feat(gateway): add listener connection limits

api/mesh/v1alpha1/gateway.proto

@@ -82,6 +82,8 @@ message MeshGateway {
   }
 
   message Listener {
+    message Resources { uint32 connection_limit = 1; }
+
     enum Protocol {
       NONE = 0;
       TCP = 1;
@@ -121,6 +123,9 @@ message MeshGateway {
     // CrossMesh enables traffic to flow to this listener only from other
     // meshes.
     bool crossMesh = 6;
+
+    // Resources is used to specify listener-specific resource settings.
+    Resources resources = 7;
   }
 
   // Conf defines the desired state of MeshGateway.

docs/generated/resources/policy_meshgateway.md

@@ -103,5 +103,11 @@
         - `crossMesh` (optional)
 
             CrossMesh enables traffic to flow to this listener only from other
-            meshes.
+            meshes.    
+
+        - `resources` (optional)
+
+            Resources is used to specify listener-specific resource settings.    
+
+            - `connectionLimit` (optional)
 

pkg/core/resources/apis/mesh/gateway_validator.go

@@ -49,33 +49,52 @@ func (g *MeshGatewayResource) Validate() error {
 	return err.OrNil()
 }
 
-func validateListenerCompatibility(path validators.PathBuilder, listeners []*mesh_proto.MeshGateway_Listener) validators.ValidationError {
+type resourceLimits struct {
+	connectionLimits map[uint32]struct{}
+	listeners        []int
+}
+
+func validateListenerCollapsibility(path validators.PathBuilder, listeners []*mesh_proto.MeshGateway_Listener) validators.ValidationError {
 	protocolsForPort := map[uint32]map[string][]int{}
 	hostnamesForPort := map[uint32]map[string][]int{}
+	limitedListenersForPort := map[uint32]resourceLimits{}
 
-	for i, ep := range listeners {
-		protocols, ok := protocolsForPort[ep.GetPort()]
+	for i, listener := range listeners {
+		protocols, ok := protocolsForPort[listener.GetPort()]
 		if !ok {
 			protocols = map[string][]int{}
 		}
 
-		hostnames, ok := hostnamesForPort[ep.GetPort()]
+		hostnames, ok := hostnamesForPort[listener.GetPort()]
 		if !ok {
 			hostnames = map[string][]int{}
 		}
 
-		protocols[ep.GetProtocol().String()] = append(protocols[ep.GetProtocol().String()], i)
+		limitedListeners, ok := limitedListenersForPort[listener.GetPort()]
+		if !ok {
+			limitedListeners = resourceLimits{
+				connectionLimits: map[uint32]struct{}{},
+			}
+		}
+
+		protocols[listener.GetProtocol().String()] = append(protocols[listener.GetProtocol().String()], i)
 
 		// An empty hostname is the same as "*", i.e. matches all hosts.
-		hostname := ep.GetHostname()
+		hostname := listener.GetHostname()
 		if hostname == "" {
 			hostname = mesh_proto.WildcardHostname
 		}
 
 		hostnames[hostname] = append(hostnames[hostname], i)
 
-		hostnamesForPort[ep.GetPort()] = hostnames
-		protocolsForPort[ep.GetPort()] = protocols
+		if l := listener.GetResources().GetConnectionLimit(); l != 0 {
+			limitedListeners.listeners = append(limitedListeners.listeners, i)
+			limitedListeners.connectionLimits[l] = struct{}{}
+		}
+
+		hostnamesForPort[listener.GetPort()] = hostnames
+		protocolsForPort[listener.GetPort()] = protocols
+		limitedListenersForPort[listener.GetPort()] = limitedListeners
 	}
 
 	err := validators.ValidationError{}
@@ -104,6 +123,15 @@ func validateListenerCompatibility(path validators.PathBuilder, listeners []*mes
 		}
 	}
 
