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      1 .TL
      2 OpenSSH Channel Close Protocol 2.0 Implementation
      3 .SH
      4 Channel Input State Diagram
      5 .PS
      6 reset
      7 l=1
      8 s=1.2
      9 ellipsewid=s*ellipsewid
     10 boxwid=s*boxwid
     11 ellipseht=s*ellipseht
     12 S1: ellipse "INPUT" "OPEN"
     13 move right 2*l from last ellipse.e
     14 S3: ellipse invis
     15 move down l from last ellipse.s
     16 S4: ellipse "INPUT" "CLOSED"
     17 move down l from 1st ellipse.s
     18 S2: ellipse "INPUT" "WAIT" "DRAIN"
     19 arrow from S1.e to S4.n
     20 box invis "rcvd CLOSE/" "shutdown_read" with .sw at last arrow.c
     21 arrow "ibuf_empty ||" "rcvd CLOSE/" "send EOF" "" from S2.e to S4.w
     22 arrow from S1.s to S2.n
     23 box invis "read_failed/" "shutdown_read" with .e at last arrow.c
     24 ellipse wid .9*ellipsewid ht .9*ellipseht at S4
     25 arrow "start" "" from S1.w+(-0.5,0) to S1.w
     26 .PE
     27 .SH
     28 Channel Output State Diagram
     29 .PS
     30 S1: ellipse "OUTPUT" "OPEN"
     31 move right 2*l from last ellipse.e
     32 S3: ellipse invis
     33 move down l from last ellipse.s
     34 S4: ellipse "OUTPUT" "CLOSED"
     35 move down l from 1st ellipse.s
     36 S2: ellipse "OUTPUT" "WAIT" "DRAIN"
     37 arrow from S1.e to S4.n
     38 box invis "write_failed/" "shutdown_write" with .sw at last arrow.c
     39 arrow "obuf_empty ||" "write_failed/" "shutdown_write" "" from S2.e to S4.w
     40 arrow from S1.s to S2.n
     41 box invis "rcvd EOF ||" "rcvd CLOSE/" "-" with .e at last arrow.c
     42 ellipse wid .9*ellipsewid ht .9*ellipseht at S4
     43 arrow "start" "" from S1.w+(-0.5,0) to S1.w
     44 .PE
     45 .SH
     46 Notes
     47 .PP
     48 The input buffer is filled with data from the socket
     49 (the socket represents the local consumer/producer of the
     50 forwarded channel).
     51 The data is then sent over the INPUT-end (transmit-end) of the channel to the
     52 remote peer.
     53 Data sent by the peer is received on the OUTPUT-end (receive-end),
     54 saved in the output buffer and written to the socket.
     55 .PP
     56 If the local protocol instance has forwarded all data on the
     57 INPUT-end of the channel, it sends an EOF message to the peer.
     58 .PP
     59 A CLOSE message is sent to the peer if
     60 both the INPUT- and the OUTOUT-half of the local
     61 end of the channel are closed.
     62 .PP
     63 The channel can be deallocated by a protocol instance
     64 if a CLOSE message he been both sent and received.
     65