New upstream version 1.16.0 upstream/1.16.0

1 files changed, 975 insertions, 0 deletions

diff --git a/shared/systemd/src/basic/fd-util.c b/shared/systemd/src/basic/fd-util.c
new file mode 100644
index 00000000..0cc0c6b5
--- /dev/null
+++ b/shared/systemd/src/basic/fd-util.c
@@ -0,0 +1,975 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+
+#include "nm-sd-adapt-shared.h"
+
+#include <errno.h>
+#include <fcntl.h>
+#include <sys/resource.h>
+#include <sys/socket.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+#include "alloc-util.h"
+#include "copy.h"
+#include "dirent-util.h"
+#include "fd-util.h"
+#include "fileio.h"
+#include "fs-util.h"
+#include "io-util.h"
+#include "macro.h"
+#include "memfd-util.h"
+#include "missing.h"
+#include "parse-util.h"
+#include "path-util.h"
+#include "process-util.h"
+#include "socket-util.h"
+#include "stdio-util.h"
+#include "util.h"
+#include "tmpfile-util.h"
+
+int close_nointr(int fd) {
+        assert(fd >= 0);
+
+        if (close(fd) >= 0)
+                return 0;
+
+        /*
+         * Just ignore EINTR; a retry loop is the wrong thing to do on
+         * Linux.
+         *
+         * http://lkml.indiana.edu/hypermail/linux/kernel/0509.1/0877.html
+         * https://bugzilla.gnome.org/show_bug.cgi?id=682819
+         * http://utcc.utoronto.ca/~cks/space/blog/unix/CloseEINTR
+         * https://sites.google.com/site/michaelsafyan/software-engineering/checkforeintrwheninvokingclosethinkagain
+         */
+        if (errno == EINTR)
+                return 0;
+
+        return -errno;
+}
+
+int safe_close(int fd) {
+
+        /*
+         * Like close_nointr() but cannot fail. Guarantees errno is
+         * unchanged. Is a NOP with negative fds passed, and returns
+         * -1, so that it can be used in this syntax:
+         *
+         * fd = safe_close(fd);
+         */
+
+        if (fd >= 0) {
+                PROTECT_ERRNO;
+
+                /* The kernel might return pretty much any error code
+                 * via close(), but the fd will be closed anyway. The
+                 * only condition we want to check for here is whether
+                 * the fd was invalid at all... */
+
+                assert_se(close_nointr(fd) != -EBADF);
+        }
+
+        return -1;
+}
+
+void safe_close_pair(int p[static 2]) {
+        assert(p);
+
+        if (p[0] == p[1]) {
+                /* Special case pairs which use the same fd in both
+                 * directions... */
+                p[0] = p[1] = safe_close(p[0]);
+                return;
+        }
+
+        p[0] = safe_close(p[0]);
+        p[1] = safe_close(p[1]);
+}
+
+void close_many(const int fds[], size_t n_fd) {
+        size_t i;
+
+        assert(fds || n_fd <= 0);
+
+        for (i = 0; i < n_fd; i++)
+                safe_close(fds[i]);
+}
+
+int fclose_nointr(FILE *f) {
+        assert(f);
+
+        /* Same as close_nointr(), but for fclose() */
+
+        if (fclose(f) == 0)
+                return 0;
+
+        if (errno == EINTR)
+                return 0;
+
+        return -errno;
+}
+
+FILE* safe_fclose(FILE *f) {
+
+        /* Same as safe_close(), but for fclose() */
+
+        if (f) {
+                PROTECT_ERRNO;
+
+                assert_se(fclose_nointr(f) != -EBADF);
+        }
+
+        return NULL;
+}
+
+DIR* safe_closedir(DIR *d) {
+
+        if (d) {
+                PROTECT_ERRNO;
+
+                assert_se(closedir(d) >= 0 || errno != EBADF);
+        }
+
+        return NULL;
+}
+
+int fd_nonblock(int fd, bool nonblock) {
+        int flags, nflags;
+
+        assert(fd >= 0);
+
+        flags = fcntl(fd, F_GETFL, 0);
+        if (flags < 0)
+                return -errno;
+
+        if (nonblock)
+                nflags = flags | O_NONBLOCK;
+        else
+                nflags = flags & ~O_NONBLOCK;
+
+        if (nflags == flags)
+                return 0;
+
+        if (fcntl(fd, F_SETFL, nflags) < 0)
+                return -errno;
+
+        return 0;
+}
+
+int fd_cloexec(int fd, bool cloexec) {
+        int flags, nflags;
+
+        assert(fd >= 0);
+
+        flags = fcntl(fd, F_GETFD, 0);
+        if (flags < 0)
+                return -errno;
+
+        if (cloexec)
+                nflags = flags | FD_CLOEXEC;
+        else
+                nflags = flags & ~FD_CLOEXEC;
+
+        if (nflags == flags)
+                return 0;
+
+        if (fcntl(fd, F_SETFD, nflags) < 0)
+                return -errno;
