Help ! Regarding libpcap issue.

[Leo]

Hi All,
I want to install libpcap from ports. But when I "make install clean", 
the box output:

.......
config.status: creating pcap_open_dead.3pcap
config.status: creating pcap_open_offline.3pcap
config.status: creating config.h
===>  Building for libpcap-1.0.0
cc -O2 -O2 -fno-strict-aliasing -pipe -I.  -DHAVE_CONFIG_H  
-D_U_="__attribute__((unused))" -c ./pcap-null.c
./pcap-null.c:44: error: conflicting types for 'pcap_activate'
./pcap/pcap.h:266: error: previous declaration of 'pcap_activate' was here
gmake: *** [pcap-null.o] Error 1
*** Error code 1

Stop in /usr/ports/net/libpcap.
[root at SLT2 /usr/ports/net/libpcap]#

I don't know why! I've update my kernel source and ports. Below is my uname:

FreeBSD  7.2-PRERELEASE FreeBSD 7.2-PRERELEASE #4: Tue Apr 28 11:22:57 
CST 2009 

Thank you!

-Leo