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Call for Testing: vlan(4) improvements (Update updated)
Contributed by tbert on Tue Apr 22 17:19:36 2014 (GMT)
from the tag-you're-it dept.

Henning Brauer (henning@) writes in to let us know that he has some vlan(4) improvements in the pipeline:

so, on vlan, to insert the vlan tag, we right now:
-copy (most of) the existing ethernet header into a ether_vlan_header
 on the stack
-fill the extra fields (tag, inside ether type) in ether_vlan_header
-set the ether type
-m_adj() to make room for the extra space ether_vlan_header needs
-m_copyback the ether_vlan_header into the mbuf

that involves moving data around, which isn't all that cheap.

now it turns out it is trivial to have ether_output prepend the
ether_vlan_header instead of the regular ethernet header, which makes
the vlan tagging essentially free in most cases.

you need a very current src tree to test this, relies on the code
shuffling in if_ethersubr.c I did a few hours ago.

If you have a setup that involves vlan(4), you can test by applying the patch the updated patch building from source and pushing some packets. As always, widespread testing is key to the continued quality of our releases.


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  Re: Call for Testing: vlan(4) improvements (Update updated) (mod -2/26)
by Daniel Gracia ( on Fri Apr 25 07:46:21 2014 (GMT)
  Very nice!

Using intensive VLAN tagging for a little WISP over here. Will check functionality ASAP.

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