This applies the change so that the applet code stops using ci_putchk()
and friends everywhere possible, for the much saferapplet_put*() instead.
The change is mechanical but large. Two or three functions used to have no
appctx and a cs derived from the appctx instead, which was a reminiscence
of old times' stream_interface. These were simply changed to directly take
the appctx. No sensitive change was performed, and the old (more complex)
API is still usable when needed (e.g. the channel is already known).
The change touched roughly a hundred of locations, with no less than 124
lines removed.
It's worth noting that the stats applet, the oldest of the series, could
get a serious lifting, as it's still very channel-centric instead of
propagating the appctx along the chain. Given that this code doesn't
change often, there's no emergency to clean it up but it would look
better.
This also follows the natural naming. There are roughly 238 changes, all
totally trivial. conn_stream-t.h has become completely void of any
"conn_stream" related stuff now (except its name).
This renames the "struct conn_stream" to "struct stconn" and updates
the descriptions in all comments (and the rare help descriptions) to
"stream connector" or "connector". This touches a lot of files but
the change is minimal. The local variables were not even renamed, so
there's still a lot of "cs" everywhere.
In the same way than for the tasks, the applets api was changed to be able
to start a new appctx on a thread subset. For now the feature is
disabled. Only appctx_new_here() is working. But it will be possible to
start an appctx on a specific thread or a subset via a mask.
A .init callback function is defined for the dns_session_applet applet. This
function finishes the appctx startup by calling appctx_finalize_startup()
and its handles the stream customization.
The session created for frontend applets is now totally owns by the
corresponding appctx. It means the appctx is now responsible to release
it. This removes the hack in stream_free() about frontend applets to be sure
to release the session.
The two functions became exact copies since there's no more special case
for the appctx owner. Let's merge them into a single one, that simplifies
the code.
This one is the pointer to the conn_stream which is always in the
endpoint that is always present in the appctx, thus it's not needed.
This patch removes it and replaces it with appctx_cs() instead. A
few occurences that were using __cs_strm(appctx->owner) were moved
directly to appctx_strm() which does the equivalent.
This patch adds a lock on the struct dgram_conn to ensure
that an other thread cannot trash a fd or alter its status
while the current thread processing it on for send/receive/connect
operations.
Starting with the 2.4 version this could cause a crash when a DNS
request is failing, setting the FD of the dgram structure to -1. If the
dgram structure is reused after that, a read access to fdtab[-1] is
attempted. The crash was only triggered when compiled with ASAN.
In previous versions the concurrency issue also exists but is less
likely to crash.
This patch must be backported until v2.4 and should be
adapt for v < 2.4.
This flag is no longer needed now that it must always match the presence
of a destination address on the backend conn_stream. Worse, before previous
patch, if it were to be accidently removed while the address is present, it
could result in a leak of that address since alloc_dst_address() would first
be called to flush it.
Its usage has a long history where addresses were stored in an area shared
with the connection, but as this is no longer the case, there's no reason
for putting this burden onto application-level code that should not focus
on setting obscure flags.
The only place where that made a small difference is in the dequeuing code
in case of queue redistribution, because previously the code would first
clear the flag, and only later when trying to deal with the queue, would
release the address. It's not even certain whether there would exist a
code path going to connect_server() without calling pendconn_dequeue()
first (e.g. retries on queue timeout maybe?).
Now the pendconn_dequeue() code will rely on SF_ASSIGNED to decide to
clear and release the address, since that flag is always set while in
a server's queue, and its clearance implies that we don't want to keep
the address. At least it remains consistent and there's no more risk of
leaking it.
This gets rid of most open-coded fcntl() calls, some of which were passed
through DISGUISE() to avoid a useless test. The FD_CLOEXEC was most often
set without preserving previous flags, which could become a problem once
new flags are created. Now this will not happen anymore.
Some older systems may routinely return EWOULDBLOCK for some syscalls
while we tend to check only for EAGAIN nowadays. Modern systems define
EWOULDBLOCK as EAGAIN so that solves it, but on a few older ones (AIX,
VMS etc) both are different, and for portability we'd need to test for
both or we never know if we risk to confuse some status codes with
plain errors.
There were few entries, the most annoying ones are the switch/case
because they require to only add the entry when it differs, but the
other ones are really trivial.
Remaining flags and associated functions are move in the conn-stream
scope. These flags are added on the endpoint and not the conn-stream
itself. This way it will be possible to get them from the mux or the
applet. The functions to get or set these flags are renamed accordingly with
the "cs_" prefix and updated to manipualte a conn-stream instead of a
stream-interface.
si_shutr(), si_shutw(), si_chk_rcv() and si_chk_snd() are moved in the
conn-stream scope and renamed, respectively, cs_shutr(), cs_shutw(),
cs_chk_rcv(), cs_chk_snd() and manipulate a conn-stream instead of a
stream-interface.
