envoyproxy/envoy

upstream ext_proc: option to wait for connection establishment

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#43540 opened on Feb 18, 2026

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enhancementext-prochelp wanted

Description

Title: upstream ext-proc: option to wait for connection establishment

Description: Upstream HTTP filters are not guaranteed to execute after upstream connection establishment: https://github.com/envoyproxy/envoy/issues/10455#issuecomment-1446519546.

Upstream HTTP filters may require information about the upstream peer (such as Peer Cert Subject/IP) and application-layer data from the request, to determine if a request may be proxied or blocked, especially in DFP use cases.

Ext-Proc filters can expose an option to wait for upstream connection establishment before sending headers and attributes to the ext-proc server, to ensure that this info is available.

Contributor guide

Tech stack
cpp
Domain
backendsecurityperformance
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.
mostly clear
Prerequisites
C++ programmingEnvoy architectureHTTP filter developmentprotobuf configuration
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
10
Research direction
Study the existing upstream HTTP filter and ext proc implementation in the Envoy codebase, particularly source/common/http/filter/ and source/extensions/filters/http/ext proc/. Understand how upstream connection establishment is sequenced with filter execution. Review the referenced issue #10455 comment for context. Propose a configuration field (e.g., 'wait for upstream connection') in the ext proc proto that delays sending headers until the upstream connection is established. Consider interactions with other filters and performance implications. Engage with maintainers on the issue to refine the design.