Configuring Gateway Network Topology (Development)
Configuring network topologies (Development)
Istio provides the ability to manage settings like X-Forwarded-For (XFF)
and X-Forwarded-Client-Cert
(XFCC), which are dependent on how the gateway workloads are deployed. This is currently an in-development feature. For more
information on X-Forwarded-For
, see the IETF’s RFC.
You might choose to deploy Istio ingress gateways in various network topologies (e.g. behind Cloud Load Balancers, a self-managed Load Balancer or directly expose the Istio ingress gateway to the Internet). As such, these topologies require different ingress gateway configurations for transporting correct client attributes like IP addresses and certificates to the workloads running in the cluster.
Configuration of XFF and XFCC headers is managed via MeshConfig
during Istio
installation or by adding a pod annotation. Note that the Meshconfig
configuration is a global setting for all gateway workloads, while pod annotations override the global setting on a per-workload basis.
To simplify configuring network topology during installation, create a single YAML file to pass to istioctl
:
$ cat <<EOF > topology.yaml
apiVersion: install.istio.io/v1alpha1
kind: IstioOperator
spec:
meshConfig:
defaultConfig:
gatewayTopology:
EOF
You can configure both of these settings using the proxy.istio.io/config
annotation to the Pod spec
of your Istio ingress gateway.
...
metadata:
annotations:
"proxy.istio.io/config": '{"gatewayTopology" : { "numTrustedProxies": 2 } }'
Configuring X-Forwarded-For Headers
Applications rely on reverse proxies to forward client attributes in a request, such as X-Forward-For
header. However, due to the variety of network
topologies Istio can be deployed in, you must set the number of trusted proxies deployed in front
of the Istio gateway proxy, so that the client address can be extracted correctly.
To set the number of trusted proxies, add the following to your topology.yaml
file.
apiVersion: install.istio.io/v1alpha1
kind: IstioOperator
spec:
meshConfig:
defaultConfig:
gatewayTopology:
numTrustedProxies: <VALUE>
For example, if you have a cloud based Load Balancer, a reverse proxy, and an Istio gateway proxy,
then <VALUE>
would be 2.
Example using X-Forwarded-For capability with httpbin
Specify
numTrustedProxies
as 2 either usingMeshConfig
or anproxy.istio.io/config
annotation. If you are usingMeshConfig
, run the following command to create a file namedtopology.yaml
and apply it to your cluster:$ cat <<EOF > topology.yaml apiVersion: install.istio.io/v1alpha1 kind: IstioOperator spec: meshConfig: defaultConfig: gatewayTopology: numTrustedProxies: 2 EOF $ istioctl install -f topology.yaml
Create an
httpbin
namespace:$ kubectl create namespace httpbin namespace/httpbin created
Set the
istio-injection
label toenabled
for sidecar injection:$ kubectl label --overwrite namespace httpbin istio-injection=enabled namespace/httpbin labeled
Deploy
httpbin
in thehttpbin
namespace:$ kubectl apply -n httpbin -f samples/httpbin/httpbin.yaml
Deploy a gateway associated with
httpbin
:$ kubectl apply -n httpbin -f samples/httpbin/httpbin-gateway.yaml
Set a local
GATEWAY_URL
environmental variable based on your Istio ingress gateway’s IP address:$ export GATEWAY_URL=$(kubectl -n istio-system get service istio-ingressgateway -o jsonpath='{.status.loadBalancer.ingress[0].ip}')
Run the following
curl
command to verify theX-Envoy-External-Address
andX-Forwarded-For
are set correctly:$ curl -H 'X-Forwarded-For: 56.5.6.7, 72.9.5.6, 98.1.2.3' $GATEWAY_URL/get?show_env=true { "args": { "show_env": "true" }, "headers": { ... "X-Envoy-External-Address": "72.9.5.6", ... "X-Forwarded-For": "56.5.6.7, 72.9.5.6, 98.1.2.3, <YOUR GATEWAY IP>", ... }, ... }
Note that the X-Envoy-External-Address
is set to the “second” from last address in the X-Forwarded-For
header
as per your numTrustedProxies
setting. Additionally, the gateway workload appends its IP in the
X-Forwarded-For
header before forwarding it to the upstream httpbin workload.
Configuring X-Forwarded-Client-Cert Headers
From Envoy’s documentation regarding XFCC:
To configure how XFCC Headers are handled, add the following to your topology.yaml
file.
apiVersion: install.istio.io/v1alpha1
kind: IstioOperator
spec:
meshConfig:
defaultConfig:
gatewayTopology:
forwardClientCertDetails: <ENUM_VALUE>
where ENUM_VALUE
can be of the following type.
ENUM_VALUE | |
---|---|
UNDEFINED | Field is not set. |
SANITIZE | Do not send the XFCC header to the next hop. This is the default value for a gateway. |
FORWARD_ONLY | When the client connection is mTLS (Mutual TLS), forward the XFCC header in the request. |
APPEND_FORWARD | When the client connection is mTLS, append the client certificate information to the request’s XFCC header and forward it. |
SANITIZE_SET | When the client connection is mTLS, reset the XFCC header with the client certificate information and send it to the next hop. |
ALWAYS_FORWARD_ONLY | Always forward the XFCC header in the request, regardless of whether the client connection is mTLS. |
See the Envoy documentation for examples of using this capability.