Gateway

 9 minute read

Gateway describes a load balancer operating at the edge of the mesh receiving incoming or outgoing HTTP/TCP connections. The specification describes a set of ports that should be exposed, the type of protocol to use, SNI configuration for the load balancer, etc.

For example, the following Gateway configuration sets up a proxy to act as a load balancer exposing port 80 and 9080 (http), 443 (https), 9443(https) and port 2379 (TCP) for ingress. The gateway will be applied to the proxy running on a pod with labels app: my-gateway-controller. While Istio will configure the proxy to listen on these ports, it is the responsibility of the user to ensure that external traffic to these ports are allowed into the mesh.

apiVersion: networking.istio.io/v1alpha3
kind: Gateway
metadata:
  name: my-gateway
  namespace: some-config-namespace
spec:
  selector:
    app: my-gateway-controller
  servers:
  - port:
      number: 80
      name: http
      protocol: HTTP
    hosts:
    - uk.bookinfo.com
    - eu.bookinfo.com
    tls:
      httpsRedirect: true # sends 301 redirect for http requests
  - port:
      number: 443
      name: https-443
      protocol: HTTPS
    hosts:
    - uk.bookinfo.com
    - eu.bookinfo.com
    tls:
      mode: SIMPLE # enables HTTPS on this port
      serverCertificate: /etc/certs/servercert.pem
      privateKey: /etc/certs/privatekey.pem
  - port:
      number: 9443
      name: https-9443
      protocol: HTTPS
    hosts:
    - "bookinfo-namespace/*.bookinfo.com"
    tls:
      mode: SIMPLE # enables HTTPS on this port
      credentialName: bookinfo-secret # fetches certs from Kubernetes secret
  - port:
      number: 9080
      name: http-wildcard
      protocol: HTTP
    hosts:
    - "*"
  - port:
      number: 2379 # to expose internal service via external port 2379
      name: mongo
      protocol: MONGO
    hosts:
    - "*"

The Gateway specification above describes the L4-L6 properties of a load balancer. A VirtualService can then be bound to a gateway to control the forwarding of traffic arriving at a particular host or gateway port.

For example, the following VirtualService splits traffic for https://uk.bookinfo.com/reviews, https://eu.bookinfo.com/reviews, http://uk.bookinfo.com:9080/reviews, http://eu.bookinfo.com:9080/reviews into two versions (prod and qa) of an internal reviews service on port 9080. In addition, requests containing the cookie “user: dev-123” will be sent to special port 7777 in the qa version. The same rule is also applicable inside the mesh for requests to the “reviews.prod.svc.cluster.local” service. This rule is applicable across ports 443, 9080. Note that http://uk.bookinfo.com gets redirected to https://uk.bookinfo.com (i.e. 80 redirects to 443).

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: bookinfo-rule
  namespace: bookinfo-namespace
spec:
  hosts:
  - reviews.prod.svc.cluster.local
  - uk.bookinfo.com
  - eu.bookinfo.com
  gateways:
  - some-config-namespace/my-gateway
  - mesh # applies to all the sidecars in the mesh
  http:
  - match:
    - headers:
        cookie:
          exact: "user=dev-123"
    route:
    - destination:
        port:
          number: 7777
        host: reviews.qa.svc.cluster.local
  - match:
    - uri:
        prefix: /reviews/
    route:
    - destination:
        port:
          number: 9080 # can be omitted if it's the only port for reviews
        host: reviews.prod.svc.cluster.local
      weight: 80
    - destination:
        host: reviews.qa.svc.cluster.local
      weight: 20

The following VirtualService forwards traffic arriving at (external) port 27017 to internal Mongo server on port 5555. This rule is not applicable internally in the mesh as the gateway list omits the reserved name mesh.

