Centralize runtime config defaults

Makefile

@@ -26,7 +26,7 @@ OBJECTS = $(SOURCES:$(SRC_DIR)/%.c=$(OBJ_DIR)/%.o)
 DEPS = $(OBJECTS:.o=.d) $(CTL_OBJECTS:.o=.d)
 TARGET = tnt
 CTL_TARGET = tntctl
-CTL_OBJECTS = $(OBJ_DIR)/tntctl.o $(OBJ_DIR)/tntctl_text.o $(OBJ_DIR)/exec_catalog.o $(OBJ_DIR)/common.o $(OBJ_DIR)/i18n.o
+CTL_OBJECTS = $(OBJ_DIR)/tntctl.o $(OBJ_DIR)/tntctl_text.o $(OBJ_DIR)/exec_catalog.o $(OBJ_DIR)/common.o $(OBJ_DIR)/config_defaults.o $(OBJ_DIR)/i18n.o
 TARGETS = $(TARGET) $(CTL_TARGET)
 
 PREFIX ?= /usr/local

docs/CHANGELOG.md

@@ -7,6 +7,8 @@
   `vX.Y.Z` tag must match `TNT_VERSION` before release assets are built.
 - Added `make package-publish-check` for verifying Arch/Homebrew source
   checksums against the final GitHub source archive after a tag exists.
+- Added a `config_defaults` module and unit coverage for runtime default
+  values, env keys, and accepted numeric ranges.
 - Added a dedicated `tntctl_text` module with unit coverage for local
   `tntctl` help and validation diagnostics.
 - Documented the stable SSH exec interface contract, including exit statuses

include/common.h

@@ -11,6 +11,8 @@
 #include <limits.h>
 #include <pthread.h>
 
+#include "config_defaults.h"
+
 /* Project Metadata */
 #define TNT_VERSION "1.0.1"
 
@@ -23,7 +25,6 @@
 #define TNT_EXIT_CONFIG 78
 
 /* Configuration constants */
-#define DEFAULT_PORT 2222
 #define MAX_MESSAGES 100
 #define MAX_USERNAME_LEN 64
 #define MAX_MESSAGE_LEN 1024
@@ -31,13 +32,17 @@
 #define MAX_COMMAND_OUTPUT_LEN 8192
 #define CLIENT_OUTBOX_CAPACITY (128 * 1024)
 #define CLIENT_OUTBOX_FLUSH_BUDGET 32768
-#define DEFAULT_MAX_CLIENTS 64
-#define MAX_CONFIGURED_CLIENTS 1024
 #define LOG_FILE "messages.log"
 #define MAX_LOG_SIZE (10 * 1024 * 1024)  /* 10 MiB */
 #define HOST_KEY_FILE "host_key"
 #define TNT_DEFAULT_STATE_DIR "."
-#define DEFAULT_IDLE_TIMEOUT 1800  /* 30 minutes */
+
+/* Backward-compatible names for older modules while config_defaults owns the
+ * actual runtime defaults and accepted ranges. */
+#define DEFAULT_PORT TNT_DEFAULT_PORT
+#define DEFAULT_MAX_CLIENTS TNT_DEFAULT_MAX_CONNECTIONS
+#define MAX_CONFIGURED_CLIENTS TNT_MAX_CONFIGURED_CLIENTS
+#define DEFAULT_IDLE_TIMEOUT TNT_DEFAULT_IDLE_TIMEOUT
 
 /* ANSI color codes */
 #define ANSI_RESET "\033[0m"

