Precedence not given to Exact headers

[mattbrandman]

Description:

What issue is being seen? Describe what should be happening instead of
the bug, for example: The expected value isn't returned, etc.
When all other things are equal but header matches are exact and regex there does not appear to be any specific precedence given to the exact match
Repro steps:
Include sample requests, environment, etc. All data and inputs
required to reproduce the bug.

apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
  name: server

spec:
  parentRefs:
    - name: gateway
      namespace: envoy-gateway
  hostnames:
    - test.backend.com
  rules:
  - backendRefs:
    - name: server
    matches:
      - headers:
        path:
          type: PathPrefix
          value: /
          - name: x-org-id
            value: test-org
            type: Exact

apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
  name: server

spec:
  parentRefs:
    - name: gateway
      namespace: envoy-gateway
  hostnames:
    - test.backend.com
  rules:
  - backendRefs:
    - name: server
    matches:
      - headers:
         path:
            type: PathPrefix
            value: /
            - name: x-org-id
              value: .*
              type: RegularExpression

Would expect top to match when org is test-org but it does not seem to be determinate or to be falling back to earliest / alphabetical at times.

My current workaround is basically redeclaring the header twice on the non-regex so the Largest number of headers match applies first to it

[arkodg]

the logic lives in https://github.com/envoyproxy/gateway/blob/main/internal/gatewayapi/sort.go
hoping someone can plug this as a test case in https://github.com/envoyproxy/gateway/tree/main/internal/gatewayapi/testdata and observe the order of the IR

[mattbrandman]

gateway/internal/gatewayapi/sort.go

Lines 66 to 80 in 3dbf9cc

	hCountI := len(x[i].HeaderMatches)
	hCountJ := len(x[j].HeaderMatches)
	if hCountI < hCountJ {
	return true
	}
	if hCountI > hCountJ {
	return false
	}
	// Equal case
	// 4. Sort based on the number of Query param matches.
	qCountI := len(x[i].QueryParamMatches)
	qCountJ := len(x[j].QueryParamMatches)
	return qCountI < qCountJ
	}

This seems to indicate that current behavior is simply counting number of matches not if they are Regex / exact / prefix

[kkk777-7]

I'd like to take this one on, if that's alright.

[arkodg]

thanks @kkk777-7 !