Map errors from FreeRTOS+TCP to mbedTLS and make read non-blocking when requesting start of frame (#452)

From the FreeRTOS documentation, pdFREERTOS_ERRNO_ENOSPC means that timeout occurred before any data could be sent or received.
- In the plaintext transport-interface implementation, we would directly return `-pdFREERTOS_ERRNO_ENOSPC`. However, an error like this can occur when the TCP buffer is full, so this ought to be retriable. Libraries that consume the transport interface interpret a return value of 0 to mean that send/recv can be invoked again to get the data. As such, we should appropriately set the return value as 0 when the status is `-pdFREERTOS_ERRNO_ENOSPC`.
- In the mbedTLS port, we would directly return whatever `FreeRTOS_send` or `FreeRTOS_recv` returns. However, sometimes, the return value can be an error. In such cases, we ought to map an error from FreeRTOS+TCP to an equivalent error in mbedTLS. In the case of `-pdFREERTOS_ERRNO_ENOSPC`, we map that to `MBEDTLS_ERR_SSL_TIMEOUT`. When the mbedTLS transport-interface send/recv wrapper sees that value, it appropriately returns 0, so that the library can retry the send/recv. I've verified that when the mbedTLS port returns an error, that same error is returned by `mbedtls_ssl_write` & `mbedtls_ssl_read`.
- The TCP socket may have a receive block time.  If bytesToRecv is greater than 1 then a frame is likely already part way through reception and blocking to wait for the desired number of bytes to be available is the
most efficient thing to do.  If bytesToRecv is 1 then this may be a speculative call to read to find the start of a new frame, in which case blocking is not desirable as it could block an entire protocol agent task for the duration of the read block time and therefore negatively impact performance.  So if bytesToRecv is 1 then don't call recv unless it is known that bytes are already available.

Co-authored-by: abhidixi11 <44424462+abhidixi11@users.noreply.github.com>
Co-authored-by: RichardBarry <3073890+RichardBarry@users.noreply.github.com>

5 files changed, 128 insertions, 23 deletions

diff --git a/FreeRTOS-Plus/Source/Application-Protocols/network_transport/freertos_plus_tcp/using_plaintext/using_plaintext.c b/FreeRTOS-Plus/Source/Application-Protocols/network_transport/freertos_plus_tcp/using_plaintext/using_plaintext.c
index 3f0906d93..d42400946 100644
--- a/FreeRTOS-Plus/Source/Application-Protocols/network_transport/freertos_plus_tcp/using_plaintext/using_plaintext.c
+++ b/FreeRTOS-Plus/Source/Application-Protocols/network_transport/freertos_plus_tcp/using_plaintext/using_plaintext.c
@@ -128,15 +128,33 @@ int32_t Plaintext_FreeRTOS_recv( NetworkContext_t * pNetworkContext,
                                  size_t bytesToRecv )
 {
     PlaintextTransportParams_t * pPlaintextTransportParams = NULL;
-    int32_t socketStatus = 0;
+    int32_t socketStatus = 1;
 
     configASSERT( ( pNetworkContext != NULL ) && ( pNetworkContext->pParams != NULL ) );
 
     pPlaintextTransportParams = pNetworkContext->pParams;
-    socketStatus = FreeRTOS_recv( pPlaintextTransportParams->tcpSocket,
-                                  pBuffer,
-                                  bytesToRecv,
-                                  0 );
+
+    /* The TCP socket may have a receive block time.  If bytesToRecv is greater 
+     * than 1 then a frame is likely already part way through reception and 
+     * blocking to wait for the desired number of bytes to be available is the
+     * most efficient thing to do.  If bytesToRecv is 1 then this may be a 
+     * speculative call to read to find the start of a new frame, in which case 
+     * blocking is not desirable as it could block an entire protocol agent 
+     * task for the duration of the read block time and therefore negatively 
+     * impact performance.  So if bytesToRecv is 1 then don't call recv unless 
+     * it is known that bytes are already available. */
+    if( bytesToRecv == 1 )
+    {
+        socketStatus = ( int32_t ) FreeRTOS_recvcount( pPlaintextTransportParams->tcpSocket );
+    }
+
+    if( socketStatus > 0 )
+    {
+        socketStatus = FreeRTOS_recv( pPlaintextTransportParams->tcpSocket,
+                                      pBuffer,
+                                      bytesToRecv,
+                                      0 );
+    }
 
     return socketStatus;
 }
@@ -156,5 +174,13 @@ int32_t Plaintext_FreeRTOS_send( NetworkContext_t * pNetworkContext,
                                   bytesToSend,
                                   0 );
 