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: bookinfo-Mongo
  namespace: bookinfo-namespace
spec:
  hosts:
  - mongosvr.prod.svc.cluster.local # name of internal Mongo service
  gateways:
  - some-config-namespace/my-gateway # can omit the namespace if gateway is in same
                                       namespace as virtual service.
  tcp:
  - match:
    - port: 27017
    route:
    - destination:
        host: mongo.prod.svc.cluster.local
        port:
          number: 5555

It is possible to restrict the set of virtual services that can bind to a gateway server using the namespace/hostname syntax in the hosts field. For example, the following Gateway allows any virtual service in the ns1 namespace to bind to it, while restricting only the virtual service with foo.bar.com host in the ns2 namespace to bind to it.

apiVersion: networking.istio.io/v1alpha3
kind: Gateway
metadata:
  name: my-gateway
  namespace: some-config-namespace
spec:
  selector:
    app: my-gateway-controller
  servers:
  - port:
      number: 80
      name: http
      protocol: HTTP
    hosts:
    - "ns1/*"
    - "ns2/foo.bar.com"

Gateway

FieldTypeDescription
serversServer[]

REQUIRED: A list of server specifications.

selectormap<string, string>

REQUIRED: One or more labels that indicate a specific set of pods/VMs on which this gateway configuration should be applied. The scope of label search is restricted to the configuration namespace in which the the resource is present. In other words, the Gateway resource must reside in the same namespace as the gateway workload instance.

Port

Port describes the properties of a specific port of a service.

FieldTypeDescription
numberuint32

REQUIRED: A valid non-negative integer port number.

protocolstring

REQUIRED: The protocol exposed on the port. MUST BE one of HTTP|HTTPS|GRPC|HTTP2|MONGO|TCP|TLS. TLS implies the connection will be routed based on the SNI header to the destination without terminating the TLS connection.

namestring

Label assigned to the port.

Server

Server describes the properties of the proxy on a given load balancer port. For example,

apiVersion: networking.istio.io/v1alpha3
kind: Gateway
metadata:
  name: my-ingress
spec:
  selector:
    app: my-ingress-gateway
  servers:
  - port:
      number: 80
      name: http2
      protocol: HTTP2
    hosts:
    - "*"

Another example

apiVersion: networking.istio.io/v1alpha3
kind: Gateway
metadata:
  name: my-tcp-ingress
spec:
  selector:
    app: my-tcp-ingress-gateway
  servers:
  - port:
      number: 27018
      name: mongo
      protocol: MONGO
    hosts:
    - "*"

The following is an example of TLS configuration for port 443

apiVersion: networking.istio.io/v1alpha3
kind: Gateway
metadata:
  name: my-tls-ingress
spec:
  selector:
    app: my-tls-ingress-gateway
  servers:
  - port:
      number: 443
      name: https
      protocol: HTTPS
    hosts:
    - "*"
    tls:
      mode: SIMPLE
      serverCertificate: /etc/certs/server.pem
      privateKey: /etc/certs/privatekey.pem
FieldTypeDescription
portPort

REQUIRED: The Port on which the proxy should listen for incoming connections.

hostsstring[]

REQUIRED. One or more hosts exposed by this gateway. While typically applicable to HTTP services, it can also be used for TCP services using TLS with SNI. A host is specified as a dnsName with an optional namespace/ prefix. The dnsName should be specified using FQDN format, optionally including a wildcard character in the left-most component (e.g., prod/*.example.com). Set the dnsName to * to select all VirtualService hosts from the specified namespace (e.g.,prod/*).

The namespace can be set to * or ., representing any or the current namespace, respectively. For example, */foo.example.com selects the service from any available namespace while ./foo.example.com only selects the service from the namespace of the sidecar. The default, if no namespace/ is specified, is */, that is, select services from any namespace. Any associated DestinationRule in the selected namespace will also be used.

A VirtualService must be bound to the gateway and must have one or more hosts that match the hosts specified in a server. The match could be an exact match or a suffix match with the server’s hosts. For example, if the server’s hosts specifies *.example.com, a VirtualService with hosts dev.example.com or prod.example.com will match. However, a VirtualService with host example.com or newexample.com will not match.

NOTE: Only virtual services exported to the gateway’s namespace (e.g., exportTo value of *) can be referenced. Private configurations (e.g., exportTo set to .) will not be available. Refer to the exportTo setting in VirtualService, DestinationRule, and ServiceEntry configurations for details.

tlsServer.TLSOptions

Set of TLS related options that govern the server’s behavior. Use these options to control if all http requests should be redirected to https, and the TLS modes to use.

defaultEndpointstring

The loopback IP endpoint or Unix domain socket to which traffic should be forwarded to by default. Format should be 127.0.0.1:PORT or unix:///path/to/socket or unix://@foobar (Linux abstract namespace).

