Rename project wg2sd -> wg2nd, new CLI + generate

1. Renamed the project from wg2sd to wg2nd
2. Modified the _gen_netdev_cfg() function to handle the MTUBytes field.
3. Add new CLI with `generate` and `install` commands
4. Modified the gen_systemd_config() function to accept keyfile_or_output_path and filename parameters.
   - user can choose the name of the keyfile on the CLI
   - user can choose alternative output filename (instead of just using
     the  interface name)

5 files changed, 367 insertions, 102 deletions

diff --git a/makefile b/makefile
index 1abde0b..d375869 100644
--- a/makefile
+++ b/makefile
@@ -24,7 +24,7 @@ DEBUGFLAGS = -ggdb -O0
 LDFLAGS = -largon2
 
 # Object files
-OBJECTS := wg2sd.o
+OBJECTS := wg2nd.o
 OBJECTS += main.o
 
 # Source directory
@@ -41,7 +41,7 @@ OBJ_DIR = obj
 DEBUG_OBJ_DIR = obj/debug
 
 # Target executable
-CMD = wg2sd
+CMD = wg2nd
 
 # Build rules
 all: CXXFLAGS += $(RELEASE_CXXFLAGS)
@@ -62,7 +62,7 @@ $(CMD): $(addprefix $(OBJ_DIR)/, $(OBJECTS))
 $(OBJ_DIR)/%.o: $(SRC_DIR)/%.cpp | $(OBJ_DIR)
 	$(CXX) $(CXXFLAGS) -c $< -o $@
 
-$(TEST_DIR)/%: $(TEST_DIR)/%.cpp $(addprefix $(OBJ_DIR)/, wg2sd.o) | $(OBJ_DIR)
+$(TEST_DIR)/%: $(TEST_DIR)/%.cpp $(addprefix $(OBJ_DIR)/, wg2nd.o) | $(OBJ_DIR)
 	$(CXX) $(CXXFLAGS) $^ $(LDFLAGS) -o $@
 
 $(OBJ_DIR) $(DEBUG_OBJ_DIR):
diff --git a/src/main.cpp b/src/main.cpp
index 19b5ced..b8c8ec6 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -1,5 +1,14 @@
+#include <iostream>
+#include <string>
+#include <vector>
+#include <filesystem>
+#include <cstdlib>
+#include <cstring>
+#include <cstdio>
+#include <getopt.h>
+
 // =====================================
-//   ERROR HANDING - FROM FCUTILS
+//	 ERROR HANDING - FROM FCUTILS
 // =====================================
 
 #include <stdio.h>
@@ -69,35 +78,122 @@ void err(char const * format, ...) {
 }
 
 // =============================================
-//   COMMAND LINE UTILITY
+//	 COMMAND LINE UTILITY
 // =============================================
 
+constexpr char const * DEFAULT_OUTPUT_PATH = "/etc/systemd/network/";
 
-#include "wg2sd.hpp"
+/*
+ * HELP AND USAGE
+ */
 
-#include <filesystem>
-#include <fstream>
-#include <iostream>
-#include <unistd.h>
-#include <sys/types.h>
-#include <sys/stat.h>
-#include <grp.h>
+void die_usage(const char *prog) {
+	err("Usage: %s { install, generate } [ OPTIONS ] { -h, CONFIG_FILE }", prog);
+	die("Use -h for help");
+}
+
+void print_help(const char *prog) {
+	err("Usage: %s { install, generate } [ OPTIONS ] { -h, CONFIG_FILE }\n", prog);
+	err("  CONFIG_FILE is the complete path to a WireGuard configuration file, used by");
+	err("  `wg-quick`. `wg2nd` will convert the WireGuard configuration to networkd");
+	err("  files.\n");
+	err("  The generated configurations are functionally equivalent to `wg-quick(8)`");
+	err("  with the following exceptions:\n");
+	err("  1. When unspecified, `wg-quick` determines whether `FwMark` and `Table` are available dynamically,");
+	err("     ensuring that the routing table and `fwmark` are not already in use. `wg2nd` sets");
+	err("     the `fwmark` to a random number (deterministically generated from the interface");
+	err("     name). If more than 500 `fwmarks` are in use, there is a non-negligible chance of a");
+	err("     collision. This would occur when there are more than 500 active WireGuard interfaces.\n");
+	err("  2. The PreUp, PostUp, PreDown, and PostDown script snippets are ignored.\n");
+	err("  3. `wg-quick(8)` installs a firewall when a default route is specified (i.e., when `0.0.0.0/0`");
+	err("     or `::/0` are specified in `AllowedIPs`). This is not installed by");
+	err("     default with `wg2nd install`. The equivalent firewall can be generated with");
+	err("     `wg2nd generate -t nft CONFIG_FILE`. Refer to `nft(8)` for details.\n");
+	err("  Actions:");
+	err("    install   Generate and install the configuration with restricted permissions");
+	err("    generate  Generate specific configuration files and write the results to stdout\n");
+	err("  Options:");
+	err("    -h        Print this help");
+	exit(EXIT_SUCCESS);
+}
 
