| .TL |
| OpenSSH Channel Close Protocol 1.5 Implementation |
| .SH |
| Channel Input State Diagram |
| .PS |
| reset |
| l=1 |
| s=1.2 |
| ellipsewid=s*ellipsewid |
| boxwid=s*boxwid |
| ellipseht=s*ellipseht |
| S1: ellipse "INPUT" "OPEN" |
| move right 2*l from last ellipse.e |
| S4: ellipse "INPUT" "CLOSED" |
| move down l from last ellipse.s |
| S3: ellipse "INPUT" "WAIT" "OCLOSED" |
| move down l from 1st ellipse.s |
| S2: ellipse "INPUT" "WAIT" "DRAIN" |
| arrow "" "rcvd OCLOSE/" "shutdown_read" "send IEOF" from S1.e to S4.w |
| arrow "ibuf_empty/" "send IEOF" from S2.e to S3.w |
| arrow from S1.s to S2.n |
| box invis "read_failed/" "shutdown_read" with .e at last arrow.c |
| arrow from S3.n to S4.s |
| box invis "rcvd OCLOSE/" "-" with .w at last arrow.c |
| ellipse wid .9*ellipsewid ht .9*ellipseht at S4 |
| arrow "start" "" from S1.w+(-0.5,0) to S1.w |
| .PE |
| .SH |
| Channel Output State Diagram |
| .PS |
| S1: ellipse "OUTPUT" "OPEN" |
| move right 2*l from last ellipse.e |
| S3: ellipse "OUTPUT" "WAIT" "IEOF" |
| move down l from last ellipse.s |
| S4: ellipse "OUTPUT" "CLOSED" |
| move down l from 1st ellipse.s |
| S2: ellipse "OUTPUT" "WAIT" "DRAIN" |
| arrow "" "write_failed/" "shutdown_write" "send OCLOSE" from S1.e to S3.w |
| arrow "obuf_empty ||" "write_failed/" "shutdown_write" "send OCLOSE" from S2.e to S4.w |
| arrow from S1.s to S2.n |
| box invis "rcvd IEOF/" "-" with .e at last arrow.c |
| arrow from S3.s to S4.n |
| box invis "rcvd IEOF/" "-" with .w at last arrow.c |
| ellipse wid .9*ellipsewid ht .9*ellipseht at S4 |
| arrow "start" "" from S1.w+(-0.5,0) to S1.w |
| .PE |
| .SH |
| Notes |
| .PP |
| The input buffer is filled with data from the socket |
| (the socket represents the local comsumer/producer of the |
| forwarded channel). |
| The data is then sent over the INPUT-end of the channel to the |
| remote peer. |
| Data sent by the peer is received on the OUTPUT-end, |
| saved in the output buffer and written to the socket. |
| .PP |
| If the local protocol instance has forwarded all data on the |
| INPUT-end of the channel, it sends an IEOF message to the peer. |
| If the peer receives the IEOF and has comsumed all |
| data he replies with an OCLOSE. |
| When the local instance receives the OCLOSE |
| he considers the INPUT-half of the channel closed. |
| The peer has his OUTOUT-half closed. |
| .PP |
| A channel can be deallocated by a protocol instance |
| if both the INPUT- and the OUTOUT-half on his |
| side of the channel are closed. |
| Note that when an instance is unable to comsume the |
| received data, he is permitted to send an OCLOSE |
| before the matching IEOF is received. |