ethercons: ethernet console driver for 5-current
Peter Jeremy
PeterJeremy at optushome.com.au
Tue Oct 21 13:26:27 PDT 2003
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
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