Server.TLSOptions

FieldTypeDescription
httpsRedirectbool

If set to true, the load balancer will send a 301 redirect for all http connections, asking the clients to use HTTPS.

modeServer.TLSOptions.TLSmode

Optional: Indicates whether connections to this port should be secured using TLS. The value of this field determines how TLS is enforced.

serverCertificatestring

REQUIRED if mode is SIMPLE or MUTUAL. The path to the file holding the server-side TLS certificate to use.

privateKeystring

REQUIRED if mode is SIMPLE or MUTUAL. The path to the file holding the server’s private key.

caCertificatesstring

REQUIRED if mode is MUTUAL. The path to a file containing certificate authority certificates to use in verifying a presented client side certificate.

credentialNamestring

The credentialName stands for a unique identifier that can be used to identify the serverCertificate and the privateKey. The credentialName appended with suffix “-cacert” is used to identify the CaCertificates associated with this server. Gateway workloads capable of fetching credentials from a remote credential store such as Kubernetes secrets, will be configured to retrieve the serverCertificate and the privateKey using credentialName, instead of using the file system paths specified above. If using mutual TLS, gateway workload instances will retrieve the CaCertificates using credentialName-cacert. The semantics of the name are platform dependent. In Kubernetes, the default Istio supplied credential server expects the credentialName to match the name of the Kubernetes secret that holds the server certificate, the private key, and the CA certificate (if using mutual TLS). Set the ISTIO_META_USER_SDS metadata variable in the gateway’s proxy to enable the dynamic credential fetching feature.

subjectAltNamesstring[]

A list of alternate names to verify the subject identity in the certificate presented by the client.

verifyCertificateSpkistring[]

An optional list of base64-encoded SHA-256 hashes of the SKPIs of authorized client certificates. Note: When both verifycertificatehash and verifycertificatespki are specified, a hash matching either value will result in the certificate being accepted.

verifyCertificateHashstring[]

An optional list of hex-encoded SHA-256 hashes of the authorized client certificates. Both simple and colon separated formats are acceptable. Note: When both verifycertificatehash and verifycertificatespki are specified, a hash matching either value will result in the certificate being accepted.

minProtocolVersionServer.TLSOptions.TLSProtocol

Optional: Minimum TLS protocol version.

maxProtocolVersionServer.TLSOptions.TLSProtocol

Optional: Maximum TLS protocol version.

cipherSuitesstring[]

Optional: If specified, only support the specified cipher list. Otherwise default to the default cipher list supported by Envoy.

Server.TLSOptions.TLSProtocol

TLS protocol versions.

NameDescription
TLS_AUTO

Automatically choose the optimal TLS version.

TLSV1_0

TLS version 1.0

TLSV1_1

TLS version 1.1

TLSV1_2

TLS version 1.2

TLSV1_3

TLS version 1.3

Server.TLSOptions.TLSmode

TLS modes enforced by the proxy

NameDescription
PASSTHROUGH

The SNI string presented by the client will be used as the match criterion in a VirtualService TLS route to determine the destination service from the service registry.

SIMPLE

Secure connections with standard TLS semantics.

MUTUAL

Secure connections to the downstream using mutual TLS by presenting server certificates for authentication.

AUTO_PASSTHROUGH

Similar to the passthrough mode, except servers with this TLS mode do not require an associated VirtualService to map from the SNI value to service in the registry. The destination details such as the service/subset/port are encoded in the SNI value. The proxy will forward to the upstream (Envoy) cluster (a group of endpoints) specified by the SNI value. This server is typically used to provide connectivity between services in disparate L3 networks that otherwise do not have direct connectivity between their respective endpoints. Use of this mode assumes that both the source and the destination are using Istio mTLS to secure traffic.

ISTIO_MUTUAL

Secure connections from the downstream using mutual TLS by presenting server certificates for authentication. Compared to Mutual mode, this mode uses certificates, representing gateway workload identity, generated automatically by Istio for mTLS authentication. When this mode is used, all other fields in TLSOptions should be empty.