This commit makes number of concurrent HTTP/2 streams per connection
configurable as a mean to fight DDoS attacks. As soon as the limit is
reached, BIND terminates the whole session.
The commit adds a global configuration
option (http-streams-per-connection) which can be overridden in an
http <name> {...} statement like follows:
http local-http-server {
...
streams-per-connection 100;
...
};
For now the default value is 100, which should be enough (e.g. NGINX
uses 128, but it is a full-featured WEB-server). When using lower
numbers (e.g. ~70), it is possible to hit the limit with
e.g. flamethrower.
This commit adds support for http-listener-clients global options as
well as ability to override the default in an HTTP server description,
like:
http local-http-server {
...
listener-clients 100;
...
};
This way we have ability to specify per-listener active connections
quota globally and then override it when required. This is exactly
what AT&T requested us: they wanted a functionality to specify quota
globally and then override it for specific IPs. This change
functionality makes such a configuration possible.
It makes sense: for example, one could have different quotas for
internal and external clients. Or, for example, one could use BIND's
internal ability to serve encrypted DoH with some sane quota value for
internal clients, while having un-encrypted DoH listener without quota
to put BIND behind a load balancer doing TLS offloading for external
clients.
Moreover, the code no more shares the quota with TCP, which makes
little sense anyway (see tcp-clients option), because of the nature of
interaction of DoH clients: they tend to keep idle opened connections
for longer periods of time, preventing the TCP and TLS client from
being served. Thus, the need to have a separate, generally larger,
quota for them.
Also, the change makes any option within "http <name> { ... };"
statement optional, making it easier to override only required default
options.
By default, the DoH connections are limited to 300 per listener. I
hope that it is a good initial guesstimate.
The ISC_MEM_DEBUGSIZE and ISC_MEM_DEBUGCTX did sanity checks on matching
size and memory context on the memory returned to the allocator. Those
will no longer needed when most of the allocator will be replaced with
jemalloc.
This commit adds two new autoconf options `--enable-doh` (enabled by
default) and `--with-libnghttp2` (mandatory when DoH is enabled).
When DoH support is disabled the library is not linked-in and support
for http(s) protocol is disabled in the netmgr, named and dig.
if a control channel listener was configured with more than one
key algorithm, message verification would be attempted with each
algorithm in turn. if the first key failed due to the wrong
signature length, the entire verification process was aborted,
rather than continuing on to try with another key.
The isc/platform.h header was left empty which things either already
moved to config.h or to appropriate headers. This is just the final
cleanup commit.
The last remaining defines needed for platforms without NAME_MAX and
PATH_MAX (I'm looking at you, GNU Hurd) were moved to isc/dir.h where
it's prevalently used.
This code gathers DNSSEC keys from key files and from the DNSKEY RRset.
It is used for the 'rndc dnssec -status' command, but will also be
needed for "checkds". Turn it into a function.
Previously, we would set the locale on a global level and that could
possibly lead to different behaviour in underlying functions. In this
commit, we change to code to use the system locale only when calling the
libidn2 functions and reset the locale back to "POSIX" when exiting the
libidn2 code.
The built-in "_bind" view does not allow recursion and therefore does
not need a large cache database. However, as "max-cache-size" is not
explicitly set for that view in the default configuration, it inherits
that setting from global options. Set "max-cache-size" for the built-in
"_bind" view to a fixed value (2 MB, i.e. the smallest allowed value) to
prevent needlessly preallocating memory for its cache RBT hash table.
Currently the implicit default for the "max-cache-size" option is "90%".
As this option is inherited by all configured views, using multiple
views can lead to memory exhaustion over time due to overcommitment.
The "max-cache-size 90%;" default also causes cache RBT hash tables to
be preallocated for every configured view, which does not really make
sense for views which do not allow recursion.
To limit this problem's potential for causing operational issues, use a
minimal-sized cache for views which do not allow recursion and do not
have "max-cache-size" explicitly set (either in global configuration or
in view configuration).
For configurations which include multiple views allowing recursion,
adjusting "max-cache-size" appropriately is still left to the operator.
The Windows support has been completely removed from the source tree
and BIND 9 now no longer supports native compilation on Windows.
