»Transparent Proxy ^Beta

Transparent proxy allows users to reach other services in the service mesh while ensuring that inbound and outbound traffic for services in the mesh are directed through the sidecar proxy. This makes it more likely that traffic is secure and only reaches intended destinations since the proxy can enforce security and policy like TLS and Service Intentions.

Previously, service mesh users would need to explicitly define upstreams for a service as a local listener on the sidecar proxy, and dial the local listener to reach the appropriate upstream. Users would also have to set intentions to allow specific services to talk to one another. Transparent proxying reduces this duplication, by determining upstreams implicitly from Service Intentions. Explicit upstreams are still supported in the proxy service registration on VMs and via the annotation in Kubernetes.

To support transparent proxying, Consul now supports a command consul connect redirect-traffic to redirect traffic through an inbound and outbound listener on the sidecar. It also watches Service Intentions and configures the Envoy proxy with the appropriate upstream IPs. If the default ACL policy is "allow", then Service Intentions are not required. In Consul on Kubernetes, the traffic redirection command is automatically set up via an init container.

»Prerequisites

Transparent proxy requires Consul >= 1.10.0.

»Kubernetes

• To use transparent proxy on Kubernetes, Consul-helm >= 0.32.0 and Consul-k8s >= 0.26.0 are required in addition to the Consul version requirements.
• If the default policy for ACLs is "deny", then Service Intentions should be set up to allow intended services to connect to each other. Otherwise, all Connect services can talk to all other services.

The Kubernetes integration takes care of registering Kubernetes services with Consul, injecting a sidecar proxy, and enabling traffic redirection.

»VMs

• For a service on a VM to be a part of the service mesh, it needs to run a Connect sidecar proxy.
• The consul connect redirect-traffic command needs to be run on the VM to set it up to redirect all inbound and outbound traffic to that VM through the sidecar proxy. Note that this will modify iptables rules on the host which can affect reachability of the VM unless the command is run within a network namespace.
• Services need to be registered with Consul.
• If the default policy for ACLs is "deny", then Service Intentions should be set up to allow intended services to connect to each other. Otherwise, all Connect services can talk to all other services.

»Configuration

»Kubernetes

Transparent proxy can be enabled in Kubernetes on the whole cluster via the Helm value:

connectInject:
  transparentProxy:
    defaultEnabled: true

It can also be enabled on a per service basis via the annotation consul.hashicorp.com/transparent-proxy=true on the Pod for each service:

apiVersion: v1
kind: Service
metadata:
  name: static-server
spec:
  selector:
    app: static-server
  ports:
    - protocol: TCP
      port: 80
      targetPort: 8080
---
apiVersion: v1
kind: ServiceAccount
metadata:
  name: static-server
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: static-server
spec:
  replicas: 1
  selector:
    matchLabels:
      app: static-server
  template:
    metadata:
      name: static-server
      labels:
        app: static-server
      annotations:
        'consul.hashicorp.com/connect-inject': 'true'
        'consul.hashicorp.com/transparent-proxy': 'true'
    spec:
      containers:
        - name: static-server
          image: hashicorp/http-echo:latest
          args:
            - -text="hello world"
            - -listen=:8080
          ports:
            - containerPort: 8080
              name: http
      serviceAccountName: static-server

»VMs

In other environments, transparent proxy can be enabled via Proxy Defaults and Service Defaults config entries, or via the proxy service registration:

# Proxy defaults apply to all proxies.
kind = "proxy-defaults"
name = "global"

mode = "transparent"
transparent_proxy {
  outbound_listener_port = 15001
}

# Service defaults apply to all instances of the web service.
kind = "service-defaults"
name = "web"

mode = "transparent"
transparent_proxy {
  outbound_listener_port = 15001
}

# Proxy service registrations apply to a single proxy instance.
name = "web-sidecar-proxy"
kind = "connect-proxy"
proxy {
  mode = "transparent"
  transparent_proxy {
    outbound_listener_port = 15001
  }
  destination_service_name = "web"
  local_service_port = 8080
}
port = 20000

Similar to mesh_gateway.mode, the new proxy mode will have the following string values:

• "" - The empty string represents the default value for the feature, and allows for the mode to be overridden by central configuration, like “service-defaults”.
• "direct" - Explicitly disables configuring transparent proxy, falling back to only configuring explicit upstreams.
• "transparent" - Explicitly enables configuring transparent proxy.

Additionally, the new Cluster config entry is scoped to the set of federated Consul datacenters and can be used to allow or block traffic to external destinations. This example shows blocking traffic to external destinations (outside of Consul's catalog):

kind = "cluster"
name = "cluster"

transparent_proxy {
  catalog_destinations_only = true
}

»Known Limitations

• For services on VMs, transparent proxy only supports one service per VM, or per network namespace. This is because the traffic redirection rules are applicable to the entire namespace (including the default namespace) and will direct all outbound traffic from the service to it’s sidecar proxy.
• Currently transparent proxy is only supported for services within a single Consul datacenter.

»Using Transparent Proxy

»Kubernetes

In Kubernetes, services can reach other services via their KubeDNS address or via Pod IPs, and that traffic will be transparently sent through the proxy. Connect services in Kubernetes are required to have a Kubernetes service selecting the Pods.

Transparent proxy is enabled by default in Consul-helm >=0.32.0. The Helm value used to enable/disable transparent proxy for all applications in a Kubernetes cluster is connectInject.transparentProxy.defaultEnabled.

Each Pod for the service will be configured with iptables rules to direct all inbound and outbound traffic through an inbound and outbound listener on the sidecar proxy. The proxy will be configured to know how to route traffic to the appropriate upstream services based on Service Intentions. This means Connect services no longer need to use the consul.hashicorp.com/connect-service-upstreams annotation to configure upstreams explicitly. Once the Service Intentions are set, they can simply address the upstream services using KubeDNS.

As of Consul-k8s >= 0.26.0 and Consul-helm >= 0.32.0, a Kubernetes service that selects application pods is required for Connect applications, i.e:

apiVersion: v1
kind: Service
metadata:
  name: sample-app
  namespace: default
spec:
  selector:
    app: sample-app
  ports:
    - protocol: TCP
      port: 80

In the example above, if another service wants to reach sample-app via transparent proxying, it can dial sample-app.default.svc.cluster.local, using KubeDNS. If ACLs with default "deny" policy are enabled, it also needs a ServiceIntention allowing it to talk to sample-app.

»VMs

To use transparent proxy on VMs, the service needs to be registered with Consul and a connect proxy needs to be added to the mesh on the VM. Then, traffic redirection rules need to be set up to direct inbound and outbound traffic through the sidecar connect proxy. Then, to enable transparent proxy mode to reach this service, you can set apply a service defaults config entry to configure the mode to be transparent as shown above in the Configuration section.

Now, once Service Intentions are set up, other services can reach this service's address via an address known to Consul, and the traffic will go through the proxy.