include/config_defaults.h

@@ -0,0 +1,47 @@
+#ifndef CONFIG_DEFAULTS_H
+#define CONFIG_DEFAULTS_H
+
+#include <stdbool.h>
+
+#define TNT_STRINGIFY_VALUE(value) #value
+#define TNT_STRINGIFY(value) TNT_STRINGIFY_VALUE(value)
+
+#define TNT_DEFAULT_PORT 2222
+#define TNT_DEFAULT_PORT_TEXT TNT_STRINGIFY(TNT_DEFAULT_PORT)
+#define TNT_DEFAULT_MAX_CONNECTIONS 64
+#define TNT_DEFAULT_MAX_CONN_PER_IP 5
+#define TNT_DEFAULT_MAX_CONN_RATE_PER_IP 10
+#define TNT_DEFAULT_RATE_LIMIT_ENABLED 1
+#define TNT_DEFAULT_IDLE_TIMEOUT 1800
+
+#define TNT_MIN_PORT 1
+#define TNT_MAX_PORT 65535
+#define TNT_MIN_CONFIGURED_CLIENTS 1
+#define TNT_MAX_CONFIGURED_CLIENTS 1024
+#define TNT_MIN_RATE_LIMIT_ENABLED 0
+#define TNT_MAX_RATE_LIMIT_ENABLED 1
+#define TNT_MIN_IDLE_TIMEOUT 0
+#define TNT_MAX_IDLE_TIMEOUT 86400
+#define TNT_MIN_SSH_LOG_LEVEL 0
+#define TNT_MAX_SSH_LOG_LEVEL 4
+
+typedef struct {
+    const char *env_name;
+    int fallback;
+    int min_value;
+    int max_value;
+} tnt_int_config_spec_t;
+
+extern const tnt_int_config_spec_t TNT_CONFIG_PORT;
+extern const tnt_int_config_spec_t TNT_CONFIG_MAX_CONNECTIONS;
+extern const tnt_int_config_spec_t TNT_CONFIG_MAX_CONN_PER_IP;
+extern const tnt_int_config_spec_t TNT_CONFIG_MAX_CONN_RATE_PER_IP;
+extern const tnt_int_config_spec_t TNT_CONFIG_RATE_LIMIT;
+extern const tnt_int_config_spec_t TNT_CONFIG_IDLE_TIMEOUT;
+extern const tnt_int_config_spec_t TNT_CONFIG_SSH_LOG_LEVEL;
+
+int tnt_config_env_int(const tnt_int_config_spec_t *spec);
+bool tnt_config_parse_int(const char *value, const tnt_int_config_spec_t *spec,
+                          int *out);
+
+#endif /* CONFIG_DEFAULTS_H */

src/chat_room.c

@@ -1,11 +1,11 @@
 #include "chat_room.h"
+#include "config_defaults.h"
 
 /* Global chat room instance */
 chat_room_t *g_room = NULL;
 
 static int room_capacity_from_env(void) {
-    return env_int("TNT_MAX_CONNECTIONS", DEFAULT_MAX_CLIENTS, 1,
+    return tnt_config_env_int(&TNT_CONFIG_MAX_CONNECTIONS);
-                   MAX_CONFIGURED_CLIENTS);
 }
 
 /* Initialize chat room */

src/cli_text.c

@@ -1,5 +1,6 @@
 #include "cli_text.h"
 
+#include "config_defaults.h"
 #include "i18n.h"
 
