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Annotation of src/usr.bin/ssh/nchan.ms, Revision 1.4

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: .\" 3. All advertising materials mentioning features or use of this software
        !            13: .\"    must display the following acknowledgement:
        !            14: .\"      This product includes software developed by Markus Friedl.
        !            15: .\" 4. The name of the author may not be used to endorse or promote products
        !            16: .\"    derived from this software without specific prior written permission.
        !            17: .\"
        !            18: .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
        !            19: .\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
        !            20: .\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
        !            21: .\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
        !            22: .\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
        !            23: .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
        !            24: .\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
        !            25: .\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
        !            26: .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
        !            27: .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
        !            28: .\"
1.1       markus     29: .TL
                     30: OpenSSH Channel Close Protocol 1.5 Implementation
                     31: .SH
                     32: Channel Input State Diagram
                     33: .PS
                     34: reset
                     35: l=1
                     36: s=1.2
                     37: ellipsewid=s*ellipsewid
                     38: boxwid=s*boxwid
                     39: ellipseht=s*ellipseht
                     40: S1: ellipse "INPUT" "OPEN"
                     41: move right 2*l from last ellipse.e
                     42: S4: ellipse "INPUT" "CLOSED"
                     43: move down l from last ellipse.s
                     44: S3: ellipse "INPUT" "WAIT" "OCLOSED"
                     45: move down l from 1st ellipse.s
                     46: S2: ellipse "INPUT" "WAIT" "DRAIN"
                     47: arrow "" "rcvd OCLOSE/" "shutdown_read" "send IEOF" from S1.e to S4.w
                     48: arrow "ibuf_empty/" "send IEOF" from S2.e to S3.w
                     49: arrow from S1.s to S2.n
                     50: box invis "read_failed/" "shutdown_read" with .e at last arrow.c
                     51: arrow  from S3.n to S4.s
                     52: box invis "rcvd OCLOSE/" "-" with .w at last arrow.c
                     53: ellipse wid .9*ellipsewid ht .9*ellipseht at S4
                     54: arrow "start" "" from S1.w+(-0.5,0) to S1.w
                     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
                     79: (the socket represents the local comsumer/producer of the
                     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.
                     88: If the peer receives the IEOF and has comsumed 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 comsume the
                     98: received data, he is permitted to send an OCLOSE
                     99: before the matching IEOF is received.