# Re: Eeck.. network protocol

David Mosberger-Tang (David.Mosberger@acm.org)
Fri, 5 Jun 1998 21:39:33 -0700

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>>>>> On Fri, 5 Jun 1998 08:49:29 -0700, "Brian Macy" <bmacy@sunshinecomputing.com> said:

Brian> Is it just me or is the SANE network protocol full of race
Brian> conditions on replies? There is now way to identify a
Brian> reply. It expects the bytes being read to be associated with
Brian> the last sent packet.

Brian> From what I can tell if you send a packet and the response
Brian> times out you are screwed. It is possible the remote saned
Brian> will still send the bytes, even if you call
Brian> SANE_NET_CANCEL. There is no way (that I can tell) that the
Brian> communication link can recover.

Brian> Even the sends could incorrectly fail under heavy system
Brian> loads, in fact I believe the watch could cause a process
Brian> deadlock. If the alarm triggers before the actual read/write
Brian> will the read timeout?

Brian> Has anyone thought about a simple frame around these things?

You do realize that the SANE network protocol is designed to run on
top of a reliable, ordered bytestream, such as TCP, right?

BTW: as suggested earlier, I think you'd benefit from looking at the
existing source code.

--david

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