Mailing List Archive: FWDing packets from a physical interface to a virtual interface

FWDing packets from a physical interface to a virtual interface

Sep 11, 2007, 3:36 PM

Post #1 of 4 (12039 views)

Hi, :)

Here is the situation:

I have a machine with 2 NICs, assume eth0 (192.168.0.10) connected to my
LAN, and eth1 (192.168.0.20) connected to Internet through a gateway.
I also, have a virtual tap0 (TUN/TAP) interface (10.0.0.1) on this
machine.

All that I want to do is simply, forwarding ALL traffic coming to eth0
from the LAN, into my tap0 interface, So I can modify them using my own
user space program which can capture packets on the tap interface and
send them on eth1 to another address somewhere in the world (through
Internet).

Since I want IP addresses unchanged, I cannot use NAT or Masquerading.
As far as I know, In this matter forwarding should be done in Layer-2 so
I'm not sure if I can use iptables to do the job.
I also have tried bridging but I was trapped in a horrible bridge loop
(Enabling STP on bridge also didn't work for me).

Any ideas? :)

Thanks,
Arash

Re: FWDing packets from a physical interface to a virtual interface [ In reply to ]

davila at nicaraguaopensource

Sep 11, 2007, 6:40 PM

Post #2 of 4 (11361 views)

Permalink

Arash:

AFAIK, you must open a path in the firewall to the vpn daemon
(port/protocol) and the daemon will be in charge of administering the
traffic between the clients and the vpn server.

Additionally, you must tell to the client where is the server (the ip
address), what device will be used (tun or tap device).

May you want ask in the mailing list for the vendor/provider of the vpn
software that you are using.

Hope this helps,

Jorge Dávila.

On Wed, 12 Sep 2007 02:06:53 +0330
Arash Yadegarnia <arash@bluehome.net> wrote:
> Hi, :)
>
> Here is the situation:
>
> I have a machine with 2 NICs, assume eth0 (192.168.0.10) connected to my
> LAN, and eth1 (192.168.0.20) connected to Internet through a gateway.
> I also, have a virtual tap0 (TUN/TAP) interface (10.0.0.1) on this
> machine.
>
> All that I want to do is simply, forwarding ALL traffic coming to eth0
> from the LAN, into my tap0 interface, So I can modify them using my own
> user space program which can capture packets on the tap interface and
> send them on eth1 to another address somewhere in the world (through
> Internet).
>
> Since I want IP addresses unchanged, I cannot use NAT or Masquerading.
> As far as I know, In this matter forwarding should be done in Layer-2 so
> I'm not sure if I can use iptables to do the job.
> I also have tried bridging but I was trapped in a horrible bridge loop
> (Enabling STP on bridge also didn't work for me).
>
> Any ideas? :)
>
> Thanks,
> Arash
>
>
>

Jorge Isaac Davila Lopez
Nicaragua Open Source
+505 430 5462
davila@nicaraguaopensource.com

Re: FWDing packets from a physical interface to a virtual interface [ In reply to ]

arash at bluehome

Sep 12, 2007, 4:32 AM

Post #3 of 4 (11331 views)

Permalink

Thanks Jorge,

I'm not using any specific VPN solution, Me and my colleagues are
developing a secure VPN solution based on kernel TUN/TAP driver.
Since we have full control over our tap interface we just need to
redirect the whole traffic coming into the eth0 (from a LAN) into the
tap interface, so we can read them (I mean Ethernet frames in Layer 2)
and send them out from the other pysical interface (eth1).
BTW, Redirecting a single or even multiple ports won't work in my
situation, because I want whole traffic in layer 2, not a specific port
number.

Thanks,
Arash

On Tue, 2007-09-11 at 19:40 -0600, Jorge Davila wrote:
> Arash:
>
> AFAIK, you must open a path in the firewall to the vpn daemon
> (port/protocol) and the daemon will be in charge of administering the
> traffic between the clients and the vpn server.

> Additionally, you must tell to the client where is the server (the ip
> address), what device will be used (tun or tap device).
>
> May you want ask in the mailing list for the vendor/provider of the vpn
> software that you are using.
>
>
> Hope this helps,
>
> Jorge DÃ¡vila.
>
> On Wed, 12 Sep 2007 02:06:53 +0330
> Arash Yadegarnia <arash@bluehome.net> wrote:
> > Hi, :)
> >
> > Here is the situation:
> >
> > I have a machine with 2 NICs, assume eth0 (192.168.0.10) connected to my
> > LAN, and eth1 (192.168.0.20) connected to Internet through a gateway.
> > I also, have a virtual tap0 (TUN/TAP) interface (10.0.0.1) on this
> > machine.
> >
> > All that I want to do is simply, forwarding ALL traffic coming to eth0
> > from the LAN, into my tap0 interface, So I can modify them using my own
> > user space program which can capture packets on the tap interface and
> > send them on eth1 to another address somewhere in the world (through
> > Internet).
> >
> > Since I want IP addresses unchanged, I cannot use NAT or Masquerading.
> > As far as I know, In this matter forwarding should be done in Layer-2 so
> > I'm not sure if I can use iptables to do the job.
> > I also have tried bridging but I was trapped in a horrible bridge loop
> > (Enabling STP on bridge also didn't work for me).
> >
> > Any ideas? :)
> >
> > Thanks,
> > Arash
> >
> >
> >
>
> Jorge Isaac Davila Lopez
> Nicaragua Open Source
> +505 430 5462
> davila@nicaraguaopensource.com
>

Re: FWDing packets from a physical interface to a virtual interface [ In reply to ]

leolistas at solutti

Sep 12, 2007, 4:45 AM

Post #4 of 4 (11365 views)

Permalink

So maybe you'll have to some bridging stuff and not
netfilter/iptables ones ....

iptables/netfilter deals basically with Layer 3 (IP) packets and not
layer 2 frames, which are the ones you're interested.

Arash Yadegarnia escreveu:
> Thanks Jorge,
>
> I'm not using any specific VPN solution, Me and my colleagues are
> developing a secure VPN solution based on kernel TUN/TAP driver.
> Since we have full control over our tap interface we just need to
> redirect the whole traffic coming into the eth0 (from a LAN) into the
> tap interface, so we can read them (I mean Ethernet frames in Layer 2)
> and send them out from the other pysical interface (eth1).
> BTW, Redirecting a single or even multiple ports won't work in my
> situation, because I want whole traffic in layer 2, not a specific port
> number.
>
> Thanks,
> Arash
>

--

Atenciosamente / Sincerily,
Leonardo Rodrigues
Solutti Tecnologia
http://www.solutti.com.br

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