dns: do not consult hosts file in reverse lookups by Archkon · Pull Request #64268 · nodejs/node

Archkon · 2026-07-03T07:32:42Z

nodejs-github-bot · 2026-07-03T07:32:48Z

Review requested:

@nodejs/net

Renegade334 · 2026-07-03T09:16:12Z

Marking as semver-major (happy to be overruled). Although we do state in the small print that .reverse() shouldn't interrogate the hosts file, it feels like there's a decent chance of something out there relying on this behaviour.

nodejs-github-bot · 2026-07-05T15:31:20Z

CI: https://ci.nodejs.org/job/node-test-pull-request/74556/

addaleax

This should come with a changes: entry in the documentation as well, even if it only aligns behavior with what is already documented. It's a significant change, and semver-major seems appropriate.

Additionally, I would strongly recommend giving this a proper commit message. Commit messages should explain:

What happened
How it happened
Why it happened this way

Right now, this PR's commit message explains very little, but most importantly, it's not explaining why this change in behavior is better than e.g. a change of the documentation to just match current reality.

dns.reverse() is documented with dns.resolve*() as always performing DNS queries without using hosts file configuration. However, c-ares ares_gethostbyaddr() honors the channel lookup order, which can include the files source and cause reverse lookups to return entries from /etc/hosts. Configure c-ares resolver channels with ARES_OPT_LOOKUPS set to "b" so getHostByAddr uses DNS/PTR lookups only. This keeps dns.reverse() aligned with dns.resolve*() and preserves the distinction from system-resolution APIs such as dns.lookup() and dns.lookupService(). This is preferable to documenting the current behavior because hosts- file reverse lookup results are platform-dependent and expose hostent alias semantics rather than DNS PTR record semantics. Signed-off-by: Archkon <180910180+Archkon@users.noreply.github.com>

addaleax

I'll approve so CI can be kicked off but one thing that stands out a bit is that this, just based on the code changes, seems to also affect regular/non-reverse lookups? That seems like a pretty significant unintentional change

nodejs-github-bot · 2026-07-06T10:59:40Z

CI: https://ci.nodejs.org/job/node-test-pull-request/74586/

nodejs-github-bot · 2026-07-06T13:18:08Z

CI: https://ci.nodejs.org/job/node-test-pull-request/74593/

Renegade334 · 2026-07-21T18:51:05Z

This will require an additional @nodejs/tsc approval to land.

mcollina

This seems a regression in functionality and not really a fix for the given issue.

mcollina

lgtm

Renegade334 · 2026-07-26T18:12:19Z

Landed in 54a5095

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 Jul 3, 2026

Renegade334 added the semver-major PRs that contain breaking changes and should be released in the next major version. label Jul 3, 2026