+
+        return 0;
+}
+
+#if 0 /* NM_IGNORED */
+_pure_ static bool fd_in_set(int fd, const int fdset[], size_t n_fdset) {
+        size_t i;
+
+        assert(n_fdset == 0 || fdset);
+
+        for (i = 0; i < n_fdset; i++)
+                if (fdset[i] == fd)
+                        return true;
+
+        return false;
+}
+
+static int get_max_fd(void) {
+        struct rlimit rl;
+        rlim_t m;
+
+        /* Return the highest possible fd, based RLIMIT_NOFILE, but enforcing FD_SETSIZE-1 as lower boundary
+         * and INT_MAX as upper boundary. */
+
+        if (getrlimit(RLIMIT_NOFILE, &rl) < 0)
+                return -errno;
+
+        m = MAX(rl.rlim_cur, rl.rlim_max);
+        if (m < FD_SETSIZE) /* Let's always cover at least 1024 fds */
+                return FD_SETSIZE-1;
+
+        if (m == RLIM_INFINITY || m > INT_MAX) /* Saturate on overflow. After all fds are "int", hence can
+                                                * never be above INT_MAX */
+                return INT_MAX;
+
+        return (int) (m - 1);
+}
+
+int close_all_fds(const int except[], size_t n_except) {
+        _cleanup_closedir_ DIR *d = NULL;
+        struct dirent *de;
+        int r = 0;
+
+        assert(n_except == 0 || except);
+
+        d = opendir("/proc/self/fd");
+        if (!d) {
+                int fd, max_fd;
+
+                /* When /proc isn't available (for example in chroots) the fallback is brute forcing through
+                 * the fd table */
+
+                max_fd = get_max_fd();
+                if (max_fd < 0)
+                        return max_fd;
+
+                for (fd = 3; fd >= 0; fd = fd < max_fd ? fd + 1 : -1) {
+                        int q;
+
+                        if (fd_in_set(fd, except, n_except))
+                                continue;
+
+                        q = close_nointr(fd);
+                        if (q < 0 && q != -EBADF && r >= 0)
+                                r = q;
+                }
+
+                return r;
+        }
+
+        FOREACH_DIRENT(de, d, return -errno) {
+                int fd = -1, q;
+
+                if (safe_atoi(de->d_name, &fd) < 0)
+                        /* Let's better ignore this, just in case */
+                        continue;
+
+                if (fd < 3)
+                        continue;
+
+                if (fd == dirfd(d))
+                        continue;
+
+                if (fd_in_set(fd, except, n_except))
+                        continue;
+
+                q = close_nointr(fd);
+                if (q < 0 && q != -EBADF && r >= 0) /* Valgrind has its own FD and doesn't want to have it closed */
+                        r = q;
+        }
+
+        return r;
+}
+
+int same_fd(int a, int b) {
+        struct stat sta, stb;
+        pid_t pid;
+        int r, fa, fb;
+
+        assert(a >= 0);
+        assert(b >= 0);
+
+        /* Compares two file descriptors. Note that semantics are
+         * quite different depending on whether we have kcmp() or we
+         * don't. If we have kcmp() this will only return true for
+         * dup()ed file descriptors, but not otherwise. If we don't
+         * have kcmp() this will also return true for two fds of the same
+         * file, created by separate open() calls. Since we use this
+         * call mostly for filtering out duplicates in the fd store
+         * this difference hopefully doesn't matter too much. */
+
+        if (a == b)
+                return true;
+
+        /* Try to use kcmp() if we have it. */
+        pid = getpid_cached();
+        r = kcmp(pid, pid, KCMP_FILE, a, b);
+        if (r == 0)
+                return true;
+        if (r > 0)
+                return false;
+        if (!IN_SET(errno, ENOSYS, EACCES, EPERM))
+                return -errno;
+
+        /* We don't have kcmp(), use fstat() instead. */
+        if (fstat(a, &sta) < 0)
+                return -errno;
+
+        if (fstat(b, &stb) < 0)
+                return -errno;
+
+        if ((sta.st_mode & S_IFMT) != (stb.st_mode & S_IFMT))
+                return false;
+
+        /* We consider all device fds different, since two device fds
+         * might refer to quite different device contexts even though
+         * they share the same inode and backing dev_t. */
+
+        if (S_ISCHR(sta.st_mode) || S_ISBLK(sta.st_mode))
+                return false;
+
+        if (sta.st_dev != stb.st_dev || sta.st_ino != stb.st_ino)