+	for _, listeners := range limitedListenersForPort {
+		if len(listeners.connectionLimits) <= 1 {
+			continue
+		}
+		for _, index := range listeners.listeners {
+			err.AddViolationAt(path.Index(index).Field("resources").Field("connectionLimit"), "conflicting values for this port")
+		}
+	}
+
 	return err
 }
 
@@ -198,7 +226,7 @@ func validateMeshGatewayConf(path validators.PathBuilder, conf *mesh_proto.MeshG
 			}))
 	}
 
-	err.Add(validateListenerCompatibility(path, conf.GetListeners()))
+	err.Add(validateListenerCollapsibility(path, conf.GetListeners()))
 
 	return err
 }

pkg/core/resources/apis/mesh/gateway_validator_test.go

@@ -86,6 +86,29 @@ conf:
     tags:
       name: http`,
 		),
+		Entry("listeners with connectionLimits", `
+type: MeshGateway
+name: gateway
+mesh: default
+selectors:
+  - match:
+      kuma.io/service: gateway
+tags:
+  product: edge
+conf:
+  listeners:
+  - protocol: HTTP
+    hostname: one.com
+    port: 99
+    resources:
+      connectionLimit: 2
+  - protocol: HTTP
+    hostname: two.com
+    port: 99
+    resources:
+      connectionLimit: 2
+`,
+		),
 	)
 
 	DescribeErrorCases(
@@ -398,7 +421,7 @@ conf:
     protocol: TCP
 `),
 
-		ErrorCases("hostname and protocol conflict",
+		ErrorCases("hostname, protocol and resource conflict",
 			[]validators.Violation{{
 				Field:   "conf.listeners[0]",
 				Message: "protocol conflicts with other listeners on this port",
@@ -411,6 +434,12 @@ conf:
 			}, {
 				Field:   "conf.listeners[1]",
 				Message: "multiple listeners for hostname on this port",
+			}, {
+				Field:   "conf.listeners[0].resources.connectionLimit",
+				Message: "conflicting values for this port",
+			}, {
+				Field:   "conf.listeners[1].resources.connectionLimit",
+				Message: "conflicting values for this port",
 			}}, `
 type: MeshGateway
 name: gateway
@@ -423,11 +452,15 @@ conf:
   - hostname: www-1.example.com
     port: 443
     protocol: TCP
+    resources:
+      connectionLimit: 2
   - hostname: www-1.example.com
     port: 443
     protocol: HTTPS
     tls:
       mode: PASSTHROUGH
+    resources:
+      connectionLimit: 1
 `),
 	)
 })

pkg/plugins/runtime/gateway/generator.go

@@ -5,6 +5,7 @@ import (
 	"sort"
 	"strings"
 
+	envoy_service_runtime_v3 "github.com/envoyproxy/go-control-plane/envoy/service/runtime/v3"
 	"github.com/pkg/errors"
 
 	mesh_proto "github.com/kumahq/kuma/api/mesh/v1alpha1"
@@ -15,6 +16,7 @@ import (
 	"github.com/kumahq/kuma/pkg/plugins/runtime/gateway/match"
 	"github.com/kumahq/kuma/pkg/plugins/runtime/gateway/merge"
 	"github.com/kumahq/kuma/pkg/plugins/runtime/gateway/route"
+	util_proto "github.com/kumahq/kuma/pkg/util/proto"
 	xds_context "github.com/kumahq/kuma/pkg/xds/context"
 	envoy_listeners "github.com/kumahq/kuma/pkg/xds/envoy/listeners"
 	envoy_names "github.com/kumahq/kuma/pkg/xds/envoy/names"
@@ -60,6 +62,7 @@ type GatewayListener struct {
 	// CrossMesh is important because for generation we need to treat such a
 	// listener as if we have HTTPS with the Mesh cert for this Dataplane
 	CrossMesh bool
+	Resources *mesh_proto.MeshGateway_Listener_Resources // TODO verify these don't conflict when merging
 }
 
