The dns_dispatchmgr object was only set in the dns_view object making it
prone to use-after-free in the dns_xfrin unit when shutting down named.
Remove dns_view_setdispatchmgr() and optionally pass the dispatchmgr
directly to dns_view_create() when it is attached and not just assigned,
so the dns_dispatchmgr doesn't cease to exist too early.
The dns_view_getdnsdispatchmgr() is now protected by the RCU lock, the
dispatchmgr reference is incremented, so the caller needs to detach from
it, and the function can return NULL in case the dns_view has been
already shut down.
Instead of an RBT for the forwarders table, use a QP trie.
We now use reference counting for dns_forwarders_t. When a forwarders
object is retrieved by dns_fwdtable_find(), it must now be explicitly
detached by the caller afterward.
QP tries require stored objects to include their names, so the
the forwarders object now has that. This obviates the need to
pass back a separate 'foundname' value from dns_fwdtable_find().
replace the red-black tree used by the negative trust anchor table
with a QP trie.
because of this change, dns_ntatable_init() can no longer fail, and
neither can dns_view_initntatable(). these functions have both been
changed to type void.
The dns_badcache unit had (yet another) own locked hashtable
implementation. Replace the hashtable used by dns_badcache with
lock-free cds_lfht implementation from liburcu.
When dns_request was canceled via dns_requestmgr_shutdown() the cancel
event would be propagated on different loop (loop 0) than the loop where
request was created on. In turn this would propagate down to isc_netmgr
where we require all the events to be called from the matching isc_loop.
Pin the dns_requests to the loops and ensure that all the events are
called on the associated loop. This in turn allows us to remove the
hashed locks on the requests and change the single .requests list to be
a per-loop list for the request accounting.
Additionally, do some extra cleanup because some race condititions are
now not possible as all events on the dns_request are serialized.
1. Change the _new, _add and _copy functions to return the new object
instead of returning 'void' (or always ISC_R_SUCCESS)
2. Cleanup the isc_ht_find() + isc_ht_add() usage - the code is always
locked with catzs->lock (mutex), so when isc_ht_find() returns
ISC_R_NOTFOUND, the isc_ht_add() must always succeed.
3. Instead of returning direct iterator for the catalog zone entries,
add dns_catz_zone_for_each_entry2() function that calls callback
for each catalog zone entry and passes two extra arguments to the
callback. This will allow changing the internal storage for the
catalog zone entries.
4. Cleanup the naming - dns_catz_<fn>_<obj> -> dns_catz_<obj>_<fn>, as an
example dns_catz_new_zone() gets renamed to dns_catz_zone_new().
view->adb may be referenced while the view is shutting down as the
zone uses a weak reference to the view and examines view->adb but
dns_view_detach call dns_adb_detach to clear view->adb.
since it is not necessary to find partial matches when looking
up names in a TSIG keyring, we can use a hash table instead of
an RBT to store them.
the tsigkey object now stores the key name as a dns_fixedname
rather than allocating memory for it.
the `name` parameter to dns_tsigkeyring_add() has been removed;
it was unneeded since the tsigkey object already contains a copy
of the name.
the opportunistic cleanup_ring() function has been removed;
it was only slowing down lookups.
- remove the 'ring' parameter from dns_tsigkey_createfromkey(),
and use dns_tsigkeyring_add() to add key objects to a keyring instead.
- add a magic number to dns_tsigkeyring_t
- change dns_tsigkeyring_dumpanddetach() to dns_tsigkeyring_dump();
we now call dns_tsigkeyring_detach() separately.
- remove 'maxgenerated' from dns_tsigkeyring_t since it never changes.
use the ISC_REFCOUNT attach/detach implementation in dns/tsig.c
so that detailed tracing can be used during refactoring.
dns_tsig_keyring_t has been renamed dns_tsigkeyring_t so the type
and the attach/detach function names will match.
- style cleanups.
- simplify the function parameters to dns_tsigkey_create():
+ remove 'restored' and 'generated', they're only ever set to false.
+ remove 'creator' because it's only ever set to NULL.
+ remove 'inception' and 'expiry' because they're only ever set to
(0, 0) or (now, now), and either way, this means "never expire".
+ remove 'ring' because we can just use dns_tsigkeyring_add() instead.
