#!/usr/bin/env bash

#
# Wrapper around autossh and start-stop-daemon for basic persistence. Intended
# to be called as a script from profile.d for automatic SSH tunnels.
#
# Takes one required option -p, the autossh monitoring port number to use. Cut
# the options off with -- and the remainder of the arguments are passed to the
# autossh binary.
#
#     $ psshd -p 9001 -- -fN -D 8001 remotehost
#
# @author Tom Ryder <tom@sanctum.geek.nz>
# @copyright 2013
#

# Path to autossh binary (not any wrapper script)
autossh='/usr/lib/autossh/autossh'

# Path to start-stop-daemon binary
startstopdaemon='/sbin/start-stop-daemon'

# Neither of those are likely to be in your PATH if you're a normal user, so we
# hardcode the paths and test for their existence
if [[ ! -x "$autossh" ]]; then
    printf "Can't execute ${autossh}!" >&2
    exit 1
elif [[ ! -x "$startstopdaemon" ]]; then
    printf "Can't execute ${startstopdaemon}!" >&2
    exit 1
fi

# Get port in options
while getopts ':p:' opt
do
    case "$opt" in
        p)
            port="$OPTARG"
            ;;
        \?)
            printf "Invalid option $OPTARG" >&2
            exit 1
            ;;
        :)
            printf "Option -$OPTARG requires an argument" >&2
            exit 1
            ;;
    esac
done
shift "$((OPTIND-1))"

# If no port, give up with usage instructions
if [[ ! -n "$port" ]]
then
    printf "USAGE: $0 -p <port number> -- <ssh arguments>"
    exit 1
fi

# Set up a PID dir
dir="${TMPDIR:-/tmp}/psshd-${UID}"
if ! mkdir -p "$dir"; then
    printf "Couldn't create directory ${dir} for PID file" >&2
    exit 1
fi

# Export the two settings autossh absolutely needs
AUTOSSH_PIDFILE="${dir}/psshd-port-${port}.pid"
AUTOSSH_PORT="$port"
export AUTOSSH_PIDFILE AUTOSSH_PORT

# Use start-stop-daemon to run it sanely
"$startstopdaemon" \
    --start \
    --quiet \
    --pidfile "$AUTOSSH_PIDFILE" \
    --exec "$autossh" \
    -- "$@"