Re: netgraph ability

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Date: Fri, 23 Apr 2004 20:35:18 +0300
To: David Yeske <dyeske@yahoo.com>

[ Redirected to -net ]

On Thu, Apr 22, 2004 at 05:50:57PM -0700, David Yeske wrote:
> I'm in a situation where I need to emulate multiple ethernet devices with
> different mac addresses. I have gotten far enough to have this.
>
> I ran ngctl and then ran
> "mkpeer . eiface hook ether"
>
> I then ran
> ifconfig ngeth0 link '00:bd:03:11:21:11'
> ifconfig ngeth0 192.168.20.5
> ifconfig sis0 192.168.23.45
>
> So basically I want to be able to ping / connect to
> 192.168.20.5 from another box on the 192.168.23.0/24 network, and have it see
> the mac address that I have set rather than the mac address of my sis0 device.
> I know I can do this with vmware, but I am trying to avoid that.
>
> Anyone know if this is possible? Is there a way to do this with the tap device
> and or arpd?
>
Using Netgraph, you can emulate any number of Ethernet interfaces
on one physical interface. Here's my recipe for you:

1. Load the ng_ether(4) module.
2. Create the required number of ng_eiface(4) nodes.
3. Connect "lower" and "upper" of sis0: and all ngethX:
    ng_ether(4) nodes to one ng_bridge(4).
4. Make sure to "ngctl msg <if>: setautosrc 0" to all
    ng_ether(4) nodes.
5. Optionally set net.link.ether.inet.log_arp_wrong_iface=0.

Here's my test (I've omitted obvious configuration steps):

# ifconfig dc0 ether
dc0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
        options=48<VLAN_MTU,POLLING>
        ether 00:10:a4:c0:c0:45

# ifconfig ngeth0
ngeth0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
        ether 00:00:00:01:02:03

# ngctl show bridge:
  Name: bridge Type: bridge ID: 0000000b Num hooks: 4
  Local hook Peer name Peer type Peer ID Peer hook
  ---------- --------- --------- ------- ---------
  link4 ngeth0 ether 00000007 lower
  link3 ngeth0 ether 00000007 upper
  link2 dc0 ether 00000002 lower
  link1 dc0 ether 00000002 upper

# ifconfig ngeth0 1.2.3.4

# tcpdump -lenx -i dc0 ether host 0:0:0:1:2:3
tcpdump: listening on dc0
20:29:05.571179 0:0:0:1:2:3 ff:ff:ff:ff:ff:ff 0806 42: arp who-has 1.2.3.4 tell 1.2.3.4
                         0001 0800 0604 0001 0000 0001 0203 0102
                         0304 0000 0000 0000 0102 0304

Cheers,

-- 
Ruslan Ermilov
ru@FreeBSD.org
FreeBSD committer

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