 void cli_text_append_help(char *buffer, size_t buf_size, size_t *pos,
@@ -12,7 +13,7 @@ void cli_text_append_help(char *buffer, size_t buf_size, size_t *pos,
         "  -d, --state-dir DIR          Store host key and logs in DIR\n"
         "      --bind ADDR              Bind to ADDR (default: 0.0.0.0)\n"
         "      --public-host HOST       Show HOST in startup connection hints\n"
-        "      --max-connections N      Global connection limit (default: 64)\n"
+        "      --max-connections N      Global connection limit (default: %d)\n"
         "      --max-conn-per-ip N      Per-IP concurrent session limit\n"
         "      --max-conn-rate-per-ip N Per-IP connection-rate limit\n"
         "      --rate-limit 0|1         Disable/enable rate-based blocking\n"
@@ -28,9 +29,9 @@ void cli_text_append_help(char *buffer, size_t buf_size, size_t *pos,
         "  TNT_STATE_DIR         State directory\n"
         "  TNT_ACCESS_TOKEN      Require this password for SSH auth\n"
         "  TNT_LANG              UI language: en or zh (default: locale)\n"
-        "  TNT_MAX_CONNECTIONS   Global connection limit (default: 64)\n"
+        "  TNT_MAX_CONNECTIONS   Global connection limit (default: %d)\n"
         "  TNT_RATE_LIMIT        Set to 0 to disable rate limiting\n"
-        "  TNT_IDLE_TIMEOUT      Idle disconnect timeout in seconds (default: 1800)\n",
+        "  TNT_IDLE_TIMEOUT      Idle disconnect timeout in seconds (default: %d)\n",
         "tnt %s - 匿名 SSH 聊天服务器\n\n"
         "用法: %s [options]\n\n"
         "选项:\n"
@@ -38,7 +39,7 @@ void cli_text_append_help(char *buffer, size_t buf_size, size_t *pos,
         "  -d, --state-dir DIR          将主机密钥和日志存放在 DIR\n"
         "      --bind ADDR              绑定到 ADDR (默认: 0.0.0.0)\n"
         "      --public-host HOST       在启动提示中显示 HOST\n"
-        "      --max-connections N      全局连接数限制 (默认: 64)\n"
+        "      --max-connections N      全局连接数限制 (默认: %d)\n"
         "      --max-conn-per-ip N      单 IP 并发会话限制\n"
         "      --max-conn-rate-per-ip N 单 IP 连接速率限制\n"
         "      --rate-limit 0|1         禁用/启用速率封禁\n"
@@ -54,16 +55,19 @@ void cli_text_append_help(char *buffer, size_t buf_size, size_t *pos,
         "  TNT_STATE_DIR         状态目录\n"
         "  TNT_ACCESS_TOKEN      要求 SSH 认证使用此密码\n"
         "  TNT_LANG              UI 语言: en 或 zh (默认跟随 locale)\n"
-        "  TNT_MAX_CONNECTIONS   全局连接数限制 (默认: 64)\n"
+        "  TNT_MAX_CONNECTIONS   全局连接数限制 (默认: %d)\n"
         "  TNT_RATE_LIMIT        设为 0 可禁用速率限制\n"
-        "  TNT_IDLE_TIMEOUT      空闲断开时间，单位秒 (默认: 1800)\n"
+        "  TNT_IDLE_TIMEOUT      空闲断开时间，单位秒 (默认: %d)\n"
     );
     const char *program = (program_name && program_name[0] != '\0')
                               ? program_name
                               : "tnt";
 
     buffer_appendf(buffer, buf_size, pos, i18n_string(help_format, lang),
-                   TNT_VERSION, program, DEFAULT_PORT);
+                   TNT_VERSION, program, TNT_DEFAULT_PORT,
+                   TNT_DEFAULT_MAX_CONNECTIONS,
+                   TNT_DEFAULT_MAX_CONNECTIONS,
+                   TNT_DEFAULT_IDLE_TIMEOUT);
 }
 
 const char *cli_text_invalid_port_format(ui_lang_t lang) {

src/config_defaults.c

@@ -0,0 +1,80 @@
+#include "config_defaults.h"
+#include "common.h"
+
+#include <stdlib.h>
+
+const tnt_int_config_spec_t TNT_CONFIG_PORT = {
+    "PORT",
+    TNT_DEFAULT_PORT,
+    TNT_MIN_PORT,
+    TNT_MAX_PORT,
+};
+
+const tnt_int_config_spec_t TNT_CONFIG_MAX_CONNECTIONS = {
+    "TNT_MAX_CONNECTIONS",
+    TNT_DEFAULT_MAX_CONNECTIONS,
+    TNT_MIN_CONFIGURED_CLIENTS,
+    TNT_MAX_CONFIGURED_CLIENTS,
+};
+
+const tnt_int_config_spec_t TNT_CONFIG_MAX_CONN_PER_IP = {
+    "TNT_MAX_CONN_PER_IP",
+    TNT_DEFAULT_MAX_CONN_PER_IP,
+    TNT_MIN_CONFIGURED_CLIENTS,
+    TNT_MAX_CONFIGURED_CLIENTS,
+};
+
+const tnt_int_config_spec_t TNT_CONFIG_MAX_CONN_RATE_PER_IP = {
+    "TNT_MAX_CONN_RATE_PER_IP",
+    TNT_DEFAULT_MAX_CONN_RATE_PER_IP,
+    TNT_MIN_CONFIGURED_CLIENTS,
+    TNT_MAX_CONFIGURED_CLIENTS,
+};
+
+const tnt_int_config_spec_t TNT_CONFIG_RATE_LIMIT = {
+    "TNT_RATE_LIMIT",
+    TNT_DEFAULT_RATE_LIMIT_ENABLED,
+    TNT_MIN_RATE_LIMIT_ENABLED,
+    TNT_MAX_RATE_LIMIT_ENABLED,
+};
+
+const tnt_int_config_spec_t TNT_CONFIG_IDLE_TIMEOUT = {
+    "TNT_IDLE_TIMEOUT",
+    TNT_DEFAULT_IDLE_TIMEOUT,
+    TNT_MIN_IDLE_TIMEOUT,
+    TNT_MAX_IDLE_TIMEOUT,
+};
+
+const tnt_int_config_spec_t TNT_CONFIG_SSH_LOG_LEVEL = {
+    "TNT_SSH_LOG_LEVEL",
+    0,
+    TNT_MIN_SSH_LOG_LEVEL,
+    TNT_MAX_SSH_LOG_LEVEL,
+};
+
+int tnt_config_env_int(const tnt_int_config_spec_t *spec) {
+    if (!spec) {
+        return 0;
+    }
+    return env_int(spec->env_name, spec->fallback, spec->min_value,
+                   spec->max_value);
+}
+
+bool tnt_config_parse_int(const char *value, const tnt_int_config_spec_t *spec,
+                          int *out) {
+    char *end = NULL;
+    long val;
+
+    if (!value || value[0] == '\0' || !spec || !out) {
+        return false;
+    }
+
+    val = strtol(value, &end, 10);
+    if (!end || *end != '\0' || val < spec->min_value ||
+        val > spec->max_value) {
+        return false;
+    }
+
+    *out = (int)val;
+    return true;
+}

