Hi,
In my C++ NOX (Zaku) app I would like to make sure that a flow is installed on
the switch. Having no better solution, I send a barrier request right after the
flow_mod, and then wait for either an error, or a barrier reply.
For this I register the flow_mod's and barrier's xids, and then compare
incoming events against those. See the pseudoish code below for an example.
Could someone familiar with the cooperative thread implementation in NOX tell
me, whether it is possible that a blocking send_openflow_command() result in
the current thread actually blocking and yielding to another one?
Particularly in this code, can it happen that sending the flow_mod completes,
but then the second call to send blocks, yielding to another thread. Then on
this other thread the incoming error message is received and dispatched to the
handler method? Resulting in the error being discarded as at that time the
PendingFlow was not even registered...
And if so, is there a way to temporarily disable this yielding, or do I better
start making the code more complex?
Thank you,
Zoltan.
------------------------------
struct PendingFlow {
uint32_t modXid;
uint32_t barrierXid;
...
}
class Example {
PendingFlow *pendingFlow;
...
void
Example::install_flow(ofp_flow_mod *mod) {
ofp_header *barrier = make_barrier();
mod->header->xid = generate_xid();
barrier->xid = generate_xid();
send_openflow_command(pi.datapath_id, &mod->header, true);
send_openflow_command(pi.datapath_id, barrier, true);
pendingFlow = new PendingFlow(mod->header->xid, barrier->xid);
...
}
Disposition
Example::handleError(const Event &e) {
const Error_event& err = assert_cast<const Error_event&>(e);
if (pendingFlow != NULL && pendingFlow.modXid == getErrorXid(err)) {
delete pendingFlow; pendingFlow = NULL;
// Process error
}
...
return CONTINUE;
}
Disposition
Example::handleBarrier(const Event &e) {
const Barrier_reply_event& barrier = assert_cast<const
Barrier_reply_event>(e);
if (pendingFlow != NULL && pendingFlow.barrierXid ==
getBarrierXid(barrier)) {
delete pendingFlow; pendingFlow = NULL;
// Process completion
}
..
return CONTINUE;
}
...
}
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