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

From: Yar Tikhiy (yar_at_comp.chem.msu.su)
Date: 05/27/04

  • Next message: Brooks Davis: "Re: VLAN_MTU (was Re: cvs commit: src/sys/dev/fxp if_fxp.c if_fxpvar.h)" 
    Date: Thu, 27 May 2004 18:10:55 +0400
To: Gleb Smirnoff <glebius@cell.sick.ru>

    [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
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