xref: /titanic_41/usr/src/cmd/ssh/doc/nchan2.ms (revision 7c478bd95313f5f23a4c958a745db2134aa03244)
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