dns: fix Windows SRV ECONNREFUSED regression by correcting c-ares fallback detection by NotVivek12 · Pull Request #61453 · nodejs/node

NotVivek12 · 2026-01-20T16:41:51Z

dns: fix Windows SRV ECONNREFUSED regression by correcting c-ares fallback detection

Summary

This PR fixes a regression introduced in Node.js v24.13.0 on Windows where DNS SRV lookups (commonly used by MongoDB connection strings) fail with ECONNREFUSED.

The issue stems from a change in c-ares behavior where the fallback resolver (loopback) is reported with port 53 rather than port 0. The existing Node.js glue layer strictly expected port 0 to identify a fallback scenario. Consequently, Node.js failed to detect the fallback, attempting to query a non-listening local stub resolver at 127.0.0.1:53 or [::1]:53.

Changes

**Updated ChannelWrap::EnsureServers**: Modified logic to treat any single loopback server (IPv4 127.0.0.1 or IPv6 ::1) as a fallback configuration, regardless of the port number reported by c-ares.
Proactive Validation: Added a call to EnsureServers() immediately before dispatching queries in the Query template to ensure the channel is correctly initialized before use.

Regression Details

Affected Version: Node.js v24.13.0
Platform: Windows 11 / Server
Error: Error: querySrv ECONNREFUSED
Last Known Good: v24.11.1

Reproduction

This issue is 100% reproducible on Windows with Node v24.13.0 using the following script (mimicking a standard Mongoose connection):

const express = require("express");
const mongoose = require("mongoose");
const app = express();

const connectDB = async () => {
  try {
    // Replace with a valid SRV URI
    const conn = await mongoose.connect("mongodb+srv://<user>:<pass>@cluster0.example.mongodb.net/db");
    console.log(`MongoDB Connected: ${conn.connection.host}`);
  } catch (error) {
    console.error('MongoDB connection failed:', error.message);
    process.exit(1);
  }
};
connectDB();

app.listen(3300, () => {
  console.log("mongodb connected at port 3300");
});

Output on v24.13.0:
Error: querySrv ECONNREFUSED _mongodb._tcp.cluster0.example.mongodb.net

Manual Verification

Built Node.js from source on Windows (VS 2022 Build Tools).
Ran the reproduction script above; connection succeeds.
Verified dns.getServers() no longer returns a single loopback address when the system resolver is active.

Risks

Low.

The logic only activates when c-ares discovers a single loopback server and the user has not manually called setServers().
If setServers() is called, is_servers_default_ becomes false, skipping this check entirely.
The logic is platform-agnostic but primarily resolves the specific behavior observed on Windows.

Workaround for users

Users on v24.13.0 can temporarily work around this by forcing DNS servers before connection:

require('dns').setServers(['8.8.8.8', '1.1.1.1']);

Checklist

Fixes regression in dns / c-ares
Tested on Windows
Tests added/verified (Manual verification performed)

nodejs-github-bot · 2026-01-20T16:41:57Z

Review requested:

@nodejs/net

Ethan-Arrowood · 2026-01-22T16:28:33Z

Do you think you could add a tests so we don't see this regression again in the future? Thanks!

NotVivek12 · 2026-01-26T13:08:19Z

Do you think you could add a tests so we don't see this regression again in the future? Thanks!

Absolutely, happy to add a test. Did you have a specific scenario in mind, or should I just cover the case from the original bug report?

NotVivek12 · 2026-01-26T13:18:37Z

Sure, I've added regression tests for this! Created two test files:

test-dns-resolvesrv.js- basic SRV resolution tests
test-dns-resolvesrv-econnrefused.js- specifically tests the ECONNREFUSED regression with MongoDB Atlas-style SRV lookups
Also added SRV record support to dns.js so we can mock SRV responses.

addaleax

Thank you @NotVivek12! This largely looks good, just have two questions here

test/cctest/test_hello_world.cc

src/cares_wrap.cc

codecov · 2026-01-27T17:42:25Z

Codecov Report

❌ Patch coverage is 11.11111% with 8 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.75%. Comparing base (f77a709) to head (358a6f9).
⚠️ Report is 14 commits behind head on main.

