Re: kerneld/multicast bug (tickled by gated)

Alan Cox (
Sun, 15 Jun 1997 18:23:06 +0100 (BST)

> It's not clear that we want to disable pppd in that way
> for general use with gated. Perhaps, if I mentioned that

The request-route stuff is obsolete, broken and not required so its not
an issue. Its also removed from 2.1.x trees. A user mode tool called diald
handles all these facilities without kernel aid. Kerneld is stil used for
the stuff it was intended (loading devices, modules, protocols etc).

> Does the linux kernel handle multicast groups being set across
> ppp links? Thank-you for your quick response.

If you set IFF_MULTICAST (which you can set yourself under Linux) then the
OS will let you set multicast groups on any device you like. Those it does
not have multicast mac address mappings for that are not point to point it
will use broadcast. This is normally correct (eg AX.25). Obviously it does
let the superuser screw things up royally in some cases too. The kernel
defaults IFF_MULTICAST to be on except for a small number of devices where
it makes no sense or which support it but so badly it is best off by default
(eg 3c501 ethernet cards, AX.25 links)