L7 Traffic Path in Ambient Mesh
In my last blog, I introduced transparent traffic intercepting and L4 routing in Ambient mode. In this blog, I will show you how L7 traffic is routed.
Jimmy Song 
In my last blog, I introduced transparent traffic intercepting and L4 routing in Ambient mode. In this blog, I will show you how L7 traffic is routed.
The figure below shows the L7 network traffic path in ambient mode.
Note: The Waypoint proxy can be located on the same node as the application, and even all of the service and the Waypoint proxy can be on the same node. I draw them on three nodes for display purposes, but it has no significant impact on the actual traffic path, except that it is no longer sent to another node via eth0.
In the following section, we will explore the process in Figure 1 from a hands-on perspective.
Environments for Waypoint Proxy
Let’s continue to view the environment description using the ambient mode Istio deployed in the previous blog. To illustrate the L7 network routing, we need to create a Gateway on top of this.
kubectl apply -f - <<EOF
apiVersion: gateway.networking.k8s.io/v1alpha2
kind: Gateway
metadata:
name: productpage
annotations:
istio.io/service-account: bookinfo-productpage
spec:
gatewayClassName: istio-mesh
EOFAfter executing this command, a Waypoint proxy is created under the default namespace; in my environment, this pod is named bookinfo-productpage-waypoint-proxy-6f88c55d59-4dzdx and is specifically used to handle L7 traffic to the productpage service ( Service B), which I will call Waypoint proxy B.
The Waypoint proxy may be deployed in a different namespace, on a different node from the workload, or both. No matter where the Waypoint proxy is situated, the L7 traffic path is unaffected.
We will omit the sections of this blog dealing with intercepting inbound and outbound traffic because the way transparent traffic is handled in ambient mesh in L4 and L7 networks is similar. Details are available in the prior blog.
We will start directly with the traffic intercepted at Ztunnel A and then forward it to Envoy port 15006.
Outbound Traffic Routing on Ztunnel A
Use the following command to dump the Envoy proxy configuration on Ztunnel A:
kubectl exec -n istio-system ztunnel-hptxk -c istio-proxy -- curl "127.0.0.1:15000/config_dump?include_eds" <ztunnel-a-all-include-eds.jsonLooking at the Listener configuration section in the ztunnel-a-all-include-eds.json file, you will see the following configuration in the ztunnel_outbound listener, based on the matching rules between the destination port and the source IP.
{
"10.8.14.226": {
"matcher": {
"matcher_tree": {
"input": {
"name": "port",
"typed_config": {
"@type": "type.googleapis.com/envoy.extensions.matching.common_inputs.network.v3.DestinationPortInput"
}
},
"exact_match_map": {
"map": {
"9080": {
"action": {
"name": "spiffe://cluster.local/ns/default/sa/sleep_to_server_waypoint_proxy_spiffe://cluster.local/ns/default/sa/bookinfo-productpage",
"typed_config": {
"@type": "type.googleapis.com/google.protobuf.StringValue",
"value": "spiffe://cluster.local/ns/default/sa/sleep_to_server_waypoint_proxy_spiffe://cluster.local/ns/default/sa/bookinfo-productpage"
}
}
}
}
}
}
}
}
}10.8.14.226 is the Cluster IP of the target service, and the service port is 9080. The traffic will be routed to the spiffe://cluster.local/ns/default/sa/sleep_to_server_waypoint_proxy_spiffe://cluster.local/ns/default/sa/bookinfo-productpage cluster. Let’s look at the configuration of that cluster.