Files with missing lines	Patch %	Lines
src/cares_wrap.cc	11.11%	8 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #61453   +/-   ##
=======================================
  Coverage   89.74%   89.75%           
=======================================
  Files         674      674           
  Lines      204360   204365    +5     
  Branches    39265    39266    +1     
=======================================
+ Hits       183412   183424   +12     
+ Misses      13251    13241   -10     
- Partials     7697     7700    +3

Files with missing lines	Coverage Δ
src/cares_wrap.cc	`61.73% <11.11%> (+1.42%)`	⬆️

... and 23 files with indirect coverage changes

🚀 New features to boost your workflow:

❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
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addaleax · 2026-01-28T17:45:40Z

@NotVivek12 Can you look at the linter failures? Looks like there's some failing tasks

nodejs-github-bot · 2026-01-28T17:55:05Z

CI: https://ci.nodejs.org/job/node-test-pull-request/71106/

NotVivek12 · 2026-01-29T04:00:50Z

@NotVivek12 Can you look at the linter failures? Looks like there's some failing tasks

Hello, ive made the changes trying to resolve these errors. Hope it works.

package-lock.json

addaleax · 2026-01-30T11:49:19Z

Kicked off CI to see how well this does, but we'll probably need to remove package-lock.json again before this can be merged

github-actions · 2026-01-30T11:57:37Z

Failed to start CI

   ⚠  Commits were pushed since the last approving review:
   ⚠  - fix fix Windows SRV ECONNREFUSED regression
   ⚠  - Merge branch 'main' of https://github.com/NotVivek12/node
   ⚠  - Merge branch 'nodejs:main' into main
   ⚠  - add regression tests
   ⚠  - remove unintentional file
   ⚠  - Merge branch 'nodejs:main' into main
   ⚠  - Merge branch 'main' of https://github.com/NotVivek12/node
   ⚠  - fix CI/CD errors
   ⚠  - Merge branch 'nodejs:main' into main
   ⚠  - Merge branch 'main' of https://github.com/NotVivek12/node
   ✘  Refusing to run CI on potentially unsafe PR

https://github.com/nodejs/node/actions/runs/21514988012

NotVivek12 · 2026-02-01T09:28:02Z

Hi @addaleax i tried looking for what caused these tests to fail and couldnt figure out what the exact issues were, could you please help me figure out what these issues were caused by, so that i could come up with the fix for these.

addaleax

Sure, let's do another one and see if/where it fails

nodejs-github-bot · 2026-02-02T00:50:45Z

CI: https://ci.nodejs.org/job/node-test-pull-request/71159/

Anjan-99 · 2026-02-02T08:11:47Z

Getting this same error in version v22.22.0 i am using this to currently work. is there any fix ?

require('dns').setServers(['8.8.8.8', '1.1.1.1']);

