Fix Asio bridge retirement and cancellation-slot crashes#99
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Fix Asio bridge retirement and cancellation-slot crashes#99cursor[bot] wants to merge 2 commits into
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Co-authored-by: dallison <dallison@users.noreply.github.com>
Co-authored-by: dallison <dallison@users.noreply.github.com>
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Jul 16, 2026
…ss validation, shadow recovery) (#109) * Fix streaming RPC cancel watcher lifetimes Streaming RPC handlers in the rpc, asio_rpc, coro_rpc and co20_rpc server backends spawned a detached cancel watcher that captured the per-request AnyStreamWriter and RpcRequest stack objects by reference. After a stream completed normally or errored, a later cancel/shutdown wakeup could resume the watcher and access freed stack memory, risking server crashes or request-id corruption. AnyStreamWriter also stored the RpcRequest by reference, extending the dangling-reference hazard. Make AnyStreamWriter own a copy of the RpcRequest and share an atomic cancellation state, have watchers capture only stable request/session IDs plus the shared state and a per-stream stop pipe, and wake each watcher when the handler returns so normal completion leaves no suspended watcher behind. Combines cursor bot PR #90. * Fix Asio wait timeouts and cancellation-slot crashes Two problems in the optional Boost.Asio coroutine backend: - async::WaitEither had no timeout support, so client wrappers such as Subscriber::Wait(fd, timeout, ctx) and reliable publisher waits discarded the caller-provided timeout and could hang forever when neither fd became ready. Added timeout support to WaitEither (with a non-suspending fast path) and passed the client deadlines through. - Asio wait/socket helpers unconditionally installed cancellation handlers on the yield_context cancellation slot. Plain boost::asio::spawn(..., detached) coroutines have no connected cancellation slot, so ordinary async pub/sub paths could abort inside Boost.Asio. Guard cancellation-slot assignment/clear with is_connected(). Combines cursor bot PR #92 (supersedes the cancellation-slot portion of PR #99). * Fix bridge retirement lifetime races Bridged reliable channels with retirement notifications could crash or wedge when retirement messages raced with bridge teardown or arrived immediately after a bridged send: - The retirement receiver was spawned (via SpawnOnNewStrand, which posts work asynchronously) with a reference to a parent coroutine's stack-owned listener socket, and the retirement notifier captured a stack-owned transmitter. Shutdown or early bridge teardown could leave spawned coroutines using destroyed sockets. - Outstanding bridged ActiveMessage tracking was updated only after the network send and shared without synchronization, so a fast peer could retire a slot before it was recorded, causing a null dereference (the old code did (*active_retirement_msgs)[slot_id]->DecRef() with no null check) or a permanently pinned reliable slot. Move the retirement listener/transmitter sockets to shared ownership and close them when parent bridge coroutines unwind so helpers wake safely. Add a synchronized BridgeRetirementState that tracks bridged ActiveMessages before sending, releases duplicate/late/failed retirements safely, and cleans up outstanding slots on teardown. Combines cursor bot PR #107 (supersedes duplicate PRs #100, #102, #106 and the bridge portions of #93 and #99). * Validate bridged channel address payloads Malformed discovery/bridge protobufs could set a channel address family while providing fewer than four address bytes. The server decoded those bytes with unchecked memcpy/reinterpret_cast in bridge subscribe and retirement handling, letting a network peer trigger out-of-bounds reads/undefined behavior and potential server crashes. Add a shared ParseChannelAddress helper that validates address length and family before decoding, and use it for both the subscribe receiver and retirement socket parsing. Combines cursor bot PR #97. * Rebuild CCB subscriber registrations on shadow recovery When a server recovered channel state from a shadow, RecoverFromShadow re-created the subscriber users but never rebuilt the recovered channel's CCB subscriber registrations, so a channel could come back with a stale or zero subscriber count until the next remap. Call RegisterExistingSubscribers() after re-adding the recovered subscribers, matching the RemapChannel path. Combines cursor bot PR #96. * Update bazel lock file * Confine bridge retirement state to one strand, drop its mutex The BridgeRetirementState vector was shared between the bridge transmitter and its retirement-reader coroutine, which ran on two separate strands, so it needed a mutex to stay correct under a multi-threaded io_context. Spawn the retirement reader on the transmitter's own strand (new AsyncRuntime::SpawnOnCurrentStrand) so the two are serialized by the strand and the mutex can be removed. They still interleave cooperatively at every suspension point, so the reader keeps draining retirements while the transmitter is parked on backpressure.
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Bug and impact
SpawnOnNewStrandcaptured retirement sockets by reference to parent coroutine locals. Under the Asio backend, spawn is deferred through a strand, so bridge teardown or early return could leave the child coroutine dereferencing destroyed stack state, causing intermittent crashes or memory corruption for bridged reliable channels using retirement notifications.yield_contextcancellation slots. User coroutines spawned normally withboost::asio::detachedhave no connected cancellation slot, so async client paths could abort inside Boost.Asio (cancellation_signal::prepare_memory) during ordinary pub/sub use.Root cause
yield_contextcame fromAsyncRuntime::SpawnTracked, which provides a connected cancellation slot.Fix
std::shared_ptrcaptured by value into deferred coroutines.is_connected()and add regression coverage for detached user coroutines.Validation
npx --yes @bazel/bazelisk test --//:coro_backend=asio //client:bridge_test //client:asio_client_test //common/async:async_testnpx --yes @bazel/bazelisk test //common/async:async_test //client:bridge_test --test_filter='BridgeTest.BasicRetirement:BridgeTest.MultipleRetirement:BridgeTest.MultipleRetirement2'