Fix head-of-line blocking and resource leak in BidirectionalRelay#713
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mlsad3 wants to merge 5 commits intoapple:mainfrom
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Fix head-of-line blocking and resource leak in BidirectionalRelay#713mlsad3 wants to merge 5 commits intoapple:mainfrom
mlsad3 wants to merge 5 commits intoapple:mainfrom
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Replace synchronous write() calls with non-blocking I/O and DispatchSourceWrite backpressure in BidirectionalRelay. When a destination fd's buffer fills (e.g. during high container launch concurrency), the relay now suspends reading and installs a write source to drain pending data, instead of blocking the dispatch queue. Also remove the shared serial DispatchQueue from UnixSocketRelayManager so each BidirectionalRelay uses its own queue. Previously, a single blocked write on any connection would freeze ALL relay connections, including unrelated commands like `docker version`.
Resume suspended read sources before cancelling in stop(). GCD will not deliver cancel handlers on suspended dispatch sources, which caused file descriptor and memory leaks when connections were torn down while under backpressure. Also guard-unwrap buf.baseAddress in drainPendingWrite. Adds test for stop() while backpressured to verify cancel handlers fire.
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Replace synchronous
write()calls inBidirectionalRelaywith non-blocking I/O andDispatchSourceWritebackpressure handling. Under concurrent vsock proxy load, a single blocked write on the shared serial dispatch queue would freeze all relay connections permanently, including unrelated new connections.Closes #712
Changes
O_NONBLOCKand handleEAGAINby suspending reads and installing a write source to drain pending dataBidirectionalRelayits own serial queue instead of sharing one fromUnixSocketRelayManager, eliminating cross-connection blockingstop()— GCD does not deliver cancel handlers on suspended dispatch sources, which caused file descriptor and memory leaks on teardown under backpressurebuf.baseAddressindrainPendingWriteTest plan
Added
BidirectionalRelayTestswith 5 tests:EAGAIN→ write source drain → resume)waitForCompletion()resolves)Tested under sustained concurrent load that previously caused permanent hangs; verified normal operations work correctly after sustained load.