src/input.c

@@ -2,6 +2,7 @@
 #include "chat_room.h"
 #include "client.h"
 #include "commands.h"
+#include "config_defaults.h"
 #include "common.h"
 #include "exec.h"
 #include "history_view.h"
@@ -20,11 +21,11 @@
 #include <string.h>
 #include <time.h>
 
-static int g_idle_timeout = DEFAULT_IDLE_TIMEOUT;
+static int g_idle_timeout = TNT_DEFAULT_IDLE_TIMEOUT;
 static ui_lang_t g_default_ui_lang = UI_LANG_EN;
 
 void input_init(void) {
-    g_idle_timeout = env_int("TNT_IDLE_TIMEOUT", DEFAULT_IDLE_TIMEOUT, 0, 86400);
+    g_idle_timeout = tnt_config_env_int(&TNT_CONFIG_IDLE_TIMEOUT);
     g_default_ui_lang = i18n_default_ui_lang();
 }
 

src/main.c

@@ -1,5 +1,6 @@
 #include "chat_room.h"
 #include "cli_text.h"
+#include "config_defaults.h"
 #include "common.h"
 #include "i18n.h"
 #include "message.h"
@@ -19,24 +20,6 @@ static void signal_handler(int sig) {
     _exit(0);
 }
 
-static bool parse_int_arg(const char *value, int min_val, int max_val,
-                          int *out) {
-    char *end = NULL;
-    long val;
-
-    if (!value || value[0] == '\0' || !out) {
-        return false;
-    }
-
-    val = strtol(value, &end, 10);
-    if (!end || *end != '\0' || val < min_val || val > max_val) {
-        return false;
-    }
-
-    *out = (int)val;
-    return true;
-}
-
 static bool is_config_token(const char *value) {
     const unsigned char *p = (const unsigned char *)value;
 
@@ -60,16 +43,16 @@ static int set_env_option(const char *name, const char *value) {
     return 0;
 }
 
-static int set_numeric_env_option(const char *env_name, const char *opt_name,
+static int set_numeric_env_option(const tnt_int_config_spec_t *spec,
-                                  const char *value, int min_val,
+                                  const char *opt_name, const char *value,
-                                  int max_val, ui_lang_t lang) {
+                                  ui_lang_t lang) {
     int parsed;
 
-    if (!parse_int_arg(value, min_val, max_val, &parsed)) {
+    if (!tnt_config_parse_int(value, spec, &parsed)) {
         fprintf(stderr, cli_text_invalid_value_format(lang), opt_name, value);
         return TNT_EXIT_USAGE;
     }
-    if (set_env_option(env_name, value) != 0) {
+    if (set_env_option(spec->env_name, value) != 0) {
         return TNT_EXIT_ERROR;
     }
     return TNT_EXIT_OK;
@@ -86,21 +69,11 @@ static bool require_option_arg(int argc, char **argv, int index,
 }
 
 int main(int argc, char **argv) {
-    int port = DEFAULT_PORT;
+    int port = tnt_config_env_int(&TNT_CONFIG_PORT);
     ui_lang_t lang = i18n_default_ui_lang();
     const char *log_check_path = NULL;
     const char *log_recover_path = NULL;
 