+                return false;
+
+        /* The fds refer to the same inode on disk, let's also check
+         * if they have the same fd flags. This is useful to
+         * distinguish the read and write side of a pipe created with
+         * pipe(). */
+        fa = fcntl(a, F_GETFL);
+        if (fa < 0)
+                return -errno;
+
+        fb = fcntl(b, F_GETFL);
+        if (fb < 0)
+                return -errno;
+
+        return fa == fb;
+}
+#endif /* NM_IGNORED */
+
+void cmsg_close_all(struct msghdr *mh) {
+        struct cmsghdr *cmsg;
+
+        assert(mh);
+
+        CMSG_FOREACH(cmsg, mh)
+                if (cmsg->cmsg_level == SOL_SOCKET && cmsg->cmsg_type == SCM_RIGHTS)
+                        close_many((int*) CMSG_DATA(cmsg), (cmsg->cmsg_len - CMSG_LEN(0)) / sizeof(int));
+}
+
+bool fdname_is_valid(const char *s) {
+        const char *p;
+
+        /* Validates a name for $LISTEN_FDNAMES. We basically allow
+         * everything ASCII that's not a control character. Also, as
+         * special exception the ":" character is not allowed, as we
+         * use that as field separator in $LISTEN_FDNAMES.
+         *
+         * Note that the empty string is explicitly allowed
+         * here. However, we limit the length of the names to 255
+         * characters. */
+
+        if (!s)
+                return false;
+
+        for (p = s; *p; p++) {
+                if (*p < ' ')
+                        return false;
+                if (*p >= 127)
+                        return false;
+                if (*p == ':')
+                        return false;
+        }
+
+        return p - s < 256;
+}
+
+int fd_get_path(int fd, char **ret) {
+        char procfs_path[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(int)];
+        int r;
+
+        xsprintf(procfs_path, "/proc/self/fd/%i", fd);
+        r = readlink_malloc(procfs_path, ret);
+        if (r == -ENOENT) {
+                /* ENOENT can mean two things: that the fd does not exist or that /proc is not mounted. Let's make
+                 * things debuggable and distinguish the two. */
+
+                if (access("/proc/self/fd/", F_OK) < 0)
+                        /* /proc is not available or not set up properly, we're most likely in some chroot
+                         * environment. */
+                        return errno == ENOENT ? -EOPNOTSUPP : -errno;
+
+                return -EBADF; /* The directory exists, hence it's the fd that doesn't. */
+        }
+
+        return r;
+}
+
+#if 0 /* NM_IGNORED */
+int move_fd(int from, int to, int cloexec) {
+        int r;
+
+        /* Move fd 'from' to 'to', make sure FD_CLOEXEC remains equal if requested, and release the old fd. If
+         * 'cloexec' is passed as -1, the original FD_CLOEXEC is inherited for the new fd. If it is 0, it is turned
+         * off, if it is > 0 it is turned on. */
+
+        if (from < 0)
+                return -EBADF;
+        if (to < 0)
+                return -EBADF;
+
+        if (from == to) {
+
+                if (cloexec >= 0) {
+                        r = fd_cloexec(to, cloexec);
+                        if (r < 0)
+                                return r;
+                }
+
+                return to;
+        }
+
+        if (cloexec < 0) {
+                int fl;
+
+                fl = fcntl(from, F_GETFD, 0);
+                if (fl < 0)
+                        return -errno;
+
+                cloexec = !!(fl & FD_CLOEXEC);
+        }
+
+        r = dup3(from, to, cloexec ? O_CLOEXEC : 0);
+        if (r < 0)
+                return -errno;
+
+        assert(r == to);
+
+        safe_close(from);
+
+        return to;
+}
+
+int acquire_data_fd(const void *data, size_t size, unsigned flags) {
+
+        _cleanup_close_pair_ int pipefds[2] = { -1, -1 };
+        char pattern[] = "/dev/shm/data-fd-XXXXXX";
+        _cleanup_close_ int fd = -1;
+        int isz = 0, r;
+        ssize_t n;
+        off_t f;
+
+        assert(data || size == 0);
+
+        /* Acquire a read-only file descriptor that when read from returns the specified data. This is much more
+         * complex than I wish it was. But here's why:
+         *
+         * a) First we try to use memfds. They are the best option, as we can seal them nicely to make them
+         *    read-only. Unfortunately they require kernel 3.17, and – at the time of writing – we still support 3.14.
