libpcap:./configure WARNING:cannot determine packet capture

I am trying to port llibpcap to QNX6.2.1,
while executing ./configure, there is the WARNING:

configure: WARNING: cannot determine packet capture interface
configure: WARNING: (see the INSTALL doc for more info)

and i ignored that, after make and make install, I program like this:
if (dev == NULL)
exit(printf("%s /n", errbuf));
the dev is always =NULL.

what should I do? need to mount io-net?