JSON_Read() warning messages enhancements (#1817)

* JSON_Read() warning messages enhancements
* Change sprintf() to snprintf() per reviewer comment

Author: davidBar-On

src/iperf_api.c

@@ -2778,6 +2778,7 @@ JSON_read(int fd, int max_size)
     char *str;
     cJSON *json = NULL;
     int rc;
+    char msg_buf[WARN_STR_LEN * 2];
 
     /*
      * Read a four-byte integer, which is the length of the JSON to follow.
@@ -2805,19 +2806,27 @@ JSON_read(int fd, int max_size)
                             json = cJSON_Parse(str);
                         }
                         else {
-                            warning("JSON size of data read does not correspond to offered length");
+                            snprintf(msg_buf, sizeof(msg_buf), "JSON size of data read does not correspond to offered length - expected %d bytes but received %d; errno=%d", hsize, rc, errno);
+                            warning(msg_buf);
                         }
 	            }
+                    else {
+                        snprintf(msg_buf, sizeof(msg_buf), "JSON data read failed; errno=%d", errno);
+                        warning(msg_buf);
+                    }
 	            free(str);
                 }
             }
 	}
 	else {
-	    warning("JSON data length overflow");
+            snprintf(msg_buf, sizeof(msg_buf), "JSON data length overflow - %d bytes JSON size is not allowed", hsize);
+	    warning(msg_buf);
 	}
     }
     else {
         warning("Failed to read JSON data size");
+        snprintf(msg_buf, sizeof(msg_buf), "Failed to read JSON data size - read returned %d; errno=%d", rc, errno);
+        warning(msg_buf);
     }
     return json;
 }