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* ip routing
@ 2003-11-30  8:24 Rainer Hochreiter
  2003-11-30 10:20 ` bert hubert
  0 siblings, 1 reply; 2+ messages in thread
From: Rainer Hochreiter @ 2003-11-30  8:24 UTC (permalink / raw)
  To: linux-kernel

hi list!

i have a problem with ip routing!

first of all my configuration:

Tux1 .... embedded linux (kernel-2.4.10) running busybox-0.60.3
          and 2 lan interfaces in different networks
          default gateway via eth0
R1, R2 .. router (linux for testing)
Tux2 .... linux with network different to Tux1/eth0/eth1

     eth0= +-----+ eth1=
                   .--|Tux1 |--.
                   |  +-----+  |
eth1= |           | eth1=
                +-----+     +-----+
   ip_forward=1 | R1  |     | R2  | ip_forward=1
                +-----+     +-----+
eth0= |           | eth0=
                   |           |
                         | eth0=
                      |Tux2 |

i want to achieve, that each packet received on Tux1/eth1 will also be
replied via this interface. this isn't the case now, because the
received packets came from a different network and therefore the replies
are sent back via Tux1/eth0 using the default route.

but the replies have to be sent even when the connection between
Tux1/et0 and R1 is not available. a possible solution is, setting a
network route for network Tux2/eth0 via Tux1/eth1, but in my special
case, i do not know from which network i'll receive the packets!

and here i reached the point where my knowledge ends;-(

i tried to solve this problem in my application running on Tux1, using
the following code:

s = socket();
bind(s, ""); // bind to Tux1/eth1
s2 = accept(s);
int yes=1;
setsockopt(s2, SOL_SOCKET, SO_DONTROUTE, &yes, sizeof(yes));

...but setting SO_DONTROUTE on socket s2 doesn't have the effect, that
the reply packets are always sent back via Tux1/eth1! 
is it possible at all to guarantee this in any case? because this means
bypassing the routing stuff!

any hints welcome!


PLEASE personally CC any answers and comment to my question - thnx!

^ permalink raw reply	[flat|nested] 2+ messages in thread

* Re: ip routing
  2003-11-30  8:24 ip routing Rainer Hochreiter
@ 2003-11-30 10:20 ` bert hubert
  0 siblings, 0 replies; 2+ messages in thread
From: bert hubert @ 2003-11-30 10:20 UTC (permalink / raw)
  To: Rainer Hochreiter; +Cc: linux-kernel

On Sun, Nov 30, 2003 at 09:24:01AM +0100, Rainer Hochreiter wrote:

>      eth0= +-----+ eth1=
>                    .--|Tux1 |--.
>                    |  +-----+  |
> eth1= |           | eth1=

I haven't read all of your problem, but you might want to look policy
routing on

--      Open source, database driven DNS Software           Linux Advanced Routing & Traffic Control HOWTO

^ permalink raw reply	[flat|nested] 2+ messages in thread

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