Remove FIXME for de-duping matches

[sjberman]

Per the ticket, I'm not able to reproduce the issue. It may have been fixed already, so closing out the ticket and removing the FIXME. If it pops up again in the future, we can reopen.

Closes #662

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[pleshakov]

here is an example of to reproduce duplicated matches:

apiVersion: gateway.networking.k8s.io/v1beta1
kind: HTTPRoute
metadata:
  name: test
spec:
  parentRefs:
    - name: gateway
  hostnames:
    - "cafe.example.com"
  rules:
    - matches:
        - path:
            type: PathPrefix
            value: /coffee
          headers:
            - name: version
              value: v2
      backendRefs:
        - name: coffee-v2-svc
          port: 80
    - matches: # same matches
        - path:
            type: PathPrefix
            value: /coffee
          headers:
            - name: version
              value: v2
      backendRefs:
        - name: coffee-v1-svc # different destination
          port: 80

leads to:

    location /coffee_prefix_route0 {
        internal;

        proxy_set_header Host $gw_api_compliant_host;
        proxy_pass http://default_coffee-v2-svc_80$request_uri;
    }

    location /coffee_prefix_route1 {
        internal;

        proxy_set_header Host $gw_api_compliant_host;
        proxy_pass http://default_coffee-v1-svc_80$request_uri;
    }

    location /coffee/ {
        set $http_matches "[{\"redirectPath\":\"/coffee_prefix_route0\",\"headers\":[\"version:v2\"]},{\"redirectPath\":\"/coffee_prefix_route1\",\"headers\":[\"version:v2\"]}]";
        js_content httpmatches.redirect;

    }

    location = /coffee {
        set $http_matches "[{\"redirectPath\":\"/coffee_prefix_route0\",\"headers\":[\"version:v2\"]},{\"redirectPath\":\"/coffee_prefix_route1\",\"headers\":[\"version:v2\"]}]";
        js_content httpmatches.redirect;

    }

where $http_matches includes duplicated matches (they test the same header for the same value).

if you put the conflicting rules above in different HTTPRoutes resources, you will duplicate matches too.

Also, it looks like we have a bug here. I would expect that for resolving conflicting rules, because the rule coffee-v2-svc goes before the rule coffee-1-svc in the HTTPRoute, it will win. @kate-osborn thoughts?

[sjberman]

@pleshakov Good find, I think the example you provided is different from what caused the original bug to be found. In that case, we had duplicate matches forwarding to the same place, so they were redundant. In this case, they are different backends, so technically not redundant, but more of a conflict defined by the user. The ordering may be a bug as you mentioned, and the duplicate matches should be taken care of in this case so only the winning backend is forwarded to.

Since this was intended to be an unscheduled, one-day task, I can close this PR and copy your comment into the bug so we can better schedule it in the future since there appears to be real work to be done here.