On Tue, Mar 21, 2017 at 01:09:47AM +0100, Linus Lüssing wrote:
> On Sun, Mar 19, 2017 at 05:55:06PM +0100, Linus Lüssing wrote:
> > On Fri, Mar 17, 2017 at 02:10:44PM +0100, Pablo Neira Ayuso wrote:
> > > Wait.
> > >
> > > May this break local multicast listener that are bound to the bridge
> > > interface? Assuming the bridge interface got an IP address, and that
> > > there is local multicast listener.
> > >
> > > Missing anything here?
> >
> > Hm, for multicast packets usually the code path a few lines
> > later in br_handle_frame_finish() should be taken instead.
> >
> > But you might be right for IP multicast packets with a unicast MAC
> > destination (due to whatever reason, for instance via DNAT'ing
> > again).
> >
> > Will check that - thanks!
>
> Ok, I tested DNAT'ing an IP multicast packet to the unicast MAC address
> of the bridge interface.
>
> Both ping-ing to an IPv4 and IPv6 multicast listener on br0 worked
> and was replied to fine, both with or without changing skb->pkt_type
> from PACKET_MULTICAST to PACKET_HOST.
> ("$ ping 224.1.0.123" and "$ ping6 ff02::1:ff40:707c%in0" from a
> network namespace, tied into the bridge via veth)
>
> Also, a DNAT'ed PACKET_BROADCAST worked, with or without changing
> it to PACKET_HOST.
>
> I also checked via tcpdump that the destination MAC was changed
> successfully.
Thanks for looking into this more in depth.
> So, so far I wasn't able to find any bugs with the current
> patch. But I think I like the idea of leaving the skb->pkt_type
> unaltered for PACKET_MULTICAST and PACKET_BROADCAST, seems cleaner.
Yes, and matching on skb->pkt_type would not break from netfilter.
> I'd just add an "if (skb->pkt_type == PACKET_OTHERHOST)" check
> then and resend a PATCH v2.
Thanks.
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