add the catch all case (#623)

istio/1.12/patches/istio/20231104-gatewayapi-catchall.patch

@@ -0,0 +1,50 @@
+diff -Naur istio/pilot/pkg/config/kube/gateway/conversion.go istio-new/pilot/pkg/config/kube/gateway/conversion.go
+--- istio/pilot/pkg/config/kube/gateway/conversion.go	2023-11-03 20:09:38.000000000 +0800
++++ istio-new/pilot/pkg/config/kube/gateway/conversion.go	2023-11-03 20:02:26.000000000 +0800
+@@ -165,6 +165,34 @@
+ 	return result
+ }
+
++// isCatchAll returns true if HTTPMatchRequest is a catchall match otherwise
++// false. Note - this may not be exactly "catch all" as we don't know the full
++// class of possible inputs As such, this is used only for optimization.
++func isCatchAllMatch(m *istio.HTTPMatchRequest) bool {
++	catchall := false
++	if m.Uri != nil {
++		switch m := m.Uri.MatchType.(type) {
++		case *istio.StringMatch_Prefix:
++			catchall = m.Prefix == "/"
++		case *istio.StringMatch_Regex:
++			catchall = m.Regex == "*"
++		}
++	}
++	// A Match is catch all if and only if it has no match set
++	// and URI has a prefix / or regex *.
++	return catchall &&
++		len(m.Headers) == 0 &&
++		len(m.QueryParams) == 0 &&
++		len(m.SourceLabels) == 0 &&
++		len(m.WithoutHeaders) == 0 &&
++		len(m.Gateways) == 0 &&
++		m.Method == nil &&
++		m.Scheme == nil &&
++		m.Port == 0 &&
++		m.Authority == nil &&
++		m.SourceNamespace == ""
++}
++
+ // getURIRank ranks a URI match type. Exact > Prefix > Regex
+ func getURIRank(match *istio.HTTPMatchRequest) int {
+ 	if match.Uri == nil {
+@@ -212,6 +240,11 @@
+ 		} else if len(routes[j].Match) == 0 {
+ 			return true
+ 		}
++		if isCatchAllMatch(routes[i].Match[0]) {
++			return false
++		} else if isCatchAllMatch(routes[j].Match[0]) {
++			return true
++		}
+ 		// Only look at match[0], we always generate only one match
+ 		m1, m2 := routes[i].Match[0], routes[j].Match[0]
+ 		r1, r2 := getURIRank(m1), getURIRank(m2)