The assembly code generated by MSVC for at least some signed comparisons
involving atomic variables incorrectly uses unsigned conditional jumps
instead of signed ones. In particular, the checks in isc_log_wouldlog()
are affected in a way which breaks logging on Windows and thus also all
system tests involving a named instance. Work around the issue by
assigning the values returned by atomic_load_acquire() calls in
isc_log_wouldlog() to local variables before performing comparisons.
(cherry picked from commit 4c4f5cccaa)
tcpdns used transport-specific functions to operate on the outer socket.
Use generic ones instead, and select the proper call in netmgr.c.
Make the missing functions (e.g. isc_nm_read) generic and add type-specific
calls (isc__nm_tcp_read). This is the preparation for netmgr TLS layer.
(cherry picked from commit 5fedd21e16)
The rwlock introduced to protect the .logconfig member of isc_log_t
structure caused a significant performance drop because of the rwlock
contention. It was also found, that the debug_level member of said
structure was not protected from concurrent read/writes.
The .dynamic and .highest_level members of isc_logconfig_t structure
were actually just cached values pulled from the assigned channels.
We introduced an even higher cache level for .dynamic and .highest_level
members directly into the isc_log_t structure, so we don't have to
access the .logconfig member in the isc_log_wouldlog() function.
(cherry picked from commit 3a24eacbb6)
We could have a race between handle closing and processing async
callback. Deactivate the handle before issuing the callback - we
have the socket referenced anyway so it's not a problem.
We introduce a isc_quota_attach_cb function - if ISC_R_QUOTA is returned
at the time the function is called, then a callback will be called when
there's quota available (with quota already attached). The callbacks are
organized as a LIFO queue in the quota structure.
It's needed for TCP client quota - with old networking code we had one
single place where tcp clients quota was processed so we could resume
accepting when the we had spare slots, but it's gone with netmgr - now
we need to notify the listener/accepter that there's quota available so
that it can resume accepting.
Remove unused isc_quota_force() function.
The isc_quote_reserve and isc_quota_release were used only internally
from the quota.c and the tests. We should not expose API we are not
using.
(cherry picked from commit d151a10f30)
Updated version and CHANGES files with new release number.
Check the API files:
- lib/bind9/api:
Source code changes, but no interface changes: increment
LIBREVISION.
- lib/dns/api:
Function dns_acl_match changed, struct dns_badcache changed,
function dns_badcache_add changed, function dns_clent_startupdate
changed, struct dns_compress changed, struct dns_resolver changed,
rwlock size changed. This means a LIBINTERFACE increment.
- lib/irs/api:
Source code changes, but no interface changes: increment
LIBREVISION.
- lib/isc/api:
The structs isc__networker and isc_nmsocket changed. This means
increment LIBINTERFACE. The functions isc_uv_export and
isc_uv_import are removed, so LIBAGE must beq zero.
- lib/isccc/api:
Source code changes, but no interface changes: increment
LIBREVISION.
- lib/isccfg/api:
Source code changes, but no interface changes: increment
LIBREVISION.
- lib/ns/api:
Function ns_clientmgr_create, ns_interfacemgr_create, and
structs ns_clientmgr, ns_interface, ns_interfacemgr changed:
increment LIBINTERFACE.
No need to update README or release notes.
Updated CHANGES: Add GitLab MR reference to entry 5357. Remove
merge conflict gone wrong ("max-ixfr-ratio" is not in 9.16).
Add /util/check-make-install.in to .gitattributes.
In isc_log_woudlog() the .logconfig member of isc_log_t structure was
accessed unlocked on the merit that there could be just a race when
.logconfig would be NULL, so the message would not be logged. This
turned not to be true, as there's also data race deeper. The accessed
isc_logconfig_t object could be in the middle of destruction, so the
pointer would be still non-NULL, but the structure members could point
to a chunk of memory no longer belonging to the object. Since we are
only accessing integer types (the log level), this would never lead to
a crash, it leads to memory access to memory area no longer belonging to
the object and this a) wrong, b) raises a red flag in thread-safety tools.
(cherry picked from commit 4d58856ff7)
The isc_mem API now crashes on memory allocation failure, and this is
the next commit in series to cleanup the code that could fail before,
but cannot fail now, e.g. isc_result_t return type has been changed to
void for the isc_log API functions that could only return ISC_R_SUCCESS.
