The way the ns_client_t .shuttingdown member was practically dead code.
The .shuttingdown would be set to true only in ns__client_put() function
meaning that we have detached from all ns_client_t .*handles and the
ns_client_t object being freed:
client->magic = 0;
client->shuttingdown = true;
[...]
isc_mem_put(manager->ctx, client, sizeof(*client))
Meanwhile the ns_client_t object is accessed like this:
isc_nmhandle_detach(&client->fetchhandle);
client->query.attributes &= ~NS_QUERYATTR_RECURSING;
client->state = NS_CLIENTSTATE_WORKING;
qctx_init(client, &devent, 0, &qctx);
client_shuttingdown = ns_client_shuttingdown(client);
if (fetch_canceled || fetch_answered || client_shuttingdown) {
[...]
}
Even if the isc_nmhandle_detach(...) was the last handle detach, it
would mean that immediatelly, after calling the isc_nmhandle_detach(),
we would be causing use-after-free, because the ns_client_t is
immediatelly destroyed after setting .shuttingdown to true.
The similar code in the query_hookresume() already noticed this:
/*
* This event is running under a client task, so it's safe to detach
* the fetch handle. And it should be done before resuming query
* processing below, since that may trigger another recursion or
* asynchronous hook event.
*/
Previously, it was possible to assign a bit of memory space in the
nmhandle to store the client data. This was complicated and prevents
further refactoring of isc_nmhandle_t caching (future work).
Instead of caching the data in the nmhandle, allocate the hot-path
ns_client_t objects from per-thread clientmgr memory context and just
assign it to the isc_nmhandle_t via isc_nmhandle_set().
The ns_client_t is always attached to ns_clientmgr_t which has
associated memory context, server context, task and threadid. Use those
directly from the ns_clientmgr_t instead of attaching it to an extra
copy in ns_client_t to make the ns_client_t more sleek and lean.
Additionally, remove some stray ns_client_t struct members that were not
used anywhere.
Some ancient versions of clang reported uninitialized memory use false
positive (see https://bugs.llvm.org/show_bug.cgi?id=14461). Since clang
4.0.1 has been long obsoleted, just remove the workarounds.
Historically, the inline keyword was a strong suggestion to the compiler
that it should inline the function marked inline. As compilers became
better at optimising, this functionality has receded, and using inline
as a suggestion to inline a function is obsolete. The compiler will
happily ignore it and inline something else entirely if it finds that's
a better optimisation.
Therefore, remove all the occurences of the inline keyword with static
functions inside single compilation unit and leave the decision whether
to inline a function or not entirely on the compiler
NOTE: We keep the usage the inline keyword when the purpose is to change
the linkage behaviour.
C11 has builtin support for _Noreturn function specifier with
convenience noreturn macro defined in <stdnoreturn.h> header.
Replace ISC_NORETURN macro by C11 noreturn with fallback to
__attribute__((noreturn)) if the C11 support is not complete.
Previously, the unreachable code paths would have to be tagged with:
INSIST(0);
ISC_UNREACHABLE();
There was also older parts of the code that used comment annotation:
/* NOTREACHED */
Unify the handling of unreachable code paths to just use:
UNREACHABLE();
The UNREACHABLE() macro now asserts when reached and also uses
__builtin_unreachable(); when such builtin is available in the compiler.
Gcc 7+ and Clang 10+ have implemented __attribute__((fallthrough)) which
is explicit version of the /* FALLTHROUGH */ comment we are currently
using.
Add and apply FALLTHROUGH macro that uses the attribute if available,
but does nothing on older compilers.
In one case (lib/dns/zone.c), using the macro revealed that we were
using the /* FALLTHROUGH */ comment in wrong place, remove that comment.
Instead of passing the "workers" variable back and forth along with
passing the single isc_nm_t instance, add isc_nm_getnworkers() function
that returns the number of netmgr threads are running.
Change the ns_interfacemgr and ns_taskmgr to utilize the newly acquired
knowledge.
In the GSS-TSIG verification code there was an alarming
variable-length array whose size came off the network, from the
signature in the request. It turned out to be safe, because the caller
had previously checked that the signature had a reasonable size.
However, the safety checks are in the generic TSIG implementation, and
the risky VLA usage was in the GSS-specific code, and they are
separated by the DST indirection layer, so it wasn't immediately
obvious that the risky VLA was in fact safe.
In fact this risky VLA was completely unnecessary, because the GSS
signature can be verified in place without being copied to the stack,
like the message covered by the signature. The `REGION_TO_GBUFFER()`
macro backwardly assigns the region in its left argument to the GSS
buffer in its right argument; this is just a pointer and length
conversion, without copying any data. The `gss_verify_mic()` call uses
both message and signature GSS buffers in a read-only manner.
