FREERTOS TCP/IP buffer fetch issue when using arp GRATUITOUS

Libraries
5

When I compare the code fragment that you show with the FreeRTOS+TCP code, I see these changes:

     case eARPTimerEvent:
     /* The ARP timer has expired, process the ARP cache. */
+    #if (arpGRATUITOUS_ARP_PERIOD == pdTRUE)
         vARPAgeCache();
+        SafeRTOSNet_debug_printf( ( "prvIPTask running: Event Type =  ARP timer has expired \r\n" ) );
+    #endif
     break;

That is a bit unexpected: vARPAgeCache() must be called unconditionally, and should not depend on any macro.
vARPAgeCache() will work on the ARP cache table, refresh old entries and remove dead entries.

The macro arpGRATUITOUS_ARP_PERIOD is only defined in FreeRTOR_ARP.c as a number, not a boolean pdTRUE or pdFALSE:

/** @brief The time between gratuitous ARPs. */
#ifndef arpGRATUITOUS_ARP_PERIOD
    #define arpGRATUITOUS_ARP_PERIOD    ( pdMS_TO_TICKS( 20000U ) )
#endif

So by default, a gratuitous ARP request will be send every 20 seconds. That is frequently.
You can overwrite that value in your FreeRTOSIPConfig.h:

Send a gratuitous ARP request every 2 minutes.
#define arpGRATUITOUS_ARP_PERIOD    ( pdMS_TO_TICKS( 120000U ) )

You wrote:

caused the stack to crash, i.e the send/receive was not able to get network buffers

Does the IP-stack crash, get an exception? Or does it run out of network buffers?
What value have you assigned to the macro ipconfigNUM_NETWORK_BUFFER_DESCRIPTORS?
How much is it now? Have you tried increasing it?

What platform are you using? Are you on a busy LAN?

Is the application receiving many UDP packets? And does receiving task get enough CPU time?
Are the UDP packets queueing up in the socket?

If there is a risk of receiving too many UDP packets, you can define ipconfigUDP_MAX_RX_PACKETS, described here. Or you can use the socket option FREERTOS_SO_UDP_MAX_RX_PACKETS.

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