VLAN_MTU (was Re: cvs commit: src/sys/dev/fxp if_fxp.c if_fxpvar.h)

[Yar Tikhiy]

[moving the discussion from the cvs lists to -net]

On Wed, May 26, 2004 at 10:41:52AM +0400, Gleb Smirnoff wrote:
> 
> Y> ng_vlan(4) could send a control command to ng_ether(4) instructing
> Y> the latter to increment the VLAN counter on the Ethernet interface
> Y> and toggle VLAN_MTU on if the counter value became equal to 1.
> 
> Two comments:
> 
> 1) Just note that it should increment VLAN counter on creating of
>    any new VLAN hook.
> 2) There may be some itermediate nodes between ng_ether and ng_vlan,
>    e.g. ng_tee(4), ng_etf(4), any custom traffic shaping or accounting
>    node.
> 
> Two deal with second issue some new mechanism should be introduced in netgraph,
> e.g. "broadcast" messages, which go down a hook spreading across all nodes,
> and only nodes with appropriate cookie will see this message delivered.
> 
> Y> Another way I see is to drop automatic fiddling with VLAN_MTU in
> Y> the first place and implement an option for ifconfig(8) so that a
> Y> user/admin can control the capability WRT a particular case, e.g.,
> Y> disable it if a NIC displays erroneous behaviour in long frame mode.
> 
> From my point of view this is a good idea.

The longer I've been thinking of the issue, the more I'm inclined
to take the latter path.  I believe that it would conform to the
good tradition of Unix to offer a user as much control as possible
and avoid doing "automagic" tricks behind user's back.

Therefore I'd like to ask the community:  Would anybody mind if
vlan(4) gave up playing with VLAN_MTU on parent interfaces
while a new option to ifconfig(8), say `vlanmtu', was introduced
so that a user could control the feature manually?

-- 
Yar