Re: MAC address issue

[David Young <dyoung%pobox.com@localhost>]

On Thu, Jan 17, 2008 at 07:45:34PM +0100, comfooc wrote:
> On 1/17/08, christos <christos%astron.com@localhost> wrote:
> > The problem was that the ifconf ioctls did not have space to store the 
> > lladdr.
> > This has changed now, and we can fix it so that for the cards that support
> > changing the mac address we can do it directly.
> 
> Will it be changed? Is someone working under this?

I will work on it this weekend.  I think that add/delete semantics are
desirable for link-layer addresses (lladdrs), however, we need to apply
several restrictions in the short term:

        1. The kernel must flag each lladdr with its properties and role:

                property        meaning
                --------        -------
                factory         lladdr was read from EEPROM
                synthetic       lladdr was produced by the kernel

                role            meaning
                ----            -------
                active          lladdr is used for both tx and rx
                                only one lladdr may be active
                inactive        lladdr is used for neither tx nor rx
                                inactive = !active

        2. For now, each lladdr must be assigned a unique preference
           number, and the most preferred lladdr is the only active
           lladdr.

Let me show some examples of how I think that this will work from the
operator's perspective.

Here is a sip(4) with one lladdr assigned.  I leave the 'address:' line
for compatibility with old scripts.  Note that the lladdr is listed a
second time.  The 'link' keyword tells us that it belongs to the AF_LINK
address family.

# ifconfig sip0
sip0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
        address: 00:00:24:c6:a5:24
        media: Ethernet autoselect (100baseTX full-duplex)
        status: active
        link 00:00:24:c6:a5:24 factory active
        inet 10.165.36.254 netmask 0xffffff00 broadcast 10.165.36.255
        inet6 fe80::200:24ff:fec6:a524%sip0 prefixlen 64 scopeid 0x1

Let us try to delete the lladdr:

# ifconfig sip0 link 00:00:24:c6:a5:24 delete
ifconfig: SIOCDIFADDR: Can't assign requested address

Let us add some lladdrs and display the new interface configuration.

# ifconfig sip0 link 02:00:00:00:00:01 preference -1
# ifconfig sip0 link 02:00:00:00:00:02 preference -2
# ifconfig sip0 link 02:00:00:00:00:03 preference -3
# ifconfig sip0
sip0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
        address: 00:00:24:c6:a5:24
        media: Ethernet autoselect (100baseTX full-duplex)
        status: active
        inet 10.165.36.254 netmask 0xffffff00 broadcast 10.165.36.255
        inet6 fe80::200:24ff:fec6:a524%sip0 prefixlen 64 scopeid 0x1
        link 00:00:24:c6:a5:24 preference 0 factory active
        link 02:00:00:00:00:01 preference -1 inactive
        link 02:00:00:00:00:02 preference -2 inactive
        link 02:00:00:00:00:03 preference -3 inactive

Let us try to add a fifth lladdr with preference equal to an
existing address:

# ifconfig sip0 link 02:00:00:00:00:04 preference -3
ifconfig: SIOCAIFADDR: Operation not supported by device

Let us activate the address 02:00:00:00:00:01.  Note that the link-local
IPv6 address should probably change as it does in this example:

# ifconfig sip0 link 02:00:00:00:00:01 preference 1
# ifconfig sip0
sip0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
        address: 02:00:00:00:00:01
        media: Ethernet autoselect (100baseTX full-duplex)
        status: active
        inet 10.165.36.254 netmask 0xffffff00 broadcast 10.165.36.255
        inet6 fe80::000:00ff:fe00:0001%sip0 prefixlen 64 scopeid 0x1
        link 02:00:00:00:00:01 preference 1 active
        link 00:00:24:c6:a5:24 preference 0 factory inactive
        link 02:00:00:00:00:02 preference -2 inactive
        link 02:00:00:00:00:03 preference -3 inactive

Dave

-- 
David Young             OJC Technologies
dyoung%ojctech.com@localhost      Urbana, IL * (217) 278-3933 ext 24