{
"version_info": "2022-11-17T03:27:45Z/82",
"cluster": {
"@type": "type.googleapis.com/envoy.config.cluster.v3.Cluster",
"name": "spiffe://cluster.local/ns/default/sa/sleep_to_server_waypoint_proxy_spiffe://cluster.local/ns/default/sa/bookinfo-productpage",
"type": "EDS",
"eds_cluster_config": {
"eds_config": {
"ads": {},
"initial_fetch_timeout": "0s",
"resource_api_version": "V3"
}
},
/* omit */
}The cluster is discovered using the EDS service. To view the EDS information for this cluster:
{
"@type": "type.googleapis.com/envoy.config.endpoint.v3.ClusterLoadAssignment",
"endpoints": [
{
"locality": {},
"lb_endpoints": [
{
"endpoint": {
"address": {
"socket_address": {
"address": "10.4.3.14",
"port_value": 15006
}
},
"health_check_config": {}
},
"health_status": "HEALTHY",
"load_balancing_weight": 1
}
]
}
],
"policy": {
"overprovisioning_factor": 140
}
}Note: The output cluster_name field is still missing here. See the GitHub issue.
Traffic is forwarded here directly to the Waypoint Proxy endpoint at 10.4.3.14:15006.
Traffic Routing Using Waypoint Proxy
Let’s dump the Envoy configuration into Waypoint Proxy B again.
kubectl exec -n default bookinfo-productpage-waypoint-proxy-6f88c55d59-4dzdx -c istio-proxy -- curl "127.0.0.1:15000/config_dump?include_eds"<waypoint-a-all-include-eds.jsonLook into the configuration of inbound_CONNECT_terminate listener:
{
"name": "inbound_CONNECT_terminate",
"active_state": {
"version_info": "2022-11-17T03:27:45Z/82",
"listener": {
"@type": "type.googleapis.com/envoy.config.listener.v3.Listener",
"name": "inbound_CONNECT_terminate",
"address": {
"socket_address": {
"address": "0.0.0.0",
"port_value": 15006
}
},
"filter_chains": [{
"filters": [{
"name": "capture_tls",
"typed_config": {
"@type": "type.googleapis.com/udpa.type.v1.TypedStruct",
"type_url": "type.googleapis.com/istio.tls_passthrough.v1.CaptureTLS"
}
},
{
"name": "envoy.filters.network.http_connection_manager",
"typed_config": {
"@type": "type.googleapis.com/envoy.extensions.filters.network.http_connection_manager.v3.HttpConnectionManager",
"stat_prefix": "inbound_hcm",
"route_config": {
"name": "local_route",
"virtual_hosts": [{
"name": "connect",
"domains": [
"*"
],
"routes": [{...},
{
"match": {
"headers": [{
"name": ":authority",
"exact_match": "10.8.14.226:9080"
}],
"connect_matcher": {}
},
"route": {
"cluster": "inbound-vip|9080|internal|productpage.default.svc.cluster.local",
"upgrade_configs": [{
"upgrade_type": "CONNECT",
"connect_config": {}
}]
}
}
]
}],
"validate_clusters": false
},
"http_filters": [...],
"tracing": {...},
"http2_protocol_options": {
"allow_connect": true
},
"use_remote_address": false,
"upgrade_configs": [{
"upgrade_type": "CONNECT"
}],
"stream_idle_timeout": "0s",
"normalize_path": true,
"request_id_extension": {...},
"path_with_escaped_slashes_action": "KEEP_UNCHANGED"
}
}
],
"transport_socket": {...},
"name": "inbound_CONNECT_terminate"
}]
},
"last_updated": "2022-11-17T06:24:51.467Z"
}
}TCP traffic destined for 10.8.14.226:9080 will be forwarded to the inbound-vip|9080|internal|productpage.default.svc.cluster.local cluster, and the HTTP method will be changed to CONNECT. To view the configuration of this cluster.