 // GatewayListenerInfo holds everything needed to generate resources for a
@@ -197,6 +200,8 @@ func (g Generator) Generate(ctx xds_context.Context, proxy *core_xds.Proxy) (*co
 		return nil, errors.Wrap(err, "error generating listener info from Proxy")
 	}
 
+	var limits []RuntimeResoureLimitListener
+
 	for _, info := range listenerInfos {
 		// This is checked by the gateway validator
 		if !SupportsProtocol(info.Listener.Protocol) {
@@ -209,25 +214,50 @@ func (g Generator) Generate(ctx xds_context.Context, proxy *core_xds.Proxy) (*co
 		}
 		resources.AddSet(cdsResources)
 
-		ldsResources, err := g.generateLDS(ctx, info, info.HostInfos)
+		ldsResources, limit, err := g.generateLDS(ctx, info, info.HostInfos)
 		if err != nil {
 			return nil, err
 		}
 		resources.AddSet(ldsResources)
 
+		if limit != nil {
+			limits = append(limits, *limit)
+		}
+
 		rdsResources, err := g.generateRDS(ctx, info, info.HostInfos)
 		if err != nil {
 			return nil, err
 		}
 		resources.AddSet(rdsResources)
 	}
 
+	resources.Add(g.generateRTDS(limits))
+
 	return resources, nil
 }
 
-func (g Generator) generateLDS(ctx xds_context.Context, info GatewayListenerInfo, hostInfos []GatewayHostInfo) (*core_xds.ResourceSet, error) {
+func (g Generator) generateRTDS(limits []RuntimeResoureLimitListener) *core_xds.Resource {
+	layer := map[string]interface{}{}
+	for _, limit := range limits {
+		layer[fmt.Sprintf("envoy.resource_limits.listener.%s.connection_limit", limit.Name)] = limit.ConnectionLimit
+	}
+
+	res := &core_xds.Resource{
+		Name:   "gateway.listeners",
+		Origin: OriginGateway,
+		Resource: &envoy_service_runtime_v3.Runtime{
+			Name:  "gateway.listeners",
+			Layer: util_proto.MustStruct(layer),
+		},
+	}
+
+	return res
+}
+
+func (g Generator) generateLDS(ctx xds_context.Context, info GatewayListenerInfo, hostInfos []GatewayHostInfo) (*core_xds.ResourceSet, *RuntimeResoureLimitListener, error) {
 	resources := core_xds.NewResourceSet()
-	listenerBuilder := GenerateListener(info)
+
+	listenerBuilder, limit := GenerateListener(info)
 
 	var gatewayHosts []GatewayHost
 	for _, hostInfo := range hostInfos {
@@ -240,7 +270,7 @@ func (g Generator) generateLDS(ctx xds_context.Context, info GatewayListenerInfo
 	}
 	res, filterChainBuilders, err := g.FilterChainGenerators.FilterChainGenerators[protocol].Generate(ctx, info, gatewayHosts)
 	if err != nil {
-		return nil, err
+		return nil, limit, err
 	}
 	resources.AddSet(res)
 
@@ -250,11 +280,11 @@ func (g Generator) generateLDS(ctx xds_context.Context, info GatewayListenerInfo
 
 	res, err = BuildResourceSet(listenerBuilder)
 	if err != nil {
-		return nil, errors.Wrapf(err, "failed to build listener resource")
+		return nil, limit, errors.Wrapf(err, "failed to build listener resource")
 	}
 	resources.AddSet(res)
 
-	return resources, nil
+	return resources, limit, nil
 }
 
 func (g Generator) generateCDS(ctx xds_context.Context, info GatewayListenerInfo, hostInfos []GatewayHostInfo) (*core_xds.ResourceSet, error) {
@@ -323,6 +353,7 @@ func MakeGatewayListener(
 			listeners[0].GetPort(),
 		),
 		CrossMesh: listeners[0].CrossMesh,
+		Resources: listeners[0].GetResources(),
 	}
 
