#!/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
#

# Name self
self=psshd

# Extend path to find autossh and start-stop-daemon binaries
PATH=/usr/lib/autossh/autossh:/sbin:$PATH

# Check we have access to the required binaries
cmds=(autossh start-stop-daemon)
for cmd in "${cmds[@]}"; do
    if ! type -p "$cmd" >/dev/null; then
        printf '%s - Could not find %s in PATH\n' "$self" "$cmd" >&2
        exit 127
    fi
done

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

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

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

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

# Use start-stop-daemon to run it sanely
start-stop-daemon \
    --start \
    --quiet \
    --pidfile "$AUTOSSH_PIDFILE" \
    --exec "$(type -p autossh)" \
    -- "$@"