-[[noreturn]] void die_usage(char const * prog) {
-	err("Usage: %s [ -o OUTPUT_PATH ] CONFIG_FILE", prog);
+void die_usage_generate(const char *prog) {
+	err("Usage: %s generate [ -h ] [ -k KEYPATH ] [ -t { network, netdev, keyfile, nft } ] CONFIG_FILE", prog);
 	die("Use -h for help");
 }
 
-void print_help(char const * prog) {
-	err("Usage: %s [ -h | -f | -o OUTPUT_PATH ] CONFIG_FILE", prog);
+void print_help_generate(const char *prog) {
+	err("Usage: %s generate [ -h ] [ -k KEYPATH ] [ -t { network, netdev, keyfile, nft } ] CONFIG_FILE\n", prog);
 	err("Options:");
-	err("-o OUTPUT_PATH\tSet the output path (default is /etc/systemd/network)");
-	err("-f            \tOutput firewall rules");
-	err("-h            \tDisplay this help message");
+	err("  -t FILE_TYPE");
+	err("     network  Generate a Network Configuration File (see systemd.network(8))");
+	err("     netdev   Generate a Virtual Device File (see systemd.netdev(8))");
+	err("     keyfile  Print the interface's private key");
+	err("     nft      Print the netfilter table `nft(8)` installed by `wg-quick(8)`\n");
+	err("  -k KEYPATH  Full path to the keyfile (a path relative to /etc/systemd/network is generated");
+	err("              if unspecified)\n");
+	err("  -h        Print this help");
 	exit(EXIT_SUCCESS);
 }
 
-using namespace wg2sd;
+void die_usage_install(const char *prog) {
+	err("Usage: %s install [ -h ] [ -f FILE_NAME ] [ -k KEYFILE ] [ -o OUTPUT_PATH ] CONFIG_FILE", prog);
+	die("Use -h for help");
+}
+
+void print_help_install(const char *prog) {
+	err("Usage: %s install [ -h ] [ -f FILE_NAME ] [ -o OUTPUT_PATH ] CONFIG_FILE\n", prog);
+	err("  `wg2nd install` translates `wg-quick(8)` configuration into corresponding");
+	err("  `networkd` configuration and installs the resulting files in `OUTPUT_PATH`.\n");
+	err("  `wg2nd install` generates a `netdev`, `network`, and `keyfile` for each");
+	err("  CONFIG_FILE. Links will be installed with a `manual` `ActivationPolicy`.");
+	err("  The interface can be brought up with `networkctl up INTERFACE` and down");
+	err("  with `networkctl down INTERFACE`.\n");
+	err("  `wg-quick(8)` installs a firewall when a default route (i.e., when `0.0.0.0/0`");
+	err("  or `::/0` is specified in `AllowedIPs`). This is not installed by default");
+	err("  with `wg2nd install`. The equivalent firewall can be generated with");
+	err("  `wg2nd generate -t nft CONFIG_FILE`.\n");
+	err("Options:");
+	err("  -o OUTPUT_PATH  The installation path (default is /etc/systemd/network)\n");
+	err("  -f FILE_NAME    The base name for the installed configuration files. The");
+	err("                  networkd-specific configuration suffix will be added");
+	err("                  (FILE_NAME.netdev for systemd-netdev(8) files,");
+	err("                  FILE_NAME.network for systemd-network(8) files,");
+	err("                  and FILE_NAME.keyfile for keyfiles)\n");
+	err("  -k KEYFILE       The name of the private keyfile\n");
+	err("  -h              Print this help");
+	exit(EXIT_SUCCESS);
+}
+
+
+/*
+ * PARSING
+ */
+
+enum class FileType {
+	NONE = 0,
+	NETWORK,
+	NETDEV,
+	KEYFILE,
+	NFT
+};
+
+
+/*
+ * INTERNAL LOGIC
+ */
+
+#include "wg2nd.hpp"
+
+#include <iostream>
+#include <fstream>
+#include <optional>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <grp.h>
+
+using namespace wg2nd;
 
