implement auto gateway Ip auto detection (#25)

Reviewed-on: #25
implemented #19

README.md

@@ -84,7 +84,7 @@ vi /etc/openuf/openuf.conf
 Example Configuration
 
 ```ini
-controller_ip   = 192.168.1.1   # UniFi controller IP
+controller_ip   =               # Empty: use IPv4 default gateway
 lan_if          = br-lan        # Default Lan interface Name
 ufmodel         = u6-inwall     # emulated model
 inform_interval = 10            # inform interval
@@ -96,6 +96,10 @@ protocol_debug_level = 0        # 0=off, 1=safe response details,
 
 ```
 
+Set `controller_ip` to a controller IPv4 address or hostname to override
+autodetection. The automatic mode uses the IPv4 default-route gateway for
+initial adoption; after adoption, the controller-provided inform URL is kept.
+
 Daemon settings live in `/etc/openuf/openuf.conf`. Adoption and controller state
 are persisted separately in `/etc/openuf/state.json`; do not copy that file
 between devices because it contains the device authentication key.

files/openuf.conf

@@ -1,6 +1,7 @@
 # openuf — configuration
 #
-# controller_ip:    UniFi controller IP address or hostname
+# controller_ip:    UniFi controller IP address or hostname; when empty,
+#                   autodetect from the IPv4 default-route gateway
 # lan_if:           primary LAN interface (used for the AP MAC and IP)
 # ufmodel:          emulated model (u6-inwall recommended)
 # inform_interval:  seconds between inform requests (minimum 5)
@@ -10,7 +11,7 @@
 # protocol_debug_level: 0=off, 1=safe response structure,
 #                       2=full decrypted response; may expose credentials
 
-controller_ip   = 10.10.10.1
+controller_ip   =
 lan_if          = br-lan
 ufmodel         = uapg2-ac-lr
 inform_interval = 10

src/config.c

@@ -1,11 +1,13 @@
 #include <stdio.h>
 #include <string.h>
 #include <stdlib.h>
+#include <ctype.h>
 #include "config.h"
 
 void config_load(openuf_config_t *cfg)
 {
     /* Defaults */
+    memset(cfg, 0, sizeof(*cfg));
     strncpy(cfg->controller_ip,   DEFAULT_CONTROLLER_IP,   sizeof(cfg->controller_ip) - 1);
     strncpy(cfg->lan_if,          DEFAULT_LAN_IF,          sizeof(cfg->lan_if) - 1);
     strncpy(cfg->ufmodel,         DEFAULT_UFMODEL,         sizeof(cfg->ufmodel) - 1);
@@ -21,15 +23,29 @@ void config_load(openuf_config_t *cfg)
 
     char line[256];
     while (fgets(line, sizeof(line), f)) {
-        /* Strip newline */
+        char *key, *val, *eq, *end;
+
         line[strcspn(line, "\r\n")] = '\0';
-        /* Skip comments / empty */
+        key = line;
-        if (line[0] == '#' || line[0] == '\0') continue;
+        while (isspace((unsigned char)*key)) key++;
+        if (*key == '#' || *key == '\0') continue;
 
-        char key[64] = {0}, val[192] = {0};
+        eq = strchr(key, '=');
-        if (sscanf(line, " %63[^= ] = %191s", key, val) != 2) continue;
+        if (!eq) continue;
+        *eq = '\0';
+        end = eq;
+        while (end > key && isspace((unsigned char)end[-1])) *--end = '\0';
 
-        if      (!strcmp(key, "controller_ip"))    strncpy(cfg->controller_ip, val, sizeof(cfg->controller_ip) - 1);
+        val = eq + 1;
+        while (isspace((unsigned char)*val)) val++;
+        end = val;
+        while (*end && !isspace((unsigned char)*end) && *end != '#') end++;
+        *end = '\0';
+
+        if      (!strcmp(key, "controller_ip")) {
+            strncpy(cfg->controller_ip, val, sizeof(cfg->controller_ip) - 1);
+            cfg->controller_ip[sizeof(cfg->controller_ip) - 1] = '\0';
+        }
         else if (!strcmp(key, "lan_if"))           strncpy(cfg->lan_if,        val, sizeof(cfg->lan_if) - 1);
         else if (!strcmp(key, "ufmodel"))          strncpy(cfg->ufmodel,       val, sizeof(cfg->ufmodel) - 1);
         else if (!strcmp(key, "inform_interval"))  cfg->inform_interval = atoi(val);

src/config.h

@@ -9,7 +9,7 @@
 #ifndef ENABLE_LOGGING
 #define ENABLE_LOGGING          1
 #endif
-#define DEFAULT_CONTROLLER_IP   "10.10.10.1"
+#define DEFAULT_CONTROLLER_IP   ""
 #define DEFAULT_LAN_IF          "br-lan"
 #define DEFAULT_UFMODEL         "uapg2-ac-lr"
 #define DEFAULT_INFORM_INTERVAL 10
@@ -39,7 +39,8 @@ typedef struct {
 } openuf_config_t;
 
