# setup (root, nohup - ipfw3 loads default-deny)
00001 0 0 allow            (interim allow-all during setup)
00100 0 0 allow udp uid maxx out
65535 0 0 deny
# final ruleset
00100 0  0 allow udp uid maxx
00200 1 40 allow tcp
00300 0  0 allow icmp
00400 0  0 allow uid root
# round 1+2+3 (root, then as maxx uid=1001)
$ id
uid=1001(maxx) gid=1001(groups=1001)
$ /tmp/raceuid 60
RACEUID-DONE no panic
$ ipfw3 show | sed -n 2p
00100 3599984 331198528 allow udp uid maxx
# total: 3,599,984 packets matched by the uid rule (check_uid executed per packet)
# while six threads raced socket/connect/send/close; no panic across all rounds