stubby: add syslog support

- Ported from @Merlin, thanks: 9ef7b80958

release/src-rt-6.x.4708/router/patches/getdns/103-add-syslog-support.patch

@@ -0,0 +1,56 @@
+--- getdns/src/compat/getentropy_linux.c
++++ getdns/src/compat/getentropy_linux.c
+@@ -16,6 +16,8 @@
+  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+  */
++#define	_GNU_SOURCE
++
+ #include "config.h"
+ 
+ /*
+--- getdns/stubby/src/stubby.c
++++ getdns/stubby/src/stubby.c
+@@ -40,6 +40,9 @@
+ #endif
+ #include <signal.h>
+ #include <limits.h>
++#if !defined(STUBBY_ON_WINDOWS) && !defined(GETDNS_ON_WINDOWS)
++#include <syslog.h>
++#endif
+ 
+ #ifdef HAVE_GETDNS_YAML2DICT
+ getdns_return_t getdns_yaml2dict(const char *str, getdns_dict **dict);
+@@ -169,6 +172,9 @@ static getdns_list *listen_list = NULL;
+ static size_t listen_count = 0;
+ static int run_in_foreground = 1;
+ static int dnssec_validation = 0;
++#if !defined(STUBBY_ON_WINDOWS) && !defined(GETDNS_ON_WINDOWS)
++static int use_syslog = 0;
++#endif
+ 
+ static void stubby_local_log(void *userarg, uint64_t system,
+ 	getdns_loglevel_type level, const char *fmt, ...);
+@@ -738,6 +744,8 @@ static void stubby_log(void *userarg, ui
+ 	tsec = (time_t) tv.tv_sec;
+ 	gmtime_s(&tm, (const time_t *) &tsec);
+ #else
++	if (use_syslog)
++		(void) vsyslog(level, fmt, ap);
+ 	gettimeofday(&tv, NULL);
+ 	gmtime_r(&tv.tv_sec, &tm);
+ #endif
+@@ -827,6 +835,13 @@ main(int argc, char **argv)
+ 		        _getdns_strerror(r));
+ 		return r;
+ 	}
++
++#if !defined(STUBBY_ON_WINDOWS) && !defined(GETDNS_ON_WINDOWS)
++	use_syslog = log_connections || !run_in_foreground;
++	if (use_syslog)
++		openlog(STUBBY_PACKAGE, LOG_PID, LOG_DAEMON);
++#endif
++
+ 	if (log_connections) {
+ 		(void) getdns_context_set_logfunc(context, NULL,
+ 	    	GETDNS_LOG_UPSTREAM_STATS, (int)log_level, stubby_log);