Use backend connect timeout when a new connection is instantiated for
rhttp. This ensures that if connect operation fails after a certain
delay, reverse_connect listener task is woken up. This allows to free
the current connection and retry a new connect.
As a consequence of this change, rev_process() may be woken up even if
connection is not reported with CO_FL_ERROR. This happens if timeout
fired before any network reported issue. Connection freeing is adjusted
as in this case MUX instance is already allocated. Use destroy callback
to release MUX context prior to the connection itself.
This patch is really useful as a side measure for a haproxy bug
impacting connect with SSL for both backend connections and active
reverse connect. This is caused by the delayed allocation of MUX
allocation. Asynchronous connect error detected at the socket layer is
not notified to upper layers. Currently, only connect timeout allows to
release this failed connection.
SNI may be specify on a server line for connecting to the remote host.
This requires to manually set it on the connection via
ssl_sock_set_servername().
This step was missing when a server line was used for active reverse
HTTP. Fix this by adding the missing ssl_sock_set_servername()
invocation inside new_reverse_conn().
Note that for the moment, no session is instantiated to carry active
reverse connection. A direct consequence of this is that SNI sample
retrieval may crash depending if it depends on session parameters. This
should be fixed by a later commit. In the meantime, this patch is
sufficient to support simple SNI value such as constant expressions.
No need to backport.
Previously, maxconn keyword was reused for a specific usage on reverse
HTTP binds to specify the number of active connect to proceed. To avoid
confusion, introduce a new dedicated keyword 'nbconn' which is specific
to reverse HTTP bind.
This new keyword is forbidden for non-reverse listener. A fatal error is
emitted during config parsing if this rule is not respected. It's safe
because it's also forbidden to mix standard and reverse addresses on the
same bind line.
Internally, nbconn value will be reassigned to 'maxconn' member of
bind_conf structure. This ensures that listener layer will automatically
reenable the preconnect task each time a connection is closed.
Support backend configuration for explicit source address on
pre-connect. These settings can be specified via "source" backend
keyword or directly on the server line.
Previously, all source parameters triggered a BUG_ON() when binding a
reverse connect listener. This was done because some settings are
incompatible with reverse connect context : this is the case for all
source settings which do not specify a fixed address but rather rely on
a frontend connection. Indeed, in case of preconnect, connection is
initiated on its own without the existence of a previous frontend
connection.
This patch allows to use a source parameter with a fixed address. All
other settings (usesrc client/clientip/hdr_ip) are rejected on listener
binding. On connection init, alloc_bind_address() is used to set the
optional source address.
new_reverse_conn() is creating its own socket with
sock_create_server_socket(). However the connect is done with
conn->ctrl->connect() which is tcp_connect_server().
tcp_connect_server() is also creating its own socket and sets it in the
struct conn, left the previous socket unclosed and leaking at each
attempt.
This patch fixes the issue by letting tcp_connect_server() handling the
socket part, and removes it in new_reverse_conn().
Listener using "rev@" address is responsible to setup connection and
reverse it using a server instance. If an error occured before reversal
is completed, proper freeing must be taken care of by the listener as no
session exists for this.
Currently, there is two locations where a connection is freed on error
before reversal inside reverse_connect protocol. Both of these were
incomplete as several function must be used to ensure connection is
properly freed. This commit fixes this by reusing the same cleaning
mechanism used inside H2 multiplexer.
One of the biggest drawback before this patch was that connection FD was
not properly removed from fdtab which caused a file-descriptor leak.
No need to backport this.
Add reporting using send_log() for preconnect operation. This is minimal
to ensure we understand the current status of listener in active reverse
connect.
To limit logging quantity, only important transition are considered.
This requires to implement a minimal state machine as a new field in
receiver structure.
Here are the logs produced :
* Initiating : first time preconnect is enabled on a listener
* Error : last preconnect attempt interrupted on a connection error
* Reaching maxconn : all necessary connections were reversed and are
operational on a listener
No need to use task_wakeup() on rev_bind_listener() to bootstrap
preconnect. A similar call is done on rev_enable_listener() which serve
both for bootstrap and also later to reinitiate attemps to maintain
maxconn if connection are freed.
When a connection is freed during preconnect before reversal, the error
must be notified to the listener to remove any connection reference and
rearm a new preconnect attempt. Currently, this can occur through 2 code
paths :
* conn_free() called directly by H2 mux
* error during conn_create_mux(). For this case, connection is flagged
with CO_FL_ERROR and reverse_connect task is woken up. The process
task handler is then responsible to call conn_free() for such
connection.
