nixos/nginx: Allow empty port for listen directive

When listening on unix sockets, it doesn't make sense to specify a port
for nginx's listen directive.

Since nginx defaults to port 80 when the port isn't specified (but the
address is), we can change the default for the option to null as well
without changing any behaviour.

nixos/lib/test-driver/test_driver/machine.py

···
         with self.nested(f"waiting for TCP port {port} on {addr}"):
             retry(port_is_open, timeout)
 
+    def wait_for_open_unix_socket(
+        self, addr: str, is_datagram: bool = False, timeout: int = 900
+    ) -> None:
+        """
+        Wait until a process is listening on the given UNIX-domain socket
+        (default to a UNIX-domain stream socket).
+        """
+
+        nc_flags = [
+            "-z",
+            "-uU" if is_datagram else "-U",
+        ]
+
+        def socket_is_open(_: Any) -> bool:
+            status, _ = self.execute(f"nc {' '.join(nc_flags)} {addr}")
+            return status == 0
+
+        with self.nested(
+            f"waiting for UNIX-domain {'datagram' if is_datagram else 'stream'} on '{addr}'"
+        ):
+            retry(socket_is_open, timeout)
+
     def wait_for_closed_port(
         self, port: int, addr: str = "localhost", timeout: int = 900
     ) -> None:

nixos/modules/services/web-servers/nginx/default.nix

···
         listenString = { addr, port, ssl, proxyProtocol ? false, extraParameters ? [], ... }:
           # UDP listener for QUIC transport protocol.
           (optionalString (ssl && vhost.quic) ("
-            listen ${addr}:${toString port} quic "
+            listen ${addr}${optionalString (port != null) ":${toString port}"} quic "
           + optionalString vhost.default "default_server "
           + optionalString vhost.reuseport "reuseport "
           + optionalString (extraParameters != []) (concatStringsSep " "
···
             in filter isCompatibleParameter extraParameters))
           + ";"))
           + "
-            listen ${addr}:${toString port} "
+            listen ${addr}${optionalString (port != null) ":${toString port}"} "
           + optionalString (ssl && vhost.http2 && oldHTTP2) "http2 "
           + optionalString ssl "ssl "
           + optionalString vhost.default "default_server "

nixos/modules/services/web-servers/nginx/vhost-options.nix

···
         options = {
           addr = mkOption {
             type = str;
-            description = lib.mdDoc "IP address.";
+            description = lib.mdDoc "Listen address.";
           };
           port = mkOption {
-            type = port;
+            type = types.nullOr port;
             description = lib.mdDoc "Port number.";
-            default = 80;
+            default = null;
           };
           ssl = mkOption {
             type = bool;
···
       example = [
         { addr = "195.154.1.1"; port = 443; ssl = true; }
         { addr = "192.154.1.1"; port = 80; }
+        { addr = "unix:/var/run/nginx.sock"; }
       ];
       description = lib.mdDoc ''
         Listen addresses and ports for this virtual host.

nixos/tests/all-tests.nix

···
   nginx-sso = handleTest ./nginx-sso.nix {};
   nginx-status-page = handleTest ./nginx-status-page.nix {};
   nginx-tmpdir = handleTest ./nginx-tmpdir.nix {};
+  nginx-unix-socket = handleTest ./nginx-unix-socket.nix {};
   nginx-variants = handleTest ./nginx-variants.nix {};
   nifi = handleTestOn ["x86_64-linux"] ./web-apps/nifi.nix {};
   nitter = handleTest ./nitter.nix {};

nixos/tests/nginx-unix-socket.nix

···
+import ./make-test-python.nix ({ pkgs, ... }:
+let
+  nginxSocketPath = "/var/run/nginx/test.sock";
+in
+{
+  name = "nginx-unix-socket";
+
+  nodes = {
+    webserver = { pkgs, lib, ... }: {
+      services.nginx = {
+        enable = true;
+        virtualHosts.localhost = {
+          serverName = "localhost";
+          listen = [{ addr = "unix:${nginxSocketPath}"; }];
+          locations."/test".return = "200 'foo'";
+        };
+      };
+    };
+  };
+
+  testScript = ''
+    webserver.wait_for_unit("nginx")
+    webserver.wait_for_open_unix_socket("${nginxSocketPath}")
+
+    webserver.succeed("curl --fail --silent --unix-socket '${nginxSocketPath}' http://localhost/test | grep '^foo$'")
+  '';
+})

pkgs/servers/http/nginx/generic.nix

···
   passthru = {
     inherit modules;
     tests = {
-      inherit (nixosTests) nginx nginx-auth nginx-etag nginx-globalredirect nginx-http3 nginx-proxyprotocol nginx-pubhtml nginx-sandbox nginx-sso nginx-status-page;
+      inherit (nixosTests) nginx nginx-auth nginx-etag nginx-globalredirect nginx-http3 nginx-proxyprotocol nginx-pubhtml nginx-sandbox nginx-sso nginx-status-page nginx-unix-socket;
       variants = lib.recurseIntoAttrs nixosTests.nginx-variants;
       acme-integration = nixosTests.acme;
     } // passthru.tests;