basic: move acquire_data_fd() and fd_duplicate_data_fd() to new data-fd-util.c

fd_duplicate_data_fd() is renamed to copy_data_fd(). This makes
the two functions have nicely similar names.

Now fd-util.[ch] is again about low-level file descriptor manipulations.
copy_data_fd() is a complex function that internally wraps the other
functions in copy.c. I want to move copy.c and the whole cluster of
related code from basic/ to shared/ later on, and this is a preparatory
step for that.

1 files changed, 0 insertions, 339 deletions

diff --git a/src/basic/fd-util.c b/src/basic/fd-util.c
index ac6a37b567..008f474344 100644
--- a/src/basic/fd-util.c
+++ b/src/basic/fd-util.c
@@ -10,14 +10,12 @@
 #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_fcntl.h"
 #include "missing_syscall.h"
 #include "parse-util.h"
@@ -523,343 +521,6 @@ int move_fd(int from, int to, int cloexec) {
         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;
-
-                CLOSE_AND_REPLACE(copy_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);
-}
-
 int fd_move_above_stdio(int fd) {
         int flags, copy;
         PROTECT_ERRNO;