 /* Parse /etc/openuf/openuf.conf (simple key=value).
- * Fills *cfg with defaults first, then overrides from file. */
+ * Fills *cfg with defaults first, then overrides from file.
+ * An empty controller_ip selects default-gateway autodetection. */
 void config_load(openuf_config_t *cfg);
 
 #endif /* OPENUF_CONFIG_H */

src/main.c

@@ -15,6 +15,7 @@
 #include <net/if.h>
 #include <sys/ioctl.h>
 #include <sys/socket.h>
+#include <net/route.h>
 #include <arpa/inet.h>
 #include <netinet/in.h>
 
@@ -64,6 +65,54 @@ static int get_ip(const char *iface, char *out, size_t sz)
     return ret;
 }
 
+/* Find the IPv4 next hop used by the kernel's default route. Prefer the
+ * configured LAN interface when more than one default route exists. */
+static int get_default_gateway(const char *preferred_iface,
+                               char *out, size_t sz)
+{
+    FILE *f = fopen("/proc/net/route", "r");
+    if (!f) return -1;
+
+    char line[256];
+    char iface[IFNAMSIZ];
+    unsigned long destination, gateway;
+    unsigned int flags, metric;
+    unsigned int best_metric = ~0U;
+    unsigned long best_gateway = 0;
+    int best_preferred = 0;
+
+    /* Skip the column headings. */
+    if (!fgets(line, sizeof(line), f)) {
+        fclose(f);
+        return -1;
+    }
+
+    while (fgets(line, sizeof(line), f)) {
+        if (sscanf(line, "%15s %lx %lx %x %*u %*u %u %*lx",
+                   iface, &destination, &gateway, &flags,
+                   &metric) != 5)
+            continue;
+        if (destination != 0 || gateway == 0 ||
+            !(flags & RTF_UP) || !(flags & RTF_GATEWAY))
+            continue;
+
+        int preferred = preferred_iface && preferred_iface[0] &&
+                        !strcmp(iface, preferred_iface);
+        if (!best_gateway || preferred > best_preferred ||
+            (preferred == best_preferred && metric < best_metric)) {
+            best_gateway = gateway;
+            best_metric = metric;
+            best_preferred = preferred;
+        }
+    }
+    fclose(f);
+
+    if (!best_gateway) return -1;
+
+    struct in_addr addr = { .s_addr = (in_addr_t)best_gateway };
+    return inet_ntop(AF_INET, &addr, out, sz) ? 0 : -1;
+}
+
 int main(int argc, char *argv[])
 {
     for (int i = 1; i < argc-1; i++)
@@ -105,9 +154,31 @@ int main(int argc, char *argv[])
     LOG("Initial device state: adopted=%d, authkey=%.8s...", state.adopted, 
         state.authkey[0] ? state.authkey : "DEFAULT");
 
-    if (!state.adopted || !state.inform_url[0])
+    /*
+     * A configured controller is an explicit override, including after
+     * adoption. With an empty setting, discover the initial controller from
+     * the default-route gateway and then preserve controller-issued state.
+     */
+    if (cfg.controller_ip[0]) {
         snprintf(state.inform_url, sizeof(state.inform_url),
                  "http://%s:%d%s", cfg.controller_ip, INFORM_PORT, INFORM_PATH);
+        LOG("Using configured controller override: %s", cfg.controller_ip);
+    } else if (!state.adopted || !state.inform_url[0]) {
+        char controller_ip[INET_ADDRSTRLEN] = {0};
+        if (get_default_gateway(cfg.lan_if, controller_ip,
+                                sizeof(controller_ip)) == 0) {
+            snprintf(state.inform_url, sizeof(state.inform_url),
+                     "http://%s:%d%s", controller_ip,
+                     INFORM_PORT, INFORM_PATH);
+            LOG("Autodetected controller from default gateway: %s",
+                controller_ip);
+        } else {
+            state.inform_url[0] = '\0';
+            fprintf(stderr,
+                    "[openuf] No controller configured and no IPv4 default "
+                    "gateway found\n");
+        }
+    }
     state_save(&state);
 
     printf("[openuf] Starting  model=%-8s  MAC=%s  IP=%s\n",
@@ -180,6 +251,20 @@ int main(int argc, char *argv[])
             last_inform = now;
             LOG("Sending inform");
 
+            /* The default route may appear after the service starts. */
+            if (!cfg.controller_ip[0] && !state.inform_url[0]) {
+                char controller_ip[INET_ADDRSTRLEN] = {0};
+                if (get_default_gateway(cfg.lan_if, controller_ip,
+                                        sizeof(controller_ip)) == 0) {
+                    snprintf(state.inform_url, sizeof(state.inform_url),
+                             "http://%s:%d%s", controller_ip,
+                             INFORM_PORT, INFORM_PATH);
+                    LOG("Autodetected controller after startup: %s",
+                        controller_ip);
+                    state_save(&state);
+                }
+            }
+
             /* Update IP each cycle */
             char new_ip[64] = {0};
             if (get_ip(cfg.lan_if, new_ip, sizeof(new_ip)) == 0 ||