[SDFAB-1054] Use p4 auto generated constants

[EmanueleGallone]

Make use of P4 constants and remove methods that iterate over p4info to retrieve ID.

depends on:

• Generate Go P4 constants for UP4 pipeline from p4info #499
• Add convenience functions to generated p4info code #508
• [SDFAB-1090] Don't set UP4 forwarding pipeline config #548

[osinstom]

LGTM, but I left minor comments that we should address before merging.

[osinstom]

what do you mean by fully exploit p4constants ? We get counterName from p4constants and counter size is retrieved from UP4's P4Info. What can we do more?

[EmanueleGallone]

switch counterID {
		case p4constants.CounterPreQosPipePreQosCounter:
			//FIXME to fully exploit p4constants, counters should be a map instead of a slice
			up4.initCounter(preQosCounterID, counterName, uint64(counterSize))
		case p4constants.CounterPostQosPipePostQosCounter:
			up4.initCounter(postQosCounterID, counterName, uint64(counterSize))
		}

all of the above code could be replaced by up4.initCounter(counterID, counterName, counterSize) .
This means that we could also get rid of

preQosCounterID = iota
postQosCounterID

That FIXME is pointing to this improvement, basically. It is not implemented because counters is a slice and it's allocating counters sequentially, in setUpfInfo().

The above simplification can be achieved, however, with a refactor on how we handle counters IMO.
Anyway, I removed that FIXME so that we can merge this and address the improvements on a later PR.

[osinstom]

ok, I see. Getting rid of preQosCounterID and postQosCounterID requires refactoring of the entire counter allocation mechanism. We can address it later.