Cleanups for ISO-TP in wolfio

* Add Doxygen comments
* Make ISOTP_Send, ISOTP_Receive and wolfSSL_SetIO_ISOTP safer
* Reorder isotp_wolfssl_ctx
* Other minor cleanups

doc/dox_comments/header_files/wolfio.h

@@ -537,3 +537,41 @@ WOLFSSL_API void  wolfSSL_CTX_SetGenCookie(WOLFSSL_CTX*, CallbackGenCookie);
     \sa wolfSSL_CTX_SetGenCookie
 */
 WOLFSSL_API void* wolfSSL_GetCookieCtx(WOLFSSL* ssl);
+
+
+/*!
+    \ingroup Setup
+
+    \brief This function sets up the ISO-TP context if wolfSSL, for use when
+    wolfSSL is compiled with WOLFSSL_ISOTP
+
+    \return 0 on success, WOLFSSL_CBIO_ERR_GENERAL on failure
+
+    \param ssl the wolfSSL context
+    \param ctx a user created ISOTP context which this function initializes
+    \param recv_fn a user CAN bus receive callback
+    \param send_fn a user CAN bus send callback
+    \param delay_fn a user microsecond granularity delay function
+    \param receive_delay a set amount of microseconds to delay each CAN bus
+    packet
+    \param receive_buffer a user supplied buffer to receive data, recommended
+    that is allocated to ISOTP_DEFAULT_BUFFER_SIZE bytes
+    \param receive_buffer_size - The size of receive_buffer
+    \param arg an arbitrary pointer sent to recv_fn and send_fn
+
+    _Example_
+    \code
+    struct can_info can_con_info;
+    isotp_wolfssl_ctx isotp_ctx;
+    char *receive_buffer = malloc(ISOTP_DEFAULT_BUFFER_SIZE);
+    WOLFSSL_CTX* ctx = wolfSSL_CTX_new(method);
+    WOLFSSL* ssl = wolfSSL_new(ctx);
+    ...
+    wolfSSL_SetIO_ISOTP(ssl, &isotp_ctx, can_receive, can_send, can_delay, 0,
+            receive_buffer, ISOTP_DEFAULT_BUFFER_SIZE, &can_con_info);
+    \endcode
+ */
+WOLFSSL_API int wolfSSL_SetIO_ISOTP(WOLFSSL *ssl, isotp_wolfssl_ctx *ctx,
+        can_recv_fn recv_fn, can_send_fn send_fn, can_delay_fn delay_fn,
+        word32 receive_delay, char *receive_buffer, int receive_buffer_size,
+        void *arg);

src/wolfio.c

@@ -2872,9 +2872,16 @@ static int isotp_send_first_frame(struct isotp_wolfssl_ctx *ctx, char *buf,
 
 int ISOTP_Send(WOLFSSL* ssl, char* buf, int sz, void* ctx)
 {
-    (void) ssl;
     int ret;
-    struct isotp_wolfssl_ctx *isotp_ctx = (struct isotp_wolfssl_ctx*) ctx;
+    struct isotp_wolfssl_ctx *isotp_ctx;
+    (void) ssl;
+
+    if (!ctx) {
+        WOLFSSL_MSG("ISO-TP requires wolfSSL_SetIO_ISOTP to be called first");
+        return WOLFSSL_CBIO_ERR_TIMEOUT;
+    }
+    isotp_ctx = (struct isotp_wolfssl_ctx*) ctx;
+
     if (sz > ISOTP_MAX_DATA_SIZE) {
         WOLFSSL_MSG("ISO-TP packets can be at most 4095 bytes");
         return WOLFSSL_CBIO_ERR_GENERAL;
@@ -2984,14 +2991,20 @@ static int isotp_receive_multi_frame(struct isotp_wolfssl_ctx *ctx)
  * incoming data, even if wolfSSL doesn't want it all yet */
 int ISOTP_Receive(WOLFSSL* ssl, char* buf, int sz, void* ctx)
 {
-    (void) ssl;
     enum isotp_frame_type type;
     int ret;
-    struct isotp_wolfssl_ctx *isotp_ctx = (struct isotp_wolfssl_ctx*)ctx;
+    struct isotp_wolfssl_ctx *isotp_ctx;
+    (void) ssl;
+
+    if (!ctx) {
+        WOLFSSL_MSG("ISO-TP requires wolfSSL_SetIO_ISOTP to be called first");
+        return WOLFSSL_CBIO_ERR_TIMEOUT;
+    }
+    isotp_ctx = (struct isotp_wolfssl_ctx*)ctx;
 
