For now, these addresses are never set. But the idea is to be able to set
client source and destination addresses at the session level without
updating the connection ones.
Functions to fill these addresses have been added: sess_get_src() and
sess_get_dst(). If not already set, these functions relies on
conn_get_src() and conn_get_dst() to fill session addresses.
And just like for conncetions, sess_src() and sess_dst() may be used to get
source and destination addresses. However, if not set, the corresponding
address from the underlying client connection is returned. When this
happens, the addresses is filled in the connection object.
This patch replaces all advanced data type aliases on
stktable_data_cast calls by standard types.
This way we could call the same stktable_data_cast
regardless of the used advanced data type as long they
are using the same std type.
It also removes all the advanced data type aliases.
Move the session_list attach point in an anonymous union. This member is
only used for backend connections. This commit is in preparation for the
support of stopping frontend idling connections which will add another
member to the union.
This change means that a special care must be taken to be sure that only
backend connections manipulate the session_list. A few BUG_ON has been
added as special guard to prevent from misuse.
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.
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.
Remove ebmb_node entry from struct connection and create a dedicated
struct conn_hash_node. struct connection contains now only a pointer to
a conn_hash_node, allocated only for connections where target is of type
OBJ_TYPE_SERVER. This will reduce memory footprints for every
connections that does not need http-reuse such as frontend connections.
Compare the connection hash when reusing a connection from the session.
This ensures that a private connection is reused only if it shares the
same set of parameters.
Historically we've been counting lots of client-triggered events in stick
tables to help detect misbehaving ones, but we've been missing the same on
the server side, and there's been repeated requests for being able to count
the server errors per URL in order to precisely monitor the quality of
service or even to avoid routing requests to certain dead services, which
is also called "circuit breaking" nowadays.
This commit introduces http_fail_cnt and http_fail_rate, which work like
http_err_cnt and http_err_rate in that they respectively count events and
their frequency, but they only consider server-side issues such as network
errors, unparsable and truncated responses, and 5xx status codes other
than 501 and 505 (since these ones are usually triggered by the client).
Note that retryable errors are purposely not accounted for, so that only
what the client really sees is considered.
With this it becomes very simple to put some protective measures in place
to perform a redirect or return an excuse page when the error rate goes
beyond a certain threshold for a given URL, and give more chances to the
server to recover from this condition. Typically it could look like this
to bypass a URL causing more than 10 requests per second:
stick-table type string len 80 size 4k expire 1m store http_fail_rate(1m)
http-request track-sc0 base # track host+path, ignore query string
http-request return status 503 content-type text/html \
lf-file excuse.html if { sc0_http_fail_rate gt 10 }
A more advanced mechanism using gpt0 could even implement high/low rates
to disable/enable the service.
Reg-test converteers_ref_cnt_never_dec.vtc was updated to test it.
A bug was introduced by the early insertion of idle connections at the
end of connect_server. It is possible to reuse a connection not yet
ready waiting for an handshake (for example with proxy protocol or ssl).
A wrong duplicate xprt_handshake_io_cb tasklet is thus registered as a
side-effect.
This triggers the BUG_ON statement of xprt_handshake_subscribe :
BUG_ON(ctx->subs && ctx->subs != es);
To counter this, a check is now present in session_get_conn to only
return a connection without the flag CO_FL_WAIT_XPRT. This might cause
sometimes the creation of dedicated server connections when in theory
reuse could have been used, but probably only occurs rarely in real
condition.
This behavior is present since commit :
MEDIUM: connection: Add private connections synchronously in session server list
It could also be further exagerated by :
MEDIUM: backend: add reused conn to sess if mux marked as HOL blocking
It can be backported up to 2.3.
NOTE : This bug seems to be only reproducible with mode tcp, for an
unknown reason. However, reuse should never happen when not in http
mode. This improper behavior will be the subject of a dedicated patch.
This bug can easily be reproducible with the following config (a
webserver is required to accept proxy protocol on port 31080) :
global
defaults
mode tcp
timeout connect 1s
timeout server 1s
timeout client 1s
listen li
bind 0.0.0.0:4444
server bla1 127.0.0.1:31080 check send-proxy-v2
with the inject client :
$ inject -u 10000 -d 10 -G 127.0.0.1:4444
This should fix the github issue #1058.
cumulative numbers of http request and http errors of counters tracked at
the session level and their rates can now be updated at the session level
thanks to two new functions. These functions are not used for now, but it
will be called to keep tracked counters up-to-date if an error occurs before
the stream creation.
Baptiste reported a new crash affecting 2.3 which can be triggered
when using H2 on the backend, with http-reuse always and with a tens
of clients doing close only. There are a few combined cases which cause
this to happen, but each time the issue is the same, an already freed
session is dereferenced in session_unown_conn().
Two cases were identified to cause this:
- a connection referencing a session as its owner, which is detached
from the session's list and is destroyed after this session ends.
The test on conn->owner before calling session_unown_conn() is not
sufficent as the pointer is not null but is not valid anymore.
- a connection that never goes idle and that gets killed form the
mux, where session_free() is called first, then conn_free() calls
session_unown_conn() which scans the just freed session for older
connections. This one is only triggered with DEBUG_UAF
The reason for this session to be present here is that it's needed during
the connection setup, to be passed to conn_install_mux_be() to mux->init()
as the owning session, but it's never deleted aftrewards. Furthermore, even
conn_session_free() doesn't delete this pointer after freeing the session
that lies there. Both do definitely result in a use-after-free that's more
easily triggered under DEBUG_UAF.
