Re: Disabling VLAN_HWTAGGING

From: Ruslan Ermilov (ru_at_FreeBSD.org)
Date: 03/29/04

  • Next message: Valentin Nechayev: "Re: race condition in ipfw restart (please review the fix)" 
    Date: Mon, 29 Mar 2004 11:12:24 +0300
To: "Jacob S. Barrett" <jbarrett@amduat.net>

    On Sat, Mar 27, 2004 at 08:48:37AM -0800, Jacob S. Barrett wrote:
    > On Saturday 27 March 2004 07:53 am, Jacob S. Barrett wrote:
    > > Well with a new "correct" MAC that pings go back and forth just fine now.
    > > I will back out all my changes and see if they still work with the hardware
    > > tagging/detagging enabled.
    >
    > OK, with the hardware support re-enabled the frame now enters the driver. It
    > is detected as VLAN frame and sent to VLAN_INPUT_TAG. The frame is then
    > delivered via lower hook to the ng_vlan where it doesn't match the vlan tag
    > so it goes out the nomatch hook. I guess with the VLAN tag stripped from the
    > frame that ng_vlan can't match it. Is this the expected behavior with
    > ng_vlan? I can just comment out the VLAN stripping line in the driver if it
    > is the expected behavior. That isn't a big deal really.
    >
    No, this is not of course expected. Can you add some debug printfs
    in the ng_vlan.c:ng_vlan_rcvdata() and see if it ever receives the
    VLAN tag, and if so, print its value (perhaps the tag is entered by
    a driver in a network byte order).

    > I haven't done a whole lot with the network interface drivers other than a few
    > minor fixes here and there, but would it be hard to add some sort of flag to
    > enable/disable the tag stripping via ifconfig? I was thinking that could be
    > down through a "linkx" flag right? If the driver got the say "link1" it
    > would down the interface, set clear the stripping config bits, and then re-up
    > the interface. Or would this be better handled by a sysctl option? Does
    > that sound safe and do-able?
    >
    Well, for IP/TCP/UDP checksumming, it's possible to switch the
    corresponding bit in the interface's enabled capabilities field.
    OTOH, switching VLAN stripping on/off requires reprogramming of
    the hardware.

    Generally, if the hardware supports IP/TCP/UDP checksumming and
    or VLAN tag removal/insertion, it's better to use it. We'd
    better find the root of the problem and fix it. ;)

    Cheers, 

    -- 
Ruslan Ermilov
ru@FreeBSD.org
FreeBSD committer

  • Next message: Valentin Nechayev: "Re: race condition in ipfw restart (please review the fix)"

    Relevant Pages

    • Re: nested vlans and ethernet frame size
      ... setting maximum ethernet frame size in freebsd? ... 1518 does that not imply at you require hardware that supports jumbo ... frames to do VLAN tag nesting? ...
      (freebsd-net)
    • Re: Regarding encryption, random numbers and "brute force" cracking
      ... It's my strong impression that Linux is fairly shoddy, ... Stripping down a Linux kernel to what is ... hardware helps as well. ... Fry's can supply (including three $1 ethernet cards) I've never had a crash ...
      (rec.arts.sf.fandom)
    • Re: Linux Newbie.
      ... stripped down OS like DSL in VMWare in "production". ... it can run any OS, no need for stripping the OS down. ... the hardware in question cannot. ... Ok, now this is solved, what is next, worldpeace or reading Usenet? ...
      (alt.os.linux.suse)