Document that returning 0 from the recv callback means EOF
Signed-off-by: Hanno Becker <hanno.becker@arm.com>
diff --git a/include/mbedtls/ssl.h b/include/mbedtls/ssl.h
index 3a14a58..bf44975 100644
--- a/include/mbedtls/ssl.h
+++ b/include/mbedtls/ssl.h
@@ -493,10 +493,11 @@
* \param buf Buffer to write the received data to
* \param len Length of the receive buffer
*
- * \return The callback must return the number of bytes received,
- * or a non-zero error code.
- * If performing non-blocking I/O, \c MBEDTLS_ERR_SSL_WANT_READ
+ * \returns If data has been received, the positive number of bytes received.
+ * \returns \c 0 if the connection has been closed.
+ * \returns If performing non-blocking I/O, \c MBEDTLS_ERR_SSL_WANT_READ
* must be returned when the operation would block.
+ * \returns Another negative error code on other kinds of failures.
*
* \note The callback may receive fewer bytes than the length of the
* buffer. It must always return the number of bytes actually
