endian-ness fix, Router Alert options on IGMP messages, and a
new keyword, "advert_metric", for fine-tuning tunnel metrics.
This also includes a new mtrace, which is also unreleased but
builds significantly on the experiences of users' troubles with
using and understanding mtrace in release 3.8 .
(unreleased does not, of course, mean untested!)
This is a candidate for both 2.2 and 2.1.6 .
f014b7e69b