On Tue, Feb 1, 2011 at 2:39 PM, John Mahoney [off-list ref] wrote:

On Tue, Feb 1, 2011 at 2:27 PM, Elvis Yoan Tamayo Mollares
[off-list ref] wrote:

quoted

hi list, during ip forwarding process, the kernel replace the source MAC
address of the package it received with my own MAC address.. My question
is: Is there any way to avoid this behavior?

That is what routing does at the ip layer. ?You may be able to
accomplish this by bridging the two ports together so that the traffic
is handled at layer 2.

As a side note, looking at the iptables target:
 -m mac --mac-source XX:XX:XX:XX:XX:XX [1]

and the kernel code for that module (net/netfilter/xt_mac.c) it
appears that the src MAC address is saved in the sk_buff and is still
accessible in the PREROUTING, INPUT, and FORWARD chains via
eth_hdr(skb)->h_source.

I do not know if that helps.  I guess my point is my first answer was
the logical one, but it may be possible if you think outside the box.

--
John

[1]http://www.faqs.org/docs/iptables/matches.html#TABLE.MACMATCH