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[openflow-discuss] oftest exposed likely (small corner case) bug in OVS

Rob Sherwood rob.sherwood at bigswitch.com
Wed Mar 21 17:02:57 PDT 2012


Hiya,

If you aren't familiar, OFTest is a set of conformance tests for
openflow switches.  We used it heavily at the ONF interop event two
weeks ago and as a result a few of us have started running it against
other switches available to us, including OVS.  Fwiw, it's available
for download from `git clone git://github.com/floodlight/oftest`.

In any case, the pktact.SingleWildcardMatch and
pktact.AllExceptOneWildcardMatch tests were failing because it looks
like OVS (v1.4 release) was  not matching vlan tagged packets when the
match wildcarded vlan but the dl_vlan value (which should be ignored,
because it is wildcarded) was non-zero.  We've worked around this in
OFTest by making sure that the dl_vlan value is zero when vlan is
wildcarded and now the test passes.

In other words:

if (ofp_match->wildcards&OFPFW_DL_VLAN) is true, then the match should
match both tagged and untagged packets, independent of the value of
ofp_match->dl_vlan.  OVS (seemingly) only matches tagged packets if
ofp_match->dl_vlan == 0.


I thought I would drop you a line just FYI -- it's seems fairly likely
this is a bug in OVS (albeit, a very minor one), but just in case
someone is running an older version of OFTest I thought it was worth
mentioning.

Hope this information is useful to someone,

- Rob
.

PS If there is any interest in contributing back to OFTest, please let
me know.  It seems like it might be used to inform some of the tests
for the ONF testing and interop WG, so it would be great to see more
participation in that.


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