76fa71f7a8
When a shutdown is reported to the mux (shutdown for reads or writes), the
connexion is immediately fully closed if the mux detects the connexion is
closed in both directions. Only the passthrough multiplexer is able to
perform this action at this stage because there is no stream and no internal
data. Other muxes perform a full connection close during the mux's release
stage. It was working quite well since recently. But, in theory, the bug is
quite old.
In fact, it seems possible for the lower layer to report an error on the
connection in same time a shutdown is performed on the mux. Depending on how
events are scheduled, the following may happen:
1. An connection error is detected at the fd layer and a wakeup is
scheduled on the mux to handle the event.
2. A shutdown for writes is performed on the mux. Here the mux decides to
fully close the connexion. If the xprt is not used to log info, it is
released.
3. The mux is finally woken up. It tries to retrieve data from the xprt
because it is not awayre there was an error. This leads to a crash
because of a NULL-deref.
By reading the code, it is not obvious. But it seems possible with SSL
connection when the handshake is rearmed. It happens when a
SSL_ERROR_WANT_WRITE is reported on a SSL_read() attempt or a
SSL_ERROR_WANT_READ on a SSL_write() attempt.
This bug is only visible if the XPRT is not used to log info. So it is no so
common.
This patch should fix the 2nd crash reported in the issue #2656. It must
first be backported as far as 2.9 and then slowly to all stable versions.
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HAProxy
HAProxy is a free, very fast and reliable reverse-proxy offering high availability, load balancing, and proxying for TCP and HTTP-based applications.
Installation
The INSTALL file describes how to build HAProxy. A list of packages is also available on the wiki.
Getting help
The discourse and the mailing-list are available for questions or configuration assistance. You can also use the slack or IRC channel. Please don't use the issue tracker for these.
The issue tracker is only for bug reports or feature requests.
Documentation
The HAProxy documentation has been split into a number of different files for ease of use. It is available in text format as well as HTML. The wiki is also meant to replace the old architecture guide.
Please refer to the following files depending on what you're looking for:
- INSTALL for instructions on how to build and install HAProxy
- BRANCHES to understand the project's life cycle and what version to use
- LICENSE for the project's license
- CONTRIBUTING for the process to follow to submit contributions
The more detailed documentation is located into the doc/ directory:
- doc/intro.txt for a quick introduction on HAProxy
- doc/configuration.txt for the configuration's reference manual
- doc/lua.txt for the Lua's reference manual
- doc/SPOE.txt for how to use the SPOE engine
- doc/network-namespaces.txt for how to use network namespaces under Linux
- doc/management.txt for the management guide
- doc/regression-testing.txt for how to use the regression testing suite
- doc/peers.txt for the peers protocol reference
- doc/coding-style.txt for how to adopt HAProxy's coding style
- doc/internals for developer-specific documentation (not all up to date)
License
HAProxy is licensed under GPL 2 or any later version, the headers under LGPL 2.1. See the LICENSE file for a more detailed explanation.