| Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 1 | .TL |
| 2 | OpenSSH Channel Close Protocol 1.5 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 | S4: ellipse "INPUT" "CLOSED" |
| 15 | move down l from last ellipse.s |
| 16 | S3: ellipse "INPUT" "WAIT" "OCLOSED" |
| 17 | move down l from 1st ellipse.s |
| 18 | S2: ellipse "INPUT" "WAIT" "DRAIN" |
| 19 | arrow "" "rcvd OCLOSE/" "shutdown_read" "send IEOF" from S1.e to S4.w |
| 20 | arrow "ibuf_empty/" "send IEOF" from S2.e to S3.w |
| 21 | arrow from S1.s to S2.n |
| 22 | box invis "read_failed/" "shutdown_read" with .e at last arrow.c |
| 23 | arrow from S3.n to S4.s |
| 24 | box invis "rcvd OCLOSE/" "-" with .w at last arrow.c |
| 25 | ellipse wid .9*ellipsewid ht .9*ellipseht at S4 |
| 26 | arrow "start" "" from S1.w+(-0.5,0) to S1.w |
| 27 | .PE |
| 28 | .SH |
| 29 | Channel Output State Diagram |
| 30 | .PS |
| 31 | S1: ellipse "OUTPUT" "OPEN" |
| 32 | move right 2*l from last ellipse.e |
| 33 | S3: ellipse "OUTPUT" "WAIT" "IEOF" |
| 34 | move down l from last ellipse.s |
| 35 | S4: ellipse "OUTPUT" "CLOSED" |
| 36 | move down l from 1st ellipse.s |
| 37 | S2: ellipse "OUTPUT" "WAIT" "DRAIN" |
| 38 | arrow "" "write_failed/" "shutdown_write" "send OCLOSE" from S1.e to S3.w |
| 39 | arrow "obuf_empty ||" "write_failed/" "shutdown_write" "send OCLOSE" from S2.e to S4.w |
| 40 | arrow from S1.s to S2.n |
| 41 | box invis "rcvd IEOF/" "-" with .e at last arrow.c |
| 42 | arrow from S3.s to S4.n |
| 43 | box invis "rcvd IEOF/" "-" with .w at last arrow.c |
| 44 | ellipse wid .9*ellipsewid ht .9*ellipseht at S4 |
| 45 | arrow "start" "" from S1.w+(-0.5,0) to S1.w |
| 46 | .PE |
| 47 | .SH |
| 48 | Notes |
| 49 | .PP |
| 50 | The input buffer is filled with data from the socket |
| 51 | (the socket represents the local comsumer/producer of the |
| 52 | forwarded channel). |
| 53 | The data is then sent over the INPUT-end of the channel to the |
| 54 | remote peer. |
| 55 | Data sent by the peer is received on the OUTPUT-end, |
| 56 | saved in the output buffer and written to the socket. |
| 57 | .PP |
| 58 | If the local protocol instance has forwarded all data on the |
| 59 | INPUT-end of the channel, it sends an IEOF message to the peer. |
| 60 | If the peer receives the IEOF and has comsumed all |
| 61 | data he replies with an OCLOSE. |
| 62 | When the local instance receives the OCLOSE |
| 63 | he considers the INPUT-half of the channel closed. |
| 64 | The peer has his OUTOUT-half closed. |
| 65 | .PP |
| 66 | A channel can be deallocated by a protocol instance |
| 67 | if both the INPUT- and the OUTOUT-half on his |
| 68 | side of the channel are closed. |
| 69 | Note that when an instance is unable to comsume the |
| 70 | received data, he is permitted to send an OCLOSE |
| 71 | before the matching IEOF is received. |