We might consider reviewing mingw-w64 port if contributed by external
party, but no development efforts will be put into making BIND 9 compile
and run on Windows again.
Previously, dumping the zones to the files were quantized, so it doesn't
slow down network IO processing. With the introduction of network
manager asynchronous threadpools, we can move the IO intensive work to
use that API and we don't have to quantize the work anymore as it the
file IO won't block anything except other zone dumping processes.
configuring with --enable-mutex-atomics flagged these incorrectly
initialised variables on systems where pthread_mutex_init doesn't
just zero out the structure.
The isc_nmiface_t type was holding just a single isc_sockaddr_t,
so we got rid of the datatype and use plain isc_sockaddr_t in place
where isc_nmiface_t was used before. This means less type-casting and
shorter path to access isc_sockaddr_t members.
At the same time, instead of keeping the reference to the isc_sockaddr_t
that was passed to us when we start listening, we will keep a local
copy. This prevents the data race on destruction of the ns_interface_t
objects where pending nmsockets could reference the sockaddr of already
destroyed ns_interface_t object.
Previously, as a way of reducing the contention between threads a
clientmgr object would be created for each interface/IP address.
We tasks being more strictly bound to netmgr workers, this is no longer
needed and we can just create clientmgr object per worker queue (ncpus).
Each clientmgr object than would have a single task and single memory
context.
This commit adds a new configuration option to set the receive and send
buffer sizes on the TCP and UDP netmgr sockets. The default is `0`
which doesn't set any value and just uses the value set by the operating
system.
There's no magic value here - set it too small and the performance will
drop, set it too large, the buffers can fill-up with queries that have
already timeouted on the client side and nobody is interested for the
answer and this would just make the server clog up even more by making
it produce useless work.
The `netstat -su` can be used on POSIX systems to monitor the receive
and send buffer errors.
all privileged tasks are complete by the time we return from
isc_task_endexclusive(), so it makes sense to reset the taskmgr
mode to non-privileged right then.
Network manager events that require interlock (pause, resume, listen)
are now always executed in the same worker thread, mgr->workers[0],
to prevent races.
"stoplistening" events no longer require interlock.
all zone loading tasks have the privileged flag, but we only want
them to run as privileged tasks when the server is being initialized;
if we privilege them the rest of the time, the server may hang for a
long time after a reload/reconfig. so now we call isc_taskmgr_setmode()
to turn privileged execution mode on or off in the task manager.
isc_task_privileged() returns true if the task's privilege flag is
set *and* the taskmgr is in privileged execution mode. this is used
to determine in which netmgr event queue the task should be run.
Previously, netmgr, taskmgr, timermgr and socketmgr all had their own
isc_<*>mgr_create() and isc_<*>mgr_destroy() functions. The new
isc_managers_create() and isc_managers_destroy() fold all four into a
single function and makes sure the objects are created and destroy in
correct order.
Especially now, when taskmgr runs on top of netmgr, the correct order is
important and when the code was duplicated at many places it's easy to
make mistake.
The former isc_<*>mgr_create() and isc_<*>mgr_destroy() functions were
made private and a single call to isc_managers_create() and
isc_managers_destroy() is required at the program startup / shutdown.
When looking for key files, we could use isdigit rather than checking
if the character is within the range [0-9].
Use (unsigned char) cast to ensure the value is representable in the
unsigned char type (as suggested by the isdigit manpage).
Change " & 0xff" occurrences to the recommended (unsigned char) type
cast.
The rndc command 'dnssec -status' only considered keys from
'dns_dnssec_findmatchingkeys' which only includes keys with accessible
private keys. Change it so that offline keys are also listed in the
status.
This commit adds support for generating backtraces on Windows and
refactors the isc_backtrace API to match the Linux/BSD API (without
the isc_ prefix)
* isc_backtrace_gettrace() was renamed to isc_backtrace(), the third
argument was removed and the return type was changed to int
* isc_backtrace_symbols() was added
* isc_backtrace_symbols_fd() was added and used as appropriate
Add a new built-in policy "insecure", to be used to gracefully unsign
a zone. Previously you could just remove the 'dnssec-policy'
configuration from your zone statement, or remove it.
