239d6c5260
f595daf1ddtest: ensure HTTPServer race condition is fixed (Matthew Zipkin)b98b10c072test: introduce a worker thread in http socket error test (Matthew Zipkin)922b08d375test: socket error handling in HTTPServer using ErrorSock mock socket (Matthew Zipkin)73da2a8a52http: prevent race condition between worker thread and I/O thread (Matthew Zipkin) Pull request description: This prevents a losing race condition that could prevent the server from reading any more requests from an HTTP client. Found and reported by the fuzzing department:7fe5f54497The Race: A connected socket can either be written to or read from based on the result of `GenerateWaitSockets()`. That method checks the `HTTPRemoteClient` flag `m_send_ready`. If it's `true` the implication is that there is data in the client's send buffer ready to go. Once that data is sent and the buffer is empty, `MaybeSendBytesFromBuffer()` sets it `false` again. The sad case was when a worker thread calling `WriteReply()` adds data to the send buffer, but before it sets `m_send_ready` to `true`, the I/O thread sends that data and empties the buffer. With the buffer unexpectedly empty, `WriteReply()` sets `m_send_ready` to `true`. The effect of this is that the socket will stay in "write" mode with nothing to write. With nothing to write, `MaybeSendBytesFromBuffer()` never sets it back to `false` and the socket is stuck forever. The Fix: Simply move `m_send_ready = true` inside the block of `WriteReply()` where `m_send_mutex` is still held. This prevents the I/O thread from emptying the send buffer while the worker thread is setting the flag. Testing: To observe the race condition, revert the first commit `"http: prevent race condition between worker thread and I/O thread"` and run the unit test from the remainder of the branch. I like to see the logs: `test_bitcoin --log_level=all --run_test=httpserver_tests -- --printtoconsole --debug=http --debug=lock' The test will fail with a small probability. The socket will get stuck and the test will abort after a 60 second timeout. To garuntee the race condition loses and fail the test every time, slow down `WriteReply()` in the worker thread: ```diff diff --git a/src/httpserver.cpp b/src/httpserver.cpp index 99e30ff663..b0c7b516d8 100644 --- a/src/httpserver.cpp +++ b/src/httpserver.cpp @@ -614,6 +614,7 @@ void HTTPRequest::WriteReply(HTTPStatusCode status, std::span<const std::byte> r } else { // Inform HTTPServer I/O that data is ready to be sent to this client // in the next loop iteration. + std::this_thread::sleep_for(500ms); m_client->m_send_ready = true; } ``` With the first commit (the fix) back in place, slowing down the worker thread like this won't fail the test. Bonus: The unit test is spread over three commits. First, a method of the socket testing setup is templated so a mock socket that intentionally raises an error can be inserted. The unit test added in that commit covers a race condition that was fixed in #35182 in response to https://github.com/bitcoin/bitcoin/pull/35182/changes#r3358889539 so we get the added benefit of covering an error path, and guaranteeing coverage of both "optimistic send" (directly from worker thread) and regular send (from a tick in the I/O loop thread). The next commit adds a worker thread to the unit test, at which point a race condition is possible but very unlikely because all requests are sent at once. Finally, we spread out the requests in the top commit and make the race condition much easier to catch. ACKs for top commit: janb84: crACKf595daf1dddergoegge: utACKf595daf1ddtheStack: Code-review ACKf595daf1ddTree-SHA512: 451982fd72724c4115e371fc6392605693d6c3207f00ffebcf027aae9253f7974b5b1165b9f46c91b5436d7fe60c7d27316fb0b79f729ab0bf8f32db2530075f
Bitcoin Core integration/staging tree
For an immediately usable, binary version of the Bitcoin Core software, see https://bitcoincore.org/en/download/.
What is Bitcoin Core?
Bitcoin Core connects to the Bitcoin peer-to-peer network to download and fully validate blocks and transactions. It also includes a wallet and graphical user interface, which can be optionally built.
Further information about Bitcoin Core is available in the doc folder.
License
Bitcoin Core is released under the terms of the MIT license. See COPYING for more information or see https://opensource.org/license/MIT.
Development Process
The master branch is regularly built (see doc/build-*.md for instructions) and tested, but it is not guaranteed to be
completely stable. Tags are created
regularly from release branches to indicate new official, stable release versions of Bitcoin Core.
The https://github.com/bitcoin-core/gui repository is used exclusively for the development of the GUI. Its master branch is identical in all monotree repositories. Release branches and tags do not exist, so please do not fork that repository unless it is for development reasons.
The contribution workflow is described in CONTRIBUTING.md and useful hints for developers can be found in doc/developer-notes.md.
Testing
Testing and code review is the bottleneck for development; we get more pull requests than we can review and test on short notice. Please be patient and help out by testing other people's pull requests, and remember this is a security-critical project where any mistake might cost people lots of money.
Automated Testing
Developers are strongly encouraged to write unit tests for new code, and to
submit new unit tests for old code. Unit tests can be compiled and run
(assuming they weren't disabled during the generation of the build system) with: ctest. Further details on running
and extending unit tests can be found in /src/test/README.md.
There are also regression and integration tests, written
in Python.
These tests can be run (if the test dependencies are installed) with: build/test/functional/test_runner.py
(assuming build is your build directory).
The CI (Continuous Integration) systems make sure that every pull request is tested on Windows, Linux, and macOS. The CI must pass on all commits before merge to avoid unrelated CI failures on new pull requests.
Manual Quality Assurance (QA) Testing
Changes should be tested by somebody other than the developer who wrote the code. This is especially important for large or high-risk changes. It is useful to add a test plan to the pull request description if testing the changes is not straightforward.
Translations
Changes to translations as well as new translations can be submitted to Bitcoin Core's Transifex page.
Translations are periodically pulled from Transifex and merged into the git repository. See the translation process for details on how this works.
Important: We do not accept translation changes as GitHub pull requests because the next pull from Transifex would automatically overwrite them again.