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Home > Posts > Supporting HTTP/3 at the ingress gateway in Istio

Supporting HTTP/3 at the ingress gateway in Istio

A few months ago I contributed experimental HTTP/3 support at the Istio ingress gateway (PR). For the HTTPS gateway servers which terminate the TLS at the gateway, it automatically adds a mirror HTTP/3 listener over QUIC provided that there is an open UDP port. If there is an HTTPS server on TCP port 443, then an HTTP/3 server is automatically created on UDP port 443 as illustrated in the diagram below. All you need to do is to flip a switch on pilot and open UDP ports.

Contents

Prerequistes

HTTP/3 over QUIC is so new as of writing this. QUIC was standardized this May end and HTTP/3 is not yet standardized (There is an IETF draft here). So creating custom builds, turning on alpha features are expected. I’m running Linux.

Kubernetes

This feature requires the supporting both TCP and UDP on the same port at the gateway. By default for Kubernetes services of type LoadBalancer this is not allowed. Since Kubernetes 1.20 there is alpha support. As documented here, it can be turned on with MixedProtocolLBSupport feature gate.

For this demo, I use Kind to provision a cluster with the following config

kind: Cluster
apiVersion: kind.x-k8s.io/v1alpha4
featureGates:
  MixedProtocolLBService: true # Very important
kubeadmConfigPatches:
- |
  apiVersion: kubeadm.k8s.io/v1beta2
  kind: ClusterConfiguration
  metadata:
    name: config
  apiServer:
    extraArgs:
      "service-account-issuer": "kubernetes.default.svc"
      "service-account-signing-key-file": "/etc/kubernetes/pki/sa.key"  
containerdConfigPatches:
  - |-
    [plugins."io.containerd.grpc.v1.cri".registry.mirrors."localhost:5000"]
      endpoint = ["http://kind-registry:5000"]

For the load balancer support, I’m using MetalLB with the following configuration. For setup and usage instructions, please refer to their documentation.

cURL

Testing the setup requires support for --http3 flag. If it is not supported out of the box, then you have to build it with Cloudflare Quiche support as documented here.

Istio

As of writing this Istio 1.12 is not yet released. So the pilot and proxy images should be built from the master branch.

Setup

Demo setup consists of

  1. Setting up Istio
  2. Deploying httpbin application
  3. Setting up gateway TLS certificates
  4. Configuring ingress gateway

Here is the demo setup

Setup

Setting up Istio

There are two important things

  1. Set PILOT_ENABLE_QUIC_LISTENERS environment variable to true on Istiod to turn on generating HTTP/3 mirror listener on the gateway
  2. Exposing both 443/UDP and 443/TCP - same port, different transport protocol

Here is an example IstioOperator spec.

apiVersion: install.istio.io/v1alpha1
kind: IstioOperator
metadata:
  name: install
spec:
  # Replace HUB and TAG to point to your
  # image repository and the custom image tag
  hub: localhost:5000
  tag: master
  components:
    ingressGateways:
    - name: istio-ingressgateway
      enabled: true
      k8s:
        service:
          ports:
          - name: status-port
            port: 15021
            targetPort: 15021
          # Both HTTPS and HTTP/3 must have
          # the same port number. Here it
          # is 443/TCP and 443/UDP
          - name: https
            port: 443
            targetPort: 8443
          - name: http3
            port: 443
            targetPort: 8443
            protocol: UDP
  values:
    pilot:
      # This is required to create mirror QUIC
      # listeners for TLS-terminated HTTPS listeners
      # on the gateway
      env:
        PILOT_ENABLE_QUIC_LISTENERS: true

Then install Istio

$ istioctl install -f istio.yaml -y

Deploying httpbin

I am using the sample httpbin provided in the main Istio repository (Link). Deploy it with good old kubectl. Make sure that Istio sidecars are injected. You can turn on istio sidecar injection at the namespace level by labeling it istio-injection=enabled or if you are using revisions (please use it to make upgrades smoother), then it is istio.io/rev=<revision-name>.

$ kubectl create namespace httpbin
$ kubectl label namespace httpbin istio-injection=enabled
$ kubectl -n httpbin apply -f \
  https://raw.githubusercontent.com/istio/istio/master/samples/httpbin/httpbin.yaml

Setting up TLS certificates for the gateway

HTTP/3 is over TLS only. In fact, using TLS is baked into QUIC, the underlying transport protocol as described in RFC-9000 and RFC-9001. So we need to generate and install certificates. For the demo, I’m using self-signed certificates.