The built-in policy "none" (or not configured) now actually means
no DNSSEC maintenance for the corresponding zone. So if you
immediately reconfigure your zone from whatever policy to "none",
your zone will temporarily be seen as bogus by validating resolvers.
This means we can remove the functions 'dns_zone_use_kasp()' and
'dns_zone_secure_to_insecure()' again. We also no longer have to
check for the existence of key state files to figure out if a zone
is transitioning to insecure.
While working on the serve-stale backports, I noticed the following
oddities:
1. In the serve-stale system test, in one case we keep track of the
time how long it took for dig to complete. In commit
aaed7f9d8c, the code removed the
exception to check for result == ISC_R_SUCCESS on stale found
answers, and adjusted the test accordingly. This failed to update
the time tracking accordingly. Move the t1/t2 time track variables
back around the two dig commands to ensure the lookups resolved
faster than the resolver-query-timeout.
2. We can remove the setting of NS_QUERYATTR_STALEOK and
DNS_RDATASETATTR_STALE_ADDED on the "else if (stale_timeout)"
code path, because they are added later when we know we have
actually found a stale answer on a stale timeout lookup.
3. We should clear the NS_QUERYATTR_STALEOK flag from the client
query attributes instead of DNS_RDATASETATTR_STALE_ADDED (that
flag is set on the rdataset attributes).
4. In 'bin/named/config.c' we should set the configuration options
in alpabetical order.
5. In the ARM, in the backports we have added "(stale)" between
"cached" and "RRset" to make more clear a stale RRset may be
returned in this scenario.
It follows a description of the steps that were leading to the deadlock:
1. `do_addzone` calls `isc_task_beginexclusive`.
2. `isc_task_beginexclusive` waits for (N_WORKERS - 1) halted tasks,
this blocks waiting for those (no. workers -1) workers to halt.
...
isc_task_beginexclusive(isc_task_t *task0) {
...
while (manager->halted + 1 < manager->workers) {
wake_all_queues(manager);
WAIT(&manager->halt_cond, &manager->halt_lock);
}
```
3. It is possible that in `task.c / dispatch()` a worker is running a
task event, if that event blocks it will not allow this worker to
halt.
4. `do_addzone` acquires `LOCK(&view->new_zone_lock);`,
5. `rmzone` event is called from some worker's `dispatch()`, `rmzone`
blocks waiting for the same lock.
6. `do_addzone` calls `isc_task_beginexclusive`.
7. Deadlock triggered, since:
- `rmzone` is wating for the lock.
- `isc_task_beginexclusive` is waiting for (no. workers - 1) to
be halted
- since `rmzone` event is blocked it won't allow the worker to halt.
To fix this, we updated do_addzone code to call isc_task_beginexclusive
before the lock is acquired, we postpone locking to the nearest required
place, same for isc_task_beginexclusive.
The same could happen with rndc modzone, so that was addressed as well.
This commit changes the taskmgr to run the individual tasks on the
netmgr internal workers. While an effort has been put into keeping the
taskmgr interface intact, couple of changes have been made:
* The taskmgr has no concept of universal privileged mode - rather the
tasks are either privileged or unprivileged (normal). The privileged
tasks are run as a first thing when the netmgr is unpaused. There
are now four different queues in in the netmgr:
1. priority queue - netievent on the priority queue are run even when
the taskmgr enter exclusive mode and netmgr is paused. This is
needed to properly start listening on the interfaces, free
resources and resume.
2. privileged task queue - only privileged tasks are queued here and
this is the first queue that gets processed when network manager
is unpaused using isc_nm_resume(). All netmgr workers need to
clean the privileged task queue before they all proceed normal
operation. Both task queues are processed when the workers are
finished.
3. task queue - only (traditional) task are scheduled here and this
queue along with privileged task queues are process when the
netmgr workers are finishing. This is needed to process the task
shutdown events.
4. normal queue - this is the queue with netmgr events, e.g. reading,
sending, callbacks and pretty much everything is processed here.
* The isc_taskmgr_create() now requires initialized netmgr (isc_nm_t)
object.
