HTTP3 support on gateway

[kristiandrucker]

Description:
I'd like to ask about HTTP3 support in Envoy Gateway. Been looking in the official gateway-api sig as well as this repository but couldn't seem to find any mention of HTTP3.
Is it a feature that needs implementing, or is it just undocumented for now?

Relevant Links:

https://www.envoyproxy.io/docs/envoy/latest/intro/arch_overview/http/http3
https://gateway-api.sigs.k8s.io/references/spec/#gateway.networking.k8s.io/v1beta1.ProtocolType

[youngnick]

Gateway API hasn't defined HTTP3 standards yet, the tracking issue is kubernetes-sigs/gateway-api#687. This is probably blocked until there's more progress there.

[tanujd11]

I think there is some progress on the gateway API issue for HTTP3 support stating no API changes are required. This to be supported by controller implementations.

[tanujd11]

Hey @arkodg I would like to work on this.

[zirain]

thanks @tanujd11

[arkodg]

looks like the implementation in Envoy has been highlighted by
kubernetes-sigs/gateway-api#687 (comment) (thanks @alibo)

what is probably needed is a way for a user to opt in at the Gateway Listener (downstream) level to enable HTTP3 at the xds listener level (alt-svc header, udp listener, quic filter ... ) or should we enable this by default ?

@LanceEa ccing you since you've built this out in Emissary, any suggestion on how we can add this opt in knob using Gateway API ?

an interim solution could be to use EnvoyPatchPolicy post v0.5.0

[tanujd11]

@arkodg Istio creates mirror listener to all HTTP ports. It is behind a feature flag however. The connection is created by client and they can decide based on alt-svc header received whether to upgrade the connection to HTTP3. In the infra a UDP port needs to be opened for the same.

[arkodg]

yeah @tanujd11 , I see 3 options here for native support

• add a feature flag in the EnvoyProxy API that enables the mirror listener by default
• we use some information from the Gateway API fields such as Gateway protocol to specifically set a HTTP3 Listener
• request for new field to be introduced in the Gateway API to fulfill this case.