Regression tests for pf tcp state.

The test suite runs on the machine LOCAL, the kernel under test is
running on REMOTE.  On LOCAL a Scapy program is simulating a
connection to REMOTE TCP echo service.  The source address is a non
existing address on FAKE_NET.  The LOCAL machine acts as a router
between REMOTE and virtual FAKE_NET_ADDR and can create ICMP packets.

The run-regress-challenge-ack subtest checks that the pf firewall
sends TCP a challenge Ack if the sequence number is out of range.

EXAMPLE

To run this test I use the following configuration files.
You should choose a different set of MAC and IP addresses.

- My local machine where I run the regression test:

/etc/hosts
# to login to qemu with SSH via IPv6 link-local
fe80::725f:caff:fe21:8d70%tap0		q70

cat /etc/hostname.tap4
lladdr fe:e1:ba:d0:d5:6d up
inet 10.188.211.17 255.255.255.0
inet6 fdd7:e83e:66bc:211::17
!route add -inet 10.188.219.0/24 127.0.0.1 -blackhole
!route add -inet6 fdd7:e83e:66bc:219::/64 ::1 -blackhole

- My qemu where the kernel under test is running

/etc/hostname.vio1
lladdr 70:5f:ca:21:8d:80
inet 10.188.211.70 255.255.255.0
inet6 fdd7:e83e:66bc:211::70
!route add -inet 10.188.219.0/24 10.188.211.17
!route add -inet6 fdd7:e83e:66bc:219::/64 fdd7:e83e:66bc:211::17

/etc/inetd.conf
chargen stream  tcp     nowait  root    internal
chargen stream  tcp6    nowait  root    internal
echo            dgram   udp6    wait    root    internal

/etc/rc.conf.local
inetd_flags=
sshd_flags=

LOCAL_IF=tap4
LOCAL_MAC=fe:e1:ba:d0:d5:6d
REMOTE_MAC=70:5f:ca:21:8d:80
REMOTE_SSH=q70

LOCAL_ADDR=10.188.211.17
REMOTE_ADDR=10.188.211.70
FAKE_NET=10.188.219.0/24
FAKE_NET_ADDR=10.188.219.188

LOCAL_ADDR6=fdd7:e83e:66bc:211::17
REMOTE_ADDR6=fdd7:e83e:66bc:211::70
FAKE_NET6=fdd7:e83e:66bc:219::/64
FAKE_NET_ADDR6=fdd7:e83e:66bc:219::188

- Fix your configuration until make check-setup passes