Source MAC address per IP packet

Hello,

for a networking application, I need to set the source MAC address
individually
for every IP packet that I send. Is this possible at all? I know that
the MAC address
can be changed in software but per IP frame? On the other hand, every
layer 2
switch does exactly this, so it must be possible in principle. Do I
need special
network controller chips that support this feature? All datasheets of
ethernet
controllers I got hands on allow you to program the MAC address but it
is then
automatically filled in for every packet.

Also, how would the programming side look like? I presume I must use
RAW sockets
but in which field would I set the source MAC address?

Thanks,

Albrecht

On Jun 15, 3:02*pm, albrechtuhlm...@gmx.net wrote:
> Hello,
>
> for a networking application, I need to set the source MAC address
> individually
> for every IP packet that I send. Is this possible at all? I know that
> the MAC address
> can be changed in software but per IP frame? On the other hand, every
> layer 2
> switch does exactly this, so it must be possible in principle. Do I
> need special
> network controller chips that support this feature? All datasheets of
> ethernet
> controllers I got hands on allow you to program the MAC address but it
> is then
> automatically filled in for every packet.
>
> Also, how would the programming side look like? I presume I must use
> RAW sockets
> but in which field would I set the source MAC address?
>
> Thanks,
>
> Albrecht

Albrecht,

For what practical, benevolent purpose would you ever need to do
this!?

hat trick

hat-trick <(E-Mail Removed)> writes:

>For what practical, benevolent purpose would you ever need to do this!?

What about replaying network traces to test (possibly modified)
packet filter rules? What about generating specifically formatted
packets to test such rules where they try to match MAC addresses
(whatever good that would do)? What about testing layer 2 switch
MAC table overflow characteristics?

best regards
Patrick

On Aug 10, 10:51*am, hat-trick <marcmath...@comcast.net> wrote:

> Albrecht,
>
> For what practical, benevolent purpose would you ever need to do
> this!?

Aside from all the others suggested, the most obvious would be if you
are implementing a transparent layer 2 switch/bridge.

DS

Am Sun, 10 Aug 2008 10:51:49 -0700 schrieb hat-trick:

> On Jun 15, 3:02Â*pm, albrechtuhlm...@gmx.net wrote:

>> for every IP packet that I send. Is this possible at all? I know that
>> the MAC address
>> can be changed in software but per IP frame? On the other hand, every
>> layer 2
>> controllers I got hands on allow you to program the MAC address but it
>> is then
>> automatically filled in for every packet.
>>
>> Also, how would the programming side look like? I presume I must use
>> RAW sockets
>> but in which field would I set the source MAC address?
>>

What about /usr/src/linux/if_ether.h ?
(struct ethhdr)

You can set the MAC address to what ever you want.

cheers