Copyright (c) 2000 Markus Friedl. All rights reserved.
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OpenSSH Channel Close Protocol 2.0 Implementation Channel Input State Diagram
S reset l=1 s=1.2 ellipsewid=s*ellipsewid boxwid=s*boxwid ellipseht=s*ellipseht S1: ellipse "INPUT" "OPEN" move right 2*l from last ellipse.e S3: ellipse invis move down l from last ellipse.s S4: ellipse "INPUT" "CLOSED" move down l from 1st ellipse.s S2: ellipse "INPUT" "WAIT" "DRAIN" arrow from S1.e to S4.n box invis "rcvd CLOSE/" "shutdown_read" with .sw at last arrow.c arrow "ibuf_empty ||" "rcvd CLOSE/" "send EOF" "" from S2.e to S4.w arrow from S1.s to S2.n box invis "read_failed ||" "rcvd EOW/" "shutdown_read" with .e at last arrow.c ellipse wid .9*ellipsewid ht .9*ellipseht at S4 arrow "start" "" from S1.w+(-0.5,0) to S1.w
E
Channel Output State DiagramS S1: ellipse "OUTPUT" "OPEN" move right 2*l from last ellipse.e S3: ellipse invis move down l from last ellipse.s S4: ellipse "OUTPUT" "CLOSED" move down l from 1st ellipse.s S2: ellipse "OUTPUT" "WAIT" "DRAIN" arrow from S1.e to S4.n box invis "write_failed/" "shutdown_write" "send EOW" with .sw at last arrow.c arrow "obuf_empty ||" "write_failed/" "shutdown_write" "" from S2.e to S4.w arrow from S1.s to S2.n box invis "rcvd EOF ||" "rcvd CLOSE/" "-" with .e at last arrow.c ellipse wid .9*ellipsewid ht .9*ellipseht at S4 arrow "start" "" from S1.w+(-0.5,0) to S1.w
E
NotesThe input buffer is filled with data from the socket (the socket represents the local consumer/producer of the forwarded channel). The data is then sent over the INPUT-end (transmit-end) of the channel to the remote peer. Data sent by the peer is received on the OUTPUT-end (receive-end), saved in the output buffer and written to the socket.
If the local protocol instance has forwarded all data on the INPUT-end of the channel, it sends an EOF message to the peer.
A CLOSE message is sent to the peer if both the INPUT- and the OUTOUT-half of the local end of the channel are closed.
The channel can be deallocated by a protocol instance if a CLOSE message he been both sent and received.