OpenBSD: Adding a "lladdr" command to netstart to change MAC address at boot

Voltar · 04-12-2006, 04:19 AM

Hello all,

I need to have the MAC address of one of my ethernet cards changed before the network is brought up and dhcp requests are sent out. I'm guessing this needs to be done in /etc/netstart but I'm unsure of what exactly I should put in there, or if it should even go in there.

I know how to change the MAC after boot with lladdr, but that doesn't exactly work for my needs. I'm using OpenBSD 3.8 if that helps.

Thanks in advance.

taylor_venable · 04-12-2006, 07:14 PM

I've never played with adjusting MAC addresses, but I think I know where you can put such a command. This is in /etc/netstart:

Code:

"dhcp")
    [ "$name" = "NONE" ] && name=
    [ "$mask" = "NONE" ] && mask=
    [ "$bcaddr" = "NONE" ] && bcaddr=
    ifconfig $if $name $mask $bcaddr $ext1 $ext2 down
    cmd="dhclient $if"
    setgateway=N
    ;;

The code you'd want to change is the line with "ifconfig $if ..." which you can wrap inside an if-clause to get the MAC address changed the way you want it, on the interface you want it. In other words, this should work:

Code:

"dhcp")
    [ "$name" = "NONE" ] && name=
    [ "$mask" = "NONE" ] && mask=
    [ "$bcaddr" = "NONE" ] && bcaddr=
    if [ "$if" = "INTERFACE" ]; then
        ifconfig $if $name $mask $bcaddr lladdr MAC_ADDR $ext1 $ext2 down
    else
        ifconfig $if $name $mask $bcaddr $ext1 $ext2 down
    fi
    cmd="dhclient $if"
    setgateway=N
    ;;

You may have to change the call to ifconfig, I'm not sure exactly what the syntax is when you're specifying an lladdr, but this should work. Of course, set INTERFACE and MAC_ADDR appropriately.

Voltar · 04-14-2006, 12:41 AM

Hey thanks a million. That didn't exactly work but it, shot out a bunch of errors at boot, but it gave me the basis for getting it to work. I'm not good with shell script or anything yet, but after a little tinkering I came up with this, which works perfect for me.

Here it is incase someone else has this question (/etc/netstart)..

Code:

....
if [ "$if" = "INTERFACE" ]; then
     ifconfig INTERFACE lladdr MAC_ADDY
fi

# Now parse the hostname.* file
....

INTERFACE = the interface (rl0, eth0, etc)
MAC_ADDY = MAC address (format: 00:00:00:00:00:00)

It goes right after the creation of the interface and right before the parsing of the hostname.* files.

Thanks again!