mdw@git.distorted.org.uk Git - tunneluser/blob - bin/outbound

   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