 void write_systemd_file(SystemdFilespec const & filespec, std::string output_path, bool secure) {
 	std::string full_path = output_path + "/" + filespec.name;
@@ -142,44 +238,23 @@ void write_systemd_file(SystemdFilespec const & filespec, std::string output_pat
 	}
 }
 
-int main(int argc, char ** argv) {
-	int opt;
-	std::filesystem::path output_path = "/etc/systemd/network";
-	bool print_firewall_rules = false;
-
-	while ((opt = getopt(argc, argv, "o:fh")) != -1) {
-		switch (opt) {
-			case 'o':
-				output_path = optarg;
-				break;
-			case 'f':
-				print_firewall_rules = true;
-				break;
-			case 'h':
-				print_help(argv[0]);
-				break;
-			default: /* '?' */
-				die_usage(argv[0]);
-		}
-	}
-
-	if (optind >= argc) {
-		die_usage(argv[0]);
-	}
-
-	std::filesystem::path config_path = argv[optind];
+SystemdConfig generate_cfg_or_die(
+	std::filesystem::path && config_path,
+	std::filesystem::path const & keyfile_or_output_path,
+	std::optional<std::string> const & filename
+	) {
 	std::fstream cfg_stream { config_path };
 
 	if(!cfg_stream.is_open()) {
 		die("Failed to open config file %s", config_path.string().c_str());
 	}
 
-	std::string interface_name = interface_name_from_filename(config_path);
-
 	SystemdConfig cfg;
 
+	std::string interface_name = interface_name_from_filename(config_path);
+
 	try {
-		cfg = wg2sd::wg2sd(interface_name, cfg_stream, output_path);
+		cfg = wg2nd::wg2nd(interface_name, cfg_stream, keyfile_or_output_path, filename);
 	} catch(ConfigurationException const & cex) {
 
 		const ParsingException * pex = dynamic_cast<const ParsingException *>(&cex);
@@ -191,16 +266,25 @@ int main(int argc, char ** argv) {
 
 	}
 
-	if(print_firewall_rules) {
-		fprintf(stdout, "%s", cfg.firewall.c_str());
+	return cfg;
+}
 
-		return 0;
-	}
+
+void wg2nd_install_internal(std::optional<std::string> && filename, std::string && keyfile_name,
+	std::filesystem::path && output_path, std::filesystem::path && config_path) {
 
 	if(!std::filesystem::path(output_path).is_absolute()) {
 		output_path = std::filesystem::absolute(output_path);
 	}
 
