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Annotation of src/usr.bin/ssh/nchan.ms, Revision 1.5.2.1

1.4       markus      1: .\"
                      2: .\" Copyright (c) 1999 Markus Friedl.  All rights reserved.
                      3: .\"
                      4: .\" Redistribution and use in source and binary forms, with or without
                      5: .\" modification, are permitted provided that the following conditions
                      6: .\" are met:
                      7: .\" 1. Redistributions of source code must retain the above copyright
                      8: .\"    notice, this list of conditions and the following disclaimer.
                      9: .\" 2. Redistributions in binary form must reproduce the above copyright
                     10: .\"    notice, this list of conditions and the following disclaimer in the
                     11: .\"    documentation and/or other materials provided with the distribution.
                     12: .\"
                     13: .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
                     14: .\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
                     15: .\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
                     16: .\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
                     17: .\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
                     18: .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
                     19: .\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
                     20: .\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
                     21: .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
                     22: .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
                     23: .\"
1.1       markus     24: .TL
                     25: OpenSSH Channel Close Protocol 1.5 Implementation
                     26: .SH
                     27: Channel Input State Diagram
                     28: .PS
                     29: reset
                     30: l=1
                     31: s=1.2
                     32: ellipsewid=s*ellipsewid
                     33: boxwid=s*boxwid
                     34: ellipseht=s*ellipseht
                     35: S1: ellipse "INPUT" "OPEN"
                     36: move right 2*l from last ellipse.e
                     37: S4: ellipse "INPUT" "CLOSED"
                     38: move down l from last ellipse.s
                     39: S3: ellipse "INPUT" "WAIT" "OCLOSED"
                     40: move down l from 1st ellipse.s
                     41: S2: ellipse "INPUT" "WAIT" "DRAIN"
                     42: arrow "" "rcvd OCLOSE/" "shutdown_read" "send IEOF" from S1.e to S4.w
                     43: arrow "ibuf_empty/" "send IEOF" from S2.e to S3.w
                     44: arrow from S1.s to S2.n
                     45: box invis "read_failed/" "shutdown_read" with .e at last arrow.c
                     46: arrow  from S3.n to S4.s
                     47: box invis "rcvd OCLOSE/" "-" with .w at last arrow.c
                     48: ellipse wid .9*ellipsewid ht .9*ellipseht at S4
                     49: arrow "start" "" from S1.w+(-0.5,0) to S1.w
1.5       markus     50: arrow from S2.ne to S4.sw
                     51: box invis "rcvd OCLOSE/     " with .e at last arrow.c
                     52: box invis " send IEOF" with .w at last arrow.c
1.1       markus     53: .PE
                     54: .SH
                     55: Channel Output State Diagram
                     56: .PS
                     57: S1: ellipse "OUTPUT" "OPEN"
                     58: move right 2*l from last ellipse.e
                     59: S3: ellipse "OUTPUT" "WAIT" "IEOF"
                     60: move down l from last ellipse.s
                     61: S4: ellipse "OUTPUT" "CLOSED"
                     62: move down l from 1st ellipse.s
                     63: S2: ellipse "OUTPUT" "WAIT" "DRAIN"
                     64: arrow "" "write_failed/" "shutdown_write" "send OCLOSE" from S1.e to S3.w
                     65: arrow "obuf_empty ||" "write_failed/" "shutdown_write" "send OCLOSE" from S2.e to S4.w
                     66: arrow from S1.s to S2.n
                     67: box invis "rcvd IEOF/" "-" with .e at last arrow.c
                     68: arrow from S3.s to S4.n
                     69: box invis "rcvd IEOF/" "-" with .w at last arrow.c
                     70: ellipse wid .9*ellipsewid ht .9*ellipseht at S4
                     71: arrow "start" "" from S1.w+(-0.5,0) to S1.w
                     72: .PE
1.2       markus     73: .SH
                     74: Notes
                     75: .PP
                     76: The input buffer is filled with data from the socket
1.5       markus     77: (the socket represents the local consumer/producer of the
1.2       markus     78: forwarded channel).
1.3       markus     79: The data is then sent over the INPUT-end (transmit-end) of the channel to the
1.2       markus     80: remote peer.
1.3       markus     81: Data sent by the peer is received on the OUTPUT-end (receive-end),
1.2       markus     82: saved in the output buffer and written to the socket.
                     83: .PP
                     84: If the local protocol instance has forwarded all data on the
                     85: INPUT-end of the channel, it sends an IEOF message to the peer.
1.5       markus     86: If the peer receives the IEOF and has consumed all
1.2       markus     87: data he replies with an OCLOSE.
                     88: When the local instance receives the OCLOSE
                     89: he considers the INPUT-half of the channel closed.
                     90: The peer has his OUTOUT-half closed.
                     91: .PP
                     92: A channel can be deallocated by a protocol instance
                     93: if both the INPUT- and the OUTOUT-half on his
                     94: side of the channel are closed.
1.5       markus     95: Note that when an instance is unable to consume the
1.2       markus     96: received data, he is permitted to send an OCLOSE
                     97: before the matching IEOF is received.