+         *
+         * b) Then, we try classic pipes. They are the second best options, as we can close the writing side, retaining
+         *    a nicely read-only fd in the reading side. However, they are by default quite small, and unprivileged
+         *    clients can only bump their size to a system-wide limit, which might be quite low.
+         *
+         * c) Then, we try an O_TMPFILE file in /dev/shm (that dir is the only suitable one known to exist from
+         *    earliest boot on). To make it read-only we open the fd a second time with O_RDONLY via
+         *    /proc/self/<fd>. Unfortunately O_TMPFILE is not available on older kernels on tmpfs.
+         *
+         * d) Finally, we try creating a regular file in /dev/shm, which we then delete.
+         *
+         * It sucks a bit that depending on the situation we return very different objects here, but that's Linux I
+         * figure. */
+
+        if (size == 0 && ((flags & ACQUIRE_NO_DEV_NULL) == 0)) {
+                /* As a special case, return /dev/null if we have been called for an empty data block */
+                r = open("/dev/null", O_RDONLY|O_CLOEXEC|O_NOCTTY);
+                if (r < 0)
+                        return -errno;
+
+                return r;
+        }
+
+        if ((flags & ACQUIRE_NO_MEMFD) == 0) {
+                fd = memfd_new("data-fd");
+                if (fd < 0)
+                        goto try_pipe;
+
+                n = write(fd, data, size);
+                if (n < 0)
+                        return -errno;
+                if ((size_t) n != size)
+                        return -EIO;
+
+                f = lseek(fd, 0, SEEK_SET);
+                if (f != 0)
+                        return -errno;
+
+                r = memfd_set_sealed(fd);
+                if (r < 0)
+                        return r;
+
+                return TAKE_FD(fd);
+        }
+
+try_pipe:
+        if ((flags & ACQUIRE_NO_PIPE) == 0) {
+                if (pipe2(pipefds, O_CLOEXEC|O_NONBLOCK) < 0)
+                        return -errno;
+
+                isz = fcntl(pipefds[1], F_GETPIPE_SZ, 0);
+                if (isz < 0)
+                        return -errno;
+
+                if ((size_t) isz < size) {
+                        isz = (int) size;
+                        if (isz < 0 || (size_t) isz != size)
+                                return -E2BIG;
+
+                        /* Try to bump the pipe size */
+                        (void) fcntl(pipefds[1], F_SETPIPE_SZ, isz);
+
+                        /* See if that worked */
+                        isz = fcntl(pipefds[1], F_GETPIPE_SZ, 0);
+                        if (isz < 0)
+                                return -errno;
+
+                        if ((size_t) isz < size)
+                                goto try_dev_shm;
+                }
+
+                n = write(pipefds[1], data, size);
+                if (n < 0)
+                        return -errno;
+                if ((size_t) n != size)
+                        return -EIO;
+
+                (void) fd_nonblock(pipefds[0], false);
+
+                return TAKE_FD(pipefds[0]);
+        }
+
+try_dev_shm:
+        if ((flags & ACQUIRE_NO_TMPFILE) == 0) {
+                fd = open("/dev/shm", O_RDWR|O_TMPFILE|O_CLOEXEC, 0500);
+                if (fd < 0)
+                        goto try_dev_shm_without_o_tmpfile;
+
+                n = write(fd, data, size);
+                if (n < 0)
+                        return -errno;
+                if ((size_t) n != size)
+                        return -EIO;
+
+                /* Let's reopen the thing, in order to get an O_RDONLY fd for the original O_RDWR one */
+                return fd_reopen(fd, O_RDONLY|O_CLOEXEC);
+        }
+
+try_dev_shm_without_o_tmpfile:
+        if ((flags & ACQUIRE_NO_REGULAR) == 0) {
+                fd = mkostemp_safe(pattern);
+                if (fd < 0)
+                        return fd;
+
+                n = write(fd, data, size);
