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diff --git a/src/util/open_limit.c b/src/util/open_limit.c
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+/*++
+/* NAME
+/* open_limit 3
+/* SUMMARY
+/* set/get open file limit
+/* SYNOPSIS
+/* #include <iostuff.h>
+/*
+/* int open_limit(int limit)
+/* DESCRIPTION
+/* The \fIopen_limit\fR() routine attempts to change the maximum
+/* number of open files to the specified limit. Specify a null
+/* argument to effect no change. The result is the actual open file
+/* limit for the current process. The number can be smaller or larger
+/* than the requested limit.
+/* DIAGNOSTICS
+/* open_limit() returns -1 in case of problems. The errno
+/* variable gives hints about the nature of the problem.
+/* LICENSE
+/* .ad
+/* .fi
+/* The Secure Mailer license must be distributed with this software.
+/* AUTHOR(S)
+/* Wietse Venema
+/* IBM T.J. Watson Research
+/* P.O. Box 704
+/* Yorktown Heights, NY 10598, USA
+/*--*/
+
+/* System libraries. */
+
+#include "sys_defs.h"
+#include <sys/time.h>
+#include <sys/resource.h>
+#include <errno.h>
+
+#ifdef USE_MAX_FILES_PER_PROC
+#include <sys/sysctl.h>
+#define MAX_FILES_PER_PROC "kern.maxfilesperproc"
+#endif
+
+/* Application-specific. */
+
+#include "iostuff.h"
+
+ /*
+ * 44BSD compatibility.
+ */
+#ifndef RLIMIT_NOFILE
+#ifdef RLIMIT_OFILE
+#define RLIMIT_NOFILE RLIMIT_OFILE
+#endif
+#endif
+
+/* open_limit - set/query file descriptor limit */
+
+int open_limit(int limit)
+{
+#ifdef RLIMIT_NOFILE
+ struct rlimit rl;
+#endif
+
+ if (limit < 0) {
+ errno = EINVAL;
+ return (-1);
+ }
+#ifdef RLIMIT_NOFILE
+ if (getrlimit(RLIMIT_NOFILE, &rl) < 0)
+ return (-1);
+ if (limit > 0) {
+
+ /*
+ * MacOSX incorrectly reports rlim_max as RLIM_INFINITY. The true
+ * hard limit is finite and equals the kern.maxfilesperproc value.
+ */
+#ifdef USE_MAX_FILES_PER_PROC
+ int max_files_per_proc;
+ size_t len = sizeof(max_files_per_proc);
+
+ if (sysctlbyname(MAX_FILES_PER_PROC, &max_files_per_proc, &len,
+ (void *) 0, (size_t) 0) < 0)
+ return (-1);
+ if (limit > max_files_per_proc)
+ limit = max_files_per_proc;
+#endif
+ if (limit > rl.rlim_max)
+ rl.rlim_cur = rl.rlim_max;
+ else
+ rl.rlim_cur = limit;
+ if (setrlimit(RLIMIT_NOFILE, &rl) < 0)
+ return (-1);
+ }
+ return (rl.rlim_cur);
+#endif
+
+#ifndef RLIMIT_NOFILE
+ return (getdtablesize());
+#endif
+}
+