{
"version_info": "2022-11-17T03:27:45Z/82",
"cluster": {
"@type": "type.googleapis.com/envoy.config.cluster.v3.Cluster",
"name": "inbound-vip|9080|internal|productpage.default.svc.cluster.local",
"type": "STATIC",
"transport_socket": {
"name": "envoy.transport_sockets.internal_upstream",
"typed_config": {
"@type": "type.googleapis.com/envoy.extensions.transport_sockets.internal_upstream.v3.InternalUpstreamTransport",
"passthrough_metadata": [
{
"kind": {
"cluster": {}
},
"name": "istio"
}
],
"transport_socket": {
"name": "envoy.transport_sockets.raw_buffer",
"typed_config": {
"@type": "type.googleapis.com/envoy.extensions.transport_sockets.raw_buffer.v3.RawBuffer"
}
}
}
},
"common_lb_config": {},
"load_assignment": {
"cluster_name": "inbound-vip|9080|internal|productpage.default.svc.cluster.local",
"endpoints": [
{
"lb_endpoints": [
{
"endpoint": {
"address": {
"envoy_internal_address": {
"server_listener_name": "inbound-vip|9080||productpage.default.svc.cluster.local"
}
}
}
}
]
}
]
}
},
"last_updated": "2022-11-17T03:27:46.137Z"
}The endpoint of the cluster is an Envoy internal listener inbound-vip|9080||productpage.default.svc.cluster.local：
{
"name": "inbound-vip|9080||productpage.default.svc.cluster.local",
"active_state": {
"version_info": "2022-11-17T03:27:45Z/82",
"listener": {
"@type": "type.googleapis.com/envoy.config.listener.v3.Listener",
"name": "inbound-vip|9080||productpage.default.svc.cluster.local",
"filter_chains": [{
"filters": [{
"name": "restore_tls",
"typed_config": {
"@type": "type.googleapis.com/udpa.type.v1.TypedStruct",
"type_url": "type.googleapis.com/istio.tls_passthrough.v1.RestoreTLS"
}
},
{
"name": "envoy.filters.network.http_connection_manager",
"typed_config": {
"@type": "type.googleapis.com/envoy.extensions.filters.network.http_connection_manager.v3.HttpConnectionManager",
"stat_prefix": "inbound_0.0.0.0_9080",
"route_config": {
"name": "inbound-vip|9080|http|productpage.default.svc.cluster.local",
"virtual_hosts": [{
"name": "inbound|http|9080",
"domains": [
"*"
],
"routes": [{
"match": {
"prefix": "/"
},
"route": {
"cluster": "inbound-vip|9080|http|productpage.default.svc.cluster.local",
"timeout": "0s",
"max_stream_duration": {
"max_stream_duration": "0s",
"grpc_timeout_header_max": "0s"
}
},
"decorator": {
"operation": ":9080/*"
},
"name": "default"
}]
}],
"validate_clusters": false
}
},
"server_name": "istio-envoy",
"use_remote_address": false,
"forward_client_cert_details": "APPEND_FORWARD",
"set_current_client_cert_details": {
"subject": true,
"dns": true,
"uri": true
},
"upgrade_configs": [{
"upgrade_type": "websocket"
}],
"stream_idle_timeout": "0s",
"normalize_path": true,
"request_id_extension": {
"typed_config": {
"@type": "type.googleapis.com/envoy.extensions.request_id.uuid.v3.UuidRequestIdConfig",
"use_request_id_for_trace_sampling": true
}
},
"path_with_escaped_slashes_action": "KEEP_UNCHANGED"
}
],
"name": "inbound-vip|9080||productpage.default.svc.cluster.local-http"
}],
"listener_filters": [{
"name": "set_dst_address",
"typed_config": {
"@type": "type.googleapis.com/xds.type.v3.TypedStruct",
"type_url": "type.googleapis.com/istio.set_internal_dst_address.v1.Config",
"value": {}
}
},
{
"name": "envoy.filters.listener.metadata_to_peer_node",
"typed_config": {
"@type": "type.googleapis.com/udpa.type.v1.TypedStruct",