The stream-interface state (SI_ST_*) is now in the conn-stream. It is a
mechanical replacement for now. Nothing special. SI_ST_* and SI_SB_* were
renamed accordingly. Utils functions to manipulate these infos were moved
under the conn-stream scope.
But it could be good to keep in mind that this part should be
reworked. Indeed, at the CS level, we only need to know if it is ready to
receive or to send. The state of conn-stream from INI to EST is only used on
the server side. The client CS is immediately set to EST. Thus current
SI_ST_* states should probably be moved to the stream to reflect the server
connection state during the establishment stage.
Flags to disable lingering and half-close are now handled at the conn-stream
level. Thus SI_FL_NOLINGER and SI_FL_NOHALF stream-int flags are replaced by
CS_FL_NOLINGER and CS_FL_NOHALF conn-stream flags.
The source and destination addresses at the applicative layer are moved from
the stream-interface to the conn-stream. This simplifies a bit the code and
it is a logicial step to remove the stream-interface.
At many places, we now use the new CS functions to get a stream or a channel
from a conn-stream instead of using the stream-interface API. It is the
first step to reduce the scope of the stream-interfaces. The main change
here is about the applet I/O callback functions. Before the refactoring, the
stream-interface was the appctx owner. Thus, it was heavily used. Now, as
far as possible,the conn-stream is used. Of course, it remains many calls to
the stream-interface API.
The conn-stream endpoint is now shared between the conn-stream and the
applet or the multiplexer. If the mux or the applet is created first, it is
responsible to also create the endpoint and share it with the conn-stream.
If the conn-stream is created first, it is the opposite.
When the endpoint is only owned by an applet or a mux, it is called an
orphan endpoint (there is no conn-stream). When it is only owned by a
conn-stream, it is called a detached endpoint (there is no mux/applet).
The last entity that owns an endpoint is responsible to release it. When a
mux or an applet is detached from a conn-stream, the conn-stream
relinquishes the endpoint to recreate a new one. This way, the endpoint
state is never lost for the mux or the applet.
It is a transient commit to prepare next changes. Now, when a conn-stream is
created from an applet or a multiplexer, an endpoint is always provided. In
addition, the API to create a conn-stream was specialized to have one
function per type.
The next step will be to share the endpoint structure.
It is a transient commit to prepare next changes. It is possible to pass a
pre-allocated endpoint to create a new conn-stream. If it is NULL, a new
endpoint is created, otherwise the existing one is used. There no more
change at the conn-stream level.
In the applets, all conn-stream are created with no pre-allocated
endpoint. But for multiplexers, an endpoint is systematically created before
creating the conn-stream.
This change is only significant for the multiplexer part. For the applets,
the context and the endpoint are the same. Thus, there is no much change. For
the multiplexer part, the connection was used to set the conn-stream
endpoint and the mux's stream was the context. But it is a bit strange
because once a mux is installed, it takes over the connection. In a
wonderful world, the connection should be totally hidden behind the mux. The
stream-interface and, in a lesser extent, the stream, still access the
connection because that was inherited from the pre-multiplexer era.
Now, the conn-stream endpoint is the mux's stream (an opaque entity for the
conn-stream) and the connection is the context. Dedicated functions have
been added to attached an applet or a mux to a conn-stream.
The appctx owner is now always a conn-stream. Thus, it can be set during the
appctx allocation. But, to do so, the conn-stream must be created first. It
is not a problem on the server side because the conn-stream is created with
the stream. On the client side, we must take care to create the conn-stream
first.
This change should ease other changes about the applets bootstrapping.
Thanks to all previous changes, it is now possible to move the
stream-interface into the conn-stream. To do so, some SI functions are
removed and their conn-stream counterparts are added. In addition, the
conn-stream is now responsible to create and release the
stream-interface. While the stream-interfaces were inlined in the stream
structure, there is now a pointer in the conn-stream. stream-interfaces are
now dynamically allocated. Thus a dedicated pool is added. It is a temporary
change because, at the end, the stream-interface structure will most
probably disappear.
To be able to move the stream-interface from the stream to the conn-stream,
all access to the SI is done via the conn-stream. This patch is limited to
the dns part.
In the same way the conn-stream has a pointer to the stream endpoint , this
patch adds a pointer to the application entity in the conn-stream
structure. For now, it is a stream or a health-check. It is mandatory to
merge the stream-interface with the conn-stream.
Because appctx is now an endpoint of the conn-stream, there is no reason to
still have the stream-interface as appctx owner. Thus, the conn-stream is
now the appctx owner.
