| 1 | #! /bin/sh |
| 2 | |
| 3 | set -e |
| 4 | case $# in |
| 5 | 2) ;; |
| 6 | *) echo >&2 "usage: $0 {start|stop|restart|status} HOST"; exit 1 ;; |
| 7 | esac |
| 8 | op=$1 host=$2 |
| 9 | |
| 10 | writefile () { |
| 11 | file=$1; shift |
| 12 | echo "$*" >"$file.new" |
| 13 | mv "$file.new" "$file" |
| 14 | } |
| 15 | |
| 16 | runssh () { ssh -T -oControlPath="./$host.ctrl" "$@"; } |
| 17 | |
| 18 | stopit () { |
| 19 | |
| 20 | ## Initial shutdown protocol. |
| 21 | writefile "$host.state" stopping |
| 22 | if [ -f "$host.pid" ]; then kill $(cat "$host.pid") 2>/dev/null || :; fi |
| 23 | rm -f "$host.pid" |
| 24 | |
| 25 | ## Shut down an existing connection if there is one. |
| 26 | if [ -S "$host.ctrl" ]; then |
| 27 | runssh -Oexit "$host" >/dev/null 2>/dev/null || : |
| 28 | fi |
| 29 | |
| 30 | ## If there's still a socket, then work out what to do. |
| 31 | if [ -e "$host.ctrl" ]; then |
| 32 | |
| 33 | ## If the connection's still running then we have a problem. |
| 34 | if runssh -Ocheck "$host" >/dev/null 2>/dev/null; then |
| 35 | echo >&2 "$0: failed to kill existing connection to $host" |
| 36 | exit 2 |
| 37 | fi |
| 38 | |
| 39 | ## Remove the stale socket. |
| 40 | rm -f "$host.ctrl" |
| 41 | fi |
| 42 | |
| 43 | ## Update the state. |
| 44 | rm -f "$host.state" "$host.pid" |
| 45 | } |
| 46 | |
| 47 | daemon () { |
| 48 | |
| 49 | ## There doesn't seem to be a better way of getting this. :-( |
| 50 | read pid <"$host.daemonpipe" |
| 51 | rm -f "$host.daemonpipe" |
| 52 | |
| 53 | ## Set up shop. |
| 54 | trap 'rm -f "$host.pid"; stopit' EXIT INT TERM |
| 55 | writefile "$host.pid" "$pid" |
| 56 | |
| 57 | ## Initial delay. |
| 58 | delay=0 |
| 59 | |
| 60 | ## Keep the connection up for as long as we can. |
| 61 | while [ -f "$host.pid" ]; do |
| 62 | |
| 63 | ## Maybe back off before trying another connection. |
| 64 | case $delay in |
| 65 | 0) |
| 66 | delay=1 |
| 67 | ;; |
| 68 | *) |
| 69 | writefile "$host.state" \ |
| 70 | "wait until $(date -d+${delay}sec +"%Y-%m-%d %H:%M:%S %z")" |
| 71 | sleep $delay |
| 72 | delay=$(( 2*$delay )) |
| 73 | if [ $delay -gt 120 ]; then delay=120; fi |
| 74 | ;; |
| 75 | esac |
| 76 | |
| 77 | ## Start a new connection. |
| 78 | writefile "$host.state" starting |
| 79 | if ! runssh -MNnf "$host" >/dev/null; then continue; fi |
| 80 | if ! runssh -Ocheck "$host" >/dev/null 2>&1; then |
| 81 | echo "connection to $host apparently stillborn" |
| 82 | continue |
| 83 | fi |
| 84 | writefile "$host.state" connected |
| 85 | delay=0 |
| 86 | |
| 87 | ## Wait until it gets torn down. The chicanery with a pipe is because |
| 88 | ## the ssh process will continue until either it gets disconnected from |
| 89 | ## the server or stdin closes -- so we have to arrange that stdin doesn't |
| 90 | ## close. Thanks to Richard Kettlewell for the suggestion. |
| 91 | rm -f "$host.pipe"; mkfifo -m400 "$host.pipe" |
| 92 | runssh -N "$host" >/dev/null <"$host.pipe" || : |
| 93 | rm -f "$host.pipe" |
| 94 | writefile "$host.state" disconnected |
| 95 | done |
| 96 | } |
| 97 | |
| 98 | startit () { |
| 99 | |
| 100 | ## If there's already a connection then we have nothing to do. |
| 101 | if runssh -Ocheck "$host" >/dev/null 2>/dev/null; then |
| 102 | echo >&2 "$0: already connected to $host" |
| 103 | exit 0 |
| 104 | fi |
| 105 | |
| 106 | ## Start a daemon which makes connections for us. This is remarkably |
| 107 | ## tricky. |
| 108 | rm -f "$host.daemonpipe"; mkfifo -m600 "$host.daemonpipe" |
| 109 | { daemon& echo $! >"$host.daemonpipe"; } 2>&1 | logger -pdaemon.notice& |
| 110 | } |
| 111 | |
| 112 | ## Main dispatch. |
| 113 | case "$op" in |
| 114 | start) startit ;; |
| 115 | stop) stopit ;; |
| 116 | restart) stopit; startit ;; |
| 117 | status) |
| 118 | if [ -f "$host.state" ] |
| 119 | then cat "$host.state" |
| 120 | else echo "down" |
| 121 | fi |
| 122 | ;; |
| 123 | *) |
| 124 | echo >&2 "usage: $0 {start|stop|restart|status} HOST" |
| 125 | exit 1 |
| 126 | ;; |
| 127 | esac |