Fix: iptables cannot be executed correctly on certain environments (#690)

Dockerfile

@@ -3,6 +3,10 @@
 
 FROM docker.io/library/node:18-alpine AS build_node_modules
 
+# Hide fund and update-notifier message
+RUN npm config set -g fund false &&\
+    npm config set -g update-notifier false
+
 # Copy Web UI
 COPY src/ /app/
 WORKDIR /app
@@ -11,6 +15,10 @@ RUN npm ci
 # This saves a lot of disk space.
 FROM docker.io/library/node:18-alpine
 
+# Hide fund and update-notifier message
+RUN npm config set -g fund false &&\
+    npm config set -g update-notifier false
+
 COPY --from=build_node_modules /app /app
 
 # Move node_modules one directory up, so during development
@@ -27,9 +35,14 @@ RUN npm i -g nodemon
 
 # Install Linux packages
 RUN apk add -U --no-cache \
+    dpkg \
+    dumb-init \
     iptables \
-    wireguard-tools \
-    dumb-init
+    iptables-legacy \
+    wireguard-tools
+
+# Symlink iptables
+RUN update-alternatives --install /sbin/iptables iptables /sbin/iptables-legacy 10 --slave /sbin/iptables-restore iptables-restore /sbin/iptables-legacy-restore --slave /sbin/iptables-save iptables-save /sbin/iptables-legacy-save
 
 # Expose Ports
 EXPOSE 51820/udp