+                if (n < 0) {
+                        r = -errno;
+                        goto unlink_and_return;
+                }
+                if ((size_t) n != size) {
+                        r = -EIO;
+                        goto unlink_and_return;
+                }
+
+                /* Let's reopen the thing, in order to get an O_RDONLY fd for the original O_RDWR one */
+                r = open(pattern, O_RDONLY|O_CLOEXEC);
+                if (r < 0)
+                        r = -errno;
+
+        unlink_and_return:
+                (void) unlink(pattern);
+                return r;
+        }
+
+        return -EOPNOTSUPP;
+}
+
+/* When the data is smaller or equal to 64K, try to place the copy in a memfd/pipe */
+#define DATA_FD_MEMORY_LIMIT (64U*1024U)
+
+/* If memfd/pipe didn't work out, then let's use a file in /tmp up to a size of 1M. If it's large than that use /var/tmp instead. */
+#define DATA_FD_TMP_LIMIT (1024U*1024U)
+
+int fd_duplicate_data_fd(int fd) {
+
+        _cleanup_close_ int copy_fd = -1, tmp_fd = -1;
+        _cleanup_free_ void *remains = NULL;
+        size_t remains_size = 0;
+        const char *td;
+        struct stat st;
+        int r;
+
+        /* Creates a 'data' fd from the specified source fd, containing all the same data in a read-only fashion, but
+         * independent of it (i.e. the source fd can be closed and unmounted after this call succeeded). Tries to be
+         * somewhat smart about where to place the data. In the best case uses a memfd(). If memfd() are not supported
+         * uses a pipe instead. For larger data will use an unlinked file in /tmp, and for even larger data one in
+         * /var/tmp. */
+
+        if (fstat(fd, &st) < 0)
+                return -errno;
+
+        /* For now, let's only accept regular files, sockets, pipes and char devices */
+        if (S_ISDIR(st.st_mode))
+                return -EISDIR;
+        if (S_ISLNK(st.st_mode))
+                return -ELOOP;
+        if (!S_ISREG(st.st_mode) && !S_ISSOCK(st.st_mode) && !S_ISFIFO(st.st_mode) && !S_ISCHR(st.st_mode))
+                return -EBADFD;
+
+        /* If we have reason to believe the data is bounded in size, then let's use memfds or pipes as backing fd. Note
+         * that we use the reported regular file size only as a hint, given that there are plenty special files in
+         * /proc and /sys which report a zero file size but can be read from. */
+
+        if (!S_ISREG(st.st_mode) || st.st_size < DATA_FD_MEMORY_LIMIT) {
+
+                /* Try a memfd first */
+                copy_fd = memfd_new("data-fd");
+                if (copy_fd >= 0) {
+                        off_t f;
+
+                        r = copy_bytes(fd, copy_fd, DATA_FD_MEMORY_LIMIT, 0);
+                        if (r < 0)
+                                return r;
+
+                        f = lseek(copy_fd, 0, SEEK_SET);
+                        if (f != 0)
+                                return -errno;
+
+                        if (r == 0) {
+                                /* Did it fit into the limit? If so, we are done. */
+                                r = memfd_set_sealed(copy_fd);
+                                if (r < 0)
+                                        return r;
+
+                                return TAKE_FD(copy_fd);
+                        }
+
+                        /* Hmm, pity, this didn't fit. Let's fall back to /tmp then, see below */
+
+                } else {
+                        _cleanup_(close_pairp) int pipefds[2] = { -1, -1 };
+                        int isz;
+
+                        /* If memfds aren't available, use a pipe. Set O_NONBLOCK so that we will get EAGAIN rather
+                         * then block indefinitely when we hit the pipe size limit */
+
+                        if (pipe2(pipefds, O_CLOEXEC|O_NONBLOCK) < 0)
+                                return -errno;
+
+                        isz = fcntl(pipefds[1], F_GETPIPE_SZ, 0);
