In my application, in a specific scenario, I need to put the tsec0 interface down, and should make tsec1 up. This part 
should be executed from QNX 'iopkt' TCP/IP stack subsystem. I tried calling the below command from there...

system ("ifconfig tsec0 down");

But when I ran this program, the device got restarted with the following message "SpvAbort SpvTaskTimeout task      UDP"

.

Later I searched for options through 'ioctl 'command. But I didn't get any direct options. Instead I saw few options to 

delete/add interface addresses. I tried with the below one to remove the IPI from tsec0 interface.

qnw_iface_list[0].if_net->if_ioctl (qnw_iface_list[0].if_net, SIOCDIFADDR, (caddr_t)&ifmr);

But this one also didn't help. Even though the command got executed, didn't find any change in device behavior. I was 
still able to ping tsec0.

Here I need the guidance on how to make the ethernet interface down/up programmatically from 'iopkt' subsystem. I am 
pretty new to QNX world, so pls bear with my ignorance