 	// Hostnames must be unique to a listener to remove ambiguity

pkg/plugins/runtime/gateway/listener_generator.go

@@ -27,7 +27,12 @@ func SupportsProtocol(p mesh_proto.MeshGateway_Listener_Protocol) bool {
 	}
 }
 
-func GenerateListener(info GatewayListenerInfo) *envoy_listeners.ListenerBuilder {
+type RuntimeResoureLimitListener struct {
+	Name            string
+	ConnectionLimit uint32
+}
+
+func GenerateListener(info GatewayListenerInfo) (*envoy_listeners.ListenerBuilder, *RuntimeResoureLimitListener) {
 	// TODO(jpeach) what we really need to do here is to
 	// generate a HTTP filter chain for each
 	// host on the same HTTPConnectionManager. Each HTTP filter
@@ -48,18 +53,29 @@ func GenerateListener(info GatewayListenerInfo) *envoy_listeners.ListenerBuilder
 		"protocol", protocol,
 	)
 
-	// TODO(jpeach) if proxy protocol is enabled, add the proxy protocol listener filter.
+	name := envoy_names.GetGatewayListenerName(info.Gateway.Meta.GetName(), protocol.String(), port)
 
+	var limits *RuntimeResoureLimitListener
+	if resources := info.Listener.Resources; resources != nil {
+		if resources.ConnectionLimit > 0 {
+			limits = &RuntimeResoureLimitListener{
+				Name:            name,
+				ConnectionLimit: resources.ConnectionLimit,
+			}
+		}
+	}
+
+	// TODO(jpeach) if proxy protocol is enabled, add the proxy protocol listener filter.
 	return envoy_listeners.NewListenerBuilder(info.Proxy.APIVersion).
 		Configure(
 			envoy_listeners.InboundListener(
-				envoy_names.GetGatewayListenerName(info.Gateway.Meta.GetName(), protocol.String(), port),
+				name,
 				address, port, core_xds.SocketAddressProtocolTCP),
 			// Limit default buffering for edge connections.
 			envoy_listeners.ConnectionBufferLimit(DefaultConnectionBuffer),
 			// Roughly balance incoming connections.
 			envoy_listeners.EnableReusePort(true),
 			// Always sniff for TLS.
 			envoy_listeners.TLSInspector(),
-		)
+		), limits
 }

pkg/plugins/runtime/gateway/listener_generator_test.go

@@ -3,7 +3,6 @@ package gateway_test
 import (
 	"path"
 
-	envoy_types "github.com/envoyproxy/go-control-plane/pkg/cache/types"
 	"github.com/envoyproxy/go-control-plane/pkg/cache/v3"
 	"github.com/ghodss/yaml"
 	. "github.com/onsi/ginkgo/v2"
@@ -84,7 +83,7 @@ data: LS0tLS1CRUdJTiBSU0EgUFJJVkFURSBLRVktLS0tLQpNSUlFb3dJQkFBS0NBUUVBM3ZWM1cvNX
 			snap, err := Do(gateway)
 			Expect(err).To(Succeed())
 
-			out, err := yaml.Marshal(MakeProtoResource(snap.Resources[envoy_types.Listener]))
+			out, err := yaml.Marshal(MakeProtoSnapshot(snap))
 			Expect(err).To(Succeed())
 
 			Expect(out).To(matchers.MatchGoldenYAML(path.Join("testdata", golden)))
@@ -218,5 +217,22 @@ conf:
     tags:
       name: example.com
 `),
+
+		Entry("should add connection limits",
+			"connection-limited-listener.yaml", `
+type: MeshGateway
+mesh: default
+name: default-gateway
+selectors:
+- match:
+    kuma.io/service: gateway-default
+conf:
+  listeners:
+  - port: 443
+    protocol: TCP
+    hostname: bar.example.com
+    resources:
+      connectionLimit: 10000
+`),
 	)
 })