+                        if (isz < 0)
+                                return -errno;
+
+                        /* Try to enlarge the pipe size if necessary */
+                        if ((size_t) isz < DATA_FD_MEMORY_LIMIT) {
+
+                                (void) fcntl(pipefds[1], F_SETPIPE_SZ, DATA_FD_MEMORY_LIMIT);
+
+                                isz = fcntl(pipefds[1], F_GETPIPE_SZ, 0);
+                                if (isz < 0)
+                                        return -errno;
+                        }
+
+                        if ((size_t) isz >= DATA_FD_MEMORY_LIMIT) {
+
+                                r = copy_bytes_full(fd, pipefds[1], DATA_FD_MEMORY_LIMIT, 0, &remains, &remains_size, NULL, NULL);
+                                if (r < 0 && r != -EAGAIN)
+                                        return r; /* If we get EAGAIN it could be because of the source or because of
+                                                   * the destination fd, we can't know, as sendfile() and friends won't
+                                                   * tell us. Hence, treat this as reason to fall back, just to be
+                                                   * sure. */
+                                if (r == 0) {
+                                        /* Everything fit in, yay! */
+                                        (void) fd_nonblock(pipefds[0], false);
+
+                                        return TAKE_FD(pipefds[0]);
+                                }
+
+                                /* Things didn't fit in. But we read data into the pipe, let's remember that, so that
+                                 * when writing the new file we incorporate this first. */
+                                copy_fd = TAKE_FD(pipefds[0]);
+                        }
+                }
+        }
+
+        /* If we have reason to believe this will fit fine in /tmp, then use that as first fallback. */
+        if ((!S_ISREG(st.st_mode) || st.st_size < DATA_FD_TMP_LIMIT) &&
+            (DATA_FD_MEMORY_LIMIT + remains_size) < DATA_FD_TMP_LIMIT) {
+                off_t f;
+
+                tmp_fd = open_tmpfile_unlinkable(NULL /* NULL as directory means /tmp */, O_RDWR|O_CLOEXEC);
+                if (tmp_fd < 0)
+                        return tmp_fd;
+
+                if (copy_fd >= 0) {
+                        /* If we tried a memfd/pipe first and it ended up being too large, then copy this into the
+                         * temporary file first. */
+
+                        r = copy_bytes(copy_fd, tmp_fd, UINT64_MAX, 0);
+                        if (r < 0)
+                                return r;
+
+                        assert(r == 0);
+                }
+
+                if (remains_size > 0) {
+                        /* If there were remaining bytes (i.e. read into memory, but not written out yet) from the
+                         * failed copy operation, let's flush them out next. */
+
+                        r = loop_write(tmp_fd, remains, remains_size, false);
+                        if (r < 0)
+                                return r;
+                }
+
+                r = copy_bytes(fd, tmp_fd, DATA_FD_TMP_LIMIT - DATA_FD_MEMORY_LIMIT - remains_size, COPY_REFLINK);
+                if (r < 0)
+                        return r;
+                if (r == 0)
+                        goto finish;  /* Yay, it fit in */
+
+                /* It didn't fit in. Let's not forget to use what we already used */
+                f = lseek(tmp_fd, 0, SEEK_SET);
+                if (f != 0)
+                        return -errno;
+
+                safe_close(copy_fd);
+                copy_fd = TAKE_FD(tmp_fd);
+
+                remains = mfree(remains);
+                remains_size = 0;
+        }
+
+        /* As last fallback use /var/tmp */
+        r = var_tmp_dir(&td);
+        if (r < 0)
+                return r;
+