+	std::filesystem::path keyfile_or_output_path = output_path;
+
+	if(!keyfile_name.empty()) {
+		keyfile_or_output_path /= keyfile_name;
+	}
+
+	SystemdConfig cfg = generate_cfg_or_die(std::move(config_path), keyfile_or_output_path, std::move(filename));
+
 	for(std::string const & warning : cfg.warnings) {
 		err("warning: %s", warning.c_str());
 	}
@@ -212,6 +296,147 @@ int main(int argc, char ** argv) {
 	for(SystemdFilespec const & spec : cfg.symmetric_keyfiles) {
 		write_systemd_file(spec, output_path, true);
 	}
+}
+
+void wg2nd_generate_internal(FileType type, std::string && config_file,
+	std::optional<std::filesystem::path> && keyfile_path) {
+
+	SystemdConfig cfg = generate_cfg_or_die(
+		std::move(config_file), std::move(keyfile_path.value_or(DEFAULT_OUTPUT_PATH)), {}
+	);
+
+	switch(type) {
+		case FileType::NFT:
+			printf("%s", cfg.firewall.c_str());
+			break;
+		case FileType::NETWORK:
+			printf("%s", cfg.network.contents.c_str());
+			break;
+		case FileType::NETDEV:
+			printf("%s", cfg.netdev.contents.c_str());
+			break;
+		case FileType::KEYFILE:
+			printf("%s", cfg.private_keyfile.contents.c_str());
+			break;
+		default:
+			break;
+	}
+}
+
+
+static int wg2nd_generate(char const * prog, int argc, char **argv) {
+	std::filesystem::path config_path = "";
+
+	FileType type = FileType::NONE;
+	std::optional<std::filesystem::path> keyfile_path = {};
+
+	int opt;
+	while ((opt = getopt(argc, argv, "ht:k:")) != -1) {
+		switch (opt) {
+			case 't':
+				if (strcmp(optarg, "network") == 0) {
+					type = FileType::NETWORK;
+				} else if (strcmp(optarg, "netdev") == 0) {
+					type = FileType::NETDEV;
+				} else if (strcmp(optarg, "keyfile") == 0) {
+					type = FileType::KEYFILE;
+				} else if (strcmp(optarg, "nft") == 0) {
+					type = FileType::NFT;
+				} else {
+					die("Unknown file type: %s", optarg);
+				}
+				break;
+			case 'k':
+				keyfile_path = optarg;
+				break;
+			case 'h':
+				print_help_generate(prog);
+				break;
+			default:
+				die_usage_generate(prog);
+		}
+	}
+
+	if (optind >= argc) {
+		die_usage_generate(prog);
+	}
+
+	config_path = argv[optind];
+
+	wg2nd_generate_internal(type, std::move(config_path), std::move(keyfile_path));
+
+	return 0;
+}
+
+static int wg2nd_install(char const * prog, int argc, char **argv) {
+	std::filesystem::path config_path = "";
+
+	std::optional<std::string> filename = {};
+	std::filesystem::path output_path = DEFAULT_OUTPUT_PATH;
+	std::string keyfile_name = "";
+
+	int opt;
+	while ((opt = getopt(argc, argv, "o:f:k:h")) != -1) {
+		switch (opt) {
+			case 'o': {
+				std::string path = optarg;
+				if(path[path.size() - 1] != '/') {
+					path.push_back('/');
+				}
+				output_path = std::move(path);
+				break;
+			}
+			case 'f':
+				filename = optarg;
+				break;
+			case 'h':
+				print_help_install(prog);
+				break;
+			case 'k':
+				keyfile_name = optarg;
+				break;
+			default:
+				die_usage_install(prog);
+		}
+	}
+
+	if (optind >= argc) {
+		die_usage_install(prog);
+	}
+
+	config_path = argv[optind];
+
+	wg2nd_install_internal(std::move(filename), std::move(keyfile_name), std::move(output_path), std::move(config_path));
+
+	return 0;
+}
+
+// The main function remains the same as before
+
+
+int main(int argc, char **argv) {
+	char const * prog = "wg2nd";
+
+	if(argc > 0) {
+		prog = argv[0];
+	}
+
+	if (argc < 2) {
+		die_usage(prog);
+	}
+
+	std::string action = argv[1];
+
+	if (action == "generate") {
+		return wg2nd_generate(prog, argc - 1, argv + 1);
+	} else if (action == "install") {
+		return wg2nd_install(prog, argc - 1, argv + 1);
+	} else if (action == "-h" || action == "--help") {
+		print_help(prog);
+	} else {
+		err("Unknown action: %s", action.c_str());
+		die_usage(prog);
+	}
 
 	return 0;
 }
diff --git a/src/wg2sd.cpp b/src/wg2nd.cpp
index 4c39a03..c53df04 100644
--- a/src/wg2sd.cpp
+++ b/src/wg2nd.cpp
@@ -1,4 +1,4 @@
-#include "wg2sd.hpp"
+#include "wg2nd.hpp"
 