"type_url": "type.googleapis.com/istio.telemetry.metadatatopeernode.v1.Config"
}
}
],
"traffic_direction": "INBOUND",
"internal_listener": {}
},
"last_updated": "2022-11-17T03:27:46.300Z"
}
}The packets will be forwarded to the cluster inbound-vip|9080|http|productpage.default.svc.cluster.local:
{
"version_info": "2022-11-17T03:27:45Z/82",
"cluster": {
"@type": "type.googleapis.com/envoy.config.cluster.v3.Cluster",
"name": "inbound-vip|9080|http|productpage.default.svc.cluster.local",
"type":"EDS",
"eds_cluster_config": {
"eds_config": {
"ads": {},
"initial_fetch_timeout": "0s",
"resource_api_version": "V3"
},
"service_name": "inbound-vip|9080|http|productpage.default.svc.cluster.local"
},
"transport_socket": {
"name": "envoy.transport_sockets.internal_upstream",
"typed_config": {
"@type": "type.googleapis.com/envoy.extensions.transport_sockets.internal_upstream.v3.InternalUpstreamTransport",
"transport_socket": {
"name": "envoy.transport_sockets.raw_buffer",
"typed_config": {
"@type": "type.googleapis.com/envoy.extensions.transport_sockets.raw_buffer.v3.RawBuffer"
}
}
}
},
"metadata": {
"filter_metadata": {
"istio": {
"services": [{
"namespace": "default",
"name": "productpage",
"host": "productpage.default.svc.cluster.local"
}]
}
}
},
"common_lb_config": {}
},
"last_updated": "2022-11-17T03:27:46.138Z"
}The cluster type is EDS, check the Endpoint configuration:
{
"endpoint_config": {
"@type": "type.googleapis.com/envoy.config.endpoint.v3.ClusterLoadAssignment",
"cluster_name": "inbound-vip|9080|http|productpage.default.svc.cluster.local",
"endpoints": [{
"locality": {
"region": "us-west2",
"zone": "us-west2-a"
},
"lb_endpoints": [{
"endpoint": {
"address": {
"envoy_internal_address": {
"server_listener_name": "inbound-pod|9080||10.4.0.5"
}
},
"health_check_config": {}
},
"health_status": "HEALTHY",
"metadata": {
"filter_metadata": {
"istio": {
"workload": "productpage-v1;default;productpage;v1;Kubernetes"
}
}
},
"load_balancing_weight": 1
}]
}],
"policy": {
"overprovisioning_factor": 140
}
}
}The packets will be forwarded to the listener inbound-pod|9080||10.4.0.5:inbound-pod|9080||10.4.0.5 cluster
{
"name": "inbound-pod|9080||10.4.0.5",
"active_state": {
"version_info": "2022-11-17T03:27:45Z/82",
"listener": {
"@type": "type.googleapis.com/envoy.config.listener.v3.Listener",
"name": "inbound-pod|9080||10.4.0.5",
"filter_chains": [{
"filters": [{
"name": "restore_tls",
"typed_config": {
"@type": "type.googleapis.com/udpa.type.v1.TypedStruct",
"type_url": "type.googleapis.com/istio.tls_passthrough.v1.RestoreTLS"
}
},
{
"name": "envoy.filters.network.http_connection_manager",
"typed_config": {
"@type": "type.googleapis.com/envoy.extensions.filters.network.http_connection_manager.v3.HttpConnectionManager",
"stat_prefix": "inbound_0.0.0.0_9080",
"route_config": {
"name": "inbound-pod|9080||10.4.0.5",
"virtual_hosts": [{
"name": "inbound|http|9080",
"domains": [
"*"
],
"routes": [{
"match": {
"prefix": "/"
},
"route": {
"cluster": "inbound-pod|9080||10.4.0.5",
"timeout": "0s",
"max_stream_duration": {
"max_stream_duration": "0s",
"grpc_timeout_header_max": "0s"
}
},
"decorator": {
"operation": ":9080/*"
},
"name":"default"
}]
}],
"validate_clusters": false
},
/* omit */
}Packets are forwarded to the inbound-pod|9080||10.4.0.5 cluster:
{
"version_info": "2022-11-17T03:27:45Z/82",
"cluster": {