- rename dns_keyring_restore() to dns_tsigkeyring_restore() to match the
rest of the functions operating on dns_tsigkeyring objects.
dns_view_find* may be called after the final call to dns_view_detach
is made which detaches view->zonetable to permit the server to
shutdown. We need to detect if view->zonetable is NULL during this
stage and appropriately recover.
This change makes the zone table lock-free for reads. Previously, the
zone table used a red-black tree, which is not thread safe, so the hot
read path acquired both the per-view mutex and the per-zonetable
rwlock. (The double locking was to fix to cleanup races on shutdown.)
One visible difference is that zones are not necessarily shut down
promptly: it depends on when the qp-trie garbage collector cleans up
the zone table. The `catz` system test checks several times that zones
have been deleted; the test now checks for zones to be removed from
the server configuration, instead of being fully shut down. The catz
test does not churn through enough zones to trigger a gc, so the zones
are not fully detached until the server exits.
After this change, it is still possible to improve the way we handle
changes to the zone table, for instance, batching changes, or better
compaction heuristics.
This is a simple replacement using the semantic patch from the previous
commit and as added bonus, one removal of previously undetected unused
variable in named/server.c.
the new dns_view_addtrustedkey() function allows a view's trust
anchors to be updated directly. this code was formerly in
dns_client_addtrustedkey(), which is now a wrapper around
dns_view_addtrustedkey().
In !7538, the shutdown procedure was simplified, but the ordering was
wrong, we need to shutdown the resolver, adb and requestmgr before
detaching those objects from the view, because there are cross
dependencies between at least the resolver and the adb.
Execute the shutdown(s) first, only when all three shutdowns have been
executed, detach those objects from the view.
This change should make sure that catalog zone update processing
doesn't happen when the catalog zone is being shut down. This
should help avoid races when offloading the catalog zone updates
in the follow-up commit.
the 'dispatchmgr' member of the resolver object is used by both
the dns_resolver and dns_request modules, and may in the future
be used by others such as dns_xfrin. it doesn't make sense for it
to live in the resolver object; this commit moves it into dns_view.
as there is no further use of isc_task in BIND, this commit removes
it, along with isc_taskmgr, isc_event, and all other related types.
functions that accepted taskmgr as a parameter have been cleaned up.
as a result of this change, some functions can no longer fail, so
they've been changed to type void, and their callers have been
updated accordingly.
the tasks table has been removed from the statistics channel and
the stats version has been updated. dns_dyndbctx has been changed
to reference the loopmgr instead of taskmgr, and DNS_DYNDB_VERSION
has been udpated as well.
callback events from dns_resolver_createfetch() are now posted
using isc_async_run.
other modules which called the resolver and maintained task/taskmgr
objects for this purpose have been cleaned up.
dns_request_create() and _createraw() now take a 'loop' parameter
and run the callback event on the specified loop.
as the task manager is no longer used, it has been removed from
the dns_requestmgr structure. the dns_resolver_taskmgr() function
is also no longer used and has been removed.
This changes the internal isc_rwlock implementation to:
Irina Calciu, Dave Dice, Yossi Lev, Victor Luchangco, Virendra
J. Marathe, and Nir Shavit. 2013. NUMA-aware reader-writer locks.
SIGPLAN Not. 48, 8 (August 2013), 157–166.
DOI:https://doi.org/10.1145/2517327.24425
(The full article available from:
http://mcg.cs.tau.ac.il/papers/ppopp2013-rwlocks.pdf)
The implementation is based on the The Writer-Preference Lock (C-RW-WP)
variant (see the 3.4 section of the paper for the rationale).
The implemented algorithm has been modified for simplicity and for usage
patterns in rbtdb.c.
The changes compared to the original algorithm:
* We haven't implemented the cohort locks because that would require a
knowledge of NUMA nodes, instead a simple atomic_bool is used as
synchronization point for writer lock.
* The per-thread reader counters are not being used - this would
require the internal thread id (isc_tid_v) to be always initialized,
even in the utilities; the change has a slight performance penalty,
so we might revisit this change in the future. However, this change
also saves a lot of memory, because cache-line aligned counters were
used, so on 32-core machine, the rwlock would be 4096+ bytes big.
* The readers use a writer_barrier that will raise after a while when
readers lock can't be acquired to prevent readers starvation.
* Separate ingress and egress readers counters queues to reduce both
inter and intra-thread contention.
