Disabling VLAN_HWTAGGING

[Ruslan Ermilov]

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 at FreeBSD.org
FreeBSD committer
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