It's legal for a single net.Conn to be shared between goroutines, for example calling Close() on <- ctx.Done() while calls are blocked in Read and Write.
The multiplexer does not impose an ordering in send: each concurrent call simply competes for the writeMutex.
Therefore sequences we considered invalid are actually possible:
Close(id) then Window(id)
Close(id) then Write(id)
Close(id) then Shutdown(id)
Previously we detected these invalid sequences and shutdown the whole multiplexer. The effect would be to completely disable port forwarding.
Instead we drop these out-of-order packets and log (just in case it's interesting). There is a very small risk that an old out-of-order packet could be mixed up with a new packet if the channel ID is reused, but we have a space of 2**32 of those so re-use is unlikely.
It's legal for a single
net.Connto be shared between goroutines, for example callingClose()on<- ctx.Done()while calls are blocked inReadandWrite.The multiplexer does not impose an ordering in
send: each concurrent call simply competes for thewriteMutex.Therefore sequences we considered invalid are actually possible:
Close(id)thenWindow(id)Close(id)thenWrite(id)Close(id)thenShutdown(id)Previously we detected these invalid sequences and shutdown the whole multiplexer. The effect would be to completely disable port forwarding.
Instead we drop these out-of-order packets and log (just in case it's interesting). There is a very small risk that an old out-of-order packet could be mixed up with a new packet if the channel ID is reused, but we have a space of 2**32 of those so re-use is unlikely.