gnrc_sock: add dynamic port range

sys/net/gnrc/sock/include/gnrc_sock_internal.h

@@ -28,6 +28,7 @@
 #include "net/af.h"
 #include "net/gnrc.h"
 #include "net/gnrc/netreg.h"
+#include "net/iana.h"
 #include "net/sock/ip.h"
 
 #include "sock_types.h"
@@ -36,6 +37,22 @@
 extern "C" {
 #endif
 
+/**
+ * @brief   Default port range for dynamic source port allocation
+ */
+#define GNRC_SOCK_DYN_PORTRANGE_MIN (IANA_DYNAMIC_PORTRANGE_MIN)
+#define GNRC_SOCK_DYN_PORTRANGE_MAX (IANA_DYNAMIC_PORTRANGE_MAX)
+#define GNRC_SOCK_DYN_PORTRANGE_NUM (GNRC_SOCK_DYN_PORTRANGE_MAX - GNRC_SOCK_DYN_PORTRANGE_MIN + 1)
+#define GNRC_SOCK_DYN_PORTRANGE_ERR (0)
+
+/**
+ * @brief   Offset for next dynamic port
+ *
+ * Currently set to a static (prime) offset, but could be random, too
+ * see https://tools.ietf.org/html/rfc6056#section-3.3.3
+ */
+#define GNRC_SOCK_DYN_PORTRANGE_OFF (17U)
+
 /**
  * @brief   Internal helper functions for GNRC
  * @internal