Re: ETHERCAP_* & ioctl()

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

On Wed, Oct 31, 2012 at 07:24:51PM +0900, Masanobu SAITOH wrote:
>  Hi, all.
> 
>  I sent the followin mail more than two years ago.
> 
> > http://mail-index.netbsd.org/tech-kern/2010/07/28/msg008613.html
> 
>  As the starting point to solve this problem, I committed the change to
> add SIOCGETHERCAP stuff.
> 
>  Example:
> > msk0: flags=8802<BROADCAST,SIMPLEX,MULTICAST> mtu 1500
> >         ec_capabilities=5<VLAN_MTU,JUMBO_MTU>
> >         ec_enabled=0
> >         address: 00:50:43:00:4b:c5
> >         media: Ethernet autoselect
> >         status: no carrier
> > wm0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
> >         
> > capabilities=7ff80<TSO4,IP4CSUM_Rx,IP4CSUM_Tx,TCP4CSUM_Rx,TCP4CSUM_Tx,UDP4CSUM_Rx,UDP4CSUM_Tx,TCP6CSUM_Rx,TCP6CSUM_Tx,UDP6CSUM_Rx,UDP6CSUM_Tx,TSO6>
> >         
> > enabled=7ff80<TSO4,IP4CSUM_Rx,IP4CSUM_Tx,TCP4CSUM_Rx,TCP4CSUM_Tx,UDP4CSUM_Rx,UDP4CSUM_Tx,TCP6CSUM_Rx,TCP6CSUM_Tx,UDP6CSUM_Rx,UDP6CSUM_Tx,TSO6>
> >         ec_capabilities=7<VLAN_MTU,VLAN_HWTAGGING,JUMBO_MTU>
> >         ec_enabled=0
> >         address: 00:1b:21:58:68:34
> >         media: Ethernet autoselect (1000baseT 
> > full-duplex,flowcontrol,rxpause,txpause)
> >         status: active
> >         inet 192.168.1.5 netmask 0xffffff00 broadcast 192.168.1.255
> >         inet6 fe80::21b:21ff:fe58:6834%wm0 prefixlen 64 scopeid 0x2
> >         inet6 2001:240:694:1:21b:21ff:fe58:6834 prefixlen 64
> 
> 
>  What do you think about this output?

I think that these flags belong within a "service hatch" rather than "on
the dashboard."  That is, shown via sysctl or ifconfig -v instead of in
the normal output of ifconfig.

What are the use-cases for reading/changing these flags?  I don't see
what an operator is supposed to do with this new information and with
these new controls.

I am curious whether these flags good for anything except diagnosing and
working around driver bugs?  I ask because I don't think the operator
can ordinarily make a better selection of hardware-capability flags than
the OS can, except insofar as the OS has bugs and forces the user to
work around them.  BTW, I think that it is the same for the checksum
offload / TSO flags as for the ethernet capability flags, but I guess
that we're kind of stuck with the checksum/TSO flags by now.

Dave

-- 
David Young
dyoung%pobox.com@localhost    Urbana, IL    (217) 721-9981