     /* Is buffer empty? If so, fill it */
     if (!isotp_ctx->receive_buffer_len) {
-            /* Can't send whilst we are receiving */
+        /* Can't send whilst we are receiving */
         if (isotp_ctx->state != ISOTP_CONN_STATE_IDLE) {
             return WOLFSSL_ERROR_WANT_READ;
         }
@@ -3047,25 +3060,15 @@ int ISOTP_Receive(WOLFSSL* ssl, char* buf, int sz, void* ctx)
     }
 }
 
-/* Setup ISPTP
- *
- * Parameters:
- * ssl - The wolfSSL context
- * ctx - A user created ISOTP context which this function initializes
- * recv_fn - A user CAN bus receive callback
- * send_fn - A user CAN bus send callback
- * delay_fn - A user microsecond granularity delay function
- * receive_delay - A set amount of microseconds to delay each CAN bus packet
- * receive_buffer - A user supplied buffer to receive data, recommended that is
- *                  allocated to ISOTP_DEFAULT_BUFFER_SIZE bytes
- * receive_buffer_size - The size of receive_buffer
- * arg - An arbitrary pointer sent to recv_fn and send_fn
- */
 int wolfSSL_SetIO_ISOTP(WOLFSSL *ssl, isotp_wolfssl_ctx *ctx,
         can_recv_fn recv_fn, can_send_fn send_fn, can_delay_fn delay_fn,
         word32 receive_delay, char *receive_buffer, int receive_buffer_size,
         void *arg)
 {
+    if (!ctx || !recv_fn || !send_fn || !delay_fn || !receive_buffer) {
+        WOLFSSL_MSG("ISO-TP has missing required parameter");
+        return WOLFSSL_CBIO_ERR_GENERAL;
+    }
     ctx->recv_fn = recv_fn;
     ctx->send_fn = send_fn;
     ctx->arg = arg;

wolfssl/wolfio.h

@@ -649,7 +649,7 @@ WOLFSSL_API void wolfSSL_SetIOWriteFlags(WOLFSSL* ssl, int flags);
     };
 
     typedef struct isotp_can_data {
-        byte data[8];
+        byte data[ISOTP_CAN_BUS_PAYLOAD_SIZE];
         byte length;
     } isotp_can_data;
 
@@ -662,25 +662,24 @@ WOLFSSL_API void wolfSSL_SetIOWriteFlags(WOLFSSL* ssl, int flags);
     typedef void (*can_delay_fn)(int microseconds);
 
     typedef struct isotp_wolfssl_ctx {
-        int socket;
         struct isotp_can_data frame;
+        char *buf_ptr;
+        char *receive_buffer;
+        char *receive_buffer_ptr;
         can_recv_fn recv_fn;
         can_send_fn send_fn;
         can_delay_fn delay_fn;
+        void *arg;
+        int receive_buffer_len;
+        int receive_buffer_size;
+        enum isotp_connection_state state;
+        word16 buf_length;
         byte sequence;
         byte flow_packets;
         byte flow_counter;
         byte frame_delay;
         byte wait_counter;
-        char *buf_ptr;
-        word16 buf_length;
         byte receive_delay;
-        char *receive_buffer;
-        char *receive_buffer_ptr;
-        int receive_buffer_len;
-        int receive_buffer_size;
-        enum isotp_connection_state state;
-        void *arg;
     } isotp_wolfssl_ctx;
 
     WOLFSSL_LOCAL int ISOTP_Receive(WOLFSSL* ssl, char* buf, int sz, void* ctx);