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Re: IFA_F_NO_NDISC (for vrrp)

To: Andrey Savochkin <saw@xxxxxxxxxxxxx>
Subject: Re: IFA_F_NO_NDISC (for vrrp)
From: Julian Anastasov <uli@xxxxxxxxxxxxxxxxxxxxxx>
Date: Mon, 12 Jun 2000 10:23:48 +0300 (EEST)
Cc: Jerome Etienne <jetienne@xxxxxxxxxx>, netdev@xxxxxxxxxxx
In-reply-to: <20000612135938.A586@xxxxxxxxxxxxx>
Sender: owner-netdev@xxxxxxxxxxx
        Hello Andrey,

On Mon, 12 Jun 2000, Andrey Savochkin wrote:

> > 
> >     I  now see  that inet_addr_type() is changed too, to
> > use  fib_lookup. I forgot about this.  Yep, with this change
> > we   can't  do  this  (to   limit  the  local  addresses  in
> > arp_solicit).   I have to wait for the final version of your
> > patch :)
> Using inet_addr_type() in arp_solicit(), especially the current one looking
> into local table only, is wrong from conceptual point of view.
> It makes decisions that can't be explained in human terms, only as some
> manipulations in C language.


> It's better not to call any checking function that to call wrong one.
> I'll call fib_select_addr() unconditionally.

        Without  calling fib_local_source() the situation is
different.   This leads arp_solicit to use limited number of
local addresses in some situations and may be will allow not
to include hidden addresses in the ARP request.

        To summarize the problem without the hidden flag. If
we  have a client  on the LAN  and our host  with the hidden
address we need:

1. route from CLIENT to Hidden address to go in the blackhole for ARP

2. the same
route from CLIENT to Hidden address to return RTN_LOCAL for non-ARP

3. arp_solicit not to include hidden addresses in the ARP request

(1)  and (2) can't  coexist in the  FIB world. May  be if we
play  with fwmark? So, we need  a way to distinguish them by
using  other methods. I'm  not sure if  we can add something
like ip add route "shared" VIP table 100. RTN_SHARED will be
handled  as RTN_LOCAL  but the  difference will  be for ARP.
This  leads to big changes in the routing (RTN_SHARED subset
of RTN_LOCAL) and I don't want to make such big changes. In
many places we will need:

if (type == RTN_LOCAL || type == RTN_SHARED)

May be if we change the RTN_ values from enum to flags, for example:

if (type & RTN_LOCAL)

In some places we will check:

if (type & RTN_SHARED)

We will have:


        But this is a big change.

        I  will continue to think  on this problem. For now,
I'm  sure I can't  do it with  current policy routing rules.
Any ideas are welcome.


Julian Anastasov <uli@xxxxxxxxxxxxxxxxxxxxxx>

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