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.
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.
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 isc__nmsocket_reset() was missing a case for raw TCP sockets (used
by RNDC and DoH) which would case a assertion failure when write timeout
would be triggered.
TCP sockets are now also properly handled in isc__nmsocket_reset().
When isc__nm_uvreq_t gets deactivated, it could be just put onto array
stack to be reused later to save some initialization time.
Unfortunately, this might hide some use-after-free errors.
Disable the inactive uvreqs caching when compiled with Address or
Thread Sanitizer.
When isc_nmhandle_t gets deactivated, it could be just put onto array
stack to be reused later to safe some initialization time.
Unfortunately, this might hide some use-after-free errors.
Disable the inactive handles caching when compiled with Address or
Thread Sanitizer.
The isc__nmsocket_t has locked array of isc_nmhandle_t that's not used
for anything. The isc__nmhandle_get() adds the isc_nmhandle_t to the
locked array (and resized if necessary) and removed when
isc_nmhandle_put() finally destroys the handle. That's all it does, so
it serves no useful purpose.
Remove the .ah_handles, .ah_size, and .ah_frees members of the
isc__nmsocket_t and .ah_pos member of the isc_nmhandle_t struct.
When the TCP, TCPDNS or TLSDNS connection times out, the isc__nm_uvreq_t
would be pushed into sock->inactivereqs before the uv_tcp_connect()
callback finishes. Because the isc__nmsocket_t keeps the list of
inactive isc__nm_uvreq_t, this would cause use-after-free only when the
sock->inactivereqs is full (which could never happen because the failure
happens in connection timeout callback) or when the sock->inactivereqs
mechanism is completely removed (f.e. when running under Address or
Thread Sanitizer).
Delay isc__nm_uvreq_t deallocation to the connection callback and only
signal the connection callback should be called by shutting down the
libuv socket from the connection timeout callback.
The keep-response-order option has been obsoleted, and in this commit,
remove the keep-response-order ACL map rendering the option no-op, the
call the isc_nm_sequential() and the now unused isc_nm_sequential()
function itself.
There was an artificial limit of 23 on the number of simultaneous
pipelined queries in the single TCP connection. The new network
managers is capable of handling "unlimited" (limited only by the TCP
read buffer size ) queries similar to "unlimited" handling of the DNS
queries receive over UDP.
Don't limit the number of TCP queries that we can process within a
single TCP read callback.
When invalid DNS message is received, there was a handling mechanism for
DoH that would be called to return proper HTTP response.
Reuse this mechanism and reset the TCP connection when the client is
blackholed, DNS message is completely bogus or the ns_client receives
response instead of query.
In some situations (unit test and forthcoming XFR timeouts MR), we need
to modify the write timeout independently of the read timeout. Add a
isc_nmhandle_setwritetimeout() function that could be called before
isc_nm_send() to specify a custom write timeout interval.
When the outgoing TCP write buffers are full because the other party is
not reading the data, the uv_write() could wait indefinitely on the
uv_loop and never calling the callback. Add a new write timer that uses
the `tcp-idle-timeout` value to interrupt the TCP connection when we are
not able to send data for defined period of time.
Before adding the write timer, we have to remove the generic sock->timer
to sock->read_timer. We don't touch the function names to limit the
impact of the refactoring.
Some operating systems (OpenBSD and DragonFly BSD) don't restrict the
IPv6 sockets to sending and receiving IPv6 packets only. Explicitly
enable the IPV6_V6ONLY socket option on the IPv6 sockets to prevent
failures from using the IPv4-mapped IPv6 address.
Previously, the netmgr/udp.c tried to detect the recvmmsg detection in
libuv with #ifdef UV_UDP_<foo> preprocessor macros. However, because
the UV_UDP_<foo> are not preprocessor macros, but enum members, the
detection didn't work. Because the detection didn't work, the code
didn't have access to the information when we received the final chunk
of the recvmmsg and tried to free the uvbuf every time. Fortunately,
the isc__nm_free_uvbuf() had a kludge that detected attempt to free in
the middle of the receive buffer, so the code worked.
However, libuv 1.37.0 changed the way the recvmmsg was enabled from
implicit to explicit, and we checked for yet another enum member
presence with preprocessor macro, so in fact libuv recvmmsg support was
never enabled with libuv >= 1.37.0.
This commit changes to the preprocessor macros to autoconf checks for
declaration, so the detection now works again. On top of that, it's now
possible to cleanup the alloc_cb and free_uvbuf functions because now,
the information whether we can or cannot free the buffer is available to
us.
This commit converts the license handling to adhere to the REUSE
specification. It specifically:
1. Adds used licnses to LICENSES/ directory
2. Add "isc" template for adding the copyright boilerplate
3. Changes all source files to include copyright and SPDX license
header, this includes all the C sources, documentation, zone files,
configuration files. There are notes in the doc/dev/copyrights file
on how to add correct headers to the new files.