-    /* Environment provides defaults; command-line flags override it. */
-    const char *port_env = getenv("PORT");
-    if (port_env && port_env[0] != '\0') {
-        char *end;
-        long val = strtol(port_env, &end, 10);
-        if (*end == '\0' && val > 0 && val <= 65535) {
-            port = (int)val;
-        }
-    }
-
     /* Parse command line arguments */
     for (int i = 1; i < argc; i++) {
         if (strcmp(argv[i], "-p") == 0 || strcmp(argv[i], "--port") == 0) {
@@ -108,7 +81,7 @@ int main(int argc, char **argv) {
             if (!require_option_arg(argc, argv, i, lang)) {
                 return TNT_EXIT_USAGE;
             }
-            if (!parse_int_arg(argv[i + 1], 1, 65535, &val)) {
+            if (!tnt_config_parse_int(argv[i + 1], &TNT_CONFIG_PORT, &val)) {
                 fprintf(stderr, cli_text_invalid_port_format(lang),
                         argv[i + 1]);
                 return TNT_EXIT_USAGE;
@@ -154,9 +127,8 @@ int main(int argc, char **argv) {
             if (!require_option_arg(argc, argv, i, lang)) {
                 return TNT_EXIT_USAGE;
             }
-            int rc = set_numeric_env_option("TNT_MAX_CONNECTIONS", argv[i],
+            int rc = set_numeric_env_option(&TNT_CONFIG_MAX_CONNECTIONS,
-                                            argv[i + 1], 1,
+                                            argv[i], argv[i + 1], lang);
-                                            MAX_CONFIGURED_CLIENTS, lang);
             if (rc != TNT_EXIT_OK) {
                 return rc;
             }
@@ -165,9 +137,8 @@ int main(int argc, char **argv) {
             if (!require_option_arg(argc, argv, i, lang)) {
                 return TNT_EXIT_USAGE;
             }
-            int rc = set_numeric_env_option("TNT_MAX_CONN_PER_IP", argv[i],
+            int rc = set_numeric_env_option(&TNT_CONFIG_MAX_CONN_PER_IP,
-                                            argv[i + 1], 1,
+                                            argv[i], argv[i + 1], lang);
-                                            MAX_CONFIGURED_CLIENTS, lang);
             if (rc != TNT_EXIT_OK) {
                 return rc;
             }
@@ -176,9 +147,8 @@ int main(int argc, char **argv) {
             if (!require_option_arg(argc, argv, i, lang)) {
                 return TNT_EXIT_USAGE;
             }
-            int rc = set_numeric_env_option("TNT_MAX_CONN_RATE_PER_IP",
+            int rc = set_numeric_env_option(&TNT_CONFIG_MAX_CONN_RATE_PER_IP,
-                                            argv[i], argv[i + 1], 1,
+                                            argv[i], argv[i + 1], lang);
-                                            MAX_CONFIGURED_CLIENTS, lang);
             if (rc != TNT_EXIT_OK) {
                 return rc;
             }
@@ -187,8 +157,8 @@ int main(int argc, char **argv) {
             if (!require_option_arg(argc, argv, i, lang)) {
                 return TNT_EXIT_USAGE;
             }
-            int rc = set_numeric_env_option("TNT_RATE_LIMIT", argv[i],
+            int rc = set_numeric_env_option(&TNT_CONFIG_RATE_LIMIT, argv[i],
-                                            argv[i + 1], 0, 1, lang);
+                                            argv[i + 1], lang);
             if (rc != TNT_EXIT_OK) {
                 return rc;
             }
@@ -197,8 +167,8 @@ int main(int argc, char **argv) {
             if (!require_option_arg(argc, argv, i, lang)) {
                 return TNT_EXIT_USAGE;
             }
-            int rc = set_numeric_env_option("TNT_IDLE_TIMEOUT", argv[i],
+            int rc = set_numeric_env_option(&TNT_CONFIG_IDLE_TIMEOUT, argv[i],
-                                            argv[i + 1], 0, 86400, lang);
+                                            argv[i + 1], lang);
             if (rc != TNT_EXIT_OK) {
                 return rc;
             }
@@ -207,8 +177,8 @@ int main(int argc, char **argv) {
             if (!require_option_arg(argc, argv, i, lang)) {
                 return TNT_EXIT_USAGE;
             }
-            int rc = set_numeric_env_option("TNT_SSH_LOG_LEVEL", argv[i],
+            int rc = set_numeric_env_option(&TNT_CONFIG_SSH_LOG_LEVEL,
-                                            argv[i + 1], 0, 4, lang);
+                                            argv[i], argv[i + 1], lang);
             if (rc != TNT_EXIT_OK) {
                 return rc;
             }