* The isc_nm_destroy() function now waits for indefinite time, but it
will print out the active objects when in tracing mode
(-DNETMGR_TRACE=1 and -DNETMGR_TRACE_VERBOSE=1), the netmgr has been
made a little bit more asynchronous and it might take longer time to
shutdown all the active networking connections.
* Previously, the isc_nm_stoplistening() was a synchronous operation.
This has been changed and the isc_nm_stoplistening() just schedules
the child sockets to stop listening and exits. This was needed to
prevent a deadlock as the the (traditional) tasks are now executed on
the netmgr threads.
* The socket selection logic in isc__nm_udp_send() was flawed, but
fortunatelly, it was broken, so we never hit the problem where we
created uvreq_t on a socket from nmhandle_t, but then a different
socket could be picked up and then we were trying to run the send
callback on a socket that had different threadid than currently
running.
Using "stale-answer-client-timeout" turns out to have unforeseen
negative consequences, and thus it is better to disable the feature
by default for the time being.
Call 'dns_zone_rekey' after a 'rndc dnssec -checkds' or 'rndc dnssec
-rollover' command is received, because such a command may influence
the next key event. Updating the keys immediately avoids unnecessary
rollover delays.
The kasp system test no longer needs to call 'rndc loadkeys' after
a 'rndc dnssec -checkds' or 'rndc dnssec -rollover' command.
The RFC7828 specifies the keepalive interval to be 16-bit, specified in
units of 100 milliseconds and the configuration options tcp-*-timeouts
are following the suit. The units of 100 milliseconds are very
unintuitive and while we can't change the configuration and presentation
format, we should not follow this weird unit in the API.
This commit changes the isc_nm_(get|set)timeouts() functions to work
with milliseconds and convert the values to milliseconds before passing
them to the function, not just internally.
- style, cleanup, and removal of unnecessary code.
- combined isc_nm_http_add_endpoint() and isc_nm_http_add_doh_endpoint()
into one function, renamed isc_http_endpoint().
- moved isc_nm_http_connect_send_request() into doh_test.c as a helper
function; remove it from the public API.
- renamed isc_http2 and isc_nm_http2 types and functions to just isc_http
and isc_nm_http, for consistency with other existing names.
- shortened a number of long names.
- the caller is now responsible for determining the peer address.
in isc_nm_httpconnect(); this eliminates the need to parse the URI
and the dependency on an external resolver.
- the caller is also now responsible for creating the SSL client context,
for consistency with isc_nm_tlsdnsconnect().
- added setter functions for HTTP/2 ALPN. instead of setting up ALPN in
isc_tlsctx_createclient(), we now have a function
isc_tlsctx_enable_http2client_alpn() that can be run from
isc_nm_httpconnect().
- refactored isc_nm_httprequest() into separate read and send functions.
isc_nm_send() or isc_nm_read() is called on an http socket, it will
be stored until a corresponding isc_nm_read() or _send() arrives; when
we have both halves of the pair the HTTP request will be initiated.
- isc_nm_httprequest() is renamed isc__nm_http_request() for use as an
internal helper function by the DoH unit test. (eventually doh_test
should be rewritten to use read and send, and this function should
be removed.)
- added implementations of isc__nm_tls_settimeout() and
isc__nm_http_settimeout().
- increased NGHTTP2 header block length for client connections to 128K.
- use isc_mem_t for internal memory allocations inside nghttp2, to
help track memory leaks.
- send "Cache-Control" header in requests and responses. (note:
currently we try to bypass HTTP caching proxies, but ideally we should
interact with them: https://tools.ietf.org/html/rfc8484#section-5.1)
Removed redundant 'listener != NULL' check.
1191cleanup:
CID 304936 (#1 of 1): Dereference before null check (REVERSE_INULL)
check_after_deref: Null-checking listener suggests that it may be null, but it has already been dereferenced on all paths leading to the check.
1192 if (listener != NULL) {
1193 isc_refcount_decrement(&listener->refs);
1194 listener->exiting = true;
1195 free_listener(listener);
1196 }
Mark Andrews
Artem Boldariev
Ondřej Surý
Evan Hunt
Matthijs Mekking
Petr Špaček
Michał Kępień
Diego Fronza