From 982f980b86d6bab4d55452d17bf3f5eb04e5f01e Mon Sep 17 00:00:00 2001
From: Alan Somers <asomers@FreeBSD.org>
Date: Tue, 21 Jun 2022 12:51:14 -0600
Subject: [PATCH] prometheus_sysctl_exporter: ignore ENOENT for mibs specified
 on the CLI

They might belong to kernel modules not currently loaded, or to other
kernel versions.  Ignoring them allows the configuration to be shared
between multiple hosts.

MFC after:	2 weeks
Sponsored by:	Axcient
Reviewed by:	rew
Differential Revision: https://reviews.freebsd.org/D35540
---
 .../prometheus_sysctl_exporter.c                  | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/usr.sbin/prometheus_sysctl_exporter/prometheus_sysctl_exporter.c b/usr.sbin/prometheus_sysctl_exporter/prometheus_sysctl_exporter.c
index e452e305d2b..931d8e965d0 100644
--- a/usr.sbin/prometheus_sysctl_exporter/prometheus_sysctl_exporter.c
+++ b/usr.sbin/prometheus_sysctl_exporter/prometheus_sysctl_exporter.c
@@ -67,13 +67,12 @@ oid_get_root(struct oid *o)
 }
 
 /* Obtains the OID for a sysctl by name. */
-static void
+static bool
 oid_get_by_name(struct oid *o, const char *name)
 {
 
 	o->len = nitems(o->id);
-	if (sysctlnametomib(name, o->id, &o->len) != 0)
-		err(1, "sysctl(%s)", name);
+	return (sysctlnametomib(name, o->id, &o->len) == 0);
 }
 
 /* Returns whether an OID is placed below another OID. */
@@ -644,7 +643,15 @@ main(int argc, char *argv[])
 		for (i = 0; i < argc; ++i) {
 			struct oid o, root;
 
-			oid_get_by_name(&root, argv[i]);
+			if (!oid_get_by_name(&root, argv[i])) {
+				/*
+				 * Ignore trees provided as arguments that
+				 * can't be found.  They might belong, for
+				 * example, to kernel modules not currently
+				 * loaded.
+				 */
+				continue;
+			}
 			o = root;
 			do {
 				oid_print(&o, &on, print_descriptions, exclude, include, fp);