50ae717624
The following patch fixes a race condition during server addr/port update : cd994407a9545a8d84e410dc0cc18c30966b70d8 BUG/MAJOR: server/addr: fix a race during server addr:svc_port updates The new update mechanism is implemented via an event update. It uses thread isolation to guarantee that no other thread is accessing server addr/port. Furthermore, to ensure server instance is not deleted just before the event handler, server instance is lookup via its ID in proxy tree. However, thread isolation is only entered after server lookup. This leaves a tiny race condition as the thread will be marked as harmless and a concurrent thread can delete the server in the meantime. This causes server_atomic_sync() to manipulated a deleted server instance to reinsert it in used_server_addr backend tree. This can cause a segfault during this operation or possibly on a future used_server_addr tree access. This issue was detected by criteo. Several backtraces were retrieved, each related to server addr_node insert or delete operation, either in srv_set_addr_desc(), or add/delete dynamic server handlers. To fix this, simply extend thread isolation section to start it before server lookup. This ensures that once retrieved the server cannot be deleted until its addr/port are updated. To ensure this issue won't happen anymore, a new BUG_ON() is added in srv_set_addr_desc(). Also note that ebpt_delete() is now called every time on delete handler as this is a safe idempotent operation. To reproduce these crashes, a script was executed to add then remove different servers every second. In parallel, the following CLI command was issued repeatdly without any delay to force multiple update on servers port : set server <srv> addr 0.0.0.0 port $((1024 + RANDOM % 1024)) This must be backported at least up to 3.0. If above mentionned patch has been selected for previous version, this commit must also be backported on them.
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.