pppd unaligned trap on Sparc/LEON3 - Questions about network config

Chris Johns chrisj at rtems.org
Thu Mar 21 21:51:36 UTC 2019

On 22/3/19 2:06 am, Cudmore, Alan P. (GSFC-5820) wrote:
> I have PPP nearly working between RTEMS/LEON3 and Linux.
> The two sides negotiate the PPP link and the PPP link seems to stay up. The
> Linux side sends occasional EchoReq packets to RTEMS, which it replies to with
> EchoRep.
> In my example, the RTEMS/LEON3 IP is and the Linux peer IP is
> The RTEMS/LEON3 board does not have any other network interfaces,
> other than the default loopback interface.
> When the Linux side sends a UDP packet to, the code I wrote in
> RTEMS to listen on port 5005 receives the packet. When I try to do the opposite,
> the RTEMS side sends a UDP packet to, but it does not seem to
> get to the Linux UDP receive code.
> I am going by this example for my network configuration:
> https://git.rtems.org/rtems/tree/testsuites/samples/pppd/netconfig.h?h=4.11
> In that configuration, the PPP “rtems_bsdnet_ifconfig” structure does not have
> the IP address, or netmask defined. Should I specify these, or does the PPP
> initialization do that for me?
> Also, should I make sure I have a gateway defined in “rtems_bsdnet_config”? If
> so, what should that be ( assuming no other network interfaces exist other than
> the PPP connection to the Linux peer )?

I think you need to manage this based on what the PPP link is doing. I do not
think you can or should handle this with static configuration settings.

> Any other clues? I suspect that it’s just a fundamental configuration issue at
> this point.

What does the routing table look like? Is there a suitable route to the remote
end of the PPP link?


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