Extended mbus_recv_frame() error codes, improved collision handling

- handling TCP connection reset and read(2) timeout

bin/mbus-serial-request-data.c

@@ -126,7 +126,7 @@ main(int argc, char **argv)
         }
     }   
 
-    if (mbus_recv_frame(handle, &reply) == -1)
+    if (mbus_recv_frame(handle, &reply) != 0)
     {
         fprintf(stderr, "Failed to receive M-Bus response frame.\n");
         return 1;

bin/mbus-serial-scan.c

@@ -97,7 +97,7 @@ main(int argc, char **argv)
         
         ret = mbus_recv_frame(handle, &reply);
 
-        if (ret == -1)
+        if (ret == -3)
         {
             continue;
         }
@@ -108,22 +108,15 @@ main(int argc, char **argv)
         if (ret == -2)
         {
             /* check for more data (collision) */
-            while (mbus_recv_frame(handle, &reply) != -1);
-            
+            mbus_recv_frame_dummy(handle);
             printf("Collision at address %d\n", address);
-            
             continue;
         } 
 
         if (mbus_frame_type(&reply) == MBUS_FRAME_TYPE_ACK)
         {
             /* check for more data (collision) */
-            while (mbus_recv_frame(handle, &reply) != -1)
-            {
-                ret = -2;
-            }
-    
-            if (ret == -2)
+            if (mbus_recv_frame_dummy(handle))
             {
                 printf("Collision at address %d\n", address);
                 

bin/mbus-serial-select-secondary.c

@@ -73,7 +73,7 @@ main(int argc, char **argv)
 
     ret = mbus_recv_frame(handle, &reply);
 
-    if (ret == -1)
+    if (ret == -3)
     {
         printf("No reply from device with secondary address %s: %s\n", argv[2], mbus_error_str());
         return 1;
@@ -93,7 +93,7 @@ main(int argc, char **argv)
             return 1;
         }
 
-        if (mbus_recv_frame(handle, &reply) == -1)
+        if (mbus_recv_frame(handle, &reply) != 0)
         {
             printf("Failed to recieve reply from selected secondary device: %s\n", mbus_error_str());
             return 1;

bin/mbus-serial-switch-baudrate.c

@@ -72,7 +72,7 @@ main(int argc, char **argv)
 
     ret = mbus_recv_frame(handle, &reply);  
     
-    if (ret == -1)
+    if (ret == -3)
     {
         printf("No reply from device\n");
         return 1;

bin/mbus-tcp-request-data.c

@@ -111,11 +111,11 @@ main(int argc, char **argv)
         }
     }   
 
-    if (mbus_recv_frame(handle, &reply) == -1)
+    if (mbus_recv_frame(handle, &reply) != 0)
     {
-        fprintf(stderr, "Failed to receive M-Bus response frame.\n");
+        fprintf(stderr, "Failed to receive M-Bus response frame: %s\n", mbus_error_str());
         return 1;
-    }    
+    }
 
     //
     // parse data and print in XML format

bin/mbus-tcp-scan.c

@@ -17,7 +17,6 @@
 #include <stdio.h>
 #include <mbus/mbus.h>
 
-
 //------------------------------------------------------------------------------
 // Execution starts here:
 //------------------------------------------------------------------------------
@@ -81,7 +80,7 @@ main(int argc, char **argv)
         
         ret = mbus_recv_frame(handle, &reply);
 
-        if (ret == -1)
+        if (ret == -3)
         {
             continue;
         }
@@ -92,28 +91,20 @@ main(int argc, char **argv)
         if (ret == -2)
         {
             /* check for more data (collision) */
-            while (mbus_recv_frame(handle, &reply) != -1);
-            
+            mbus_recv_frame_dummy(handle);
             printf("Collision at address %d\n", address);
-            
             continue;
         } 
 
         if (mbus_frame_type(&reply) == MBUS_FRAME_TYPE_ACK)
         {
             /* check for more data (collision) */
-            while (mbus_recv_frame(handle, &reply) != -1)
-            {
-                ret = -2;
-            }
-    
-            if (ret == -2)
+            if (mbus_recv_frame_dummy(handle))
             {
                 printf("Collision at address %d\n", address);
-                
                 continue;
             }
-                
+
             printf("Found a M-Bus device at address %d\n", address);
         }
     }

bin/mbus-tcp-select-secondary.c

@@ -59,7 +59,7 @@ main(int argc, char **argv)
 
     ret = mbus_recv_frame(handle, &reply);
 
-    if (ret == -1)
+    if (ret == -3)
     {
         printf("No reply from device with secondary address %s: %s\n", argv[3], mbus_error_str());
         return 1;
@@ -79,7 +79,7 @@ main(int argc, char **argv)
             return 1;
         }
 
-        if (mbus_recv_frame(handle, &reply) == -1)
+        if (mbus_recv_frame(handle, &reply) != 0)
         {
             printf("Failed to recieve reply from selected secondary device: %s\n", mbus_error_str());
             return 1;

mbus/mbus-protocol-aux.c

@@ -1407,6 +1407,24 @@ mbus_recv_frame(mbus_handle * handle, mbus_frame *frame)
     return result;
 }
 
+int mbus_recv_frame_dummy(mbus_handle *handle)
+{
+    int err, received;
+    mbus_frame reply;
+
+    received = 0;
+    while (1)
+    {
+        err = mbus_recv_frame(handle, &reply);
+        if (err != -2 && err != 0)
+            break;
+
+        received = 1;
+    }
+
+    return received;
+}
+
 int
 mbus_send_frame(mbus_handle * handle, mbus_frame *frame)
 {
@@ -1601,7 +1619,7 @@ mbus_sendrecv_request(mbus_handle *handle, int address, mbus_frame *reply, int m
         if (debug)
             printf("%s: debug: receiving response frame #%d\n", __PRETTY_FUNCTION__, frame_count);
     