src/ratelimit.c

@@ -1,4 +1,5 @@
 #include "ratelimit.h"
+#include "config_defaults.h"
 #include "common.h"
 #include <arpa/inet.h>
 #include <pthread.h>
@@ -27,16 +28,20 @@ static pthread_mutex_t g_rate_limit_lock = PTHREAD_MUTEX_INITIALIZER;
 static int g_total_connections = 0;
 static pthread_mutex_t g_conn_count_lock = PTHREAD_MUTEX_INITIALIZER;
 
-static int g_max_connections = 64;
+static int g_max_connections = TNT_DEFAULT_MAX_CONNECTIONS;
-static int g_max_conn_per_ip = 5;
+static int g_max_conn_per_ip = TNT_DEFAULT_MAX_CONN_PER_IP;
-static int g_max_conn_rate_per_ip = 10;
+static int g_max_conn_rate_per_ip = TNT_DEFAULT_MAX_CONN_RATE_PER_IP;
-static int g_rate_limit_enabled = 1;
+static int g_rate_limit_enabled = TNT_DEFAULT_RATE_LIMIT_ENABLED;
 
 void ratelimit_init(void) {
-    g_max_connections        = env_int("TNT_MAX_CONNECTIONS",       64, 1, 1024);
+    g_max_connections =
-    g_max_conn_per_ip        = env_int("TNT_MAX_CONN_PER_IP",        5, 1, 1024);
+        tnt_config_env_int(&TNT_CONFIG_MAX_CONNECTIONS);
-    g_max_conn_rate_per_ip   = env_int("TNT_MAX_CONN_RATE_PER_IP",  10, 1, 1024);
+    g_max_conn_per_ip =
-    g_rate_limit_enabled     = env_int("TNT_RATE_LIMIT",             1, 0,    1);
+        tnt_config_env_int(&TNT_CONFIG_MAX_CONN_PER_IP);
+    g_max_conn_rate_per_ip =
+        tnt_config_env_int(&TNT_CONFIG_MAX_CONN_RATE_PER_IP);
+    g_rate_limit_enabled =
+        tnt_config_env_int(&TNT_CONFIG_RATE_LIMIT);
 }
 
 /* Caller MUST hold g_rate_limit_lock. */

src/ssh_server.c

@@ -1,6 +1,7 @@
 #include "ssh_server.h"
 #include "bootstrap.h"
 #include "commands.h"
+#include "config_defaults.h"
 #include "exec.h"
 #include "input.h"
 #include "ratelimit.h"
@@ -23,7 +24,7 @@
 
 /* Global SSH bind instance */
 static ssh_bind g_sshbind = NULL;
-static int g_listen_port = DEFAULT_PORT;
+static int g_listen_port = TNT_DEFAULT_PORT;
 
 static time_t g_server_start_time = 0;
 

src/tntctl.c

@@ -1,4 +1,5 @@
 #include "common.h"
+#include "config_defaults.h"
 #include "exec_catalog.h"
 #include "i18n.h"
 #include "tntctl_text.h"
@@ -145,7 +146,7 @@ static int run_ssh(char **ssh_argv) {
 }
 
 int main(int argc, char **argv) {
-    const char *port = "2222";
+    const char *port = TNT_DEFAULT_PORT_TEXT;
     const char *login = NULL;
     const char *host_key_checking = NULL;
     const char *known_hosts = NULL;

src/tntctl_text.c

@@ -1,5 +1,6 @@
 #include "tntctl_text.h"
 