+    if( socketStatus == -pdFREERTOS_ERRNO_ENOSPC )
+    {
+        /* The TCP buffers could not accept any more bytes so zero bytes were sent.
+         * This is not necessarily an error that should cause a disconnect
+         * unless it persists. */
+        socketStatus = 0;
+    }
+
     return socketStatus;
 }
diff --git a/FreeRTOS-Plus/Source/Application-Protocols/network_transport/freertos_plus_tcp/using_plaintext/using_plaintext.h b/FreeRTOS-Plus/Source/Application-Protocols/network_transport/freertos_plus_tcp/using_plaintext/using_plaintext.h
index 7ef7a2e50..cdfeae0dd 100644
--- a/FreeRTOS-Plus/Source/Application-Protocols/network_transport/freertos_plus_tcp/using_plaintext/using_plaintext.h
+++ b/FreeRTOS-Plus/Source/Application-Protocols/network_transport/freertos_plus_tcp/using_plaintext/using_plaintext.h
@@ -118,6 +118,10 @@ PlaintextTransportStatus_t Plaintext_FreeRTOS_Disconnect( const NetworkContext_t
 
 /**
  * @brief Receives data from an established TCP connection.
+ * 
+ * @note When the number of bytes requested is 1, the TCP socket’s Rx stream
+ * is checked for available bytes to read. If there are none, this function
+ * immediately returns 0 without blocking.
  *
  * @param[in] pNetworkContext The network context containing the TCP socket
  * handle.
diff --git a/FreeRTOS-Plus/Source/Utilities/mbedtls_freertos/mbedtls_error.c b/FreeRTOS-Plus/Source/Utilities/mbedtls_freertos/mbedtls_error.c
index fe3415d07..2aad41608 100644
--- a/FreeRTOS-Plus/Source/Utilities/mbedtls_freertos/mbedtls_error.c
+++ b/FreeRTOS-Plus/Source/Utilities/mbedtls_freertos/mbedtls_error.c
@@ -1,5 +1,5 @@
 /*
- * FreeRTOS Error Code Stringification utilies for mbed TLS v2.16.0
+ * FreeRTOS V202011.00
  * Copyright (C) 2020 Amazon.com, Inc. or its affiliates.  All Rights Reserved.
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy of
@@ -18,6 +18,10 @@
  * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
  * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ * https://www.FreeRTOS.org
+ * https://github.com/FreeRTOS
+ *
  */
 
 /**
diff --git a/FreeRTOS-Plus/Source/Utilities/mbedtls_freertos/mbedtls_error.h b/FreeRTOS-Plus/Source/Utilities/mbedtls_freertos/mbedtls_error.h
index 73df1a36d..191250096 100644
--- a/FreeRTOS-Plus/Source/Utilities/mbedtls_freertos/mbedtls_error.h
+++ b/FreeRTOS-Plus/Source/Utilities/mbedtls_freertos/mbedtls_error.h
@@ -1,5 +1,5 @@
 /*
- * FreeRTOS Error Code Stringification utilities for mbed TLS v2.16.0
+ * FreeRTOS V202011.00
  * Copyright (C) 2020 Amazon.com, Inc. or its affiliates.  All Rights Reserved.
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy of
@@ -18,6 +18,10 @@
  * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
  * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ * https://www.FreeRTOS.org
+ * https://github.com/FreeRTOS
+ *
  */
 
