Annotation of src/usr.bin/ssh/nchan.ms, Revision 1.8
1.8 ! djm 1: .\" $OpenBSD: nchan.ms,v 1.7 2001/01/29 01:58:17 niklas Exp $
! 2: .\"
1.7 niklas 3: .\"
1.4 markus 4: .\" Copyright (c) 1999 Markus Friedl. All rights reserved.
1.8 ! djm 5: .\"
1.4 markus 6: .\" Redistribution and use in source and binary forms, with or without
7: .\" modification, are permitted provided that the following conditions
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9: .\" 1. Redistributions of source code must retain the above copyright
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11: .\" 2. Redistributions in binary form must reproduce the above copyright
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13: .\" documentation and/or other materials provided with the distribution.
1.8 ! djm 14: .\"
1.4 markus 15: .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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1.1 markus 26: .TL
27: OpenSSH Channel Close Protocol 1.5 Implementation
28: .SH
29: Channel Input State Diagram
30: .PS
31: reset
32: l=1
33: s=1.2
34: ellipsewid=s*ellipsewid
35: boxwid=s*boxwid
36: ellipseht=s*ellipseht
37: S1: ellipse "INPUT" "OPEN"
38: move right 2*l from last ellipse.e
39: S4: ellipse "INPUT" "CLOSED"
40: move down l from last ellipse.s
41: S3: ellipse "INPUT" "WAIT" "OCLOSED"
42: move down l from 1st ellipse.s
43: S2: ellipse "INPUT" "WAIT" "DRAIN"
44: arrow "" "rcvd OCLOSE/" "shutdown_read" "send IEOF" from S1.e to S4.w
45: arrow "ibuf_empty/" "send IEOF" from S2.e to S3.w
46: arrow from S1.s to S2.n
47: box invis "read_failed/" "shutdown_read" with .e at last arrow.c
48: arrow from S3.n to S4.s
49: box invis "rcvd OCLOSE/" "-" with .w at last arrow.c
50: ellipse wid .9*ellipsewid ht .9*ellipseht at S4
51: arrow "start" "" from S1.w+(-0.5,0) to S1.w
1.5 markus 52: arrow from S2.ne to S4.sw
53: box invis "rcvd OCLOSE/ " with .e at last arrow.c
54: box invis " send IEOF" with .w at last arrow.c
1.1 markus 55: .PE
56: .SH
57: Channel Output State Diagram
58: .PS
59: S1: ellipse "OUTPUT" "OPEN"
60: move right 2*l from last ellipse.e
61: S3: ellipse "OUTPUT" "WAIT" "IEOF"
62: move down l from last ellipse.s
63: S4: ellipse "OUTPUT" "CLOSED"
64: move down l from 1st ellipse.s
65: S2: ellipse "OUTPUT" "WAIT" "DRAIN"
66: arrow "" "write_failed/" "shutdown_write" "send OCLOSE" from S1.e to S3.w
67: arrow "obuf_empty ||" "write_failed/" "shutdown_write" "send OCLOSE" from S2.e to S4.w
68: arrow from S1.s to S2.n
69: box invis "rcvd IEOF/" "-" with .e at last arrow.c
70: arrow from S3.s to S4.n
71: box invis "rcvd IEOF/" "-" with .w at last arrow.c
72: ellipse wid .9*ellipsewid ht .9*ellipseht at S4
73: arrow "start" "" from S1.w+(-0.5,0) to S1.w
74: .PE
1.2 markus 75: .SH
76: Notes
77: .PP
78: The input buffer is filled with data from the socket
1.5 markus 79: (the socket represents the local consumer/producer of the
1.2 markus 80: forwarded channel).
1.3 markus 81: The data is then sent over the INPUT-end (transmit-end) of the channel to the
1.2 markus 82: remote peer.
1.3 markus 83: Data sent by the peer is received on the OUTPUT-end (receive-end),
1.2 markus 84: saved in the output buffer and written to the socket.
85: .PP
86: If the local protocol instance has forwarded all data on the
87: INPUT-end of the channel, it sends an IEOF message to the peer.
1.5 markus 88: If the peer receives the IEOF and has consumed all
1.2 markus 89: data he replies with an OCLOSE.
90: When the local instance receives the OCLOSE
91: he considers the INPUT-half of the channel closed.
92: The peer has his OUTOUT-half closed.
93: .PP
94: A channel can be deallocated by a protocol instance
95: if both the INPUT- and the OUTOUT-half on his
96: side of the channel are closed.
1.5 markus 97: Note that when an instance is unable to consume the
1.2 markus 98: received data, he is permitted to send an OCLOSE
99: before the matching IEOF is received.