(cherry picked from commit 0b793166d0)
On Windows, C11 localtime_r() and gmtime_r() functions are not
available. While localtime() and gmtime() functions are already thread
safe because they use Thread Local Storage, it's quite ugly to #ifdef
around every localtime_r() and gmtime_r() usage to make the usage also
thread-safe on POSIX platforms.
The commit adds wrappers around Windows localtime_s() and gmtime_s()
functions.
NOTE: The implementation of localtime_s and gmtime_s in Microsoft CRT
are incompatible with the C standard since it has reversed parameter
order and errno_t return type.
(cherry picked from commit 08f4c7d6c0)
This commit simplifies a bit the lock management within dns_resolver_prime()
and prime_done() functions by means of turning resolver's attribute
"priming" into an atomic_bool and by creating only one dependent object on the
lock "primelock", namely the "primefetch" attribute.
By having the attribute "priming" as an atomic type, it save us from having to
use a lock just to test if priming is on or off for the given resolver context
object, within "dns_resolver_prime" function.
The "primelock" lock is still necessary, since dns_resolver_prime() function
internally calls dns_resolver_createfetch(), and whenever this function
succeeds it registers an event in the task manager which could be called by
another thread, namely the "prime_done" function, and this function is
responsible for disposing the "primefetch" attribute in the resolver object,
also for resetting "priming" attribute to false.
It is important that the invariant "priming == false AND primefetch == NULL"
remains constant, so that any thread calling "dns_resolver_prime" knows for sure
that if the "priming" attribute is false, "primefetch" attribute should also be
NULL, so a new fetch context could be created to fulfill this purpose, and
assigned to "primefetch" attribute under the lock protection.
To honor the explanation above, dns_resolver_prime is implemented as follow:
1. Atomically checks the attribute "priming" for the given resolver context.
2. If "priming" is false, assumes that "primefetch" is NULL (this is
ensured by the "prime_done" implementation), acquire "primelock"
lock and create a new fetch context, update "primefetch" pointer to
point to the newly allocated fetch context.
3. If "priming" is true, assumes that the job is already in progress,
no locks are acquired, nothing else to do.
To keep the previous invariant consistent, "prime_done" is implemented as follow:
1. Acquire "primefetch" lock.
2. Keep a reference to the current "primefetch" object;
3. Reset "primefetch" attribute to NULL.
4. Release "primefetch" lock.
5. Atomically update "priming" attribute to false.
6. Destroy the "primefetch" object by using the temporary reference.
This ensures that if "priming" is false, "primefetch" was already reset to NULL.
It doesn't make any difference in having the "priming" attribute not protected
by a lock, since the visible state of this variable would depend on the calling
order of the functions "dns_resolver_prime" and "prime_done".
As an example, suppose that instead of using an atomic for the "priming" attribute
we employed a lock to protect it.
Now suppose that "prime_done" function is called by Thread A, it is then preempted
before acquiring the lock, thus not reseting "priming" to false.
In parallel to that suppose that a Thread B is scheduled and that it calls
"dns_resolver_prime()", it then acquires the lock and check that "priming" is true,
thus it will consider that this resolver object is already priming and it won't do
any more job.
Conversely if the lock order was acquired in the other direction, Thread B would check
that "priming" is false (since prime_done acquired the lock first and set "priming" to false)
and it would initiate a priming fetch for this resolver.
An atomic variable wouldn't change this behavior, since it would behave exactly the
same, depending on the function call order, with the exception that it would avoid
having to use a lock.
There should be no side effects resulting from this change, since the previous
implementation employed use of the more general resolver's "lock" mutex, which
is used in far more contexts, but in the specifics of the "dns_resolver_prime"
and "prime_done" it was only used to protect "primefetch" and "priming" attributes,
which are not used in any of the other critical sections protected by the same lock,
thus having zero dependency on those variables.
There was a very slim chance of a race between isc_socket_detach and
process_fd: isc_socket_detach decrements references to 0, and before it
calls destroy gets preempted. Second thread calls process_fd, increments
socket references temporarily to 1, and then gets preempted, first thread
then hits assertion in destroy() as the reference counter is now 1 and
not 0.
(cherry picked from commit 81ba0fe0e6)
When --with-zlib is passed to ./configure (or when the latter
autodetects zlib's presence), libisc uses certain zlib functions and
thus libisc's users should be linked against zlib in that case. Adjust
Makefile variables appropriately to prevent shared build failures caused
by underlinking.
(cherry picked from commit fc967ba092)
