Add debug-level asserts for poor time or configuration to prevent blo…

…cking in uxr_create_session

* Added asserts that protect against time going backwards or staying static
* Added information to header on a call being blocking and for how long
* Increased const-correctecness of time handling
* Add assert for handling narrowing conversion of time
* Add CMake protection for incorrectly configuring options that can block for unreasonable amount of time
* CMake should theoretically remove the asserts in release mode, so there should be no overhead
* Reference: https://stackoverflow.com/questions/34302265/does-cmake-build-type-release-imply-dndebug
* Closes eProsima#350

Signed-off-by: Ryan Friedman <[email protected]>

CMakeLists.txt

@@ -56,6 +56,9 @@ set(UCLIENT_MAX_INPUT_BEST_EFFORT_STREAMS 1 CACHE STRING "Set the maximum number
 set(UCLIENT_MAX_INPUT_RELIABLE_STREAMS 1 CACHE STRING "Set the maximum number of input reliable streams for session.")
 set(UCLIENT_MAX_SESSION_CONNECTION_ATTEMPTS 10 CACHE STRING "Set the number of connection attemps.")
 set(UCLIENT_MIN_SESSION_CONNECTION_INTERVAL 1000 CACHE STRING "Set the connection interval in milliseconds.")
+if(${UCLIENT_MIN_SESSION_CONNECTION_INTERVAL} LESS_EQUAL 0)
+    message(FATAL_ERROR "UCLIENT_MIN_SESSION_CONNECTION_INTERVAL is out of range")
+endif()
 set(UCLIENT_MIN_HEARTBEAT_TIME_INTERVAL 100 CACHE STRING "Set the time interval between heartbeats in milliseconds.")
 set(UCLIENT_UDP_TRANSPORT_MTU 512 CACHE STRING "Set the UDP transport MTU.")
 set(UCLIENT_TCP_TRANSPORT_MTU 512 CACHE STRING "Set the TCP transport MTU.")

include/uxr/client/core/session/session.h

@@ -303,6 +303,9 @@ UXRDLLAPI void uxr_set_performance_callback(
 /**
  * @brief Creates a new session with the Agent.
  *        This function logs in a session, enabling any other XRCE communication with the Agent.
+ *        It blocks  for a time proportional to 
+ *        (UXR_CONFIG_MAX_SESSION_CONNECTION_ATTEMPTS * UXR_CONFIG_MIN_SESSION_CONNECTION_INTERVAL)
+ *        until a response from the Agent is received.
  * @param session   A uxrSesssion structure previously initialized.
  * @return  true in case of successful session establishment, and false in other case.
  */

src/c/core/session/session.c

@@ -20,6 +20,9 @@
 #include <uxr/client/profile/multithread/multithread.h>
 #include "../../profile/shared_memory/shared_memory_internal.h"
 
+#include <assert.h>
+#include <limits.h>
+
 #ifdef UCLIENT_PROFILE_SHARED_MEMORY
 #define PROFILE_SHARED_MEMORY_ADD_SIZE 21
 #else
@@ -749,13 +752,19 @@ bool wait_session_status(
     {
         send_message(session, buffer, length);
 
-        int64_t start_timestamp = uxr_millis();
-        int remaining_time = UXR_CONFIG_MIN_SESSION_CONNECTION_INTERVAL;
+        const int64_t start_timestamp = uxr_millis();
+        int64_t remaining_time = UXR_CONFIG_MIN_SESSION_CONNECTION_INTERVAL;
+        assert(remaining_time > 0);
 
         do
         {
-            listen_message(session, remaining_time);
-            remaining_time = UXR_CONFIG_MIN_SESSION_CONNECTION_INTERVAL - (int)(uxr_millis() - start_timestamp);
+            assert(remaining_time <= INT_MAX); // Protect the narrowing conversion
+            listen_message(session, (int)remaining_time);
+            const int64_t current_timestamp = uxr_millis();
+            assert(current_timestamp >= start_timestamp);
+            const int64_t elapsed_time = current_timestamp - start_timestamp;
+            assert(UXR_CONFIG_MIN_SESSION_CONNECTION_INTERVAL >= elapsed_time);
+            remaining_time = UXR_CONFIG_MIN_SESSION_CONNECTION_INTERVAL - elapsed_time;
         } while (remaining_time > 0 && session->info.last_requested_status == UXR_STATUS_NONE);
     }