 #include <exception>
 #include <sstream>
@@ -27,7 +27,7 @@ std::string hashed_keyfile_name(std::string const & priv_key) {
 
 	uint8_t hash[HASHLEN];
 
-	argon2i_hash_raw(t_cost, m_cost, parallelism, key, keylen, SALT, sizeof(SALT), hash, HASHLEN);
+	argon2id_hash_raw(t_cost, m_cost, parallelism, key, keylen, SALT, sizeof(SALT), hash, HASHLEN);
 
 	constexpr char KEYFILE_EXT[] = ".keyfile";
 
@@ -47,8 +47,29 @@ std::string hashed_keyfile_name(std::string const & priv_key) {
 	return std::string { filename } ;
 }
 
+uint32_t deterministic_fwmark(std::string const & interface_name) {
+	constexpr uint8_t const SALT[] = {
+		0x90, 0x08, 0x82, 0xd7, 0x75, 0x68, 0xf4, 0x8e,
+		0x90, 0x74, 0x0c, 0x74, 0x0d, 0xf4, 0xfb, 0x91,
+		0xe5, 0x44, 0x87, 0x7e, 0xce, 0x48, 0xcf, 0x01,
+	};
+
+	uint8_t const * key = reinterpret_cast<uint8_t const *>(interface_name.c_str());
+	uint32_t keylen = interface_name.size();
+
+	uint32_t mark;
+
+	uint8_t t_cost = 2;
+	uint32_t m_cost = 1 << 10;
+	uint32_t parallelism = 1;
+
+	argon2id_hash_raw(t_cost, m_cost, parallelism, key, keylen, SALT, sizeof(SALT), &mark, sizeof(mark));
+
+	return mark;
+}
+
 
-namespace wg2sd {
+namespace wg2nd {
 
 	std::string interface_name_from_filename(std::filesystem::path config_path) {
 		std::string interface_name = config_path.filename().string();
@@ -219,6 +240,8 @@ namespace wg2sd {
 					}
 
 					cfg.intf.listen_port = port;
+				} else if (key == "MTU") {
+					cfg.intf.mtu = value;
 				} else if (key == "PreUp") {
 					cfg.intf.preup = value;
 				} else if (key == "PostUp") {
@@ -303,7 +326,7 @@ namespace wg2sd {
 		return cfg;
 	}
 
-	static void _write_table(std::stringstream & firewall, Config const & cfg, std::vector<std::string_view> addrs, bool ipv4) {
+	static void _write_table(std::stringstream & firewall, Config const & cfg, std::vector<std::string_view> addrs, bool ipv4, uint32_t fwd_table) {
 		char const * ip = ipv4 ? "ip" : "ip6";
 
 		firewall << "table " << ip << " " << cfg.intf.name << " {\n"
@@ -323,13 +346,13 @@ namespace wg2sd {
 		         << "\n"
 		         << "  chain postmangle {\n"
 		         << "    type filter hook postrouting priority mangle; policy accept;\n"
-		         << "    meta l4proto udp meta mark " << std::hex << cfg.intf.table << std::dec << "ct mark set meta mark;\n"
+		         << "    meta l4proto udp meta mark 0x" << std::hex << fwd_table << std::dec << " ct mark set meta mark;\n"
 		         << "  }\n"
 		         << "}\n";
 		
 	}
 
-	std::string _gen_nftables_firewall(Config const & cfg) {
+	std::string _gen_nftables_firewall(Config const & cfg, uint32_t fwd_table) {
 		std::stringstream firewall;
 
 		std::vector<std::string_view> ipv4_addrs;
@@ -343,39 +366,31 @@ namespace wg2sd {
 			}
 		}
 
-		_write_table(firewall, cfg, ipv4_addrs, true);
-
-		firewall << "\n";
+		if(ipv4_addrs.size() > 0) {
+			_write_table(firewall, cfg, ipv4_addrs, true, fwd_table);
+			firewall << "\n";
+		}
 