Thanks to previous changes, it is now possible to set an appctx as endpoint
for a conn-stream. This means the appctx is no longer linked to the
stream-interface but to the conn-stream. Thus, a pointer to the conn-stream
is explicitly stored in the stream-interface. The endpoint (connection or
appctx) can be retrieved via the conn-stream.
The crash that was fixed by commit 7045590d8 ("BUG/MAJOR: dns: attempt
to lock globaly for msg waiter list instead of use barrier") was now
completely analysed and confirmed to be partially a result of the
debugging code added to LIST_INLIST(), which was looking at both
pointers and their reciprocals, and that, if used in a concurrent
context, could perfectly return false if a neighbor was being added or
removed while the current one didn't change, allowing the LIST_APPEND
to fail.
As the LIST API was not designed to be used in a concurrent context,
we should not rely on LIST_INLIST() but on the newly introduced
LIST_INLIST_ATOMIC().
This patch simply reverts the commit above to switch to the new test,
saving a lock during potentially long operations. It was verified that
the check doesn't fail anymore.
It is unsure what the performance impact of the fix above could be in
some contexts. If any performance regression is observed, it could make
sense to backport this patch, along with the previous commit introducing
the LIST_INLIST_ATOMIC() macro.
A few places have been caught triggering late bugs recently, always cases
of use-after-free because a freed element was still found in one of the
lists. This patch adds a few checks for such elements in dns_session_free()
before the final pool_free() and dns_session_io_handler() before adding
elements to lists to make sure they remain consistent. They do not trigger
anymore now.
When dns_session_release() calls dns_session_free(), it was shown that
it might still be attached there:
Program terminated with signal SIGSEGV, Segmentation fault.
#0 0x00000000006437d7 in dns_session_free (ds=0x7f895439e810) at src/dns.c:768
768 BUG_ON(!LIST_ISEMPTY(&ds->ring.waiters));
[Current thread is 1 (Thread 0x7f895bbe2700 (LWP 31792))]
(gdb) bt
#0 0x00000000006437d7 in dns_session_free (ds=0x7f895439e810) at src/dns.c:768
#1 0x0000000000643ab8 in dns_session_release (appctx=0x7f89545a4ff0) at src/dns.c:805
#2 0x000000000062e35a in si_applet_release (si=0x7f89545a5550) at include/haproxy/stream_interface.h:236
#3 0x000000000063150f in stream_int_shutw_applet (si=0x7f89545a5550) at src/stream_interface.c:1697
#4 0x0000000000640ab8 in si_shutw (si=0x7f89545a5550) at include/haproxy/stream_interface.h:437
#5 0x0000000000643103 in dns_session_io_handler (appctx=0x7f89545a4ff0) at src/dns.c:725
#6 0x00000000006d776f in task_run_applet (t=0x7f89545a5100, context=0x7f89545a4ff0, state=81924) at src/applet.c:90
#7 0x000000000068b82b in run_tasks_from_lists (budgets=0x7f895bbbf5c0) at src/task.c:611
#8 0x000000000068c258 in process_runnable_tasks () at src/task.c:850
#9 0x0000000000621e61 in run_poll_loop () at src/haproxy.c:2636
#10 0x0000000000622328 in run_thread_poll_loop (data=0x8d7440 <ha_thread_info+64>) at src/haproxy.c:2807
#11 0x00007f895c54a06b in start_thread () from /lib64/libpthread.so.0
#12 0x00007f895bf3772f in clone () from /lib64/libc.so.6
(gdb) p &ds->ring.waiters
$1 = (struct list *) 0x7f895439e8a8
(gdb) p ds->ring.waiters
$2 = {
n = 0x7f89545a5078,
p = 0x7f89545a5078
}
(gdb) p ds->ring.waiters->n
$3 = (struct list *) 0x7f89545a5078
(gdb) p *ds->ring.waiters->n
$4 = {
n = 0x7f895439e8a8,
p = 0x7f895439e8a8
}
Let's always detach it before freeing so that it remains possible to
check the dns_session's ring before releasing it, and possibly catch
bugs.
The barrier is insufficient here to protect the waiters list as we can
definitely catch situations where ds->waiter shows an inconsistency
whereby the element is not attached when entering the "if" block and
is already attached when attaching it later.
This patch uses a larger lock to maintain consistency. Without it the
code would crash in 30-180 minutes under heavy stress, always showing
the same problem (ds->waiter->n->p != &ds->waiter). Now it seems to
always resist, suggesting that this was indeed the problem.
This will have to be backported to 2.4.
Using tcp, after a session release and free, the session can remain
attached to the list of sessions with a response message waiting for
a commit (ds->waiter). This results to a use after free of this
session.
Also, on some error path and after free, a session could remain attached
to the lists of available idle/free sessions (ds->list).
