Hi Rob,

Thanks for your response. I'm still trying to figure out exactly what
I'm doing that is causing this problem. Here is a longer packet trace.
What I'm trying to do is hijack a tcp connection and send it to to
another machine. In order to do this I need to install two flowmods
(One for each direction).

Packet #18 in this trace is what fires off this series of events. Then
packet #19,20 are the corresponding flow mods to do this.  Packet #23
is the error message saying Specified buffer has already been used.

Even given this error everything seems to work so the flow mods are
getting installed (I believe) . I'm curious if the issue is because of
the command I'm using to install the flowmods.

The first flowmod is triggered from the packet so I know the buffer ID
so I do the following to install it like this:

 inst.install_datapath_flow(dpid, flow, CACHE_TIMEOUT,
    openflow.OFP_FLOW_PERMANENT, actions,
    bufid, openflow.OFP_DEFAULT_PRIORITY,
    inport, buf)

The second one I want to  push the flow ahead of time so I use:

inst.install_datapath_flow(dpid, flow, CACHE_TIMEOUT,
    openflow.OFP_FLOW_PERMANENT, actions,
    None, openflow.OFP_DEFAULT_PRIORITY,
    None, None);

# note there is no bufid yet to use.

Do you think this is what is causing this message?


Thanks,

Aaron















On Thu, Jun 23, 2011 at 5:04 PM, Ben Pfaff <b...@nicira.com> wrote:
> On Thu, Jun 23, 2011 at 01:57:43PM -0700, Rob Sherwood wrote:
>> My guess (should be confirmed) is that each packet_in references the
>> same buffer_id, so that the first flow_mod response releases the
>> queued packet or packets and then subsequent ones are generating the
>> error -- the buffer_id has already been used.
>
> Consecutive packet_ins in OVS won't use the same buffer_id.
>



-- 
Aaron O. Rosen
Masters Student - Network Communication
306B Fluor Daniel

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