Merge pull request #4644 from shota-0129/shota-0129/feat-docker-dns-protection

feat: Add Docker DNS protection to firewall script

.devcontainer/init-firewall.sh

@@ -2,6 +2,9 @@
 set -euo pipefail  # Exit on error, undefined vars, and pipeline failures
 IFS=$'\n\t'       # Stricter word splitting
 
+# 1. Extract Docker DNS info BEFORE any flushing
+DOCKER_DNS_RULES=$(iptables-save -t nat | grep "127\.0\.0\.11" || true)
+
 # Flush existing rules and delete existing ipsets
 iptables -F
 iptables -X
@@ -11,6 +14,16 @@ iptables -t mangle -F
 iptables -t mangle -X
 ipset destroy allowed-domains 2>/dev/null || true
 
+# 2. Selectively restore ONLY internal Docker DNS resolution
+if [ -n "$DOCKER_DNS_RULES" ]; then
+    echo "Restoring Docker DNS rules..."
+    iptables -t nat -N DOCKER_OUTPUT 2>/dev/null || true
+    iptables -t nat -N DOCKER_POSTROUTING 2>/dev/null || true
+    echo "$DOCKER_DNS_RULES" | xargs -L 1 iptables -t nat
+else
+    echo "No Docker DNS rules to restore"
+fi
+
 # First allow DNS and localhost before any restrictions
 # Allow outbound DNS
 iptables -A OUTPUT -p udp --dport 53 -j ACCEPT