt_deletenode calls with dns_qp_deletename. For removing
the name from the nsec tree, we no longer first have to find it: we can
just remove the key (retrieved by name).
Replace dns_rbt_addnode calls with dns_qp_insert. With QP, it sometimes
makes more sense to first lookup the name and see if there is an
existing node (rather than create new data, insert, find out a node
already exists, and destroy the data again). This is done with
dns_qp_getname(), which is more lightweight than dns_qp_lookup(),
and we are only interested in if there is already a leaf node for this
name or not.
replace the string "rbt" throughout BIND with "qp" so that
qpdb databases will be used by default instead of rbtdb.
rbtdb databases can still be used by specifying "database rbt;"
in a zone statement.
- Copy rbtdb.c, rbt-zonedb.c and rbt-cachedb.c to qp-*.
- Added qpmethods.
- Added a new structure dns_qpdata that will replace dns_rbtnode.
- Replaced normal, nsec, and nsec3 dns_rbt trees with dns_qp tries.
- Replaced dns_rbt_create() calls with dns_qp_create().
- Replaced the dns_rbt_destroy() call with dns_qp_destroy().
- Create a dns_qpdata struct and create/destroy methods.
This commit will not build.
[GL #3709] reordered the dns_rdataset_disassociate call to after
the dns_resolver_createfetch call resulting in qctx->nsrrset still
being associated when dns_resolver_createfetch is called in
resume_dslookup (7e4e125e). Revert that part of the change and add
comments as to why the multiple dns_rdataset_disassociate calls are
where they are.
The TCP dispatch connected callbacks could be called synchronously which
in turn could destroy xfrin before we return from dns_xfrin_create().
Delay the calling the callback called from tcp_dispatch_connect() by
calling it always asynchronously.
Instead of getting the loop from the zone every time, attach the xfrin
directly to the loop. This also allows to remove the extra safety tid
checks from the dns_xfrin unit.
It was discovered that the TTL-based cleaning could build up
a significant backlog of the rdataset headers during the periods where
the top of the TTL heap isn't expired yet. Make the TTL-based cleaning
more aggressive by cleaning more headers from the heap when we are
adding new header into the RBTDB.
It was discovered that an expired header could sit on top of the heap
a little longer than desireable. Remove expired headers (headers with
rdh_ttl set to 0) from the heap completely, so they don't block the next
TTL-based cleaning.
Instead of juggling with node locks in a cycle, cleanup the node we are
just pruning and send any the parent that's also subject to the pruning
to the prune tree via normal way (e.g. enqueue pruning on the parent).
This simplifies the code and also spreads the pruning load across more
event loop ticks which is better for lock contention as less things run
in a tight loop.
The log message for commit 24381cc36d
explained:
In some older BIND 9 branches, the extra queuing overhead eliminated by
this change could be remotely exploited to cause excessive memory use.
Due to architectural shift, this branch is not vulnerable to that issue,
but applying the fix to the latter is nevertheless deemed prudent for
consistency and to make the code future-proof.
However, it turned out that having a single queue for the nodes to be
pruned increased lock contention to a level where cleaning up nodes from
the RBTDB took too long, causing the amount of memory used by the cache
to grow indefinitely over time.
This commit reverts the change to the pruning mechanism introduced by
commit 24381cc36d as BIND branches newer
than 9.16 were not affected by the excessive event queueing overhead
issue mentioned in the log message for the above commit.
dns__cacherbt_expireheader can unlink / free header_prev underneath
it. Use ISC_LIST_TAIL after calling dns__cacherbt_expireheader
instead to get the next pointer to be processed.
This commit ensures that worker threads are not sleeping (by using
select()) when '-T transferslowly/transferstuck' test options are
used. This commit converts synchronous implementation of the code into
an asynchronous one based on timers.
The resolver's code was not ready to failures when trying to establish
a connection via TCP-based transports (e.g. when creating TLS contexts
before establishing a TLS connection).
This commit fixes that.
The warnings (see below) seem to be false-positives. Address them
by adding runtime checks.
resolver.c:1627:10: warning: Access to field 'tid' results in a dereference of a null pointer (loaded from variable 'fctx') [core.NullDereference]
1627 | REQUIRE(fctx->tid == isc_tid());
| ^~~~~~~~~
../../lib/isc/include/isc/util.h:332:34: note: expanded from macro 'REQUIRE'
332 | #define REQUIRE(e) ISC_REQUIRE(e)
| ^
../../lib/isc/include/isc/assertions.h:45:11: note: expanded from macro 'ISC_REQUIRE'
45 | ((void)((cond) || \
| ^~~~
resolver.c:10335:6: warning: Access to field 'depth' results in a dereference of a null pointer (loaded from variable 'fctx') [core.NullDereference]
10335 | if (fctx->depth > depth) {
| ^~~~~~~~~~~
2 warnings generated.
- the DNS_DB_NSEC3ONLY and DNS_DB_NONSEC3 flags are mutually
exclusive; it never made sense to set both at the same time.
to enforce this, it is now a fatal error to do so. the
dbiterator implementation has been cleaned up to remove
code that treated the two as independent: if nonsec3 is
true, we can be certain nsec3only is false, and vice versa.
- previously, iterating a database backwards omitted
NSEC3 records even if DNS_DB_NONSEC3 had not been set. this
has been corrected.
- when an iterator reaches the origin node of the NSEC3 tree, we
need to skip over it and go to the next node in the sequence.
the NSEC3 origin node is there for housekeeping purposes and
never contains data.
- the dbiterator_test unit test has been expanded, several
incorrect expectations have been fixed. (for example, the
expected number of iterations has been reduced by one; we were
previously counting the NSEC3 origin node and we should not
have been doing so.)
- create_node() in rbt.c cannot fail
- the dns_rbt_*name() functions, which are wrappers around
dns_rbt_[add|find|delete]node(), were never used except in tests.
this change isn't really necessary since RBT is likely to go away
eventually anyway. but keeping the API as simple as possible while it
persists is a good thing, and may reduce confusion while QPDB is being
developed from RBTDB code.
these values pertain to whether a node is in the main, nsec, or nsec3
tree of an RBTDB. they need to be moved to a more generic location so
they can also be used by QPDB.
(this is in db.h rather than db_p.h because rbt.c needs access to it.
technically, that's a layer violation, but it's a long-existing one;
refactoring to get rid of it would be a large hassle, and eventually
we expect to remove rbt.c anyway.)
when the QPDB is implemented, we will need to have both qpdb_p.h and
rbtdb_p.h. in order to prevent name collisions or code duplication,
this commit adds a generic private header file, db_p.h, containing
structures and macros that will be used by both databases.
some functions and structs have been renamed to more specifically refer
to the RBT database, in order to avoid namespace collision with similar
things that will be needed by the QPDB later.
refactor the wildcard matching code to make it a bit easier to
understand, in hopes that it will reduce the difficulty of converting
from RBTDB to QPDB later.
there are also some minor optimizations: previously, after stepping
backward to find the predecessor, we stepped back foward *from* the
predecessor to find the successor. we now reset the rbtnode chain to
its original starting point before stepping forward; this eliminates
some unnecessary processing. and, if neither predecessor nor successor
is found, we return early rather than carrying on with an unnecessary
effort to match labels.
Coverity detected that address->type.sa was too small when copying
a struct sockaddr_sin6, use the alterative union element
address->type.sin6 instead.
