bah_humbug

> resolvconf(8) is a shell script which does not validate its input. A lack of quoting meant that shell commands pass as input to resolvconf(8) may be executed.

The fix consists of implementing an XXX present since the code was added:

    /*
     * XXX validate that domain name only contains valid characters
     * for two reasons: 1) correctness, 2) we do not want to pass
     * possible malicious, unescaped characters like `` to a script
     * or program that could be exploited that way.
     */

https://www.freebsd.org/security/patches/SA-25:12/rtsold.pat...

The definition of antisymmetric relations is an unusual one. As given, it's incompatible with the definition of reflexivity (presumably there's an implicit assumption on `a ≠ b`).

The usual definition is `x ≤ y AND y ≤ x → x = y`.