Networking: Still waiting for mbuf cluster

Mirko Markov mmarkov at
Fri Oct 24 17:39:17 UTC 2003

Rolf Schroedter wrote:

> My RTEMS application communicates with a Linux-PC via connectionless 
> UDP socket,
> receiving and replying UDP packets every ~20 milliseconds.
> After a few minutes the application stops communicating.
> The application is still running, but no more UDP packets are received.
> From time to time a message is displayed at the console:
>    "Still waiting for mbuf cluster."
> With [ethereal] I see that correct UDP packets are coming from the PC.
> Additionally the PC is sending ARP requests:
>    "Who has ? Tell"
> which are also not answered by RTEMS.
> What does this mean ?
> How can the UDP communication be restarted ?
> Any suggestions are highly appreciated.
> Rolf.
Try to configure larger number of mbufs and mbuf clusters in 
rtems_bsdnet_config structure.
You may have to enlarge heap size, also.

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