Re: PATCH: VLAN support for 3c59x/3c90x

From: Willy Tarreau (willy_at_w.ods.org)
Date: 07/31/04

  • Next message: Ben Greear: "Re: PATCH: VLAN support for 3c59x/3c90x" 
    Date:	Sat, 31 Jul 2004 19:05:51 +0200
To: Ben Greear <greearb@candelatech.com>

    Hi Ben,

    On Sat, Jul 31, 2004 at 10:03:31AM -0700, Ben Greear wrote:
     
    > VLAN allows you to continue using the ethX interface as a regular
    > ethernet interface, so you do not generally want it's MTU to be set
    > to 1504 because then the other peer ethernet interfaces would also
    > have to be set to 1504. I believe it is much better to silently let
    > the extra 4 bytes pass but NOT advertise this extra 4 bytes to
    > anything that actually cares about MTU.

    I 100% agree with you on this one, but I don't see how playing with
    change_mtu() would change anything. Ideally, we would need to export
    the level 2 limit (imposed by hardware and intermediate switches) to
    other drivers such as 802_1q, and let only the IP stack rely on dev->mtu.

    I've seen several drivers which silently add 4 bytes to the hardware
    config when CONFIG_VLAN is set. I find it better than fooling the IP
    stack into using 1504 bytes, which is a disaster on UDP !

    Cheers,
    Willy

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  • Next message: Ben Greear: "Re: PATCH: VLAN support for 3c59x/3c90x"

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