net/sock/dtls : Expose to Kconfig

sys/net/sock/Kconfig

@@ -29,3 +29,19 @@ config SOCK_URLPATH_MAXLEN
         This value is used in sock_urlsplit().
 
 endif # KCONFIG_USEMODULE_SOCK_UTIL
+
+menuconfig KCONFIG_USEMODULE_SOCK_DTLS
+    bool "Configure SOCK DTLS"
+    depends on USEMODULE_SOCK_DTLS
+
+if KCONFIG_USEMODULE_SOCK_DTLS
+
+config DTLS_HANDSHAKE_BUFSIZE_EXP
+    int "Exponent for the DTLS buffer size (resulting in the buffer size 2^n)"
+    default 8
+    help
+        As the buffer size ALWAYS needs to be power of two, this option
+        represents the exponent of 2^n, which will be used as the size of the
+        buffer. The buffer is used to hold credentials during DTLS handshakes.
+
+endif # KCONFIG_USEMODULE_SOCK_DTLS