#!/bin/sh
# The rules around the tunnel to Jellyfin at home (ADR 0032, D5), set by wg-quick as
# the tunnel comes up and taken away as it goes (wg-jellyfin.conf), so they live
# exactly as long as it: `wg-jellyfin-rules.sh up|down <interface>`. As
# /etc/wireguard/wg-jellyfin-rules.sh on the instance's server (root, 0700).
#
# - Forwarded (Docker's DOCKER-USER, before Docker's own rules): into the tunnel only
#   Caddy (172.30.80.2, its fixed address on edge) to Jellyfin (10.61.96.2:8096), out
#   of it only the replies; everything else dropped. Docker then masquerades Caddy's
#   requests as the tunnel's 10.61.96.1, which the home end sees as its proxy.
# - To the host itself (INPUT): only replies from the tunnel, so the home end reaches
#   neither sshd nor anything else listening here.
#
# IPv4 alone: the tunnel carries no IPv6 (D3). Needs Docker's chains, so the tunnel
# starts after Docker (wg-quick-after-docker.conf).

set -eu

action=$1
interface=$2
forward=halkyon-jellyfin-forward
input=halkyon-jellyfin-input

case "$action" in
up)
  iptables -N "$forward"
  iptables -A "$forward" -i "$interface" -m conntrack --ctstate ESTABLISHED,RELATED -j RETURN
  iptables -A "$forward" -o "$interface" -s 172.30.80.2 -d 10.61.96.2 -p tcp --dport 8096 -j RETURN
  iptables -A "$forward" -j DROP
  iptables -I DOCKER-USER -i "$interface" -j "$forward"
  iptables -I DOCKER-USER -o "$interface" -j "$forward"

  iptables -N "$input"
  iptables -A "$input" -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT
  iptables -A "$input" -j DROP
  iptables -I INPUT -i "$interface" -j "$input"
  ;;
down)
  # Whatever is there of it, so a half-made set goes too.
  iptables -D DOCKER-USER -i "$interface" -j "$forward" 2>/dev/null || true
  iptables -D DOCKER-USER -o "$interface" -j "$forward" 2>/dev/null || true
  iptables -F "$forward" 2>/dev/null || true
  iptables -X "$forward" 2>/dev/null || true
  iptables -D INPUT -i "$interface" -j "$input" 2>/dev/null || true
  iptables -F "$input" 2>/dev/null || true
  iptables -X "$input" 2>/dev/null || true
  ;;
*)
  echo "usage: $0 up|down <interface>" >&2
  exit 2
  ;;
esac