fix race condition when accepting streams #2874
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lucas-clemente
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What's happening here is the following: In
AcceptStreamwe check if the stream we want to return already exists: https://github.com/lucas-clemente/quic-go/blob/629272c7138e9f2824d5cbf5d629e801339301d7/streams_map_incoming_generic.go#L64-L73It does not. Before advance to the
selectstatement, the go routine is preempted andGetOrOpenStreamis called and the stream is created. SincenewStreamChanis an unbuffered channel,GetOrOpenStreamdoesn't send on that channel:https://github.com/lucas-clemente/quic-go/blob/629272c7138e9f2824d5cbf5d629e801339301d7/streams_map_incoming_generic.go#L116-L122
Now
AcceptStreamwill never return the stream, as it's now blocking on theselectstatement.The solution is simple: make
newStreamChana channel of capacity 1.