Add polling function for network contexts
This commit adds a function `mbedtls_net_poll` to the network module
allowing to check if a network context is available for read or write.
diff --git a/include/mbedtls/net_sockets.h b/include/mbedtls/net_sockets.h
index de33552..2777b79 100644
--- a/include/mbedtls/net_sockets.h
+++ b/include/mbedtls/net_sockets.h
@@ -45,12 +45,17 @@
#define MBEDTLS_ERR_NET_UNKNOWN_HOST -0x0052 /**< Failed to get an IP address for the given hostname. */
#define MBEDTLS_ERR_NET_BUFFER_TOO_SMALL -0x0043 /**< Buffer is too small to hold the data. */
#define MBEDTLS_ERR_NET_INVALID_CONTEXT -0x0045 /**< The context is invalid, eg because it was free()ed. */
+#define MBEDTLS_ERR_NET_POLL_FAILED -0x0047 /**< Polling the net context failed. */
+#define MBEDTLS_ERR_NET_BAD_INPUT_DATA -0x0049 /**< Input invalid. */
#define MBEDTLS_NET_LISTEN_BACKLOG 10 /**< The backlog that listen() should use. */
#define MBEDTLS_NET_PROTO_TCP 0 /**< The TCP transport protocol */
#define MBEDTLS_NET_PROTO_UDP 1 /**< The UDP transport protocol */
+#define MBEDTLS_NET_POLL_READ 1 /**< Used in \c mbedtls_net_poll to check for pending data */
+#define MBEDTLS_NET_POLL_WRITE 2 /**< Used in \c mbedtls_net_poll to check if write possible */
+
#ifdef __cplusplus
extern "C" {
#endif
@@ -132,6 +137,29 @@
void *client_ip, size_t buf_size, size_t *ip_len );
/**
+ * \brief Check and wait for the context to be ready for read/write
+ *
+ * \param ctx Socket to check
+ * \param rw Bitflag composed of MBEDTLS_NET_POLL_READ and
+ * MBEDTLS_NET_POLL_WRITE specifying the events
+ * to wait for:
+ * - If MBEDTLS_NET_POLL_READ is set, the function
+ * will return as soon as the net context is available
+ * for reading.
+ * - If MBEDTLS_NET_POLL_WRITE is set, the function
+ * will return as soon as the net context is available
+ * for writing.
+ * \param timeout Maximal amount of time to wait before returning,
+ * in milliseconds. If \c timeout is zero, the
+ * function returns immediately. If \c timeout is
+ * -1u, the function blocks potentially indefinitely.
+ *
+ * \return Bitmask composed of MBEDTLS_NET_POLL_READ/WRITE
+ * on success or timeout, or a negative return code otherwise.
+ */
+int mbedtls_net_poll( mbedtls_net_context *ctx, uint32_t rw, uint32_t timeout );
+
+/**
* \brief Set the socket blocking
*
* \param ctx Socket to set