Re: IPv6: what is required of lower layers?

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

Hi,

On Wed, Apr 05, 2023 at 01:03:55PM -0000, Michael van Elst wrote:
> The tun client (who reads /dev/tun* and the prepended address) may
> need to do something similar, that's why it gets the scoped address.

tun(8) says this is an IOCTL thing - TUNSLMODE(1) will do this
("prepend... network destination address").

OpenVPN uses TUNSIFHEAD(1) which will only prepend an uint32_t
(htonl(AF_INET*)) and then the unmodified IPv6 packet is sent to
userland.

But indeed, I have bumped into the encoded scope address when trying to
make sense of what the route socket returns for link-local gateways :-)
(some of the BSDs in some versions still have the embedded scope, some
others have not... forgot the details)

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