1 files changed, 98 insertions, 0 deletions
diff --git a/src/libnetdata/os/close_range.c b/src/libnetdata/os/close_range.c
new file mode 100644
index 00000000..56d5c252
--- /dev/null
+++ b/src/libnetdata/os/close_range.c
@@ -0,0 +1,98 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#include "../libnetdata.h"
+
+static int fd_is_valid(int fd) {
+    errno_clear();
+    return fcntl(fd, F_GETFD) != -1 || errno != EBADF;
+}
+
+int os_get_fd_open_max(void) {
+    static int fd_open_max = CLOSE_RANGE_FD_MAX;
+
+    if(fd_open_max != CLOSE_RANGE_FD_MAX)
+        return fd_open_max;
+
+    if(fd_open_max == CLOSE_RANGE_FD_MAX || fd_open_max == -1) {
+        struct rlimit rl;
+        if (getrlimit(RLIMIT_NOFILE, &rl) == 0 && rl.rlim_max != RLIM_INFINITY)
+            fd_open_max = rl.rlim_max;
+    }
+
+#ifdef _SC_OPEN_MAX
+    if(fd_open_max == CLOSE_RANGE_FD_MAX || fd_open_max == -1) {
+        fd_open_max = sysconf(_SC_OPEN_MAX);
+    }
+#endif
+
+    if(fd_open_max == CLOSE_RANGE_FD_MAX || fd_open_max == -1) {
+        // Arbitrary default if everything else fails
+        fd_open_max = 65535;
+    }
+
+    return fd_open_max;
+}
+
+void os_close_range(int first, int last) {
+#if defined(HAVE_CLOSE_RANGE)
+    if(close_range(first, last, 0) == 0) return;
+#endif
+
+#if defined(OS_LINUX)
+    DIR *dir = opendir("/proc/self/fd");
+    if (dir != NULL) {
+        struct dirent *entry;
+        while ((entry = readdir(dir)) != NULL) {
+            int fd = str2i(entry->d_name);
+            if (fd >= first && (last == CLOSE_RANGE_FD_MAX || fd <= last) && fd_is_valid(fd))
+                (void)close(fd);
+        }
+        closedir(dir);
+        return;
+    }
+#endif
+
+    // Fallback to looping through all file descriptors if necessary
+    if (last == CLOSE_RANGE_FD_MAX)
+        last = os_get_fd_open_max();
+
+    for (int fd = first; fd <= last; fd++) {
+        if (fd_is_valid(fd)) (void)close(fd);
+    }
+}
+
+static int compare_ints(const void *a, const void *b) {
+    int int_a = *((int*)a);
+    int int_b = *((int*)b);
+    return (int_a > int_b) - (int_a < int_b);
+}
+
+void os_close_all_non_std_open_fds_except(const int fds[], size_t fds_num) {
+    if (fds_num == 0 || fds == NULL) {
+        os_close_range(STDERR_FILENO + 1, CLOSE_RANGE_FD_MAX);
+        return;
+    }
+
+    // copy the fds array to ensure we will not alter them
+    int fds_copy[fds_num];
+    memcpy(fds_copy, fds, sizeof(fds_copy));
+
+    qsort(fds_copy, fds_num, sizeof(int), compare_ints);
+
+    int start = STDERR_FILENO + 1;
+    size_t i = 0;
+
+    // filter out all fds with a number smaller than our start
+    for (; i < fds_num; i++)
+        if(fds_copy[i] >= start) break;
+
+    // call os_close_range() as many times as needed
+    for (; i < fds_num; i++) {
+        if (fds_copy[i] > start)
+            os_close_range(start, fds_copy[i] - 1);
+
+        start = fds_copy[i] + 1;
+    }
+
+    os_close_range(start, CLOSE_RANGE_FD_MAX);
+}