 /**
diff --git a/FreeRTOS-Plus/Source/Utilities/mbedtls_freertos/mbedtls_freertos_port.c b/FreeRTOS-Plus/Source/Utilities/mbedtls_freertos/mbedtls_freertos_port.c
index ae7852b82..20d5d8156 100644
--- a/FreeRTOS-Plus/Source/Utilities/mbedtls_freertos/mbedtls_freertos_port.c
+++ b/FreeRTOS-Plus/Source/Utilities/mbedtls_freertos/mbedtls_freertos_port.c
@@ -1,23 +1,27 @@
 /*
+ * FreeRTOS V202011.00
  * Copyright (C) 2020 Amazon.com, Inc. or its affiliates.  All Rights Reserved.
  *
- * Permission is hereby granted, free of charge, to any person obtaining a copy
- * of this software and associated documentation files (the "Software"), to deal
- * in the Software without restriction, including without limitation the rights
- * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
- * copies of the Software, and to permit persons to whom the Software is
- * furnished to do so, subject to the following conditions:
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to
+ * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+ * the Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
  *
- * The above copyright notice and this permission notice shall be included in
- * all copies or substantial portions of the Software.
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
  *
  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
- * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
- * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
- * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
- * SOFTWARE.
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+ * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ * https://www.FreeRTOS.org
+ * https://github.com/FreeRTOS
+ *
  */
 
 /**
@@ -33,6 +37,18 @@
 #include "mbedtls_config.h"
 #include "threading_alt.h"
 #include "mbedtls/entropy.h"
+#include "mbedtls/ssl.h"
+
+/*-----------------------------------------------------------*/
+
+/**
+ * @brief The number of bytes in a standard TLS record header.
+ *
+ * @note This only applies to a standard TCP+TLS connection.
+ *       DTLS has a different length for its record headers.
+ *
+ */
+#define TLS_RECORD_HEADER_BYTE_LENGTH    5
 
 /*-----------------------------------------------------------*/
 
@@ -96,13 +112,39 @@ int mbedtls_platform_send( void * ctx,
                            size_t len )
 {
     Socket_t socket;
+    BaseType_t sendStatus = 0;
+    int returnStatus = -1;
 
     configASSERT( ctx != NULL );
     configASSERT( buf != NULL );
 
     socket = ( Socket_t ) ctx;
+    sendStatus = FreeRTOS_send( socket, buf, len, 0 );
+
+    switch( sendStatus )
+    {
+        /* Socket was closed or just got closed. */
+        case -pdFREERTOS_ERRNO_ENOTCONN:
+        /* Not enough memory for the socket to create either an Rx or Tx stream. */
+        case -pdFREERTOS_ERRNO_ENOMEM:
+        /* Socket is not valid, is not a TCP socket, or is not bound. */
+        case -pdFREERTOS_ERRNO_EINVAL:
+        /* Socket received a signal, causing the read operation to be aborted. */
+        case -pdFREERTOS_ERRNO_EINTR:
+            returnStatus = MBEDTLS_ERR_SSL_INTERNAL_ERROR;
+            break;
+
+        /* A timeout occurred before any data could be sent. */
+        case -pdFREERTOS_ERRNO_ENOSPC:
+            returnStatus = MBEDTLS_ERR_SSL_TIMEOUT;
+            break;
+
+        default:
+            returnStatus = ( int ) sendStatus;
+            break;
+    }
 
-    return ( int ) FreeRTOS_send( socket, buf, len, 0 );
+    return returnStatus;
 }
 
 /*-----------------------------------------------------------*/
@@ -121,13 +163,38 @@ int mbedtls_platform_recv( void * ctx,
                            size_t len )
 {
     Socket_t socket;
+    BaseType_t recvStatus = 0;
+    int returnStatus = -1;
 
     configASSERT( ctx != NULL );
     configASSERT( buf != NULL );
 
     socket = ( Socket_t ) ctx;
 
-    return ( int ) FreeRTOS_recv( socket, buf, len, 0 );
+    recvStatus = FreeRTOS_recv( socket, buf, len, 0 );
+
+    switch( recvStatus )
+    {
+        /* No data could be sent because the socket was or just got closed. */
+        case -pdFREERTOS_ERRNO_ENOTCONN:
+        /* No data could be sent because there was insufficient memory. */
+        case -pdFREERTOS_ERRNO_ENOMEM:
+        /* No data could be sent because xSocket was not a valid TCP socket. */
+        case -pdFREERTOS_ERRNO_EINVAL:
+            returnStatus = MBEDTLS_ERR_SSL_INTERNAL_ERROR;
+            break;
+
+        /* A timeout occurred before any data could be received. */
+        case 0:
+            returnStatus = MBEDTLS_ERR_SSL_WANT_READ;
+            break;
+
+        default:
+            returnStatus = ( int ) recvStatus;
+            break;
+    }
+
+    return returnStatus;
 }
 
 /*-----------------------------------------------------------*/