Multi-hop SSH port forwarding

ssh_forward.sh

#!/bin/bash

ssh_forward() {
    if [[ $# == 0 || $1 == "-h" || $1 == "--help" ]]; then
        echo "Multi-hop SSH port forwarding"
        echo
        echo "Usage: ssh_forward [--dryrun, -d] --port PORT HOST [HOST2 ...]"
        return 1
    fi

    DRYRUN=
    PORT=
    HOSTS=()
    while (( $# > 0 )); do
        case $1 in
            --dryrun|-d)
                DRYRUN=1
                ;;
            --port)
                shift
                PORT=$1
                ;;
            *)
                HOSTS+=( "$1" )
                ;;
        esac
        shift
    done

    if [[ -z $PORT ]]; then
        echo "ERROR: port not specified"
        return 1
    fi

    if [[ ${#HOSTS[@]} == 0 ]]; then
        echo "ERROR: no hosts specified"
        return 1
    fi

    NUM_HOSTS=${#HOSTS[@]}
    COMMAND=
    for (( ii = $NUM_HOSTS - 1; ii >= 0; ii-- )); do
        FLAGS=$( (( $ii == $NUM_HOSTS - 1 )) && echo "-NL" || echo "-L" )
        COMMAND="ssh $FLAGS $PORT:localhost:$PORT ${HOSTS[ii]} $COMMAND"
    done

    echo "$COMMAND"
    if [[ -z $DRYRUN ]]; then
        $COMMAND
    fi
    return 0
}