-        if (mbus_recv_frame(handle, next_frame) == -1)
+        if (mbus_recv_frame(handle, next_frame) != 0)
         {
             MBUS_ERROR("%s: Failed to receive M-Bus response frame.\n", __PRETTY_FUNCTION__);
             retval = 1;
@@ -1743,7 +1761,7 @@ mbus_select_secondary_address(mbus_handle * handle, const char *mask)
 
     ret = mbus_recv_frame(handle, &reply);
 
-    if (ret == -1)
+    if (ret == -3)
     {
         return MBUS_PROBE_NOTHING;
     }    
@@ -1751,20 +1769,14 @@ mbus_select_secondary_address(mbus_handle * handle, const char *mask)
     if (ret == -2)
     {
         /* check for more data (collision) */
-        while (mbus_recv_frame(handle, &reply) != -1);
-
+        mbus_recv_frame_dummy(handle);
         return MBUS_PROBE_COLLISION;
     }
 
     if (mbus_frame_type(&reply) == MBUS_FRAME_TYPE_ACK)
     {
         /* check for more data (collision) */
-        while (mbus_recv_frame(handle, &reply) != -1)
-        {
-            ret = -2;
-        }
-
-        if (ret == -2)
+        if (mbus_recv_frame_dummy(handle))
         {
             return MBUS_PROBE_COLLISION;
         }
@@ -1809,7 +1821,7 @@ mbus_probe_secondary_address(mbus_handle * handle, const char *mask, char *match
 
         ret = mbus_recv_frame(handle, &reply);
 
-        if (ret == -1)
+        if (ret == -3)
         {
             return MBUS_PROBE_NOTHING;
         }
@@ -1905,7 +1917,7 @@ int mbus_read_slave(mbus_handle * handle, mbus_address *address, mbus_frame * re
         }
     } 
 
-    if (mbus_recv_frame(handle, reply) == -1)
+    if (mbus_recv_frame(handle, reply) != 0)
     {
         MBUS_ERROR("%s: Failed to receive M-Bus response frame.\n",
                    __PRETTY_FUNCTION__);

mbus/mbus-protocol-aux.h

@@ -179,6 +179,15 @@ int mbus_disconnect(mbus_handle * handle);
 int mbus_recv_frame(mbus_handle * handle, mbus_frame *frame);
 
 /** 
+ * Used for handling collisions. Blocks as long as receiving frames or corrupted data.
+ *
+ * @param handle Initialized handle
+ *
+ * @return Zero when nothing received, one otherwise.
+ */
+int mbus_recv_frame_dummy(mbus_handle * handle);
+
+/**
  * Sends frame using "unified" handle
  * 
  * @param handle Initialized handle

mbus/mbus-tcp.c

@@ -21,6 +21,7 @@
 #include <stdio.h>
 #include <string.h>
 #include <strings.h>
+#include <errno.h>
 
 #include <mbus/mbus.h>
 #include <mbus/mbus-tcp.h>
@@ -161,69 +162,59 @@ mbus_tcp_send_frame(mbus_tcp_handle *handle, mbus_frame *frame)
 //------------------------------------------------------------------------------
 //
 //------------------------------------------------------------------------------
-int
-mbus_tcp_recv_frame(mbus_tcp_handle *handle, mbus_frame *frame)
+int mbus_tcp_recv_frame(mbus_tcp_handle *handle, mbus_frame *frame)
 {
     char buff[PACKET_BUFF_SIZE];
-    int len, remaining, nread, timeouts;
-    
-    if (handle == NULL || frame == NULL)
-    {
+    int len, remaining, nread;
+
+    if (handle == NULL || frame == NULL) {
         fprintf(stderr, "%s: Invalid parameter.\n", __PRETTY_FUNCTION__);
         return -1;
     }
 
-    memset((void *)buff, 0, sizeof(buff));
+    memset((void *) buff, 0, sizeof(buff));
 
     //
     // read data until a packet is received
     //
     remaining = 1; // start by reading 1 byte
     len = 0;
-    timeouts = 0;
 
     do {
-    
-        if ((nread = read(handle->sock, &buff[len], remaining)) == -1)
-        {
+retry:
+        nread = read(handle->sock, &buff[len], remaining);
+        switch (nread) {
+        case -1:
+            if (errno == EINTR)
+                goto retry;
+
+            if (errno == EAGAIN || errno == EWOULDBLOCK) {
+                mbus_error_str_set("M-Bus tcp transport layer timeout has been reached.");
+                return -3;
+            }
+
             mbus_error_str_set("M-Bus tcp transport layer failed to read data.");
             return -1;
+        case 0:
+            mbus_error_str_set("M-Bus tcp transport layer connection closed by remote host.");
+            return -4;
+        default:
+            len += nread;
         }
-        
-        if (nread == 0)
-        {
-            timeouts++;
-            
-            if (timeouts >= 3)
-            {
-                // abort to avoid endless loop
-                fprintf(stderr, "%s: Timeout\n", __PRETTY_FUNCTION__);
-                break;
-            }
-        }
-
-        len += nread;
-
     } while ((remaining = mbus_parse(frame, buff, len)) > 0);
-    
-    if (len == 0)
-    {
-        // No data received
-        return -1;
-    }
-    
+
     //
     // call the receive event function, if the callback function is registered
-    // 
+    //
     if (_mbus_recv_event)
         _mbus_recv_event(MBUS_HANDLE_TYPE_TCP, buff, len);
-      
-    if (remaining != 0)
-    {
+
+    if (remaining < 0) {
         mbus_error_str_set("M-Bus layer failed to parse data.");
         return -2;
     }
-  
+
     return 0;
 }
 
+