Re: ethercons: ethernet console driver for 5-current

On Mon, Oct 20, 2003 at 12:13:27PM -0400, Robert Watson wrote:
>  After reading a FREENIX
>paper this summer on a Linux ethernet console driver, I took a pass at
>implementing ethernet console support for FreeBSD.

A very worthy cause.  I'm sure this has come up before but I think
you're the first person to produce actual code.  Something that you
don't seem to address is security - which surprised me.

>  This driver is similar
>to the Linux driver, although not binary-compatible on the wire,
>...
>As with the Linux driver, communication happens at the ethernet link
>layer, using protocol number 0x0666 (entertaining choice).

If Linux is using 0x0666, we should probably pick a different number
since we're not wire compatible.  Though coming up with a common
protocol would be even better.

>  In general, the wire protocol is
>probably the weakest part of the endeavor, but I'm having trouble finding
>documentation for a decent wire console protocol that doesn't come with an
>entire network stack attached.

MOP (as you point out later) or LAT have the advantage of being more
standard, but I'm not sure how well documented they are.

>  A series of tunables and sysctls is available to tune the
>behavior of ethercons:
>kern.ethercons.ifnet_raise
>kern.ethercons.interface_preference
>kern.ethercons.target

Is there any way to specify ifconfig options?  "media" and "mediaopts"
in particular may need to be specified to get the interface to talk to
the associated switch.

I presume kern.ethercons.target only specifies the MAC address
inserted into transmitted packets.  Is there any way to restrict the
src address(es) of received packets?  Does ethercons have any concept
of a current session or will it accept incoming packets from anywhere
at any time?  The latter case would seem undesirable as (IMHO) it
makes it too easy to accidently send a command to the wrong system

Peter