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Ben Lindstrom8bceffb2001-10-04 21:16:57 +00001.\" $OpenBSD: nchan2.ms,v 1.2 2001/10/03 10:05:57 markus Exp $
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Damien Miller33b13562000-04-04 14:38:59 +100025.TL
26OpenSSH Channel Close Protocol 2.0 Implementation
27.SH
28Channel Input State Diagram
29.PS
30reset
31l=1
32s=1.2
33ellipsewid=s*ellipsewid
34boxwid=s*boxwid
35ellipseht=s*ellipseht
36S1: ellipse "INPUT" "OPEN"
37move right 2*l from last ellipse.e
38S3: ellipse invis
39move down l from last ellipse.s
40S4: ellipse "INPUT" "CLOSED"
41move down l from 1st ellipse.s
42S2: ellipse "INPUT" "WAIT" "DRAIN"
43arrow from S1.e to S4.n
44box invis "rcvd CLOSE/" "shutdown_read" with .sw at last arrow.c
45arrow "ibuf_empty ||" "rcvd CLOSE/" "send EOF" "" from S2.e to S4.w
46arrow from S1.s to S2.n
47box invis "read_failed/" "shutdown_read" with .e at last arrow.c
48ellipse wid .9*ellipsewid ht .9*ellipseht at S4
49arrow "start" "" from S1.w+(-0.5,0) to S1.w
50.PE
51.SH
52Channel Output State Diagram
53.PS
54S1: ellipse "OUTPUT" "OPEN"
55move right 2*l from last ellipse.e
56S3: ellipse invis
57move down l from last ellipse.s
58S4: ellipse "OUTPUT" "CLOSED"
59move down l from 1st ellipse.s
60S2: ellipse "OUTPUT" "WAIT" "DRAIN"
61arrow from S1.e to S4.n
62box invis "write_failed/" "shutdown_write" with .sw at last arrow.c
63arrow "obuf_empty ||" "write_failed/" "shutdown_write" "" from S2.e to S4.w
64arrow from S1.s to S2.n
65box invis "rcvd EOF ||" "rcvd CLOSE/" "-" with .e at last arrow.c
66ellipse wid .9*ellipsewid ht .9*ellipseht at S4
67arrow "start" "" from S1.w+(-0.5,0) to S1.w
68.PE
69.SH
70Notes
71.PP
72The input buffer is filled with data from the socket
73(the socket represents the local consumer/producer of the
74forwarded channel).
75The data is then sent over the INPUT-end (transmit-end) of the channel to the
76remote peer.
77Data sent by the peer is received on the OUTPUT-end (receive-end),
78saved in the output buffer and written to the socket.
79.PP
80If the local protocol instance has forwarded all data on the
81INPUT-end of the channel, it sends an EOF message to the peer.
82.PP
83A CLOSE message is sent to the peer if
84both the INPUT- and the OUTOUT-half of the local
85end of the channel are closed.
86.PP
87The channel can be deallocated by a protocol instance
88if a CLOSE message he been both sent and received.