When max-transfer-*-out timeouts were reintroduced, the log message
about starting the timer was errorneously left as ISC_LOG_ERROR.
Change the log level of said message to ISC_LOG_DEBUG(1).
The clang-format-15 has new option InsertBraces that could add missing
branches around single line statements. Use that to our advantage
without switching to not-yet-released LLVM version to add missing braces
in couple of places.
As incremental rehashing has been added to isc_ht implementation, we
need to test whether the rehashing works.
Update the isc_ht unit test to test:
* preinitialized hash table large enough to hold all the elements
* smallest hash table that fully grows to hold all the elements
* partially preinitialized hash table that grows
* iterating while rehashing is in progress
Previously, an incremental hash table resizing was implemented for the
dns_rbt_t hash table implementation. Using that as a base, also
implement the incremental hash table resizing also for isc_ht API
hashtables:
1. During the resize, allocate the new hash table, but keep the old
table unchanged.
2. In each lookup, delete, or iterator operation, check both tables.
3. Perform insertion operations only in the new table.
4. At each insertion also move <r> elements from the old table to
the new table.
5. When all elements are removed from the old table, deallocate it.
To ensure that the old table is completely copied over before the new
table itself needs to be enlarged, it is necessary to increase the
size of the table by a factor of at least (<r> + 1)/<r> during resizing.
In our implementation <r> is equal to 1.
The downside of this approach is that the old table and the new table
could stay in memory for longer when there are no new insertions into
the hash table for prolonged periods of time as the incremental
rehashing happens only during the insertions.
The fetch can be in the shutting down state when resume_dslookup() is
trying to operate on it.
This is also a security issue, because a malicious actor can set up a
name server which delays certain queries in such a way that the fetch
will time out and shut down, which will cause named to crash.
Add a check to see if the fetch has the shutting down attribute set,
and cancel any further operations on it in such case.
A similar bug had been fixed earlier for the resume_qmin() function,
see [GL #966].
This is an optimisation as we can skip a lot of pointless work when we
know there is a DNAME there.
When we have a partial match and a DNAME above the QNAME, the closest
encloser has the same owner as the DNAME, will have the DNAME bit set
in the type map, and we wouldn't use it as we would return the
DNAME + RRSIG(DNAME) instead.
So there is no point in looking for it nor in attempting to check that
it is valid for the QNAME.
'setup_delegation' depends on 'foundname' being the value returned
by 'dns_rbt_findnode' in the cache and 'find_coveringnsec' was
modifying 'foundname' when a covering NSEC was not found.
When sock->closehandle_cb is set, we need to run nmhandle_detach_cb()
asynchronously to ensure correct order of multiple packets processing in
the isc__nm_process_sock_buffer(). When not run asynchronously, it
would cause:
a) out-of-order processing of the return codes from processbuffer();
b) stack growth because the next TCP DNS message read callback will
be called from within the current TCP DNS message read callback.
The sock->closehandle_cb is set to isc__nm_resume_processing() for TCP
sockets which calls isc__nm_process_sock_buffer(). If the read callback
(called from isc__nm_process_sock_buffer()->processbuffer()) doesn't
attach to the nmhandle (f.e. because it wants to drop the processing or
we send the response directly via uv_try_write()), the
isc__nm_resume_processing() (via .closehandle_cb) would call
isc__nm_process_sock_buffer() recursively.
The below shortened code path shows how the stack can grow:
1: ns__client_request(handle, ...);
2: isc_nm_tcpdns_sequential(handle);
3: ns_query_start(client, handle);
4: query_lookup(qctx);
5: query_send(qctcx->client);
6: isc__nmhandle_detach(&client->reqhandle);
7: nmhandle_detach_cb(&handle);
8: sock->closehandle_cb(sock); // isc__nm_resume_processing
9: isc__nm_process_sock_buffer(sock);
10: processbuffer(sock); // isc__nm_tcpdns_processbuffer
11: isc_nmhandle_attach(req->handle, &handle);
12: isc__nm_readcb(sock, req, ISC_R_SUCCESS);
13: isc__nm_async_readcb(NULL, ...);
14: uvreq->cb.recv(...); // ns__client_request
Instead, if 'sock->closehandle_cb' is set, we need to run detach the
handle asynchroniously in 'isc__nmhandle_detach', so that on line 8 in
the code flow above does not start this recursion. This ensures the
correct order when processing multiple packets in the function
'isc__nm_process_sock_buffer()' and prevents the stack growth.
When not run asynchronously, the out-of-order processing leaves the
first TCP socket open until all requests on the stream have been
processed.
