extmod/mbedtls: Implement recommended DTLS features, make optional.

- DTLS spec recommends HelloVerify and Anti Replay protection be enabled,
  and these are enabled in the default mbedTLS config. Implement them here.

- To help compensate for the possible increase in code size, add a
  MICROPY_PY_SSL_DTLS build config macro that's enabled for EXTRA and
  above by default.

This allows bare metal mbedTLS ports to use DTLS with HelloVerify support.

This work was funded through GitHub Sponsors.

Signed-off-by: Angus Gratton <angus@redyak.com.au>

1 files changed, 11 insertions, 1 deletions

diff --git a/tests/extmod/tls_dtls.py b/tests/extmod/tls_dtls.py
index b2d716769..a475cce8c 100644
--- a/tests/extmod/tls_dtls.py
+++ b/tests/extmod/tls_dtls.py
@@ -34,9 +34,19 @@ client_socket = DummySocket()
 # Wrap the DTLS Server
 dtls_server_ctx = SSLContext(PROTOCOL_DTLS_SERVER)
 dtls_server_ctx.verify_mode = CERT_NONE
-dtls_server = dtls_server_ctx.wrap_socket(server_socket, do_handshake_on_connect=False)
+dtls_server = dtls_server_ctx.wrap_socket(
+    server_socket, do_handshake_on_connect=False, client_id=b'dummy_client_id'
+)
 print("Wrapped DTLS Server")
 
+# wrap DTLS server with invalid client_id
+try:
+    dtls_server = dtls_server_ctx.wrap_socket(
+        server_socket, do_handshake_on_connect=False, client_id=4
+    )
+except OSError:
+    print("Failed to wrap DTLS Server with invalid client_id")
+
 # Wrap the DTLS Client
 dtls_client_ctx = SSLContext(PROTOCOL_DTLS_CLIENT)
 dtls_client_ctx.verify_mode = CERT_NONE