[monitoring-plugins] fixup! Rework maxfd/open_max to avoid unused ...

[Lorenz Kästle]

    Module: monitoring-plugins
    Branch: master
    Commit: 0162cb2d4f7040e3b2d48095182f87ce565866a5
    Author: RincewindsHat <12514511+RincewindsHat at users.noreply.github.com>
 Committer: Lorenz Kästle <lorenz.kaestle at netways.de>
      Date: Sun Mar  5 16:03:37 2023 +0100
       URL: https://www.monitoring-plugins.org/repositories/monitoring-plugins/commit/?id=0162cb2

fixup! Rework maxfd/open_max to avoid unused variables

---

 lib/maxfd.c | 26 ++++++++++++++++++++++++++
 lib/maxfd.h |  9 +++++++++
 2 files changed, 35 insertions(+)

diff --git a/lib/maxfd.c b/lib/maxfd.c
new file mode 100644
index 0000000..dcd4d3d
--- /dev/null
+++ b/lib/maxfd.c
@@ -0,0 +1,26 @@
+#include "./maxfd.h"
+#include <errno.h>
+
+long open_max (void) {
+	long maxfd = 0L;
+	/* Try sysconf(_SC_OPEN_MAX) first, as it can be higher than OPEN_MAX.
+	 * If that fails and the macro isn't defined, we fall back to an educated
+	 * guess. There's no guarantee that our guess is adequate and the program
+	 * will die with SIGSEGV if it isn't and the upper boundary is breached. */
+
+#ifdef _SC_OPEN_MAX
+	errno = 0;
+	if ((maxfd = sysconf (_SC_OPEN_MAX)) < 0) {
+		if (errno == 0)
+			maxfd = DEFAULT_MAXFD;   /* it's indeterminate */
+		else
+			die (STATE_UNKNOWN, _("sysconf error for _SC_OPEN_MAX\n"));
+	}
+#elif defined(OPEN_MAX)
+	return OPEN_MAX
+#else	/* sysconf macro unavailable, so guess (may be wildly inaccurate) */
+	return DEFAULT_MAXFD;
+#endif
+
+	return(maxfd);
+}
diff --git a/lib/maxfd.h b/lib/maxfd.h
new file mode 100644
index 0000000..0d734c5
--- /dev/null
+++ b/lib/maxfd.h
@@ -0,0 +1,9 @@
+#ifndef _MAXFD_
+#define _MAXFD_
+
+#define DEFAULT_MAXFD  256   /* fallback value if no max open files value is set */
+#define MAXFD_LIMIT   8192   /* upper limit of open files */
+
+long open_max (void);
+
+#endif // _MAXFD_