+        tmp_fd = open_tmpfile_unlinkable(td, O_RDWR|O_CLOEXEC);
+        if (tmp_fd < 0)
+                return tmp_fd;
+
+        if (copy_fd >= 0) {
+                /* If we tried a memfd/pipe first, or a file in /tmp, and it ended up being too large, than copy this
+                 * into the temporary file first. */
+                r = copy_bytes(copy_fd, tmp_fd, UINT64_MAX, COPY_REFLINK);
+                if (r < 0)
+                        return r;
+
+                assert(r == 0);
+        }
+
+        if (remains_size > 0) {
+                /* Then, copy in any read but not yet written bytes. */
+                r = loop_write(tmp_fd, remains, remains_size, false);
+                if (r < 0)
+                        return r;
+        }
+
+        /* Copy in the rest */
+        r = copy_bytes(fd, tmp_fd, UINT64_MAX, COPY_REFLINK);
+        if (r < 0)
+                return r;
+
+        assert(r == 0);
+
+finish:
+        /* Now convert the O_RDWR file descriptor into an O_RDONLY one (and as side effect seek to the beginning of the
+         * file again */
+
+        return fd_reopen(tmp_fd, O_RDONLY|O_CLOEXEC);
+}
+#endif /* NM_IGNORED */
+
+int fd_move_above_stdio(int fd) {
+        int flags, copy;
+        PROTECT_ERRNO;
+
+        /* Moves the specified file descriptor if possible out of the range [0…2], i.e. the range of
+         * stdin/stdout/stderr. If it can't be moved outside of this range the original file descriptor is
+         * returned. This call is supposed to be used for long-lasting file descriptors we allocate in our code that
+         * might get loaded into foreign code, and where we want ensure our fds are unlikely used accidentally as
+         * stdin/stdout/stderr of unrelated code.
+         *
+         * Note that this doesn't fix any real bugs, it just makes it less likely that our code will be affected by
+         * buggy code from others that mindlessly invokes 'fprintf(stderr, …' or similar in places where stderr has
+         * been closed before.
+         *
+         * This function is written in a "best-effort" and "least-impact" style. This means whenever we encounter an
+         * error we simply return the original file descriptor, and we do not touch errno. */
+
+        if (fd < 0 || fd > 2)
+                return fd;
+
+        flags = fcntl(fd, F_GETFD, 0);
+        if (flags < 0)
+                return fd;
+
+        if (flags & FD_CLOEXEC)
+                copy = fcntl(fd, F_DUPFD_CLOEXEC, 3);
+        else
+                copy = fcntl(fd, F_DUPFD, 3);
+        if (copy < 0)
+                return fd;
+
+        assert(copy > 2);
+
+        (void) close(fd);
+        return copy;
+}
+
+#if 0 /* NM_IGNORED */
+int rearrange_stdio(int original_input_fd, int original_output_fd, int original_error_fd) {
+
+        int fd[3] = { /* Put together an array of fds we work on */
+                original_input_fd,
+                original_output_fd,
+                original_error_fd
+        };
+
+        int r, i,
+                null_fd = -1,                /* if we open /dev/null, we store the fd to it here */
+                copy_fd[3] = { -1, -1, -1 }; /* This contains all fds we duplicate here temporarily, and hence need to close at the end */
+        bool null_readable, null_writable;
+
+        /* Sets up stdin, stdout, stderr with the three file descriptors passed in. If any of the descriptors is
+         * specified as -1 it will be connected with /dev/null instead. If any of the file descriptors is passed as
+         * itself (e.g. stdin as STDIN_FILENO) it is left unmodified, but the O_CLOEXEC bit is turned off should it be
+         * on.
+         *
+         * Note that if any of the passed file descriptors are > 2 they will be closed — both on success and on
+         * failure! Thus, callers should assume that when this function returns the input fds are invalidated.
+         *
+         * Note that when this function fails stdin/stdout/stderr might remain half set up!
