Before this change, in pf, exclusions used a pass out quick which gave
them higher precedence than any other rule independent of subnet width.
As reported in #265 this causes exclusion from one instance of sshuttle
to also take effect on other instances because quick aborts the
evaluation of rules across all anchors.
This commit changes the precedence of rules so quick can now be
dropped. The new order is defined by the following rule, from
subnet_weight:
"We need to go from smaller, more specific, port ranges, to larger,
less-specific, port ranges. At each level, we order by subnet
width, from most-specific subnets (largest swidth) to
least-specific. On ties, excludes come first."
* Fixes support for OpenBSD (6.1+)
As reported in #219, new versions of OpenBSD ship with a different
pfioc_rule struct. This commit adjusts the offset to match the new struct.
* Fixes tests for OpenBSD 6.1+
Having the tests in a `tests` directory in root is the most common
approach. Also moved pytest's conftest.py into `tests` making the
fixture available for client and server tests.