nodejs-github-bot · 2026-02-03T00:50:35Z

Commit Queue failed

- Loading data for nodejs/node/pull/61453
✔  Done loading data for nodejs/node/pull/61453
----------------------------------- PR info ------------------------------------
Title      dns: fix Windows SRV ECONNREFUSED regression by correcting c-ares fallback detection (#61453)
   ⚠  Could not retrieve the email or name of the PR author's from user's GitHub profile!
Branch     NotVivek12:main -> nodejs:main
Labels     c++, cares, author ready, needs-ci
Commits    12
 - fix fix Windows SRV ECONNREFUSED regression
 - Merge branch 'main' of https://github.com/NotVivek12/node
 - Merge branch 'nodejs:main' into main
 - add regression tests
 - remove unintentional file
 - Merge branch 'nodejs:main' into main
 - Merge branch 'main' of https://github.com/NotVivek12/node
 - fix CI/CD errors
 - Merge branch 'nodejs:main' into main
 - Merge branch 'main' of https://github.com/NotVivek12/node
 - Merge branch 'nodejs:main' into main
 - remove the unintentional file
Committers 2
 - notvivek12 <vivekjoshi82015@gmail.com>
 - GitHub <noreply@github.com>
PR-URL: https://github.com/nodejs/node/pull/61453
Reviewed-By: Anna Henningsen <anna@addaleax.net>
------------------------------ Generated metadata ------------------------------
PR-URL: https://github.com/nodejs/node/pull/61453
Reviewed-By: Anna Henningsen <anna@addaleax.net>
--------------------------------------------------------------------------------
   ℹ  This PR was created on Tue, 20 Jan 2026 16:41:51 GMT
   ✔  Approvals: 1
   ✔  - Anna Henningsen (@addaleax): https://github.com/nodejs/node/pull/61453#pullrequestreview-3736915722
   ✔  Last GitHub CI successful
   ℹ  Last Full PR CI on 2026-02-02T00:50:45Z: https://ci.nodejs.org/job/node-test-pull-request/71159/
- Querying data for job/node-test-pull-request/71159/
✔  Build data downloaded
   ✔  Last Jenkins CI successful
--------------------------------------------------------------------------------
   ✔  No git cherry-pick in progress
   ✔  No git am in progress
   ✔  No git rebase in progress
--------------------------------------------------------------------------------
- Bringing origin/main up to date...
From https://github.com/nodejs/node
 * branch                  main       -> FETCH_HEAD
✔  origin/main is now up-to-date
- Downloading patch for 61453
From https://github.com/nodejs/node
 * branch                  refs/pull/61453/merge -> FETCH_HEAD
✔  Fetched commits as bdceaa211714..8327d4147038
--------------------------------------------------------------------------------
error: commit 0683f486da242ed3a754b8416b043eafa8a95277 is a merge but no -m option was given.
fatal: cherry-pick failed
[main de09739b90] fix fix Windows SRV ECONNREFUSED regression
 Author: notvivek12 <vivekjoshi82015@gmail.com>
 Date: Tue Jan 20 22:00:39 2026 +0530
 1 file changed, 21 insertions(+), 6 deletions(-)
   ✘  Failed to apply patches

https://github.com/nodejs/node/actions/runs/21612134326

NotVivek12 · 2026-02-03T01:15:31Z

@addaleax What could i do to fix this issue?

izaa · 2026-02-03T12:54:41Z

please fix this asap!

…lback detection Newer c-ares versions set tcp_port/udp_port to 53 instead of 0, which caused the loopback detection to fail. This fix: - Removes the port check from loopback detection - Adds IPv6 loopback (::1) support - Calls EnsureServers() before each DNS query PR-URL: nodejs#61453 Reviewed-By: Anna Henningsen <anna@addaleax.net>

NotVivek12 · 2026-02-03T16:57:17Z

please fix this asap!

I've fixed it

Anjan-99 · 2026-02-03T17:37:00Z

Can you explain how to fix that

nodejs-github-bot · 2026-02-04T06:34:08Z

CI: https://ci.nodejs.org/job/node-test-pull-request/71188/

nodejs-github-bot · 2026-02-04T11:19:13Z

CI: https://ci.nodejs.org/job/node-test-pull-request/71194/

Newer c-ares versions set tcp_port/udp_port to 53 instead of 0, which caused the loopback detection to fail. This fix: - Removes the port check from loopback detection - Adds IPv6 loopback (::1) support - Calls EnsureServers() before each DNS query PR-URL: #61453 Reviewed-By: Anna Henningsen <anna@addaleax.net>

addaleax · 2026-02-04T15:08:32Z

Landed in 8c32389 (adjusted commit message during merge to make it adhere to our linter rules)

nodejs-github-bot added c++ Issues and PRs that require attention from people who are familiar with C++. cares Issues and PRs related to the c-ares dependency or the cares_wrap binding. needs-ci PRs that need a full CI run. labels Jan 20, 2026

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NotVivek12 commented Jan 20, 2026

dns: fix Windows SRV ECONNREFUSED regression by correcting c-ares fallback detection

Summary

Changes

Regression Details

Reproduction

Manual Verification

Risks

Checklist

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