Re: nd6_free assumes all routers are processed by kernel RA

[Gert Doering <gert%greenie.muc.de@localhost>]

Hi,

On Sat, Aug 24, 2019 at 10:01:37AM +0700, Robert Elz wrote:
> Sending the packet by first sending a NS for the target addr, to see if it
> happens to be on the local link (about which we have no idea what prefix
> may have been allocated) would be a reasonable thing to do - if we get
> a reply (including from the router, acting as a proxy-NDP-server if that
> is what it wants to do) then we can go ahead and send the packet.   

This is not actually a reasonable thing to do - in your scenario, this would
mean "send a NS for every single v6 address out there that you want to talk
to, and since no NA ever comes back, the application would run into the same
timeout behaviour as before".

Even if you have something that does proxy-NDP, it would still be a bad 
idea to fill the local neighbour table with an entry for every single
communication partner out there (people did - and do - this in v4, 
point a default route "to ethernet" and rely on proxy ARP for packets
to go to the router, and all good it does is "hide configuration errors").

gert
-- 
"If was one thing all people took for granted, was conviction that if you 
 feed honest figures into a computer, honest figures come out. Never doubted 
 it myself till I met a computer with a sense of humor."
                             Robert A. Heinlein, The Moon is a Harsh Mistress

Gert Doering - Munich, Germany                             gert%greenie.muc.de@localhost