This patch makes sure that the owner is always deleted after detaching
or killing the session. However it is currently not possible to clear
the owner right after a synchronous init because the proxy protocol
apparently needs it (a reg test checks this), and if we leave it past
the connection setup with the session not attached anywhere, it's hard
to catch the right moment to detach it. This means that the session may
remain in conn->owner as long as the connection has never been added to
nor removed from the session's idle list. Given that this patch needs to
remain simple enough to be backported, instead it adds a workaround in
session_unown_conn() to detect that the element is already not attached
anywhere.
This fix absolutely requires previous patch "CLEANUP: connection: do not
use conn->owner when the session is known" otherwise the situation will
be even worse, as some places used to rely on conn->owner instead of the
session.
The fix could theorically be backported as far as 1.8. However, the code
in this area has significantly changed along versions and there are more
risks of breaking working stuff than fixing real issues there. The issue
was really woken up in two steps during 2.3-dev when slightly reworking
the idle conns with commit 08016ab82 ("MEDIUM: connection: Add private
connections synchronously in session server list") and when adding
support for storing used H2 connections in the session and adding the
necessary call to session_unown_conn() in the muxes. But the same test
managed to crash 2.2 when built in DEBUG_UAF and patched like this,
proving that we used to already leave dangling pointers behind us:
| diff --git a/include/haproxy/connection.h b/include/haproxy/connection.h
| index f8f235c1a..dd30b5f80 100644
| --- a/include/haproxy/connection.h
| +++ b/include/haproxy/connection.h
| @@ -458,6 +458,10 @@ static inline void conn_free(struct connection *conn)
| sess->idle_conns--;
| session_unown_conn(sess, conn);
| }
| + else {
| + struct session *sess = conn->owner;
| + BUG_ON(sess && sess->origin != &conn->obj_type);
| + }
|
| sockaddr_free(&conn->src);
| sockaddr_free(&conn->dst);
It's uncertain whether an existing code path there can lead to dereferencing
conn->owner when it's bad, though certain suspicious memory corruption bugs
make one think it's a likely candidate. The patch should not be hard to
adapt there.
Backports to 2.1 and older are left to the appreciation of the person
doing the backport.
A reproducer consists in this:
global
nbthread 1
listen l
bind :9000
mode http
http-reuse always
server s 127.0.0.1:8999 proto h2
frontend f
bind :8999 proto h2
mode http
http-request return status 200
Then this will make it crash within 2-3 seconds:
$ h1load -e -r 1 -c 10 http://0:9000/
If it does not, it might be that DEBUG_UAF was not used (it's harder then)
and it might be useful to restart.
At a few places we used to rely on conn->owner to retrieve the session
while the session is already known. This is not correct because at some
of these points the reason the connection's owner was still the session
(instead of NULL) is a mistake. At one place a comparison is even made
between the session and conn->owner assuming it's valid without checking
if it's NULL. Let's clean this up to use the session all the time.
Note that this will be needed for a forthcoming fix and will have to be
backported.
Till now we would keep a per-thread queue of pending incoming connections
for which we would store:
- the listener
- the accepted FD
- the source address
- the source address' length
And these elements were first used in session_accept_fd() running on the
target thread to allocate a connection and duplicate them again. Doing
this induces various problems. The first one is that session_accept_fd()
may only run on file descriptors and cannot be reused for QUIC. The second
issue is that it induces lots of memory copies and that the listerner
queue thrashes a lot of cache, consuming 64 bytes per entry.
This patch changes this by allocating the connection before queueing it,
and by only placing the connection's pointer into the queue. Indeed, the
first two calls used to initialize the connection already store all the
information above, which can be retrieved from the connection pointer
alone. So we just have to pop one pointer from the target thread, and
pass it to session_accept_fd() which only needs the FD for the final
settings.
This starts to make the accept path a bit more transport-agnostic, and
saves memory and CPU cycles at the same time (1% connection rate increase
was noticed with 4 threads). Thanks to dividing the accept-queue entry
size from 64 to 8 bytes, its size could be increased from 256 to 1024
connections while still dividing the overall size by two. No single
queue full condition was met.
One minor drawback is that connection may be allocated from one thread's
pool to be used into another one. But this already happens a lot with
connection reuse so there is really nothing new here.
The session_get_conn() must now be used to look for an available connection
matching a specific target for a given session. This simplifies a bit the
connect_server() function.
When a connection is marked as private, it is now added in the session server
list. We don't wait a stream is detached from the mux to do so. When the
connection is created, this happens after the mux creation. Otherwise, it is
performed when the connection is marked as private.
To allow that, when a connection is created, the session is systematically set
as the connectin owner. Thus, a backend connection has always a owner during its
creation. And a private connection has always a owner until its death.
Note that outside the detach() callback, if the call to session_add_conn()
failed, the error is ignored. In this situation, we retry to add the connection
into the session server list in the detach() callback. If this fails at this
step, the multiplexer is destroyed and the connection is closed.
extern struct dict server_name_dict was moved from the type file to the
main file. A handful of inlined functions were moved at the bottom of
the file. Call places were updated to use server-t.h when relevant, or
to simply drop the entry when not needed.