  1. Parameters for the certificate (Like SAN). Save it as httpbin.cfg
[req]
default_bits       = 2048
prompt             = no
distinguished_name = req_distinguished_name
req_extensions     = san_reqext

[ req_distinguished_name ]
countryName         = XX
stateOrProvinceName = YY
organizationName    = QuicCorp

[ san_reqext ]
subjectAltName      = @alt_names

[alt_names]
DNS.0   = httpbin.quic-corp.com
  1. Generate TLS certificates and keys with the following script. Here, I’m using openssl. You can use other tools like cfssl as well.
$ openssl req -x509 -sha256 -nodes -days 365 -newkey rsa:4096 -subj \
    "/C=XX/ST=YY/O=QuicCorp" -keyout quiccorp-ca.key -out quiccorp-ca.crt

$ openssl req -out httpbin.csr -newkey rsa:2048 -nodes \
    -keyout httpbin.key -config httpbin.cnf

$ openssl x509 -req -days 365 -CA quiccorp-ca.crt -CAkey quiccorp-ca.key \
    -set_serial 0 -in httpbin.csr -out httpbin.crt \
    -extfile httpbin.cnf -extensions san_reqext
  1. Install the certificates
$ kubectl -n istio-system create secret tls httpbin-cred \
    --key=httpbin.key --cert=httpbin.crt

Istio configuration

Remember, HTTP/3 listener is generated automatically for TLS-terminated HTTPS listener. Currently, specifying that a port is HTTP/3-only is not yet supported. This is because HTTP/3 support is not widespread yet and the most common use case is for the clients like Google Chrome to become aware of HTTP/3 support with alt-svc HTTP header in the response when they first use HTTP/1.1 or HTTP/2 over TCP.

Configure the gateway. Notice that there is no explicit HTTP/3 related configuration

apiVersion: networking.istio.io/v1beta1
kind: Gateway
metadata:
  name: httpbin-gateway
spec:
  selector:
    app: istio-ingressgateway
    istio: ingressgateway
  servers:
  - port:
      number: 443
      name: https
      protocol: HTTPS
    hosts:
    - httpbin.quic-corp.com
    tls:
      mode: SIMPLE
      credentialName: httpbin-cred

Configure the route

apiVersion: networking.istio.io/v1beta1
kind: VirtualService
metadata:
  name: httpbin-route
spec:
  hosts:
  - httpbin.quic-corp.com
  gateways:
  - httpbin-gateway
  http:
  - name: httpbin-default-route
    route:
    - destination:
        host: httpbin.httpbin.svc.cluster.local
        port: 
          number: 8000

Once these routes are applied, check if two listeners are created

$ istioctl proxy-config listeners istio-ingressgateway-6fdcddbb8b-9rpkx.istio-system
ADDRESS PORT  MATCH                      DESTINATION
0.0.0.0 8443  SNI: httpbin.quic-corp.com Route: https.443.https.httpbin-gateway.istio-system
0.0.0.0 8443  SNI: httpbin.quic-corp.com Route: https.443.https.httpbin-gateway.istio-system
0.0.0.0 15021 ALL                        Inline Route: /healthz/ready*
0.0.0.0 15090 ALL                        Inline Route: /stats/prometheus*

Where did the other inbound listener come from? Let us dive deeper into the config. Let us start with checking listener names

$ istioctl proxy-config listeners istio-ingressgateway-6fdcddbb8b-9rpkx.istio-system \
    --address 0.0.0.0 --port 8443 -o json | jq -r '.[].name'
0.0.0.0_8443
udp_0.0.0.0_8443

UDP?? Remember that QUIC uses UDP. So could this be related to QUIC? Let us dive deeper. The output is huge and only the relevant part is shown here. So pipe it to a pager like less

{
  "transportSocket": {
      "name": "envoy.transport_sockets.quic",
      "typedConfig": {
          "@type": "type.googleapis.com/envoy.extensions.transport_sockets.quic.v3.QuicDownstreamTransport",
          "downstreamTlsContext": {
              "commonTlsContext": {
                  "tlsCertificateSdsSecretConfigs": [
                      {
                          "name": "kubernetes://httpbin-cred",
                          "sdsConfig": {
                              "ads": {},
                              "resourceApiVersion": "V3"
                          }
                      }
                  ],
                  "alpnProtocols": [
                      "h3"
                  ]
              },
              "requireClientCertificate": false
          }
      }
  }
}

Well…The one with udp prefix is a QUIC listener!