+#include "config_defaults.h"
 #include "exec_catalog.h"
 #include "i18n.h"
 
@@ -61,7 +62,7 @@ void tntctl_text_append_usage(char *buffer, size_t buf_size, size_t *pos,
         "Usage: tntctl [options] host command [args...]\n"
         "\n"
         "Options:\n"
-        "  -p, --port PORT        SSH port (default: 2222)\n"
+        "  -p, --port PORT        SSH port (default: " TNT_DEFAULT_PORT_TEXT ")\n"
         "  -l, --login USER       SSH login name for exec identity\n"
         "  --host-key-checking MODE\n"
         "                         OpenSSH host-key mode: yes, accept-new, no\n"
@@ -74,7 +75,7 @@ void tntctl_text_append_usage(char *buffer, size_t buf_size, size_t *pos,
         "用法: tntctl [options] host command [args...]\n"
         "\n"
         "选项:\n"
-        "  -p, --port PORT        SSH 端口 (默认: 2222)\n"
+        "  -p, --port PORT        SSH 端口 (默认: " TNT_DEFAULT_PORT_TEXT ")\n"
         "  -l, --login USER       SSH 登录名，用作 exec 身份\n"
         "  --host-key-checking MODE\n"
         "                         OpenSSH 主机密钥模式: yes, accept-new, no\n"

tests/unit/Makefile

@@ -14,6 +14,7 @@ UTF8_SRC = ../../src/utf8.c
 MESSAGE_SRC = ../../src/message.c
 MESSAGE_LOG_SRC = ../../src/message_log.c
 COMMON_SRC = ../../src/common.c
+CONFIG_DEFAULTS_SRC = ../../src/config_defaults.c
 COMMAND_CATALOG_SRC = ../../src/command_catalog.c
 CLI_TEXT_SRC = ../../src/cli_text.c
 TNTCTL_TEXT_SRC = ../../src/tntctl_text.c
@@ -27,7 +28,7 @@ HELP_TEXT_SRC = ../../src/help_text.c
 MANUAL_TEXT_SRC = ../../src/manual_text.c
 RATELIMIT_SRC = ../../src/ratelimit.c
 
-TESTS = test_utf8 test_message test_chat_room test_history_view test_i18n test_system_message test_command_catalog test_exec_catalog test_help_text test_manual_text test_cli_text test_tntctl_text test_ratelimit
+TESTS = test_utf8 test_message test_chat_room test_history_view test_i18n test_system_message test_command_catalog test_exec_catalog test_help_text test_manual_text test_cli_text test_tntctl_text test_ratelimit test_config_defaults
 
 .PHONY: all clean run
 
@@ -39,7 +40,7 @@ test_utf8: test_utf8.c $(UTF8_SRC)
 test_message: test_message.c $(MESSAGE_SRC) $(MESSAGE_LOG_SRC) $(UTF8_SRC) $(COMMON_SRC)
 	$(CC) $(CFLAGS) -o $@ $^ $(LDFLAGS)
 
-test_chat_room: test_chat_room.c $(CHAT_ROOM_SRC) $(MESSAGE_SRC) $(MESSAGE_LOG_SRC) $(UTF8_SRC) $(COMMON_SRC)
+test_chat_room: test_chat_room.c $(CHAT_ROOM_SRC) $(MESSAGE_SRC) $(MESSAGE_LOG_SRC) $(UTF8_SRC) $(COMMON_SRC) $(CONFIG_DEFAULTS_SRC)
 	$(CC) $(CFLAGS) -o $@ $^ $(LDFLAGS)
 
 test_history_view: test_history_view.c $(HISTORY_VIEW_SRC)
@@ -69,7 +70,10 @@ test_cli_text: test_cli_text.c $(CLI_TEXT_SRC) $(COMMON_SRC)
 test_tntctl_text: test_tntctl_text.c $(TNTCTL_TEXT_SRC) $(EXEC_CATALOG_SRC) $(COMMON_SRC)
 	$(CC) $(CFLAGS) -o $@ $^ $(LDFLAGS)
 