4. Handle the rest that can't be modified via .reuse/dep5 file. The
binary (or otherwise unmodifiable) files could have license places
next to them in <foo>.license file, but this would lead to cluttered
repository and most of the files handled in the .reuse/dep5 file are
system test files.
The isc_queue_new() was using dirty tricks to allocate the head and tail
members of the struct aligned to the cacheline. We can now use
isc_mem_get_aligned() to allocate the structure to the cacheline
directly.
Use ISC_OS_CACHELINE_SIZE (64) instead of arbitrary ALIGNMENT (128), one
cacheline size is enough to prevent false sharing.
Cleanup the unused max_threads variable - there was actually no limit on
the maximum number of threads. This was changed a while ago.
On FreeBSD, the pthread primitives are not solely allocated on stack,
but part of the object lives on the heap. Missing pthread_*_destroy
causes the heap memory to grow and in case of fast lived object it's
possible to run out-of-memory.
Properly destroy the leaking mutex (worker->lock) and
the leaking condition (sock->cond).
Previously, when TCP accept failed, we have logged a message with
ISC_LOG_ERROR level. One common case, how this could happen is that the
client hits TCP client quota and is put on hold and when resumed, the
client has already given up and closed the TCP connection. In such
case, the named would log:
TCP connection failed: socket is not connected
This message was quite confusing because it actually doesn't say that
it's related to the accepting the TCP connection and also it logs
everything on the ISC_LOG_ERROR level.
Change the log message to "Accepting TCP connection failed" and for
specific error states lower the severity of the log message to
ISC_LOG_INFO.
This commit adds an isc_nm_socket_type() function which can be used to
obtain a handle's socket type.
This change obsoletes isc_nm_is_tlsdns_handle() and
isc_nm_is_http_handle(). However, it was decided to keep the latter as
we eventually might end up supporting multiple HTTP versions.
Change 5756 (GL #2854) introduced build errors when using
'configure --disable-doh'. To fix this, isc_nm_is_http_handle() is
now defined in all builds, not just builds that have DoH enabled.
Missing code comments were added both for that function and for
isc_nm_is_tlsdns_handle().
This commit adds an isc_nm_set_min_answer_ttl() function which is
intended to to be used to give a hint to the underlying transport
regarding the answer TTL.
The interface is intentionally kept generic because over time more
transports might benefit from this functionality, but currently it is
intended for DoH to set "max-age" value within "Cache-Control" HTTP
header (as recommended in the RFC8484, section 5.1 "Cache
Interaction").
It is no-op for other DNS transports for the time being.
it is possible for udp_recv_cb() to fire after the socket
is already shutting down and statichandle is NULL; we need to
create a temporary handle in this case.
route/netlink sockets don't have stats counters associated with them,
so it's now necessary to check whether socket stats exist before
incrementing or decrementing them. rather than relying on the caller
for this, we now just pass the socket and an index, and the correct
stats counter will be updated if it exists.
isc_nm_routeconnect() opens a route/netlink socket, then calls a
connect callback, much like isc_nm_udpconnect(), with a handle that
can then be monitored for network changes.
Internally the socket is treated as a UDP socket, since route/netlink
sockets follow the datagram contract.
After support for route/netlink sockets is merged, not all sockets
will have stats counters associated with them, so it's now necessary
to check whether socket stats exist before incrementing or decrementing
them. rather than relying on the caller for this, we now just pass the
socket and an index, and the correct stats counter will be updated if
it exists.
This commit makes BIND verify that zone transfers are allowed to be
done over the underlying connection. Currently, it makes sense only
for DoT, but the code is deliberately made to be protocol-agnostic.
The intention of having this function is to have a predicate to check
if a zone transfer could be performed over the given handle. In most
cases we can assume that we can do zone transfers over any stream
transport except DoH, but this assumption will not work for zone
transfers over DoT (XoT), as the RFC9103 requires ALPN to happen,
which might not be the case for all deployments of DoT.
- The `timeout_action` parameter to dns_dispatch_addresponse() been
replaced with a netmgr callback that is called when a dispatch read
times out. this callback may optionally reset the read timer and
resume reading.
- Added a function to convert isc_interval to milliseconds; this is used
to translate fctx->interval into a value that can be passed to
dns_dispatch_addresponse() as the timeout.
- Note that netmgr timeouts are accurate to the millisecond, so code to
check whether a timeout has been reached cannot rely on microsecond
accuracy.
- If serve-stale is configured, then a timeout received by the resolver
may trigger it to return stale data, and then resume waiting for the
read timeout. this is no longer based on a separate stale timer.
- The code for canceling requests in request.c has been altered so that
it can run asynchronously.
- TCP timeout events apply to the dispatch, which may be shared by
multiple queries. since in the event of a timeout we have no query ID
to use to identify the resp we wanted, we now just send the timeout to
the oldest query that was pending.