Duplicated steps where done both in conn_free() and process task
handler. These are now removed. To facilitate code maintenance,
dedicated operation have been centralized in a new function
rev_notify_preconn_err() which is called by conn_free().
If maxconn is not set for preconnect, it assumes we want to establish a
single connection. However, this does not work properly in case the
connection is closed after reversal. Listener is not resumed by protocol
layer to attempt a new preconnect.
To fix this, explicitely set maxconn to 1 in the listener instance if
none is defined. This ensures the behavior is consistent. A BUG_ON() has
been added to validate we never try to use a listener with a 0 maxconn.
Prevent using transparent servers for pre-connect on startup by emitting
a fatal error. This is used to ensure we never try to connect to a
target with an unspecified destination address or port.
addr member of server structure is not set consistently depending on the
server address type. When using <IP:PORT> notation, its port is properly
set. However, when using <HOSTNAME:PORT>, only IP address is set after
startup name resolution but its port is left to 0.
This behavior causes preconnect to not be functional when using server
with hostname for startup name resolution. Indeed, only srv.addr is used
as connect argument through function new_reverse_conn(). To fix this,
rely on srv.svc_port : this member is always set for servers using IP or
hostname. This is similar to connect_server() on the backend side.
This does not need to be backported.
HTTP/2 demux must be handled with care for active reverse connection.
Until accept has been completed, it should be forbidden to handle
HEADERS frame as session is not yet ready to handle streams.
To implement this, use the flag H2_CF_DEM_TOOMANY which blocks demux
process. This flag is automatically set just after conn_reverse()
invocation. The flag is removed on rev_accept_conn() callback via a new
H2 ctl enum. H2 tasklet is woken up to restart demux process.
As a side-effect, reporting in H2 mux may be blocked as demux functions
are used to convert error status at the connection level with
CO_FL_ERROR. To ensure error is reported for a reverse connection, check
h2c_is_dead() specifically for this case in h2_wake(). This change also
has its own side-effect : h2c_is_dead() conditions have been adjusted to
always exclude !h2c->conn->owner condition which is always true for
reverse connection or else H2 mux may kill them unexpectedly.
An error can occured on a reverse connection before accept is completed.
In this case, no parent session can be notified. Instead, wake up the
receiver task on conn_create_mux().
As a counterpart to this, receiver task is extended to match CO_FL_ERROR
flag on pending connection. In this case, the onnection is freed. The
task is then requeued with a 1 second delay to start a new reverse
connection attempt.
Implement active reverse connection initialization. This is done through
a new task stored in the receiver structure. This task is instantiated
via bind callback and first woken up via enable callback.
Task handler is separated into two halves. On the first step, a new
connection is allocated and stored in <pend_conn> member of the
receiver. This new client connection will proceed to connect using the
server instance referenced in the bind_conf.
When connect has successfully been executed and HTTP/2 connection is
ready for exchange after SETTINGS, reverse_connect task is woken up. As
<pend_conn> is still set, the second halve is executed which only
execute listener_accept(). This will in turn execute accept_conn
callback which is defined to return the pending connection.
The task is automatically requeued inside accept_conn callback if bind
maxconn is not yet reached. This allows to specify how many connection
should be opened. Each connection is instantiated and reversed serially
one by one until maxconn is reached.
conn_free() has been modified to handle failure if a reverse connection
fails before being accepted. In this case, no session exists to notify
about the failure. Instead, reverse_connect task is requeud with a 1
second delay, giving time to fix a possible network issue. This will
allow to attempt a new connection reverse.
Note that for the moment connection rebinding after accept is disabled
for simplicity. Extra operations are required to migrate an existing
connection and its stack to a new thread which will be implemented
later.
Implement parsing for "rev@" addresses on bind line. On config parsing,
server name is stored on the bind_conf.
Several new callbacks are defined on reverse_connect protocol to
complete parsing. listen callback is used to retrieve the server
instance from the bind_conf server name. If found, the server instance
is stored on the receiver. Checks are implemented to ensure HTTP/2
protocol only is used by the server.
A new protocol named "reverse_connect" is created. This will be used to
instantiate connections that are opened by a reverse bind.
For the moment, only a minimal set of callbacks are defined with no real
work. This will be extended along the next patches.
