fix: use connect_pass_through flag instead of workaround for TCP regression by penalosa · Pull Request #9506 · cloudflare/workers-sdk

penalosa · 2025-06-06T11:07:18Z

This PR reverts the workaround from #9246 and implements the proper fix for the TCP connection regression by adding the connect_pass_through compatibility flag to the globalOutbound worker.

Background

In Miniflare v4.15.0, a global outbound service was introduced to strip CF-Connecting-IP headers
This triggered a bug in workerd where the connect() API and globalOutbound setting caused TCP ingress failures (issue Regression with TCP connections in 4.15.0 #9238)
@edmundhung added a workaround in fix: strips CF-Connecting-IP header within Wrangler #9246 that disabled the global outbound approach and used a JavaScript injection instead
@kentonv fixed the underlying issue in Implement connect_pass_through experimental compat flag. workerd#4171 by adding the connect_pass_through compatibility flag

Changes

Reverted the workaround: Used git revert d033a7da1 to cleanly remove Edmund's temporary fix
Added the proper fix: Include compatibilityFlags: ["connect_pass_through"] in the outbound service worker configuration in packages/miniflare/src/plugins/core/index.ts:840

Impact

Fixes the TCP connection regression that was affecting local development
Removes the temporary JavaScript injection workaround
Uses the cleaner global outbound service approach as originally intended
Requires workerd version that includes Implement connect_pass_through experimental compat flag. workerd#4171

Tests
- TODO (before merge)
- Tests included
- Tests not necessary because:
Wrangler / Vite E2E Tests CI Job required? (Use "e2e" label or ask maintainer to run separately)
- I don't know
- Required
- Not required because: only affects Miniflare internal worker configuration
Public documentation
- TODO (before merge)
- Cloudflare docs PR(s):
- Documentation not necessary because: internal implementation change, no user-facing API changes
Wrangler V3 Backport
- TODO (before merge)
- Wrangler PR: Backport changes from #9506 #9618
- Not necessary because:

🤖 Generated with Claude Code

changeset-bot · 2025-06-06T11:07:23Z

🦋 Changeset detected

Latest commit: 21f899f

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 5 packages

Name	Type
miniflare	Patch
wrangler	Patch
@cloudflare/pages-shared	Patch
@cloudflare/vite-plugin	Patch
@cloudflare/vitest-pool-workers	Patch

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pkg-pr-new · 2025-06-06T11:09:51Z

create-cloudflare

npm i https://pkg.pr.new/create-cloudflare@9506

@cloudflare/kv-asset-handler

npm i https://pkg.pr.new/@cloudflare/kv-asset-handler@9506

miniflare

npm i https://pkg.pr.new/miniflare@9506

@cloudflare/pages-shared

npm i https://pkg.pr.new/@cloudflare/pages-shared@9506

@cloudflare/unenv-preset

npm i https://pkg.pr.new/@cloudflare/unenv-preset@9506

@cloudflare/vite-plugin

npm i https://pkg.pr.new/@cloudflare/vite-plugin@9506

@cloudflare/vitest-pool-workers

npm i https://pkg.pr.new/@cloudflare/vitest-pool-workers@9506

@cloudflare/workers-editor-shared

npm i https://pkg.pr.new/@cloudflare/workers-editor-shared@9506

wrangler

npm i https://pkg.pr.new/wrangler@9506

commit: 21f899f

petebacondarwin

Claude forgot a changeset

packages/wrangler/src/__tests__/api/startDevWorker/startWorker.test.ts

penalosa · 2025-06-06T11:44:06Z

The deleted test (packages/wrangler/src/__tests__/api/startDevWorker/startWorker.test.ts) was specifically testing the JavaScript injection workaround that we're removing. Since we now use the proper workerd compatibility flag fix, this test is no longer relevant. The CF-Connecting-IP functionality is already covered by the existing Miniflare tests.

github-actions · 2025-06-06T11:45:06Z

Failed to automatically backport this PR's changes to Wrangler v3. Please manually create a PR targeting the v3-maintenance branch with your changes. Thank you for helping us keep Wrangler v3 supported!

Depending on your changes, running git rebase --onto v3-maintenance main penalosa/use-new-compat-flag might be a good starting point.

Notes:

your PR branch should be named v3-backport-9506
add the skip-v3-pr label to the current PR to stop this workflow from failing

This reverts commit d033a7d.

…orker Add the connect_pass_through compatibility flag to the outbound service worker that strips CF-Connecting-IP headers. This resolves the TCP connection regression that was introduced when using globalOutbound service with workerd's connect() API. The connect_pass_through flag was added in workerd PR #4171 to fix the underlying issue, allowing us to remove the JavaScript injection workaround and use the cleaner global outbound approach. 🤖 Generated with [Claude Code](https://claude.ai/code) Co-Authored-By: Claude <noreply@anthropic.com>

…geset - Add 'experimental' compat flag alongside 'connect_pass_through' - Add changeset for the TCP regression fix - The deleted test was specific to the workaround we're replacing

penalosa requested a review from a team as a code owner June 6, 2025 11:07

workers-devprod added this to workers-sdk Jun 6, 2025

github-project-automation bot moved this to Untriaged in workers-sdk Jun 6, 2025

petebacondarwin reviewed Jun 6, 2025

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packages/wrangler/src/__tests__/api/startDevWorker/startWorker.test.ts Show resolved Hide resolved

petebacondarwin approved these changes Jun 9, 2025

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github-project-automation bot moved this from Untriaged to Approved in workers-sdk Jun 9, 2025

penalosa mentioned this pull request Jun 16, 2025

Backport changes from #9506 #9618

Closed

9 tasks

penalosa and others added 7 commits June 16, 2025 15:50

Revert "fix: strips CF-Connecting-IP header within Wrangler (#9246)"

a3e7406

This reverts commit d033a7d.

fix: add connect_pass_through and experimental compat flags, add chan…

4891c31

…geset - Add 'experimental' compat flag alongside 'connect_pass_through' - Add changeset for the TCP regression fix - The deleted test was specific to the workaround we're replacing

human fixups

a16e53f

fix lockfile

2342afd

fix lockfile

fb2b7a0

fix lockfile

21f899f

penalosa force-pushed the penalosa/use-new-compat-flag branch from cb612f0 to 21f899f Compare June 16, 2025 14:52

penalosa added the skip-v3-pr label Jun 16, 2025

penalosa added this pull request to the merge queue Jun 16, 2025

Merged via the queue into main with commit 36113c2 Jun 16, 2025
31 of 36 checks passed

penalosa deleted the penalosa/use-new-compat-flag branch June 16, 2025 15:11

github-project-automation bot moved this from Approved to Done in workers-sdk Jun 16, 2025

workers-devprod mentioned this pull request Jun 16, 2025

Version Packages #9579

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penalosa mentioned this pull request Jul 15, 2025

wip: strip cf-connecting-ip header #8471

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fix: use connect_pass_through flag instead of workaround for TCP regression#9506

fix: use connect_pass_through flag instead of workaround for TCP regression#9506
penalosa merged 7 commits intomainfrom
penalosa/use-new-compat-flag

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