pf tests: test ALTQ CBQ on top of if_vlan

[kp]

Summary

The main purpose of this test is to verify that we can use ALTQ on top
of if_vlan, but while we're here we also exercise the CBQ code. There's
already a basis test for HFSC, so it makes sense to test another
algorithm while we test if_vlan.

MFC after: 1 week
Sponsored by: Rubicon Communications, LLC ("Netgate")

[donner]

tests/sys/netpfil/pf/altq.sh

134

How do you ensure, that the packets send before are still not delivered, so the queue is empty now? Looks like an scheduling dependency race condition.

How about:

• prefill the queue (like now)
• the secondary ping tries to send multiple packets within a short interval
• check, if all packets of the secondary ping are received back

[kp]

Make the test slightly more robust by sending 5 packets, all of which we expect
to get dropped and allowing one to make it through.