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