there were TSAN error reports because of conflicting uses of
node->dirty and node->nsec, which were in the same qword.
this could be resolved by separating them, but we could also
make them into atomic values and remove some node locking.
there were some structure names used in qpcache.c and qpzone.c that
were too similar to each other and could be confusing when debugging.
they have been changed as follows:
in qcache.c:
- changed_t was unused, and has been removed
- search_t -> qpc_search_t
- qpdb_rdatasetiter_t -> qpc_rditer_t
- qpdb_dbiterator_t -> qpc_dbiter_t
in qpzone.c:
- qpdb_changed_t -> qpz_changed_t
- qpdb_changedlist_t -> qpz_changedlist_t
- qpdb_version_t -> qpz_version_t
- qpdb_versionlist_t -> qpz_versionlist_t
- qpdb_search_t -> qpz_search_t
- qpdb_load_t -> qpz_search_t
when calling dns_qp_lookup() from qpcache, instead of passing
'foundname' so that a name would be constructed from the QP key,
we now just use the name field in the node data. this makes
dns_qp_lookup() run faster.
the same optimization has also been added to qpzone.
the documentation for dns_qp_lookup() has been updated to
discuss this performance consideration.
- remove unneeded struct members and misleading comments.
- remove unused parameters for static functions.
- rename 'find_callback' to 'delegating' for consistency with qpzone;
the find callback mechanism is not used in QP databases.
- change dns_qpdata_t to qpcnode_t (QP cache node), and dns_qpdb_t to
qpcache_t, as these types are only accessed locally.
- also change qpdata_t in qpzone.c to qpznode_t (QP zone node), for
consistency.
- make the refcount declarations for qpcnode_t and qpznode_t static,
using the new ISC_REFCOUNT_STATIC macros.
the previous commit introduced a possible race in getsigningtime()
where the rdataset header could change between being found on the
heap and being bound.
getsigningtime() now looks at the first element of the heap, gathers the
locknum, locks the respective lock, and retrieves the header from the
heap again. If the locknum has changed, it will rinse and repeat.
Theoretically, this could spin forever, but practically, it almost never
will as the heap changes on the zone are very rare.
we simplify matters further by changing the dns_db_getsigningtime()
API call. instead of passing back a bound rdataset, we pass back the
information the caller actually needed: the resigning time, owner name
and type of the rdataset that was first on the heap.
in RBTDB, the heap was used by zone databases for resigning, and
by the cache for TTL-based cache cleaning. the cache use case required
very frequent updates, so there was a separate heap for each of the
node lock buckets.
qpzone is for zones only, so it doesn't need to support the cache
use case; the heap will only be touched when the zone is updated or
incrementally signed. we can simplify the code by using only a single
heap.
an assertion could be triggered in the QPDB cache if a DNAME
was found above a queried NS, because the 'foundname' value was
not correctly updated to point to the zone cut.
the same mistake existed in qpzone and has been fixed there as well.
every node of a QP database contains a copy of the nodename,
which is used as the key for the QP-trie. previously, the name
was stored as a dns_fixedname object, which has room for up to
255 characters. we can reduce the space consumed by dynamically
allocating a dns_name object that's just long enough for the name
to be stored.
The dns_qpiter_next() was called without checking the return value. If
we cannot move the iterator forward, there is no use in calling the
step() function.
/lib/dns/qpzone.c: 2804 in activeempty()
2798 * of the name we were searching for. Step the iterator
2799 * forward, then step() will continue forward until it
2800 * finds a node with active data. If that node is a
2801 * subdomain of the one we were looking for, then we're
2802 * at an active empty nonterminal node.
2803 */
>>> CID 487882: Error handling issues (CHECKED_RETURN)
>>> Calling "dns_qpiter_next" without checking return value (as is done elsewhere 26 out of 27 times).
2804 dns_qpiter_next(it, NULL, NULL, NULL);
2805 return (step(search, it, FORWARD, next) &&
2806 dns_name_issubdomain(next, current));
2807 }
qpzone does not support cache semantics, so dns_db_addrdataset(),
_deleterdataset() and _subtractrdataset() can't be run with
version == NULL; there's no need to check for it.
we can also clean up free_qpdb() a bit since current_version
is always non-NULL.
because dns_qpmulti_commit() can be time consuming, it's inefficient
to open and commit a qpmulti transaction for each rdataset being loaded
into a database. we can improve load time by opening a qpmulti
transaction before adding a group of rdatasets and then committing it
afterward.
this commit adds 'setup' and 'commit' functions to dns_rdatacallbacks_t,
which can be called before and after the loops in which 'add' is
called in dns_master_load() and axfr_apply().
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.
this has been addressed by maintaining a separate "erefs" counter for
external references to the node. this is the same approach used in the
"qpdb-lite" database in commit e91fbd8dea.
while troubleshooting this issue, some compile errors were discovered
when building with DNS_DB_NODETRACE; those have also been fixed.
finish importing the database API methods from RBTDB to qpzone:
issecure, nodecount, getnsec3parameters, findnsec3node, setsigningtime,
getsigningtime, getsize, setgluecachestats, locknode, unlocknode, and
addglue.
add database API methods needed to apply updates to an existing zone
database (newversion, addrdataset, subtractrdataset and deleterdataset).
it is now possible to apply journals to zone databases after loading, so
named-checkzone -J works correctly.
add database API method implementations needed to iterate and dump
a qpzone database to a file (createiterator, allrdatasets and
attachversion, plus dbiterator and rdatasetiter methods).
named-checkzone -D can now dump the contents of most zones,
but zone cuts are not correctly detected.
add database API methods needed for loading rdatasets into memory
(currentversion, beginload, endload), plus the methods used by
zone_postload() for zone consistency checks (getoriginnode, find,
findnode, findrdataset, attachnode, detachnode, deletedata).
the QP trie doesn't support the find callback mechanism available
in dns_rbt_findnode() which allows examination of intermediate nodes
while searching, so the detection of wildcard and delegation nodes
is now done by scanning QP chains after calling dns_qp_lookup().
Note that the lookup in previous_closest_nsec() cannot return
ISC_R_NOTFOUND. In RBTDB, we checked for this return value and
ovewrote the result with ISC_R_NOMORE if it occurred. In the
qpzone implementation, we insist that this return value cannot happen.
dns_qp_lookup() would only return ISC_R_NOTFOUND if we asked for a
name outside the zone's authoritative domain, and we never do that
when looking up a predecessor NSEC record.
named-checkzone is now able to load a zone and check it for errors,
but cannot dump it.
