envoyproxy/envoy

Add support of additional %UPSTREAM% variables to custom headers

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#13,897 opened on Nov 4, 2020

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area/httpdesign proposalhelp wanted

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Description

One of our customers is using the Envoy tap filter to retrieve transport information and add them to their request/response headers, as documented here : https://www.envoyproxy.io/docs/envoy/latest/configuration/http/http_conn_man/headers.html#custom-request-response-headers

At this point, very few %UPSTREAM% variable names are supported : %UPSTREAM_METADATA([“namespace”, “key”, …])% %UPSTREAM_REMOTE_ADDRESS%

They wish additional %UPSTREAM% variables were supported, such as %UPSTREAM_LOCAL_ADDRESS%.

Thanks !

Contributor guide

Research direction
Look at the existing variable expansion code in Envoy (likely in source/common/http/header formatter.cc or similar) to understand how current %UPSTREAM ...% variables are handled, then add support for new variables like %UPSTREAM LOCAL ADDRESS% following the same pattern.
Tech stack
None
Domain
backendinfrastructure
Issue type
Feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
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++Git
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
65