-		_write_table(firewall, cfg, ipv6_addrs, false);
+		if(ipv6_addrs.size() > 0) {
+			_write_table(firewall, cfg, ipv6_addrs, false, fwd_table);
+		}
 
 		return firewall.str();
 	}
 
-	static std::string _gen_netdev_cfg(Config const & cfg, uint32_t fwd_table, std::string const & private_keyfile,
-			std::vector<SystemdFilespec> & symmetric_keyfiles, std::string const & output_path) {
+	static std::string _gen_netdev_cfg(Config const & cfg, uint32_t fwd_table, std::filesystem::path const & private_keyfile,
+			std::vector<SystemdFilespec> & symmetric_keyfiles) {
 		std::stringstream netdev;
 
-		netdev << "# Autogenerated by wg2sd\n";
+		netdev << "# Autogenerated by wg2nd\n";
 		netdev << "[NetDev]\n";
 		netdev << "Name = " << cfg.intf.name << "\n";
 		netdev << "Kind = wireguard\n";
 		netdev << "Description = " << cfg.intf.name << " - wireguard tunnel\n";
-
-		if(!cfg.intf.mtu.empty()) {
-			netdev << "MTUBytes = " << cfg.intf.mtu << "\n";
-		}
-
 		netdev << "\n";
 
 		netdev << "[WireGuard]\n";
-		netdev << "PrivateKeyFile = " << output_path;
-
-		if(output_path.back() != '/') {
-			netdev << "/";
-		}
-
-		netdev << private_keyfile << "\n";
+		netdev << "PrivateKeyFile = " << private_keyfile.string() << "\n";
 
 		if(cfg.intf.listen_port.has_value()) {
 			netdev << "ListenPort = " << cfg.intf.listen_port.value() << "\n";
@@ -441,11 +456,18 @@ namespace wg2sd {
 	static std::string _gen_network_cfg(Config const & cfg, uint32_t fwd_table) {
 		std::stringstream network;
 
-		network << "# Autogenerated by wg2sd\n";
+		network << "# Autogenerated by wg2nd\n";
 		network << "[Match]\n";
 		network << "Name = " << cfg.intf.name << "\n";
 		network << "\n";
 
+		network << "[Link]" << "\n";
+		network << "ActivationPolicy = manual\n";
+		if(!cfg.intf.mtu.empty()) {
+			network << "MTUBytes = " << cfg.intf.mtu << "\n";
+		}
+		network << "\n";
+
 		network << "[Network]\n";
 		for(std::string const & addr : cfg.intf.addresses) {
 			network << "Address = " << addr << "\n";
@@ -523,19 +545,21 @@ namespace wg2sd {
 		return network.str();
 	}
 
-	static uint32_t _random_table() {
-		std::random_device rd;
-		std::mt19937 rng { rd() };
+	static uint32_t _deterministic_random_table(std::string const & interface_name) {
 
 		uint32_t table = 0;
 		while(table == 0 or table == MAIN_TABLE or table == LOCAL_TABLE) {
-			table = rng() % UINT32_MAX;
+			table = deterministic_fwmark(interface_name);
 		}
 
 		return table;
 	}
 
-	SystemdConfig gen_systemd_config(Config const & cfg, std::string const & output_path) {
+	SystemdConfig gen_systemd_config(
+		Config const & cfg,
+		std::filesystem::path const & keyfile_or_output_path,
+		std::optional<std::string> const & filename
+	) {
 
 		// If the table is explicitly specified with Table=<number>,
 		// all routes are added to this table.
@@ -549,11 +573,18 @@ namespace wg2sd {
 		// table.
 		//
 		// If Table=off, no routes are added.
-		uint32_t fwd_table = _random_table();
+		uint32_t fwd_table = _deterministic_random_table(cfg.intf.name);
 
 		std::vector<SystemdFilespec> symmetric_keyfiles;
 
-		std::string private_keyfile = hashed_keyfile_name(cfg.intf.private_key);
+		std::filesystem::path keyfile_path;
+
+		if(keyfile_or_output_path.has_filename()) {
+			keyfile_path = keyfile_or_output_path;
+		} else {
+			std::string private_keyfile = hashed_keyfile_name(cfg.intf.private_key);
+			keyfile_path = keyfile_or_output_path / private_keyfile;
+		}
 
 		std::vector<std::string> warnings;
 
