MAC problems

[Jarosław Nozderko]

FreeBSD version: 5.1-RELEASE
 
Hi,

 I'm quite new to FreeBSD. I've check list archives and 
read a handbook, but I didn't find solution to my problem 
and I hope this is not off-topic.
I've installed 5.1-RELEASE, enabled ACLs on the filesystems 
and I wanted to test MAC features. I'm also new to MAC, so 
perhaps this is some my mistake.
When I enable mac_biba or mac_lomac  (in loader.conf) without
any configuration, it seems to block networking:
 
jarek at skorpion jarek> ping 192.168.65.100
PING 192.168.65.100 (192.168.65.100): 56 data bytes
ping: sendto: Permission denied
ping: sendto: Permission denied
ping: sendto: Permission denied
^C
--- 192.168.65.100 ping statistics ---
3 packets transmitted, 0 packets received, 100% packet loss

On the other side, when mac_mls is loaded, networking works,
but starting X server fails with message "Couldn't mmap /dev/vga"
(I don't see /dev/vga device regardless of MAC policy loaded)
 
Is it normal, or is something wrong ?
Is any additional documentation about MAC available, more than
papers at http://www.trustedbsd.org ? I'd like to learn a bit more.
 
Regards and thanks for any help,
Jarek