From 823be7f47b1e2299fe2b0b5bc4fedb4993a1e09a Mon Sep 17 00:00:00 2001
From: Max Kellermann <max.kellermann@ionos.com>
Date: Sun, 22 Oct 2023 07:30:57 +0200
Subject: [PATCH] Instance: implement Zeroconf publisher

---
 src/Instance.cxx | 18 +++++++++++++++++-
 src/Main.cxx     |  4 ++++
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/src/Instance.cxx b/src/Instance.cxx
index 028c06c..c13a1cc 100644
--- a/src/Instance.cxx
+++ b/src/Instance.cxx
@@ -78,7 +78,23 @@ Instance::AddListener(const ListenerConfig &config)
 	listeners.emplace_front(*this, config.Create(SOCK_STREAM));
 
 #ifdef HAVE_AVAHI
-	// TODO
+	auto &listener = listeners.front();
+
+	if (!config.zeroconf_service.empty()) {
+		/* ask the kernel for the effective address via
+		   getsockname(), because it may have changed, e.g. if
+		   the kernel has selected a port for us */
+		const auto local_address = listener.GetLocalAddress();
+		if (local_address.IsDefined()) {
+			const char *const interface = config.interface.empty()
+				? nullptr
+				: config.interface.c_str();
+
+			avahi_services.emplace_front(config.zeroconf_service.c_str(),
+						     interface, local_address,
+						     config.v6only);
+		}
+	}
 #endif // HAVE_AVAHI
 }
 
diff --git a/src/Main.cxx b/src/Main.cxx
index 6ae620b..f8c50c9 100644
--- a/src/Main.cxx
+++ b/src/Main.cxx
@@ -60,6 +60,10 @@ try {
 	for (const auto &i : config.listeners)
 		instance.AddListener(i);
 
+#ifdef HAVE_AVAHI
+	instance.EnableZeroconf();
+#endif // HAVE_AVAHI
+
 #ifdef HAVE_LIBSYSTEMD
 	/* tell systemd we're ready */
 	sd_notify(0, "READY=1");