@@ -572,27 +603,30 @@ if(!cfg.intf.field_.empty()) { \
 			warnings.push_back("[Interface] section contains a field \"PreUp\" which does not have a systemd-networkd analog");
 		}
 
+		std::string const & basename = filename.value_or(cfg.intf.name);
+
 		return SystemdConfig {
 			.netdev = {
-				.name = cfg.intf.name + ".netdev",
-				.contents = _gen_netdev_cfg(cfg, fwd_table, private_keyfile, symmetric_keyfiles, output_path),
+				.name = basename + ".netdev",
+				.contents = _gen_netdev_cfg(cfg, fwd_table, keyfile_path, symmetric_keyfiles),
 			},
 			.network = {
-				.name = cfg.intf.name + ".network",
+				.name = basename + ".network",
 				.contents = _gen_network_cfg(cfg, fwd_table)
 			},
 			.private_keyfile = {
-				.name = private_keyfile,
+				.name = keyfile_path.filename(),
 				.contents = cfg.intf.private_key + "\n",
 			},
 			.symmetric_keyfiles = std::move(symmetric_keyfiles),
 			.warnings = std::move(warnings),
-			.firewall = _gen_nftables_firewall(cfg),
+			.firewall = _gen_nftables_firewall(cfg, fwd_table),
 		};
 	}
 
-	SystemdConfig wg2sd(std::string const & interface_name, std::istream & stream, std::string const & output_path) {
-		return gen_systemd_config(parse_config(interface_name, stream), output_path);
+	SystemdConfig wg2nd(std::string const & interface_name, std::istream & stream,
+			std::filesystem::path const & keyfile_or_output_path, std::optional<std::string> const & filename) {
+		return gen_systemd_config(parse_config(interface_name, stream), keyfile_or_output_path, filename);
 	}
 
 }
diff --git a/src/wg2sd.hpp b/src/wg2nd.hpp
index e80a284..7bf7f54 100644
--- a/src/wg2sd.hpp
+++ b/src/wg2nd.hpp
@@ -9,7 +9,7 @@
 
 #include <cstdint>
 
-namespace wg2sd {
+namespace wg2nd {
 
 	struct Interface {
 		// File name, or defaults to "wg"
@@ -134,8 +134,14 @@ namespace wg2sd {
 
 	Config parse_config(std::string const & interface_name, std::istream & stream);
 
-	SystemdConfig gen_systemd_config(Config const & cfg, std::string const & output_path);
+	SystemdConfig gen_systemd_config(
+		Config const & cfg,
+		std::filesystem::path const & keyfile_or_output_path,
+		std::optional<std::string> const & filename
+	);
 
-	SystemdConfig wg2sd(std::string const & interface_name, std::istream & stream, std::string const & output_path);
+	SystemdConfig wg2nd(std::string const & interface_name, std::istream & stream,
+		std::filesystem::path const & keyfile_or_output_path,
+		std::optional<std::string> const & filename);
 
 };
diff --git a/test/wg2sd_test.cpp b/test/wg2nd_test.cpp
index 5d57ac9..39b0766 100644
--- a/test/wg2sd_test.cpp
+++ b/test/wg2nd_test.cpp
@@ -1,17 +1,17 @@
 #include "utest.h"
 
-#include "wg2sd.hpp"
+#include "wg2nd.hpp"
 #include <sstream>
 #include <array>
 
-namespace wg2sd {
+namespace wg2nd {
 	extern bool _is_default_route(std::string const & cidr);
 	extern bool _is_ipv4_route(std::string const & cidr);
 };
 
-using namespace wg2sd;
+using namespace wg2nd;
 
-UTEST(wg2sd, ip_helpers) {
+UTEST(wg2nd, ip_helpers) {
 
 	std::array<std::string, 8> default_routes = {
 		"0/0",
@@ -121,7 +121,7 @@ const char * INVALID_CONFIG = (
 );
 
 
-UTEST(wg2sd, parses_config) {
+UTEST(wg2nd, parses_config) {
 
 	// CONFIG1
 	std::istringstream ss { CONFIG1 };