Demo time

First note down the address of the Ingress gateway

$ kubectl -n istio-system get svc
NAME                   TYPE           CLUSTER-IP      EXTERNAL-IP    PORT(S)                                       AGE
istio-ingressgateway   LoadBalancer   10.96.112.53    172.18.200.1   15021:32534/TCP,443:31597/TCP,443:31597/UDP   79m
istiod                 ClusterIP      10.96.255.123   <none>         15010/TCP,15012/TCP,443/TCP,15014/TCP         79m

$ export INGRESS_IP=172.18.200.1

I have a custom build of curl called qcurl which supports sending HTTP/3 request with --http3 flag. curl here is the standard curl available in the software repositories. For demo purposes, I’m skipping TLS certificate verification. Don’t this if it is not a demo.

Let us first send HTTP/2 request

$ curl -svk --http2 --resolve httpbin.quic-corp.com:443:$INGRESS_IP https://httpbin.quic-corp.com/headers
[ Output truncated ]
...
> GET /headers HTTP/2
> Host: httpbin.quic-corp.com
> user-agent: curl/7.76.1
> accept: */*
...
< HTTP/2 200 
< server: istio-envoy
< date: Wed, 27 Oct 2021 05:05:59 GMT
< content-type: application/json
< content-length: 601
< access-control-allow-origin: *
< access-control-allow-credentials: true
< x-envoy-upstream-service-time: 1
< alt-svc: h3=":443"; ma=86400
< 
{
  "headers": {
    "Accept": "*/*", 
    "Host": "httpbin.quic-corp.com", 
    "User-Agent": "curl/7.76.1", 
    "X-B3-Parentspanid": "819c2b2cab59bbe8", 
    "X-B3-Sampled": "0", 
    "X-B3-Spanid": "0462ac631afb5f84", 
    "X-B3-Traceid": "3fa44e3bbbcd21a3819c2b2cab59bbe8", 
    "X-Envoy-Attempt-Count": "1", 
    "X-Envoy-Internal": "true", 
    "X-Forwarded-Client-Cert": "By=spiffe://cluster.local/ns/httpbin/sa/httpbin;Hash=97bf9c90d4a5b9bb8f5da3e825dfa34f04631400420649394741807a320aa0a1;Subject=\"\";URI=spiffe://cluster.local/ns/istio-system/sa/istio-ingressgateway-service-account"
  }
}

Yayyy! It is working. In particular notice this header

alt-svc: h3=":443"; ma=86400

It indicates that HTTP/3 is supported. h3 is the ALPN sent with the TLS handshake. Clients supporting HTTP/3 can use this information to connect with QUIC for the future connections. Now, let us send an HTTP/3 request

$ qcurl -svk --http3 --resolve httpbin.quic-corp.com:443:$INGRESS_IP https://httpbin.quic-corp.com/headers
* Added httpbin.quic-corp.com:443:172.18.200.1 to DNS cache
* Hostname httpbin.quic-corp.com was found in DNS cache
*   Trying 172.18.200.1:443...
* Connect socket 5 over QUIC to 172.18.200.1:443
* Sent QUIC client Initial, ALPN: h3,h3-29,h3-28,h3-27
* Connected to httpbin.quic-corp.com () port 443 (#0)
* h3 [:method: GET]
* h3 [:path: /headers]
* h3 [:scheme: https]
* h3 [:authority: httpbin.quic-corp.com]
* h3 [user-agent: curl/7.78.0-DEV]
* h3 [accept: */*]
* Using HTTP/3 Stream ID: 0 (easy handle 0xa64260)
> GET /headers HTTP/3
> Host: httpbin.quic-corp.com
> user-agent: curl/7.78.0-DEV
> accept: */*
> 
< HTTP/3 200
< server: istio-envoy
< date: Wed, 27 Oct 2021 05:08:46 GMT
< content-type: application/json
< content-length: 642
< access-control-allow-origin: *
< access-control-allow-credentials: true
< x-envoy-upstream-service-time: 2
< alt-svc: h3=":443"; ma=86400
< 
{
  "headers": {
    "Accept": "*/*", 
    "Host": "httpbin.quic-corp.com", 
    "Transfer-Encoding": "chunked", 
    "User-Agent": "curl/7.78.0-DEV", 
    "X-B3-Parentspanid": "d9f3d78e3f6ddc5c", 
    "X-B3-Sampled": "0", 
    "X-B3-Spanid": "3f6c920b02a92b73", 
    "X-B3-Traceid": "d5c22cd31ddec119d9f3d78e3f6ddc5c", 
    "X-Envoy-Attempt-Count": "1", 
    "X-Envoy-Internal": "true", 
    "X-Forwarded-Client-Cert": "By=spiffe://cluster.local/ns/httpbin/sa/httpbin;Hash=97bf9c90d4a5b9bb8f5da3e825dfa34f04631400420649394741807a320aa0a1;Subject=\"\";URI=spiffe://cluster.local/ns/istio-system/sa/istio-ingressgateway-service-account"
  }
}

And….. IT WORKS!

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