in_node_exporter_metrics: Skip ipv6 metrics collection when disabled

[piwai]

The stat() pre-check on /proc/net/sockstat6 will avoid having lots of "no such file or directory" errors when trying to collect ipv6 metrics on hosts where ipv6 is disabled.

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Fluent Bit is licensed under Apache 2.0, by submitting this pull request I understand that this code will be released under the terms of that license.

Summary by CodeRabbit

• Bug Fixes
  • Improved detection and error handling when IPv6 socket statistics are unavailable, avoiding erroneous failures on systems without IPv6 metrics.
  • Added safer path validation to prevent malformed IPv6 proc paths from causing errors and to skip missing files gracefully.

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• plugins/in_node_exporter_metrics/ne_sockstat_linux.c

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📝 Walkthrough

Walkthrough

Adds filesystem existence checks for IPv6 sockstat in the Linux node exporter metrics plugin: includes system headers and updates sockstat_update() to construct the IPv6 procfs path, validate its length, call stat(), skip IPv6 collection on ENOENT, or proceed to read/parse when present. (50 words)

Changes

IPv6 Availability Detection

Layer / File(s)	Summary
Header additions plugins/in_node_exporter_metrics/ne_sockstat_linux.c	Adds #include <sys/stat.h>, #include <errno.h>, and #include <limits.h> to support path sizing and stat()/errno handling.
Local state / buffers plugins/in_node_exporter_metrics/ne_sockstat_linux.c	Introduces path_len, ipv6_proc_path[PATH_MAX], and struct stat st in sockstat_update() for IPv6 proc path construction and stat() result storage.
IPv6 availability check plugins/in_node_exporter_metrics/ne_sockstat_linux.c	Constructs ctx->path_procfs + "/net/sockstat6", validates snprintf length (returns -1 on overflow), calls stat() and returns 0 (with debug log) if stat() fails with ENOENT, otherwise continues.
Parsing continuation plugins/in_node_exporter_metrics/ne_sockstat_linux.c	Keeps existing IPv6 parsing logic (tokenizing lines like TCP6:, UDP6:) but only executes it after the stat() guard and subject to ne_utils_file_read_lines() success.

Sequence Diagram(s)

(Skipped — changes are a small availability check and do not introduce multi-component sequential control flow warranting a diagram.)

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly related PRs

• in_node_exporter_metrics: add Linux sockstat collector #10718: Modifies the same ne_sockstat_linux.c to add headers and an IPv6 /proc path existence pre-check.

Suggested reviewers

• edsiper
• cosmo0920

Poem

🐰 I hop along the procfs lane,
I sniff sockstat6 for any gain,
If missing, I politely say "nope",
Else I read and parse with hope,
Metrics safe — and that's my refrain.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main change: adding a pre-check to skip IPv6 metrics collection when IPv6 is disabled, which aligns with the stat() check on /proc/net/sockstat6.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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[coderabbitai]

Actionable comments posted: 1

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Inline comments:
In `@plugins/in_node_exporter_metrics/ne_sockstat_linux.c`:
- Around line 172-175: The ipv6_proc_path buffer is fixed at 32 bytes which can
truncate path_procfs and the code currently treats any stat() error as IPv6
disabled; change ipv6_proc_path to use PATH_MAX, after snprintf() verify the
returned length fits (detect truncation) and handle that as an error, call
stat() and only treat ENOENT as "IPv6 disabled" (set ipv6_enabled = 0); for any
other stat() failures propagate/allow ne_utils_file_read_lines() to handle and
log them rather than returning early; update references in this function to use
the new PATH_MAX-sized ipv6_proc_path and the ENOENT check.

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• plugins/in_node_exporter_metrics/ne_sockstat_linux.c

[piwai]

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[edsiper]

thank you