gluon-radvd-filterd: Do not write respondd info if batman server

package/gluon-radv-filterd/src/respondd.c

@@ -5,6 +5,8 @@
 #include <net/ethernet.h>
 #include <stdio.h>
 #include <string.h>
+#include <unistd.h>
+#include <fcntl.h>
 
 #include "mac.h"
 
@@ -37,6 +39,19 @@ static struct json_object * get_radv_filter() {
 }
 
 static struct json_object * respondd_provider_statistics() {
+	char buf[6];
+	int fd = open("/sys/class/net/bat0/mesh/gw_mode", O_RDONLY);
+	if (fd == -1) {
+		perror("error opening gateway info file");
+		return NULL;
+	}
+	memset(buf, 0, sizeof(buf));
+	read(fd, buf, sizeof(buf));
+	close(fd);
+	if (strncmp(buf, "server", 6) == 0) {
+		// We are a batman gateway, do not write gateway6
+		return NULL;
+	}
 	struct json_object *ret = json_object_new_object();
 
 	json_object_object_add(ret, "gateway6", get_radv_filter());