If the pipelining is disabled on the TCP via `keep-response-order`
configuration option, named would keep the first socket in lingering
CLOSE_WAIT state when the client sends an incomplete packet and then
closes the connection from the client side.
When caching glue, we need to ensure that there is no closer
source of truth for the name. If the owner name for the glue
record would be answered by a locally configured zone, do not
cache.
When caching additional and glue data *not* from a forwarder, we must
check that there is no "forward only" clause covering the owner name
that would take precedence. Such names would normally be allowed by
baliwick rules, but a "forward only" zone introduces a new baliwick
scope.
If we are using a fowarder, in addition to checking that names to
be cached are subdomains of the forwarded namespace, we must also
check that there are no subsidiary forwarded namespaces which would
take precedence. To be safe, we don't cache any responses if the
forwarding configuration has changed since the query was sent.
Change the isc_interval_t implementation from separate data type and
separate implementation to be shim implementation on top of isc_time_t.
The distinction between isc_interval_t and isc_time_t has been kept
because they are semantically different - isc_interval_t is relative and
isc_time_t is absolute, but this allows isc_time_t and isc_interval_t to
be freely interchangeable, f.e. this:
isc_time_t *t1;
isc_interval_t *interval;
isc_time_t *t2;
isc_interval_set(interval, isc_time_seconds(t2), isc_time_nanoseconds(t2);;
isc_time_subtract(t1, interval, t2);
isc_interval_set(interval, isc_time_seconds(t2), isc_time_nanoseconds(t2));
to just:
isc_time_t *t1;
isc_interval_t *interval;
isc_time_t *t2;
isc_time_subtract(t1, t2, interval);
without introducing a whole set of new functions.
The isc_timer_reset() now works only with intervals for once timers.
This makes the API almost 1:1 compatible with the libuv timers making
the further refactoring possible.
There were two places where expires argument (absolute isc_time_t value)
was being used. Both places has been converted to use relative interval
argument in preparation of simplification and refactoring of isc_timer
API.
The isc_timer_create() function was a bit conflated. It could have been
used to create a timer and start it at the same time. As there was a
single place where this was done before (see the previous commit for
nta.c), this was cleaned up and the isc_timer_create() function was
changed to only create new timer.
In nta.c, it was the only place where the active timer was created
directly instead of first creating inactive timer and then starting it
with isc_timer_reset().
Change the code to create inactive timer first, so we can refactor the
isc_timer_create() function.
In httpd.c, the send callback can directly call read callback without
calling isc_nm_resumeread(). When per-send timeout was added, this
could lead to use-after-free when shutting down the named.
Cleanup the way how we attach to .readhandle and .sendhandle, so there's
assurance that .readhandle will be always non-NULL when reading and
.sendhandle will be always non-NULL when sending.
Additionally, it was found that the implementation ignored the
"Connection: close" header and it worked only accidentally by closing
the connection after the first read from the TCP socket. This has been
also fixed.
Previously, the established TCP connections (both client and server)
would be gracefully closed waiting for the write timeout.
Don't wait for TCP connections to gracefully shutdown, but directly
reset them for faster shutdown.
Previously, there was a single per-socket write timer that would get
restarted for every new write. This turned out to be insufficient
because the other side could keep reseting the timer, and never reading
back the responses.
Change the single write timer to per-send timer which would in turn
reset the TCP connection on the first send timeout.
The C17 standard deprecated ATOMIC_VAR_INIT() macro (see [1]). Follow
the suite and remove the ATOMIC_VAR_INIT() usage in favor of simple
assignment of the value as this is what all supported stdatomic.h
implementations do anyway:
* MacOSX.plaform: #define ATOMIC_VAR_INIT(__v) {__v}
* Gcc stdatomic.h: #define ATOMIC_VAR_INIT(VALUE) (VALUE)
1. http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p1138r0.pdf
Previously, the function(s) in the commit subject could fail for various
reasons - mostly allocation failures, or other functions returning
different return code than ISC_R_SUCCESS. Now, the aforementioned
function(s) cannot ever fail and they would always return ISC_R_SUCCESS.
Change the function(s) to return void and remove the extra checks in
the code that uses them.
Previously, the function(s) in the commit subject could fail for various
reasons - mostly allocation failures, or other functions returning
different return code than ISC_R_SUCCESS. Now, the aforementioned
function(s) cannot ever fail and they would always return ISC_R_SUCCESS.
Change the function(s) to return void and remove the extra checks in
the code that uses them.
Previously, the function(s) in the commit subject could fail for various
reasons - mostly allocation failures, or other functions returning
different return code than ISC_R_SUCCESS. Now, the aforementioned
function(s) cannot ever fail and they would always return ISC_R_SUCCESS.
