tunnel.sh

#!/usr/bin/env bash
set -eEo pipefail

SSH_TRACE=
[[ "$TRACE" = "1" ]] && set -x && SSH_TRACE="-vvv"

SSH_TARGET=merickel.org
CONTROL_PATH=$(pwd)/.ssh-${SSH_TARGET}
SOCKET_PATH=$(pwd)/docker.sock

log() {
    echo "$@" 1>&2
}

info() {
    log "[info]" "$@"
}

debug() {
    log "[debug]" "$@"
}

abort() {
    log "[error]" "$@"
    exit 1
}

is_running() {
    ssh -S "$CONTROL_PATH" -O check "$SSH_TARGET" > /dev/null 2>&1
}

start() {
    info "starting tunnel ..."
    rm -f "$SOCKET_PATH" "$CONTROL_PATH"
    ssh $SSH_TRACE \
        -M -S "$CONTROL_PATH" -o ControlPersist=no \
        -fNT -L "$SOCKET_PATH:/var/run/docker.sock" \
        "$SSH_TARGET"
    debug "tunnel started"
}

start_if_needed() {
    if ! is_running; then
        start
    fi
}

sub_start() {
    if is_running; then
        abort "tunnel is already running"
    fi
    start
}

sub_stop() {
    if ! is_running; then
        abort "tunnel is not running"
    fi
    ssh $SSH_TRACE -S "$CONTROL_PATH" -O exit "$SSH_TARGET"
    rm -f "$SOCKET_PATH" "$CONTROL_PATH"
}

sub_check() {
    if is_running; then
        info "tunnel is running"
    else
        abort "tunnel is not running"
    fi
}

sub_env() {
    start_if_needed
    echo "export DOCKER_HOST=unix://$SOCKET_PATH"
}

sub_exec() {
    # shellcheck source=/dev/null
    source <(sub_env)
    exec "$@"
}

subcommand=$1
shift
if ! declare -f "sub_$subcommand" > /dev/null 2>&1; then
    abort "\"$subcommand\" is not a valid subcommand"
fi
"sub_${subcommand}" "$@"