As of the 2.5.47 kernel, the new, native Linux IPSec implementation
actually (sort of) works. Bert Hubert has been playing with this code, and
has put together a quick
HOWTO on how to make it go. Anybody who is interested in a solid,
stable IPSec implementation in 2.6 (and almost all of us are, whether we
realize it or not) should consider having a look and testing it out.