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1 | .\" $OpenBSD: nchan.ms,v 1.8 2003/11/21 11:57:03 djm Exp $ | |
2 | .\" | |
3 | .\" | |
4 | .\" Copyright (c) 1999 Markus Friedl. All rights reserved. | |
5 | .\" | |
6 | .\" Redistribution and use in source and binary forms, with or without | |
7 | .\" modification, are permitted provided that the following conditions | |
8 | .\" are met: | |
9 | .\" 1. Redistributions of source code must retain the above copyright | |
10 | .\" notice, this list of conditions and the following disclaimer. | |
11 | .\" 2. Redistributions in binary form must reproduce the above copyright | |
12 | .\" notice, this list of conditions and the following disclaimer in the | |
13 | .\" documentation and/or other materials provided with the distribution. | |
14 | .\" | |
15 | .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR | |
16 | .\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES | |
17 | .\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. | |
18 | .\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, | |
19 | .\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT | |
20 | .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, | |
21 | .\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY | |
22 | .\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT | |
23 | .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF | |
24 | .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | |
25 | .\" | |
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 | |
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 | |
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 | |
75 | .SH | |
76 | Notes | |
77 | .PP | |
78 | The input buffer is filled with data from the socket | |
79 | (the socket represents the local consumer/producer of the | |
80 | forwarded channel). | |
81 | The data is then sent over the INPUT-end (transmit-end) of the channel to the | |
82 | remote peer. | |
83 | Data sent by the peer is received on the OUTPUT-end (receive-end), | |
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. | |
88 | If the peer receives the IEOF and has consumed all | |
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. | |
97 | Note that when an instance is unable to consume the | |
98 | received data, he is permitted to send an OCLOSE | |
99 | before the matching IEOF is received. |