On Sun 12 Dec 2021 at 16:54:34 +0100, Anders Magnusson wrote:
> Yes, true. It's I myself that added that flag, wondering what I was
> thinking? :-)
It looks like IFF_MULTICAST is also used to mean "can *send*
multicasts". See ip_output.c:
/*
* If the packet is multicast or broadcast, confirm that
* the outgoing interface can transmit it.
*/
if (((m->m_flags & M_MCAST) &&
(ifp->if_flags & IFF_MULTICAST) == 0) ||
((m->m_flags & M_BCAST) &&
(ifp->if_flags & (IFF_BROADCAST|IFF_POINTOPOINT)) == 0)) {
IP_STATINC(IP_STAT_NOROUTE);
error = ENETUNREACH;
goto bad;
}
Searching for IFF_ALLMULTI, it seems like it's only really used internal
to drivers and to report to userland, not for the kernel to use in any
kind of routing decision.
-Olaf.
--
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