52a3d807fc
When a filter is registered on the data, it means it may change the payload
length by rewritting data. It means consumers of the message cannot trust the
expected length of payload as announced by the producer. The commit 8bd835b2d2
("MEDIUM: filters/htx: Don't rely on HTX extra field if payload is filtered")
was pushed to solve this issue. When the HTTP payload of a message is filtered,
the extra field is set to 0 to be sure it will never be used by error by any
consumer. However, it is not enough.
Indeed, the filters must be called before fowarding some data. They cannot be
by-passed. But if a consumer is unable to flush the HTX message, some outgoing
data can remain blocked in the channel's buffer. If some new data are then
pushed because there is some room in the channel's buffe, the producer will set
the HTX extra field. At this stage, if the consumer is unblocked and can send
again data, it is possible to call it to forward outgoing data blocked in the
channel's buffer before waking the stream up to filter new input data. It is the
purpose of the data fast-forwarding. In this case, the HTX extra field will be
seen by the consumer. It is unexpected and leads to undefined behavior.
One consequence of this bug is to perform a wrong chunking on compressed
messages, leading to processing errors at the end of the message, reported as
"ID--" in logs.
To fix the bug, a HTX flag is added to state the payload of the current HTX
message is altered. When this flag is set (HTX_FL_ALTERED_PAYLOAD), the HTX
extra field must not be trusted. And to keep things simple, when this flag is
set, the HTX extra field is automatically set to 0 when the HTX message is
loaded, in htxbuf() function.
It is probably the less intrusive way to fix the bug for now. But this part must
be reviewed to save meta-info of the HTX message outside of the message itself.
This commit should solve the issue #2741. It must be backported as far as 2.9.
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.