envoyproxy/envoy

HTTP/3 hot restart should be supported with eBPF

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#34,731 opened on Jun 13, 2024

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area/hot_restartarea/quicenhancementhelp wanted

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Description

In #19454, software-level support was added for HTTP/3 during hot restart, in which packets are forwarded from parent instance to child instance for the duration of the hot restart handoff.

Ideally this soft support could be bypassed using eBPF filters to deliver packets to the right instance first time.

To achieve this it would be necessary to:

  • have the QUIC eBPF rule direct packets to the newer instance if they don't have an instance ID in the QUIC header.
  • have the QUIC ID generator include encoding an instance ID.
  • have the QUIC eBPF rule direct packets to the specified instance if they do have an instance ID.
  • modify the hot restart behavior that causes the new instance to not listen until the parent is shut down, to listen immediately if there is eBPF support available. (Probably in pause())

Contributor guide

Research direction
Study the existing QUIC connection ID generator and eBPF rule implementations. Understand the hot restart handoff mechanism for UDP listeners. Then implement instance ID encoding, eBPF packet direction rules, and modify the listener pause behavior.
Tech stack
cpp
Domain
backend
Issue type
Feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
4
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
3-5 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
C++eBPFQUICEnvoy internals
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
20