libknot/probe: use fchmod(777) on Linux only (doesn't work on BSD*)

src/libknot/probe/probe.c

@@ -123,6 +123,13 @@ int knot_probe_set_consumer(knot_probe_t *probe, const char *dir, uint16_t idx)
 
 	probe->consumer = true;
 
+#if defined(__linux__)
+	if (fchmod(probe->fd, S_IRWXU | S_IRWXG | S_IRWXO) != 0) {
+		close(probe->fd);
+		return knot_map_errno();
+	}
+#endif
+
 	(void)unlink(probe->path.sun_path);
 
 	ret = bind(probe->fd, (const struct sockaddr *)(&probe->path),
@@ -131,11 +138,6 @@ int knot_probe_set_consumer(knot_probe_t *probe, const char *dir, uint16_t idx)
 		return knot_map_errno();
 	}
 
-	if (fchmod(probe->fd, S_IRWXU | S_IRWXG | S_IRWXO) != 0) {
-		close(probe->fd);
-		return knot_map_errno();
-	}
-
 	return KNOT_EOK;
 }
 

src/libknot/probe/probe.h

@@ -61,6 +61,8 @@ int knot_probe_set_producer(knot_probe_t *probe, const char *dir, uint16_t idx);
 /*!
  * \brief Initializes one probe consumer.
  *
+ * \note The socket permissions are set to 777 on Linux!
+ *
  * \param probe  Probe context.
  * \param dir    Unix socket directory.
  * \param idx    Probe ID (counted from 1).