- There was some additional refactoring in the resolver: combining
fctx_join() and fctx_try_events() into one function to reduce code
duplication, and using fixednames in fetchctx and fetchevent.
- Incidental fix: new_adbaddrinfo() can't return NULL anymore, so the
code can be simplified.
- The read timer must always be stopped when reading stops.
- Read callbacks can now call isc_nm_read() again in TCP, TCPDNS and
TLSDNS; previously this caused an assertion.
- The wrong failure code could be sent after a UDP recv failure because
the if statements were in the wrong order. the check for a NULL
address needs to be after the check for an error code, otherwise the
result will always be set to ISC_R_EOF.
- When aborting a read or connect because the netmgr is shutting down,
use ISC_R_SHUTTINGDOWN. (ISC_R_CANCELED is now reserved for when the
read has been canceled by the caller.)
- A new function isc_nmhandle_timer_running() has been added enabling a
callback to check whether the timer has been reset after processing a
timeout.
- Incidental netmgr fix: always use isc__nm_closing() instead of
referencing sock->mgr->closing directly
- Corrected a few comments that used outdated function names.
Previously isc_nm_read() required references on the handle to be at
least 2, under the assumption that it would only ever be called from a
connect or accept callback. however, it can also be called from a read
callback, in which case the reference count might be only 1.
On TCPDNS/TLSDNS read callback, the socket buffer could be reallocated
if the received contents would be larger than the buffer. The existing
code would not preserve the contents of the existing buffer which lead
to the loss of the already received data.
This commit changes the isc_mem_put()+isc_mem_get() with isc_mem_reget()
to preserve the existing contents of the socket buffer.
The netmgr, has an internal cache for freed active handles. This cache
was allocated using isc_mem_allocate()/isc_mem_free() API because it was
simpler to reallocate the cache when we needed to grow it. The new
isc_mem_reget() function could be used here reducing the need to use
isc_mem_allocate() API which is tad bit slower than isc_mem_get() API.
this commit removes isc__nm_tcpdns_keepalive() and
isc__nm_tlsdns_keepalive(); keepalive for these protocols and
for TCP will now be set directly from isc_nmhandle_keepalive().
protocols that have an underlying TCP socket (i.e., TLS stream
and HTTP), now have protocol-specific routines, called by
isc_nmhandle_keeaplive(), to set the keepalive value on the
underlying socket.
previously, receiving a keepalive option had no effect on how
long named would keep the connection open; there was a place to
configure the keepalive timeout but it was never used. this commit
corrects that.
this also fixes an error in isc__nm_{tcp,tls}dns_keepalive()
in which the sense of a REQUIRE test was reversed; previously this
error had not been noticed because the functions were not being
used.
Instead of disabling the fragmentation on the UDP sockets, we now
disable the Path MTU Discovery by setting IP(V6)_MTU_DISCOVER socket
option to IP_PMTUDISC_OMIT on Linux and disabling IP(V6)_DONTFRAG socket
option on FreeBSD. This option sets DF=0 in the IP header and also
ignores the Path MTU Discovery.
As additional mitigation on Linux, we recommend setting
net.ipv4.ip_no_pmtu_disc to Mode 3:
Mode 3 is a hardend pmtu discover mode. The kernel will only accept
fragmentation-needed errors if the underlying protocol can verify
them besides a plain socket lookup. Current protocols for which pmtu
events will be honored are TCP, SCTP and DCCP as they verify
e.g. the sequence number or the association. This mode should not be
enabled globally but is only intended to secure e.g. name servers in
namespaces where TCP path mtu must still work but path MTU
information of other protocols should be discarded. If enabled
globally this mode could break other protocols.
It was discovered that setting the thread affinity on both the netmgr
and netthread threads lead to inconsistent recursive performance because
sometimes the netmgr and netthread threads would compete over single
resource and sometimes not.
Removing setting the affinity causes a slight dip in the authoritative
performance around 5% (the measured range was from 3.8% to 7.8%), but
the recursive performance is now consistently good.
In the jemalloc merge request, we missed the fact that ah_frees and ah_handles
are reallocated which is not compatible with using isc_mem_get() for allocation
and isc_mem_put() for deallocation. This commit reverts that part and restores
use of isc_mem_allocate() and isc_mem_free().
Current mempools are kind of hybrid structures - they serve two
purposes:
1. mempool with a lock is basically static sized allocator with
pre-allocated free items
2. mempool without a lock is a doubly-linked list of preallocated items
The first kind of usage could be easily replaced with jemalloc small
sized arena objects and thread-local caches.
The second usage not-so-much and we need to keep this (in
libdns:message.c) for performance reasons.
The isc_mem_allocate() comes with additional cost because of the memory
tracking. In this commit, we replace the usage with isc_mem_get()
because we track the allocated sizes anyway, so it's possible to also
replace isc_mem_free() with isc_mem_put().
