Merge pull request #4272 from norio-nomura/enable-mDNS-in-guest-using-systemd-on-macOS-host

pkg/cidata: Enable mDNS in guest using `systemd`

Author: AkihiroSuda

pkg/cidata/cidata.TEMPLATE.d/boot/06-enable-mdns-on-systemd.sh

@@ -0,0 +1,36 @@
+#!/bin/bash
+
+# SPDX-FileCopyrightText: Copyright The Lima Authors
+# SPDX-License-Identifier: Apache-2.0
+
+set -eux -o pipefail
+
+# Do nothing on OpenRC systems (e.g., Alpine Linux)
+if [[ -f /sbin/openrc-run ]]; then
+	exit 0
+fi
+
+# It depends on systemd-resolved
+command -v systemctl >/dev/null 2>&1 || exit 0
+command -v resolvectl >/dev/null 2>&1 || exit 0
+
+# Configure systemd-resolved to enable mDNS resolution globally
+enable_mdns_conf_path=/etc/systemd/resolved.conf.d/00-lima-enable-mdns.conf
+enable_mdns_conf_content="[Resolve]
+MulticastDNS=yes
+"
+# Create /etc/systemd/resolved.conf.d/00-lima-enable-mdns.conf if its content is different
+if ! diff -q <(echo "${enable_mdns_conf_content}") "${enable_mdns_conf_path}" >/dev/null 2>&1; then
+	mkdir -p "$(dirname "${enable_mdns_conf_path}")"
+	echo "${enable_mdns_conf_content}" >"${enable_mdns_conf_path}"
+	systemctl daemon-reload
+	systemctl restart systemd-resolved.service
+fi
+
+# On Ubuntu, systemd.network's configuration won't work.
+# See: https://unix.stackexchange.com/a/652582
+# So we need to enable mDNS per-link using resolvectl.
+for iface in $(resolvectl status | sed -n -E 's/^Link +[0-9]+ \(([^)]+)\)/\1/p'); do
+	# This setting is volatile and will be lost on reboot, so we need to set it every time
+	resolvectl mdns "${iface}" yes
+done