#!/bin/sh -ue
#
# Run named port forwards indefinitely.
#       - Cameron Simpson <cs@zip.com.au> 08jul2008
#

: ${VARRUN:=$HOME/var/run}
: ${LOGDIR:=$HOME/var/log}
: ${PORTFWD_TARGETS:-''}

trace=set-x
once=
stop=
sshcfg=$HOME/rc/ssh/config-pf
fwdcfg=$HOME/rc/ssh/portfwd

cmd=`basename "$0"`
usage="Usage: $cmd [-1] [-stop] targets...
  -1    Once. Do not restart the tunnel if it dies.
  -stop Stop named port forwards instead of starting them.
  -F    Ssh configuration file with clause for target.
If targets is \"ALL\" then if -stop it means all running portforwards
otherwise it means all clauses named *-ALL in the ssh configuration file."

opts=
badopts=

while [ $# -gt 0 ]
do
  case $1 in
    -1) once=1 opts="$opts $1" ;;
    -F) sshcfg=$2 opts="$opts $1 $2"; shift ;;
    -stop)
        stop=1 opts="$opts $1" ;;
    --) shift; break ;;
    -?*)echo "$cmd: unrecognised option: $1" >&2
        badopts=1
        ;;
    *)  break ;;
  esac
  shift
done

if [ $# = 0 ]
then
  set -- $PORTFWD_TARGETS
  if [ $# -gt 0 ]
  then
    echo "$cmd: no targets, using \$PORTFWD_TARGETS: $*" >&2
  else
    echo "$cmd: missing targets and missing/empty \$PORTFWD_TARGETS" >&2
    badopts=1
  fi
fi

[ $badopts ] && { echo "$usage" >&2; exit 2; }

not()
{ "$@" || return 0
  return 1
}

ok2portfwd()
{
  flag PORTFWD_ANYWAY && return 0
  flag PORTFWD_DISABLE && return 1
  ssh-add -l >/dev/null || return 1
  netstat -rn | egrep '^(default|0\.0\.0\.0) +[1-9]' >/dev/null || return 1
  [ -x "$HOME/bin-local/do-portfwd" ] || return 0
  "$HOME/bin-local/do-portfwd"
}

# send SIGTERM to a process and wait for it to exit
synckill()
{ _synckill_verbose=
  if [ "x$1" = x-v ]
  then  shift
        _synckill_verbose=1
  fi
  kill "$1" || return 1
  while kill -0 "$1" 2>/dev/null && sleep 1
  do  [ -z "$_synckill_verbose" ] || printf .
  done
  [ -z "$_synckill_verbose" ] || echo
}

if [ "x$*" = xALL ]
then
  if [ $stop ]
  then  set -- `ls "$VARRUN/." | sed -n 's/^portfwd\.//p'`
  else  set -- `sed -n 'y/	/ /
                        s/$/ /
                        s/^  *//
                        s/  */  /g
                        s/^[Hh][Oo][Ss][Tt] .* \([^ ][^ ]*-ALL\) .*/\1/p' "$sshcfg"`
  fi
fi

if [ $# -gt 1 ]
then
  ( set -x
    for target
    do
      "$0" $opts -- "$target" &
    done
    wait
  )
  exit $?
fi

target=$1
shift

xit=0
monpid=
sshpid=
trap ': trap on 1 2 and 15 ...
      if [ -n "$sshpid" ]
      then
        printf "%s" "$cmd: $target: SIGTERM received, killing ssh ($sshpid) "
        synckill -v "$sshpid"
        if [ -n "$monpid" ]
        then
          printf "%s" "$cmd: $target: SIGTERM received, also killing monitor ($monpid) "
          synckill -v "$monpid"
        fi
      fi
      exit 1
     ' 1 2 15

first=1
while :
do
  # reload config on every pass
  cfg_pidfile=portfwd.$target.pid
  cfg_command=:
  cfg_outlog=portfwd-$target    # /dev/null
  cfg_monitor=
  if [ -s "$fwdcfg" ]
  then
    wcv=`winclausevars "$fwdcfg" "$target" cfg`
    eval "$wcv"
  fi
  case $cfg_pidfile in
    /*) ;; *) cfg_pidfile=$VARRUN/$cfg_pidfile ;;
  esac
  case $cfg_outlog in
    /*) ;; *) cfg_outlog=$LOGDIR/$cfg_outlog ;;
  esac
  if opid=`ifpid -q -v "$cfg_pidfile"`
  then
    printf "%s" "$cmd: stopping $target, pid $opid "
    synckill -v "$opid" || :
    >"$cfg_pidfile"
  else
    if [ "$stop" ]
    then  echo "$cmd: no valid pid to kill in $cfg_pidfile" >&2
    fi
  fi

  [ $stop ] && exit 0

  $trace \
    sshto ServerAliveInterval=37 -n -F "$sshcfg" "$target" \
      "( $cfg_command ) </dev/null &
     "'exec 1>&2
       while sleep 61 && printf " "; do :; done
      ' \
    >>"$cfg_outlog" </dev/null &
  sshpid=$!
  echo "$sshpid" >"$cfg_pidfile"
  echo "$target: $cfg_pidfile: $sshpid"
  [ $first ] || alert "RESTARTED: sshpf $target" &

  # start monitor
  if [ -n "$cfg_monitor" ]
  then
    sh -c "$cfg_monitor" &
    monpid=$!
  else
    monpid=
  fi

  # wait for tunnel to exit or tunnel permission to expire
  while pfx "ssh-$target" kill -0 "$sshpid" && ok2portfwd
  do  sleep 2
  done
  if synckill "$sshpid"
  then
    sshpid=
    alert "KILLED: sshpf $target" &
  else
    sshpid=
    alert "EXITED: sshpf $target" &
  fi

  # stop monitor
  [ -z "$monpid" ] || kill "$monpid" 2>/dev/null

  [ $once ] && break

  # pause before restart, and indefinitely if no tunnel permission
  while :
  do
    sleep 2
    ok2portfwd && break
  done

  first=
done

exit $xit