common: share LAN discovery settings

Move ping and Avahi/mDNS configuration into a shared LAN discovery module so kusanagi and enzo both publish their .local names, resolve each other on the LAN, and answer ping.

Keep mDNS scoped to the shared Wi-Fi interface instead of using Avahi's global firewall helper.

Assisted-by: OpenAI:gpt-5

1 files changed, 22 insertions, 0 deletions

diff --git a/common/lan-discovery.nix b/common/lan-discovery.nix
new file mode 100644
index 0000000..f12971f
--- /dev/null
+++ b/common/lan-discovery.nix
@@ -0,0 +1,22 @@
+# LAN reachability and mDNS discovery shared by all machines.
+{ ... }:
+
+{
+  # Allow IPv4 ICMP echo requests so hosts can be found with ping.
+  networking.firewall.allowPing = true;
+
+  # Avahi/mDNS: publish <hostname>.local and resolve other *.local LAN names.
+  # Keep the multicast DNS firewall opening scoped to the Wi-Fi LAN interface.
+  networking.firewall.interfaces.wlp8s0.allowedUDPPorts = [ 5353 ];
+  services.avahi = {
+    enable = true;
+    nssmdns4 = true;
+    openFirewall = false;
+    allowInterfaces = [ "wlp8s0" ];
+    publish = {
+      enable = true;
+      addresses = true;
+      workstation = true;
+    };
+  };
+}