+         *
+         * O_CLOEXEC is turned off for all three file descriptors (which is how it should be for
+         * stdin/stdout/stderr). */
+
+        null_readable = original_input_fd < 0;
+        null_writable = original_output_fd < 0 || original_error_fd < 0;
+
+        /* First step, open /dev/null once, if we need it */
+        if (null_readable || null_writable) {
+
+                /* Let's open this with O_CLOEXEC first, and convert it to non-O_CLOEXEC when we move the fd to the final position. */
+                null_fd = open("/dev/null", (null_readable && null_writable ? O_RDWR :
+                                             null_readable ? O_RDONLY : O_WRONLY) | O_CLOEXEC);
+                if (null_fd < 0) {
+                        r = -errno;
+                        goto finish;
+                }
+
+                /* If this fd is in the 0…2 range, let's move it out of it */
+                if (null_fd < 3) {
+                        int copy;
+
+                        copy = fcntl(null_fd, F_DUPFD_CLOEXEC, 3); /* Duplicate this with O_CLOEXEC set */
+                        if (copy < 0) {
+                                r = -errno;
+                                goto finish;
+                        }
+
+                        safe_close(null_fd);
+                        null_fd = copy;
+                }
+        }
+
+        /* Let's assemble fd[] with the fds to install in place of stdin/stdout/stderr */
+        for (i = 0; i < 3; i++) {
+
+                if (fd[i] < 0)
+                        fd[i] = null_fd;        /* A negative parameter means: connect this one to /dev/null */
+                else if (fd[i] != i && fd[i] < 3) {
+                        /* This fd is in the 0…2 territory, but not at its intended place, move it out of there, so that we can work there. */
+                        copy_fd[i] = fcntl(fd[i], F_DUPFD_CLOEXEC, 3); /* Duplicate this with O_CLOEXEC set */
+                        if (copy_fd[i] < 0) {
+                                r = -errno;
+                                goto finish;
+                        }
+
+                        fd[i] = copy_fd[i];
+                }
+        }
+
+        /* At this point we now have the fds to use in fd[], and they are all above the stdio range, so that we
+         * have freedom to move them around. If the fds already were at the right places then the specific fds are
+         * -1. Let's now move them to the right places. This is the point of no return. */
+        for (i = 0; i < 3; i++) {
+
+                if (fd[i] == i) {
+
+                        /* fd is already in place, but let's make sure O_CLOEXEC is off */
+                        r = fd_cloexec(i, false);
+                        if (r < 0)
+                                goto finish;
+
+                } else {
+                        assert(fd[i] > 2);
+
+                        if (dup2(fd[i], i) < 0) { /* Turns off O_CLOEXEC on the new fd. */
+                                r = -errno;
+                                goto finish;
+                        }
+                }
+        }
+
+        r = 0;
+
+finish:
+        /* Close the original fds, but only if they were outside of the stdio range. Also, properly check for the same
+         * fd passed in multiple times. */
+        safe_close_above_stdio(original_input_fd);
+        if (original_output_fd != original_input_fd)
+                safe_close_above_stdio(original_output_fd);
+        if (original_error_fd != original_input_fd && original_error_fd != original_output_fd)
+                safe_close_above_stdio(original_error_fd);
+
+        /* Close the copies we moved > 2 */
+        for (i = 0; i < 3; i++)
+                safe_close(copy_fd[i]);
+
+        /* Close our null fd, if it's > 2 */
+        safe_close_above_stdio(null_fd);
+
+        return r;
+}
+
+int fd_reopen(int fd, int flags) {
+        char procfs_path[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(int)];
+        int new_fd;
+
+        /* Reopens the specified fd with new flags. This is useful for convert an O_PATH fd into a regular one, or to
+         * turn O_RDWR fds into O_RDONLY fds.
+         *
+         * This doesn't work on sockets (since they cannot be open()ed, ever).
+         *
+         * This implicitly resets the file read index to 0. */
+
+        xsprintf(procfs_path, "/proc/self/fd/%i", fd);
+        new_fd = open(procfs_path, flags);
+        if (new_fd < 0)
+                return -errno;
+
+        return new_fd;
+}
+
+int read_nr_open(void) {
+        _cleanup_free_ char *nr_open = NULL;
+        int r;
+
+        /* Returns the kernel's current fd limit, either by reading it of /proc/sys if that works, or using the
+         * hard-coded default compiled-in value of current kernels (1M) if not. This call will never fail. */
+
+        r = read_one_line_file("/proc/sys/fs/nr_open", &nr_open);
+        if (r < 0)
+                log_debug_errno(r, "Failed to read /proc/sys/fs/nr_open, ignoring: %m");
+        else {
+                int v;
+
+                r = safe_atoi(nr_open, &v);
+                if (r < 0)
+                        log_debug_errno(r, "Failed to parse /proc/sys/fs/nr_open value '%s', ignoring: %m", nr_open);
+                else
+                        return v;
+        }
+
+        /* If we fail, fallback to the hard-coded kernel limit of 1024 * 1024. */
+        return 1024 * 1024;
+}
+#endif /* NM_IGNORED */