"@type": "type.googleapis.com/envoy.config.cluster.v3.Cluster",
"name": "inbound-pod|9080||10.4.0.5",
"type": "STATIC",
"transport_socket": {
"name": "envoy.transport_sockets.internal_upstream",
"typed_config": {
"@type": "type.googleapis.com/envoy.extensions.transport_sockets.internal_upstream.v3.InternalUpstreamTransport",
"passthrough_metadata": [
{
"kind": {
"host": {}
},
"name": "tunnel"
},
{
"kind": {
"host": {}
},
"name": "istio"
}
],
"transport_socket": {
"name": "envoy.transport_sockets.raw_buffer",
"typed_config": {
"@type": "type.googleapis.com/envoy.extensions.transport_sockets.raw_buffer.v3.RawBuffer"
}
}
}
},
"common_lb_config": {},
"load_assignment": {
"cluster_name": "inbound-pod|9080||10.4.0.5",
"endpoints": [
{
"lb_endpoints": [
{
"endpoint": {
"address": {
"envoy_internal_address": {
"server_listener_name": "inbound_CONNECT_originate",
"endpoint_id": "10.4.0.5:9080"
}
}
},
"metadata": {
"filter_metadata": {
"tunnel": {
"destination": "10.4.0.5:9080",
"address": "10.4.0.5:15008"
}
}
}
}
]
}
]
}
},
"last_updated": "2022-11-17T03:27:46.139Z"
}The cluster is of type STATIC, which contains the HBONE tunnel configuration (HTTP/2 CONNECT address is 10.4.0.15008), and the endpoint is the Envoy internal listener inbound_CONNECT_originate:
{
"name": "inbound_CONNECT_originate",
"active_state": {
"version_info": "2022-11-17T03:27:45Z/82",
"listener": {
"@type": "type.googleapis.com/envoy.config.listener.v3.Listener",
"name": "inbound_CONNECT_originate",
"filter_chains": [
{
"filters": [
{
"name": "envoy.filters.network.tcp_proxy",
"typed_config": {
"@type": "type.googleapis.com/envoy.extensions.filters.network.tcp_proxy.v3.TcpProxy",
"stat_prefix": "inbound_CONNECT_originate",
"cluster": "inbound_CONNECT_originate",
"tunneling_config": {
"hostname": "%DYNAMIC_METADATA(tunnel:destination)%",
"headers_to_add": [
{
"header": {
"key": "x-envoy-original-dst-host",
"value": "%DYNAMIC_METADATA(["tunnel", "destination"])%"
}
}
]
}
}
}
]
}
],
"use_original_dst": false,
"listener_filters": [
{
"name": "set_dst_address",
"typed_config": {
"@type": "type.googleapis.com/xds.type.v3.TypedStruct",
"type_url": "type.googleapis.com/istio.set_internal_dst_address.v1.Config",
"value": {}
}
}
],
"internal_listener": {}
},
"last_updated": "2022-11-17T03:27:46.339Z"
}
}Description:
- set_dst_address in listener_filters sets the destination address to 10.4.0.5.15008.
- A new header is added to the tunnel: x-envoy-original-dst-host, which has the value 10.4.0.5:9080.
- The endpoint of this cluster is the inbound_CONNECT_originate cluster.
Look into the inbound_CONNECT_originate cluster:
{
"version_info": "2022-11-17T03:27:45Z/82",
"cluster": {
"@type": "type.googleapis.com/envoy.config.cluster.v3.Cluster",
"name":"inbound_CONNECT_originate",
"type": "ORIGINAL_DST",
"connect_timeout": "2s",
"lb_policy": "CLUSTER_PROVIDED",
"cleanup_interval": "60s",
/* omit */
}This cluster, which is of type ORIGINAL_DST, creates a direct HBONE tunnel with the upstream in order to send packets to port 15008 on Pod B. The traffic intercepting and routing of the Ztunnel in Node B is the same as in L4, so I won’t go over it here.dsr5t
Summarizing the L7 Processing in Ambient Mesh
L7 traffic routing is based on L4 with the addition of the Waypoint proxy, which is more complex to handle in Envoy. We can also create HPAs to scale it dynamically.
Jimmy Song 
