I asked this question on Stackoverflow (even offered a bounty) and IRC: http://stackoverflow.com/questions/13117502/twisted-conch-flow-control --
I have a Twisted Conch SSH server and the typical scenario is this: git via OpenSSH client >>--- WAN1 --->> Twisted conch svr >>--- WAN2 -->> Git server There will be occassions that the 'git push' is sending data faster over WAN1 than I can proxy it over WAN2, so I need to tell the client to slow down (well before any TCP packet loss causes adjustments the TCP window size) to avoid buffering too much on the Twisted server. Reading the RFC for SSH this is accomplished with not acknowledging via adj window this will then cause the git push to block on syscall write to the pipe backed by openssh. Looking at conch/ssh/connection.py:L216 in the method def ssh_CHANNEL_DATA(self, packet): I can accomplish this with setting localWindowSize to 0, and inflight data will still land as the predicate on 230 should still pass (give localWindowLeft). I am wondering if this is the correct approach or am I missing something blindly obvious with regards to flow control with Twisted SSH Conch? * Note: I acknowledge there are methods placeholders for stopWriting and startWriting on (channel) that I can override so I have hooks to control the other side of the transmission 'git pull', but Im interested in first leg. Also IPush/IPull producer dont seem applicable at this level and I cant see how I can tie in these higher abstraction without butchering conch? -- Matt Freeman - @nonuby - http://blog.nonuby.com
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