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Markus Friedl markus at openbsd.org
Thu Nov 8 22:25:19 EST 2001


hi,

if i understand you correctly your problem is that you and i disagree
about what 'window size' means and what data/length is included in the
'window'

if i send a
	byte      SSH_MSG_CHANNEL_DATA
	uint32    recipient channel
	string    data
packet in OpenSSH, i count only the actual size of the data,
and not the size of the complete packet as sent on the wire.

draft-ietf-secsh-connect-11.txt says:
	"The window size is decremented by the amount of data sent."

i don't think that the additional 1+4+4 bytes (byte,uint32,uint32)
should be included in the window size counter. but i could be wrong.
perhaps the draft is ambiguous about this.

what do other implementations do?

i think that only the size of the actual 'payload' data should be
included in the window size, because you usually send
SSH_MSG_CHANNEL_WINDOW_ADJUST messages if you have consumed the data
(e.g. written the data to a socket).

when forwarding/consuming the data received on a channel, OpenSSH does
no longer know over how many packets this data was originally
distributed. so only the length of the payload, the amount of data
written to the 'consumer-socket' can be used to caculate the size for
SSH_MSG_CHANNEL_WINDOW_ADJUST.

-m



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