func buildDestination()

in pkg/ingress/kube/gateway/istio/conversion.go [1146:1236]
80 lines of code
24 McCabe index (conditional complexity)

func buildDestination(ctx configContext, to k8s.BackendRef, ns string, enforceRefGrant bool) (*istio.Destination, *ConfigError) {
	// check if the reference is allowed
	if enforceRefGrant {
		refs := ctx.AllowedReferences
		if toNs := to.Namespace; toNs != nil && string(*toNs) != ns {
			if !refs.BackendAllowed(gvk.HTTPRoute, to.Name, *toNs, ns) {
				return &istio.Destination{}, &ConfigError{
					Reason:  InvalidDestinationPermit,
					Message: fmt.Sprintf("backendRef %v/%v not accessible to a route in namespace %q (missing a ReferenceGrant?)", to.Name, *toNs, ns),
				}
			}
		}
	}

	namespace := ptr.OrDefault((*string)(to.Namespace), ns)
	var invalidBackendErr *ConfigError
	if nilOrEqual((*string)(to.Group), "") && nilOrEqual((*string)(to.Kind), gvk.Service.Kind) {
		// Service
		if to.Port == nil {
			// "Port is required when the referent is a Kubernetes Service."
			return nil, &ConfigError{Reason: InvalidDestination, Message: "port is required in backendRef"}
		}
		if strings.Contains(string(to.Name), ".") {
			return nil, &ConfigError{Reason: InvalidDestination, Message: "serviceName invalid; the name of the Service must be used, not the hostname."}
		}
		hostname := fmt.Sprintf("%s.%s.svc.%s", to.Name, namespace, ctx.Domain)
		if ctx.Context.GetService(hostname, namespace, gvk.Service.Kind) == nil {
			invalidBackendErr = &ConfigError{Reason: InvalidDestinationNotFound, Message: fmt.Sprintf("backend(%s) not found", hostname)}
		}
		return &istio.Destination{
			// TODO: implement ReferencePolicy for cross namespace
			Host: hostname,
			Port: &istio.PortSelector{Number: uint32(*to.Port)},
		}, invalidBackendErr
	}
	if nilOrEqual((*string)(to.Group), features.MCSAPIGroup) && nilOrEqual((*string)(to.Kind), "ServiceImport") {
		// Service import
		hostname := fmt.Sprintf("%s.%s.svc.clusterset.local", to.Name, namespace)
		if !features.EnableMCSHost {
			// They asked for ServiceImport, but actually don't have full support enabled...
			// No problem, we can just treat it as Service, which is already cross-cluster in this mode anyways
			hostname = fmt.Sprintf("%s.%s.svc.%s", to.Name, namespace, ctx.Domain)
		}
		if to.Port == nil {
			// We don't know where to send without port
			return nil, &ConfigError{Reason: InvalidDestination, Message: "port is required in backendRef"}
		}
		if strings.Contains(string(to.Name), ".") {
			return nil, &ConfigError{Reason: InvalidDestination, Message: "serviceName invalid; the name of the Service must be used, not the hostname."}
		}
		if ctx.Context.GetService(hostname, namespace, "ServiceImport") == nil {
			invalidBackendErr = &ConfigError{Reason: InvalidDestinationNotFound, Message: fmt.Sprintf("backend(%s) not found", hostname)}
		}
		return &istio.Destination{
			Host: hostname,
			Port: &istio.PortSelector{Number: uint32(*to.Port)},
		}, invalidBackendErr
	}
	if nilOrEqual((*string)(to.Group), gvk.ServiceEntry.Group) && nilOrEqual((*string)(to.Kind), "Hostname") {
		// Hostname synthetic type
		if to.Port == nil {
			// We don't know where to send without port
			return nil, &ConfigError{Reason: InvalidDestination, Message: "port is required in backendRef"}
		}
		if to.Namespace != nil {
			return nil, &ConfigError{Reason: InvalidDestination, Message: "namespace may not be set with Hostname type"}
		}
		hostname := string(to.Name)
		if ctx.Context.GetService(hostname, namespace, "Hostname") == nil {
			invalidBackendErr = &ConfigError{Reason: InvalidDestinationNotFound, Message: fmt.Sprintf("backend(%s) not found", hostname)}
		}
		return &istio.Destination{
			Host: string(to.Name),
			Port: &istio.PortSelector{Number: uint32(*to.Port)},
		}, invalidBackendErr
	}
	if equal((*string)(to.Group), "networking.higress.io") && nilOrEqual((*string)(to.Kind), "Service") {
		var port *istio.PortSelector
		if to.Port != nil {
			port = &istio.PortSelector{Number: uint32(*to.Port)}
		}
		return &istio.Destination{
			Host: string(to.Name),
			Port: port,
		}, nil
	}
	return &istio.Destination{}, &ConfigError{
		Reason:  InvalidDestinationKind,
		Message: fmt.Sprintf("referencing unsupported backendRef: group %q kind %q", ptr.OrEmpty(to.Group), ptr.OrEmpty(to.Kind)),
	}
}