Fix a teardown race in HttpProxyStateTracker

[Ben Hillis (benhillis)]

Fix a teardown race in HttpProxyStateTracker

HttpProxyStateTracker::QueryProxySettingsAsync() published the WinHTTP resolver/session handles and reset m_requestFinished only after calling WinHttpGetProxySettingsEx(). Since that call can complete (or fail synchronously) before it even returns, the destructor could run concurrently with request setup: it could observe m_requestFinished still signaled and tear down the message queue / unregister the proxy-change notification while a request was still starting up, or tear down handles before they were fully published.

This PR fixes that by:

• Adding a lock (m_requestLock) that serializes handle creation/teardown between QueryProxySettingsAsync, RequestCompleted, and the destructor, plus an m_stopping flag so no new request can start once teardown has begun.
• Marking the request as in-flight (resetting m_requestFinished and setting m_queryState) before calling WinHttpGetProxySettingsEx, so the destructor can't proceed past m_requestFinished.wait() while a request is actually outstanding.
• Setting WINHTTP_OPTION_CONTEXT_VALUE on the resolver handle so that WINHTTP_CALLBACK_STATUS_HANDLE_CLOSING always carries a valid context — including when WinHttpGetProxySettingsEx fails synchronously (which produces no completion callback) — so RequestClosed() reliably runs and re-signals m_requestFinished instead of leaving it stuck.
• Reordering the constructor to register the proxy-change notification before submitting the initial query, so a throw during registration can't leave a queued task running against a partially-constructed object.

Testing

• Full local build.
• Multiple rounds of code review.
• Repeated concurrent wsl -e / wsl --shutdown races (including tight construct-then-shutdown loops) with no crashes or hangs observed, and the service PID remained stable throughout.

[Copilot]

Pull request overview

This PR fixes a teardown/startup race in HttpProxyStateTracker (WSL service) around WinHTTP async proxy queries, ensuring the tracker can’t begin a new query while teardown is in progress and that request lifetime is reliably tracked even when WinHTTP completes (or fails) synchronously.

Changes:

• Added a request lifecycle lock (m_requestLock) plus m_stopping to serialize request startup/teardown and prevent new requests during destruction.
• Marked requests as in-flight before calling WinHttpGetProxySettingsEx to prevent teardown from observing a “finished” state while a request is actually starting.
• Set WINHTTP_OPTION_CONTEXT_VALUE on the resolver handle so WINHTTP_CALLBACK_STATUS_HANDLE_CLOSING always has a valid context, enabling RequestClosed() to reliably re-signal m_requestFinished.
• Reordered constructor operations to register proxy-change notifications before submitting the initial query task.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/windows/service/exe/LxssHttpProxy.h	Introduces request lifecycle synchronization members (m_requestLock, m_stopping) and guards WinHTTP handles with the new lock.
src/windows/service/exe/LxssHttpProxy.cpp	Applies the new synchronization to query start/completion/destruction, sets resolver context via WINHTTP_OPTION_CONTEXT_VALUE, and reorders initialization to avoid partially-constructed usage.

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated no new comments.