kern/120958: no response to ICMP traffic on interface configured with a link-local address

[Bruce M. Simpson]

I looked at this very briefly.

It's gnarly because in_canforward() is a candidate for inlining and is a 
predicate which is being overloaded with different meanings by 
ip_forward()/ip_input() and icmp_reflect().

So whilst the fix is most likely a 3 liner, it risks making the code 
look crap. We genuinely don't want to forward 169.254.0.0/16 traffic, 
however we genuinely need to reply to ICMP which originates from these 
ranges.

bms at FreeBSD.org wrote:
> Synopsis: no response to ICMP traffic on interface configured with a link-local address
>
> Responsible-Changed-From-To: bms->freebsd-net
> Responsible-Changed-By: bms
> Responsible-Changed-When: Fri 22 Feb 2008 21:23:23 UTC
> Responsible-Changed-Why: 
> The secretary disavows all knowledge of your actions.
> ["Responsible" implies "I'll fix it", I said no such thing.. I *MIGHT*
> get around to it, but "Responsible" implies there's an obligation.
> Cheeky linimon!]
>
> http://www.freebsd.org/cgi/query-pr.cgi?pr=120958
>