Extension headers and firewalls

[Florian Weimer]

* Cameron Byrne:

> Per RFC 2460, firewalls and routers should not be processing extension
> headers.

Per RFC 2460, firewalls and routers should not look at port numbers
and other upper-layer protocol data.  RFC 2460 (and the whole IPv6
header design) optimizes for a use case that does not exist anymore,
software-based forwarding strictly according to destination address.

Deprecating extension headers is one way forward, except that DNSSEC
needs fragmentation.