Unsolicited Neighbor Solicitations disabled for 20 years

[Edgar Fuß <ef%math.uni-bonn.de@localhost>]

> Is there a way of manually triggering an Unsolicited Neighbor Solicitation 
> (the IPv6 equivalent of a gratuitous ARP)?
> 
> When adding an adress to an interface, one should be sent, but I see only the 
> DAD and a Mulicast join.
After digging through the source for the past days, I've made some progress.

It looks like the code paths for generating GARPs and Unsol NAs are completely 
different because ARP is an ethernet-only thing while ND is L2 agnostic.

So while GARPs are generated in lla_rt_output() in the RTM_ADD case, Unsol NAs 
should probably be generated in nd6_rtrequest() (which ifa_rtrequest points to 
in the IPv6 case). But the code part that seems should in fact generate them 
is #if 0'd out with a comment /* XXX it does not work */ for more than 
20 years. Unfortunately, itojun@ is no longer with us to explain why he 
disabled that part.

Any experts on this area? Would it make sense to look at how other projects 
using KAME (who would that be?) handle that case?