#!/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."

badopts=

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

if [ $# = 0 ]
then
  if [ -n "$PORTFWD_TARGETS" ]
  then
    set -- $PORTFWD_TARGETS
  else
    echo "$cmd: missing targets and no \$PORTFWD_TARGETS envvar" >&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

for target
do
  cfg_pidfile=portfwd.$target.pid
  cfg_command=:
  cfg_outlog=/dev/null
  cfg_monitor=
  if [ -s "$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"
  fi

  if [ -z "$stop" ]
  then
    ( sshpid=
      trap 'if [ -n "$sshpid" ]
            then
              printf "%s" "$cmd: $target: SIGTERM received, killing ssh "
              synckill -v "$sshpid"
            fi
            exit 1
           ' 1 15
      first=1
      while :
      do
        $trace \
          sshto -n -F "$sshcfg" "$target" \
            "( $cfg_command ) &
           "'exec 1>&2
             exec 3<&0
             cat <&3 >/dev/null &
             catpid=$$
             exec 3<&-
             while sleep 61 && echo . && kill -0 "$catpid" 2>/dev/null
             do :
             done
             kill "$catpid" 2>/dev/null
            ' \
          >>"$cfg_outlog" &
        sshpid=$!
        [ $first ] || alert "RESTARTED: sshpf $target" &
        if [ -n "$cfg_monitor" ]
        then
          sh -c "$cfg_monitor" &
          monpid=$!
        else
          monpid=
        fi
        while kill -0 "$sshpid" && ok2portfwd
        do  sleep 2
        done
        if synckill "$sshpid"
        then
          sshpid=
          alert "KILLED: sshpf $target" &
        else
          sshpid=
          alert "EXITED: sshpf $target" &
        fi
        [ -z "$monpid" ] || kill "$monpid" 2>/dev/null
        [ $once ] && break
        while not ok2portfwd
        do sleep 2
        done
        first=
      done
    ) </dev/null 1>&2 &
    echo $! >"$cfg_pidfile"
    echo "$target: $cfg_pidfile: $!"
  fi
done