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From: =?ISO-8859-2?Q?=A9tefan_Gula?= <steweg@ynet.sk>
Date: Tue, 17 Jan 2012 10:56:51 +0100
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Subject: Re: [patch v2, kernel version 3.2.1] net/ipv4/ip_gre: Ethernet
 multipoint GRE over IP
To: David Lamparter <equinox@diac24.net>
Cc: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>,
        "David S. Miller" <davem@davemloft.net>,
        James Morris <jmorris@namei.org>,
        Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
        Patrick McHardy <kaber@trash.net>, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org
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Dňa 17. januára 2012 10:50, David Lamparter <equinox@diac24.net> napísal/a:
> On Mon, Jan 16, 2012 at 11:52:25PM +0100, Štefan Gula wrote:
>> Dňa 16. januára 2012 21:29, David Lamparter <equinox@diac24.net> napísal/a:
>> > At the risk of repeating myself, Linux GRE support already has
>> > provisions for multipoint tunnels. And unlike your code, those reuse the
>> > existing neighbor table infrastructure, including all of its user
>> > interface and introspection capabilities.
>> >
>> > It's actually slightly visible in your patch:
>> >
>> > On Mon, Jan 16, 2012 at 08:45:14PM +0100, Štefan Gula wrote:
>> >> +++ linux-3.2.1-my/net/ipv4/ip_gre.c  2012-01-16 20:42:03.000000000 +0100
>> >> @@ -716,7 +942,19 @@ static netdev_tx_t ipgre_tunnel_xmit(str
>> > [...]
>> >>               /* NBMA tunnel */
>> >>
>> >>               if (skb_dst(skb) == NULL) {
>> >
>> >
>> > -David
>>
>> That code you are referring to is used only for routed traffic inside
>> GRE - L3 traffic over L3 routed infrastructure. My patch is dealing
>> with L2 traffic over L3 routed infrastructure - so the decision here
>> is based on destination MAC addresses and not based on IPv4/IPv6
>> addresses.
>
> Yes, it currently only does IPv4/IPv6 -> IPv4 through the neighbor
> table. That doesn't mean it can't be extended to handle ethernet
> addresses the same way.
>
>
> -David

Routing mechanisms and switching mechanisms works completely
different, in switching you simply don't have anything like next-hop
from routing, which can be resolved by utilizing modified ARP message
and there is also absolutely no hierarchy in MAC address (like you
have in routing table), so I seriously doubt that it can be done the
same way, but I am opened to ideas here. So how would you do like to
do that?