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

[Brooks Davis]

On Thu, May 27, 2004 at 06:10:55PM +0400, Yar Tikhiy wrote:
> [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?

This seems OK as long as you enabled VLAN_MTU by default as I see you
have just done with fxp.

-- Brooks

-- 
Any statement of the form "X is the one, true Y" is FALSE.
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