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GeezerVison is showing github.com — dns: fix crash on setServers with port 0 by lazerg · Pull Request #65009 · nodejs/node

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@lazerg

@lazerg lazerg commented Aug 4, 2026

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dns.setServers(['1.1.1.1:0']) aborts the process:

Assertion failed: portValue->Int32Value(env->context()).FromJust()

SetServers() in src/cares_wrap.cc checked the port with CHECK(portValue->Int32Value(env->context()).FromJust()). That asserts the port value is non-zero, not that the conversion succeeded, so a port of 0 trips it. The family value had the same problem. Both now use Maybe::To(), like the rest of the file.

c-ares already treats port 0 as "use the default port", so 1.1.1.1:0 becomes 1.1.1.1:53. [::1]:0 behaved that way already, since the bracketed-IPv6 branch in lib/internal/dns/utils.js coerces 0 to 53 before it ever reaches C++.

Fixes: #65006

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@lazerg
dns: fix crash on setServers with port 0
948d758 
Signed-off-by: Lazizbek Ergashev <[email protected]>
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nodejs-github-bot commented Aug 4, 2026

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Review requested:

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@nodejs-github-bot 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 Aug 4, 2026
Renegade334
Renegade334 reviewed Aug 4, 2026
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Comment thread src/cares_wrap.cc Resolved

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@lazerg
dns: keep type assertions in SetServers
42c89ee
Renegade334
Renegade334 approved these changes Aug 4, 2026
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👍

Note that this preserves the previous behaviour of crashing the process if the port was greater than INT_MAX. Indeed, even below that point, any port value greater than 65535 overflows:

> dns.setServers(['1.1.1.1:65535', '1.1.1.1:65536', '1.1.1.1:65537'])
> dns.getServers()
[ '1.1.1.1:65535', '1.1.1.1', '1.1.1.1:1' ]

If you're happy, I think it would be a worthwhile addition to add validation to the port values, either as part of this PR or as a follow-up PR?

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@lazerg

lazerg commented Aug 4, 2026

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Thanks for the review. I couldn't reproduce the wraparound though — on this branch (c-ares 1.34.8, bundled, untouched by this diff):

> dns.setServers(['1.1.1.1:65535', '1.1.1.1:65536', '1.1.1.1:65537'])
Uncaught Error [ERR_DNS_SET_SERVERS_FAILED]: c-ares failed to set servers: "Misformatted string" [...]

ares_parse_port() (deps/cares/src/lib/str/ares_str.c) already caps at 65535 via ares_str_parse_uint(str, 65535UL, &val), so the CSV parse fails and the whole call throws, restoring the previous server list. That check is unrelated to this PR's diff, so it should behave the same on main.

Might be version-dependent on your end. Since I can't reproduce silent corruption on the current bundled c-ares, I'd rather not scope-creep this PR with validatePort() unless you still want the earlier/clearer JS-side error as its own improvement — happy to open that as a follow-up if so.
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mcollina
mcollina approved these changes Aug 4, 2026
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lgtm

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@mcollina mcollina added the request-ci Add this label to start a Jenkins CI on a PR. Only starts once the PR has an approving review. label Aug 4, 2026
@Renegade334 Renegade334 added author ready PRs with CI started, the required approvals, and no outstanding review comments. commit-queue-squash PRs the Commit Queue should land as one squashed commit. labels Aug 4, 2026
@github-actions github-actions Bot removed the request-ci Add this label to start a Jenkins CI on a PR. Only starts once the PR has an approving review. label Aug 4, 2026
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@codecov

codecov Bot commented Aug 4, 2026 •
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Codecov Report

❌ Patch coverage is 50.00000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.29%. Comparing base (ece8bbe) to head (42c89ee).
⚠️ Report is 19 commits behind head on main.

Files with missing lines Patch % Lines
src/cares_wrap.cc 50.00% 0 Missing and 2 partials ⚠️
Additional details and impacted files 
@@            Coverage Diff             @@
##             main   #65009      +/-   ##
==========================================
- Coverage   90.29%   90.29%   -0.01%     
==========================================
  Files         762      759       -3     
  Lines      247646   247605      -41     
  Branches    46709    46672      -37     
==========================================
- Hits       223619   223564      -55     
- Misses      15485    15516      +31     
+ Partials     8542     8525      -17
Files with missing lines Coverage Δ
src/cares_wrap.cc 62.93% <50.00%> (ø)

... and 54 files with indirect coverage changes

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@Renegade334 Renegade334 mentioned this pull request Aug 4, 2026
dns: validate port range in setServers() #65021
Merged
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CI: https://ci.nodejs.org/job/node-test-pull-request/75482/
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@Renegade334 Renegade334 added the commit-queue PRs queued for automated landing through the Commit Queue. label Aug 4, 2026
pimterry
pimterry approved these changes Aug 5, 2026
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@nodejs-github-bot nodejs-github-bot removed the commit-queue PRs queued for automated landing through the Commit Queue. label Aug 6, 2026
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nodejs-github-bot merged commit ee64033 into nodejs:main Aug 6, 2026
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Landed in ee64033
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aduh95 pushed a commit that referenced this pull request Aug 13, 2026
@lazerg @aduh95
dns: fix crash on setServers with port 0
0b64b5d 
Signed-off-by: Lazizbek Ergashev <[email protected]>
PR-URL: #65009
Fixes: #65006
Reviewed-By: René <[email protected]>
Reviewed-By: Matteo Collina <[email protected]>
Reviewed-By: Tim Perry <[email protected]>
aduh95 pushed a commit that referenced this pull request Aug 25, 2026
@lazerg @aduh95
dns: fix crash on setServers with port 0
e9327d1 
Signed-off-by: Lazizbek Ergashev <[email protected]>
PR-URL: #65009
Fixes: #65006
Reviewed-By: René <[email protected]>
Reviewed-By: Matteo Collina <[email protected]>
Reviewed-By: Tim Perry <[email protected]>
@github-actions github-actions Bot mentioned this pull request Aug 25, 2026
2026-08-26, Version 26.8.0 (Current) #65551
Merged
aduh95 pushed a commit that referenced this pull request Aug 27, 2026
@lazerg @aduh95
dns: fix crash on setServers with port 0
37b9e9a 
Signed-off-by: Lazizbek Ergashev <[email protected]>
PR-URL: #65009
Fixes: #65006
Reviewed-By: René <[email protected]>
Reviewed-By: Matteo Collina <[email protected]>
Reviewed-By: Tim Perry <[email protected]>
@github-actions github-actions Bot mentioned this pull request Sep 7, 2026
2026-09-08, Version 24.21.0 'Krypton' (LTS) #65873
Merged
@robobun robobun mentioned this pull request Oct 29, 2026
dns: refuse setServers() ports above 65535 oven-sh/bun#47302
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@mcollina mcollina mcollina approved these changes
@pimterry pimterry pimterry approved these changes
@Renegade334 Renegade334 Renegade334 approved these changes

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author ready PRs with CI started, the required approvals, and no outstanding review comments. 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. commit-queue-squash PRs the Commit Queue should land as one squashed commit. needs-ci PRs that need a full CI run.

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dns.setServers.apply triggers SIGABRT when passed an address with port 0

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@lazerg @nodejs-github-bot @mcollina @pimterry @Renegade334
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