The dns_adb would serialize all fetches on a single task. Create a
per-thread task, so the fetches will stay local to the thread that
initiated the fetch.
The dns_rpz_zones structure was using .refs and .irefs for strong and
weak reference counting. Rewrite the unit to use just a single
reference counting + shutdown sequence (dns_rpz_destroy_rpzs) that must
be called by the creator of the dns_rpz_zones_t object. Remove the
reference counting from the dns_rpz_zone structure as it is not needed
because the zone objects are fully embedded into the dns_rpz_zones
structure and dns_rpz_zones_t object must never be destroyed before all
dns_rpz_zone_t objects.
The dns_rps_zones_t reference counting uses the new ISC_REFCOUNT_TRACE
capability - enable by defining DNS_RPZ_TRACE in the dns/rpz.h header.
Additionally, add magic numbers to the dns_rpz_zone and dns_rpz_zones
structures.
There were a number of places where the zone table should have been
locked, but wasn't, when dns_zt_apply was called.
Added a isc_rwlocktype_t type parameter to dns_zt_apply and adjusted
all calls to using it. Removed locks in callers.
The call to dns_view_flushcache() is done under exclusive mode, but we
still need to check if view->adb is still attached before calling
dns_adb_flush() because the shutdown might have been already
initialized. This most likely only a theoretical problem on shutdown
because there's either no way how to initiate cache flush when shutting
down or very slim window where the `rndc flush` would have to hit the
slim time during named shutdown.
When starting priming from dns_view_find(), the dns_view shutdown could
be initiated by different thread, detaching from the resolver. Use
dns_view_getresolver() to attach to the resolver under view->lock, so we
don't try to call dns_resolver_prime() with NULL pointer.
There are more accesses to view->resolver, (and also view->adb and
view->requestmgr that suffer from the same problem) in the dns_view
module, but they are all done in exclusive mode or under a view->lock.
Mostly generated automatically with the following semantic patch,
except where coccinelle was confused by #ifdef in lib/isc/net.c
@@ expression list args; @@
- UNEXPECTED_ERROR(__FILE__, __LINE__, args)
+ UNEXPECTED_ERROR(args)
@@ expression list args; @@
- FATAL_ERROR(__FILE__, __LINE__, args)
+ FATAL_ERROR(args)
Getting the recorded value of 'edns-udp-size' from the resolver requires
strong attach to the dns_view because we are accessing `view->resolver`.
This is not the case in places (f.e. dns_zone unit) where `.udpsize` is
accessed. By moving the .udpsize field from `struct dns_resolver` to
`struct dns_view`, we can access the value directly even with weakly
attached dns_view without the need to lock the view because `.udpsize`
can be accessed after the dns_view object has been shut down.
The dns_view implements weak and strong reference counting. When strong
reference counting reaches zero, the adb, ntatable and resolver objects
are shut down and detached.
In dns_zone and dns_nta the dns_view was weakly attached, but the
view->resolver reference was accessed directly leading to dereferencing
the NULL pointer.
Add dns_view_getresolver() method which attaches to view->resolver
object under the lock (if it still exists) ensuring the dns_resolver
will be kept referenced until not needed.
Previously:
* applications were using isc_app as the base unit for running the
application and signal handling.
* networking was handled in the netmgr layer, which would start a
number of threads, each with a uv_loop event loop.
* task/event handling was done in the isc_task unit, which used
netmgr event loops to run the isc_event calls.
In this refactoring:
* the network manager now uses isc_loop instead of maintaining its
own worker threads and event loops.
* the taskmgr that manages isc_task instances now also uses isc_loopmgr,
and every isc_task runs on a specific isc_loop bound to the specific
thread.
* applications have been updated as necessary to use the new API.
* new ISC_LOOP_TEST macros have been added to enable unit tests to
run isc_loop event loops. unit tests have been updated to use this
where needed.
* isc_timer was rewritten using the uv_timer, and isc_timermgr_t was
completely removed; isc_timer objects are now directly created on the
isc_loop event loops.
* the isc_timer API has been simplified. the "inactive" timer type has
been removed; timers are now stopped by calling isc_timer_stop()
instead of resetting to inactive.
* isc_manager now creates a loop manager rather than a timer manager.
* modules and applications using isc_timer have been updated to use the
new API.
