envoyproxy/envoy

filter chain match extensibility

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#18,685 opened on Oct 19, 2021

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area/listenerarea/metadatahelp wanted

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Description

Filter chain matching algorithm is fairly rigid and has some flaws (e.g. the fixed ordering requires duplication of chains causing complexity in xDS code). It is also not extensible since it forces the use of real stream properties (like destination IP).

The proposal is to add a match condition based on dynamic metadata. We also propose to make metadata match first priority before destination port match so that it can be added incrementally. If a listener chooses to use metadata matching, that would take effect by overriding existing matching.

Contributor guide

Research direction
Examine the current filter chain matching implementation in Envoy and propose a design for dynamic metadata matching. Consider the implications on current ordering and xDS code.
Tech stack
cpp
Domain
api
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.
Over 1 week
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++Envoy internals
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
20