-test_ratelimit: test_ratelimit.c $(RATELIMIT_SRC) $(COMMON_SRC)
+test_ratelimit: test_ratelimit.c $(RATELIMIT_SRC) $(COMMON_SRC) $(CONFIG_DEFAULTS_SRC)
+	$(CC) $(CFLAGS) -o $@ $^ $(LDFLAGS)
+
+test_config_defaults: test_config_defaults.c $(CONFIG_DEFAULTS_SRC) $(COMMON_SRC)
 	$(CC) $(CFLAGS) -o $@ $^ $(LDFLAGS)
 
 run: all
@@ -111,6 +115,9 @@ run: all
 	@echo ""
 	@echo "=== Running Rate Limit Tests ==="
 	./test_ratelimit
+	@echo ""
+	@echo "=== Running Config Defaults Tests ==="
+	./test_config_defaults
 
 clean:
 	rm -f $(TESTS) *.o test_messages.log

tests/unit/test_config_defaults.c

@@ -0,0 +1,66 @@
+#include "config_defaults.h"
+
+#include <assert.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#define TEST(name) static void test_##name(void)
+#define RUN_TEST(name) do { \
+    printf("Running %s... ", #name); \
+    test_##name(); \
+    printf("ok\n"); \
+} while (0)
+
+TEST(specs_expose_runtime_defaults) {
+    assert(TNT_CONFIG_PORT.fallback == TNT_DEFAULT_PORT);
+    assert(TNT_CONFIG_MAX_CONNECTIONS.fallback ==
+           TNT_DEFAULT_MAX_CONNECTIONS);
+    assert(TNT_CONFIG_MAX_CONN_PER_IP.fallback ==
+           TNT_DEFAULT_MAX_CONN_PER_IP);
+    assert(TNT_CONFIG_MAX_CONN_RATE_PER_IP.fallback ==
+           TNT_DEFAULT_MAX_CONN_RATE_PER_IP);
+    assert(TNT_CONFIG_RATE_LIMIT.fallback ==
+           TNT_DEFAULT_RATE_LIMIT_ENABLED);
+    assert(TNT_CONFIG_IDLE_TIMEOUT.fallback == TNT_DEFAULT_IDLE_TIMEOUT);
+    assert(TNT_CONFIG_PORT.min_value == TNT_MIN_PORT);
+    assert(TNT_CONFIG_PORT.max_value == TNT_MAX_PORT);
+}
+
+TEST(parse_uses_spec_ranges) {
+    int out = 0;
+
+    assert(tnt_config_parse_int("2222", &TNT_CONFIG_PORT, &out));
+    assert(out == 2222);
+    assert(!tnt_config_parse_int("0", &TNT_CONFIG_PORT, &out));
+    assert(!tnt_config_parse_int("65536", &TNT_CONFIG_PORT, &out));
+    assert(!tnt_config_parse_int("abc", &TNT_CONFIG_PORT, &out));
+    assert(!tnt_config_parse_int("", &TNT_CONFIG_PORT, &out));
+
+    assert(tnt_config_parse_int("0", &TNT_CONFIG_IDLE_TIMEOUT, &out));
+    assert(out == 0);
+    assert(!tnt_config_parse_int("86401", &TNT_CONFIG_IDLE_TIMEOUT, &out));
+}
+
+TEST(env_reader_uses_fallback_and_range) {
+    unsetenv(TNT_CONFIG_MAX_CONNECTIONS.env_name);
+    assert(tnt_config_env_int(&TNT_CONFIG_MAX_CONNECTIONS) ==
+           TNT_DEFAULT_MAX_CONNECTIONS);
+
+    setenv(TNT_CONFIG_MAX_CONNECTIONS.env_name, "128", 1);
+    assert(tnt_config_env_int(&TNT_CONFIG_MAX_CONNECTIONS) == 128);
+
+    setenv(TNT_CONFIG_MAX_CONNECTIONS.env_name, "0", 1);
+    assert(tnt_config_env_int(&TNT_CONFIG_MAX_CONNECTIONS) ==
+           TNT_DEFAULT_MAX_CONNECTIONS);
+
+    unsetenv(TNT_CONFIG_MAX_CONNECTIONS.env_name);
+}
+
+int main(void) {
+    printf("Running config defaults unit tests...\n\n");
+    RUN_TEST(specs_expose_runtime_defaults);
+    RUN_TEST(parse_uses_spec_ranges);
+    RUN_TEST(env_reader_uses_fallback_and_range);
+    printf("\nAll 3 tests passed!\n");
+    return 0;
+}