This patch ensure to remove the session from those external lists
before a free.
This patch should be backported to all version including
the dns over tcp (2.4)
We'll need to improve the API to pass other arguments in the future, so
let's start to adapt better to the current use cases. task_new() is used:
- 18 times as task_new(tid_bit)
- 18 times as task_new(MAX_THREADS_MASK)
- 2 times with a single bit (in a loop)
- 1 in the debug code that uses a mask
This patch provides 3 new functions to achieve this:
- task_new_here() to create a task on the calling thread
- task_new_anywhere() to create a task to be run anywhere
- task_new_on() to create a task to run on a specific thread
The change is trivial and will allow us to later concentrate the
required adaptations to these 3 functions only. It's still possible
to call task_new() if needed but a comment was added to encourage the
use of the new ones instead. The debug code was not changed and still
uses it.
appctx_new() is exclusively called with tid_bit and it only uses the
mask to pass it to the accompanying task. There is no point requiring
the caller to know about a mask there, nor is there any point in
creating an applet outside of the context of its own thread anyway.
Let's drop this and pass tid_bit to task_new() directly.
Some of the Lua doc and a few places still used "Haproxy" or "HAproxy".
There was even one "HA proxy". A few of them were in an example of VTest
output, indicating that VTest ought to be fixed as well. No big deal but
better address all the remaining ones so that these inconsistencies stop
spreading around.
The current "ADD" vs "ADDQ" is confusing because when thinking in terms
of appending at the end of a list, "ADD" naturally comes to mind, but
here it does the opposite, it inserts. Several times already it's been
incorrectly used where ADDQ was expected, the latest of which was a
fortunate accident explained in 6fa922562 ("CLEANUP: stream: explain
why we queue the stream at the head of the server list").
Let's use more explicit (but slightly longer) names now:
LIST_ADD -> LIST_INSERT
LIST_ADDQ -> LIST_APPEND
LIST_ADDED -> LIST_INLIST
LIST_DEL -> LIST_DELETE
The same is true for MT_LISTs, including their "TRY" variant.
LIST_DEL_INIT keeps its short name to encourage to use it instead of the
lazier LIST_DELETE which is often less safe.
The change is large (~674 non-comment entries) but is mechanical enough
to remain safe. No permutation was performed, so any out-of-tree code
can easily map older names to new ones.
The list doc was updated.
This patch replaces roughly all occurrences of an HA_ATOMIC_ADD(&foo, 1)
or HA_ATOMIC_SUB(&foo, 1) with the equivalent HA_ATOMIC_INC(&foo) and
HA_ATOMIC_DEC(&foo) respectively. These are 507 changes over 45 files.
For a long time we've had fdtab[].ev and fdtab[].state which contain two
arbitrary sets of information, one is mostly the configuration plus some
shutdown reports and the other one is the latest polling status report
which also contains some sticky error and shutdown reports.
These ones used to be stored into distinct chars, complicating certain
operations and not even allowing to clearly see concurrent accesses (e.g.
fd_delete_orphan() would set the state to zero while fd_insert() would
only set the event to zero).
This patch creates a single uint with the two sets in it, still delimited
at the byte level for better readability. The original FD_EV_* values
remained at the lowest bit levels as they are also known by their bit
value. The next step will consist in merging the remaining bits into it.
The whole bits are now cleared both in fd_insert() and _fd_delete_orphan()
because after a complete check, it is certain that in both cases these
functions are the only ones touching these areas. Indeed, for
_fd_delete_orphan(), the thread_mask has already been zeroed before a
poller can call fd_update_event() which would touch the state, so it
is certain that _fd_delete_orphan() is alone. Regarding fd_insert(),
only one thread will get an FD at any moment, and it as this FD has
already been released by _fd_delete_orphan() by definition it is certain
that previous users have definitely stopped touching it.
Strictly speaking there's no need for clearing the state again in
fd_insert() but it's cheap and will remove some doubts during some
troubleshooting sessions.
It's been too short for quite a while now and is now full. It's still
time to extend it to 32-bits since we have room for this without
wasting any space, so we now gained 16 new bits for future flags.
The values were not reassigned just in case there would be a few
hidden u16 or short somewhere in which these flags are placed (as
it used to be the case with stream->pending_events).
The patch is tagged MEDIUM because this required to update the task's
process() prototype to use an int instead of a short, that's quite a
bunch of places.
When dns_connect_nameserver() is called, the nameserver has always a dgram
field properly defined. The caller, dns_send_nameserver(), already performed
the appropriate verification.
When a DNS session is created, the call to ring_attach() never fails. The
ring is freshly initialized and there is other watcher on it. Thus, the call
always succeeds.
Instead of catching an error that must never happen, we use the DISGUISE()
macro to make static analyzers happy.