Change the function(s) to return void and remove the extra checks in
the code that uses them.
Previously the socket code would set the TCPv6 maximum segment size to
minimum value to prevent IP fragmentation for TCP. This was not yet
implemented for the network manager.
Implement network manager functions to set and use minimum MTU socket
option and set the TCP_MAXSEG socket option for both IPv4 and IPv6 and
use those to clamp the TCP maximum segment size for TCP, TCPDNS and
TLSDNS layers in the network manager to 1220 bytes, that is 1280 (IPv6
minimum link MTU) minus 40 (IPv6 fixed header) minus 20 (TCP fixed
header)
We already rely on a similar value for UDP to prevent IP fragmentation
and it make sense to use the same value for IPv4 and IPv6 because the
modern networks are required to support IPv6 packet sizes. If there's
need for small TCP segment values, the MTU on the interfaces needs to be
properly configured.
The IPV6_USE_MIN_MTU socket option directs the IP layer to limit the
IPv6 packet size to the minimum required supported MTU from the base
IPv6 specification, i.e. 1280 bytes. Many implementations of TCP
running over IPv6 neglect to check the IPV6_USE_MIN_MTU value when
performing MSS negotiation and when constructing a TCP segment despite
MSS being defined to be the MTU less the IP and TCP header sizes (60
bytes for IPv6). This leads to oversized IPv6 packets being sent
resulting in unintended Path Maximum Transport Unit Discovery (PMTUD)
being performed and to fragmented IPv6 packets being sent.
Add and use a function to set socket option to limit the MTU on IPv6
sockets to the minimum MTU (1280) both for UDP and TCP.
For each algorithm there must be a key performing the KSK and
ZSK rolls. After reading the keys from named.conf check that
each algorithm present has both rolls. CSK implicitly has both
rolls.
When get_dispatch() returns an error code, the dns_request_createraw()
function jumps to the `cleanup` label, which will leave a previous
attachment to the `request` pointer unattached.
Fix the issue by jumping to the `detach` label instead.
Formerly, the gen.h header contained a compatibility layer between Win32
and POSIX platforms. Since we have already dropped the Win32 build, we
can merged gen.h into gen.c as the header file is not used elsewhere.
The current implementation of isc_queue uses Michael-Scott lock-free
queue that in turn uses hazard pointers. It was discovered that the way
we use the isc_queue, such complicated mechanism isn't really needed,
because most of the time, we either execute the work directly when on
nmthread (in case of UDP) or schedule the work from the matching
nmthreads.
Replace the current implementation of the isc_queue with a simple locked
ISC_LIST. There's a slight improvement - since copying the whole list
is very lightweight - we move the queue into a new list before we start
the processing and locking just for moving the queue and not for every
single item on the list.
NOTE: There's a room for future improvements - since we don't guarantee
the order in which the netievents are processed, we could have two lists
- one unlocked that would be used when scheduling the work from the
matching thread and one locked that would be used from non-matching
thread.
The order in which the netievents are processed on the network manager
loop is not guaranteed. Therefore the recv/read callback can come
earlier than the send/write callback.
The dns_request API wasn't ready for this reordering and it was
destroying the dns_request_t object before the send callback has been
called.
Add additional attach/detach in the req_send()/req_senddone() functions
to make sure we don't destroy the dns_request_t while it's still being
references by asynchronous call.
BIND unconditionally uses shims for BN_GENCB_new(), BN_GENCB_free(),
and BN_GENCB_get_arg() for all LibreSSL versions and, correctly, for
OpenSSL <1.1.0 versions.
This breaks LibreSSL compilation starting with LibreSSL 3.5.0.
Use autoconf check instead to check whether the family of the functions
are available.
LibreSSL 3.5.0 fails to compile with these shims. We could have just
removed the LibreSSL check from the pre-processor condition, but it
seems that these shims are no longer needed because all the supported
versions of OpenSSL and LibreSSL have those functions.
According to EVP_ENCRYPTINIT(3) manual page in LibreSSL,
EVP_CIPHER_CTX_new() and EVP_CIPHER_CTX_free() first appeared in
OpenSSL 0.9.8b, and have been available since OpenBSD 4.5.
the "zone" clause can be documented using, for instance,
`cfg_test --zonegrammar primary", which prints only
options that are valid in primary zones. this was not
the method being used when generating the named.conf
man page; instead, "zone" was documented with all possible
options, and no zone types at all.
this commit removes "zone" from the generic documentation
and adds include statements in named.conf.rst so that
correct zone grammars will be included in the man page.
