This can be used for creating temporary disks to thin clients, as a kind of "remote tmpfs". See also: https://www.redhat.com/archives/libguestfs/2020-March/msg00134.html --- plugins/data/nbdkit-data-plugin.pod | 1 + plugins/file/nbdkit-file-plugin.pod | 1 + plugins/linuxdisk/nbdkit-linuxdisk-plugin.pod | 7 +- plugins/memory/nbdkit-memory-plugin.pod | 3 +- plugins/tmpdisk/nbdkit-tmpdisk-plugin.pod | 157 +++++++ configure.ac | 2 + plugins/tmpdisk/Makefile.am | 66 +++ plugins/tmpdisk/tmpdisk.c | 426 ++++++++++++++++++ 8 files changed, 660 insertions(+), 3 deletions(-) diff --git a/plugins/data/nbdkit-data-plugin.pod b/plugins/data/nbdkit-data-plugin.pod index 057392d3..ef8d1e08 100644 --- a/plugins/data/nbdkit-data-plugin.pod +++ b/plugins/data/nbdkit-data-plugin.pod @@ -269,6 +269,7 @@ L<nbdkit-null-plugin(1)>, L<nbdkit-partitioning-plugin(1)>, L<nbdkit-pattern-plugin(1)>, L<nbdkit-random-plugin(1)>, +L<nbdkit-tmpdisk-plugin(1)>, L<nbdkit-zero-plugin(1)>, L<https://github.com/libguestfs/nbdkit/blob/master/plugins/data/disk2d...;, L<https://en.wikipedia.org/wiki/Base64>;. diff --git a/plugins/file/nbdkit-file-plugin.pod b/plugins/file/nbdkit-file-plugin.pod index d538b127..0c1cfd57 100644 --- a/plugins/file/nbdkit-file-plugin.pod +++ b/plugins/file/nbdkit-file-plugin.pod @@ -111,6 +111,7 @@ L<nbdkit(1)>, L<nbdkit-plugin(3)>, L<nbdkit-split-plugin(1)>, L<nbdkit-partitioning-plugin(1)>, +L<nbdkit-tmpdisk-plugin(1)>, L<nbdkit-noextents-filter(1)>. =head1 AUTHORS diff --git a/plugins/linuxdisk/nbdkit-linuxdisk-plugin.pod b/plugins/linuxdisk/nbdkit-linuxdisk-plugin.pod index 3cac883c..53f4d89d 100644 --- a/plugins/linuxdisk/nbdkit-linuxdisk-plugin.pod +++ b/plugins/linuxdisk/nbdkit-linuxdisk-plugin.pod @@ -24,7 +24,9 @@ symbolic links, block special devices etc. To create a FAT-formatted virtual floppy disk, see L<nbdkit-floppy-plugin(1)>. To create a CD/ISO, see -L<nbdkit-iso-plugin(1)>. +L<nbdkit-iso-plugin(1)>. To create an empty filesystem for each +client that connects (like a "remote tmpfs") use +L<nbdkit-tmpdisk-plugin(1)>. =head1 EXAMPLES @@ -184,7 +186,8 @@ L<nbdkit-file-plugin(1)>, L<nbdkit-floppy-plugin(1)>, L<nbdkit-iso-plugin(1)>, L<nbdkit-partition-filter(1)>, -L<nbdkit-partitioning-plugin(1)>. +L<nbdkit-partitioning-plugin(1)>, +L<nbdkit-tmpdisk-plugin(1)>, =head1 AUTHORS diff --git a/plugins/memory/nbdkit-memory-plugin.pod b/plugins/memory/nbdkit-memory-plugin.pod index ccdc017d..bc565c55 100644 --- a/plugins/memory/nbdkit-memory-plugin.pod +++ b/plugins/memory/nbdkit-memory-plugin.pod @@ -103,7 +103,8 @@ L<nbdkit-plugin(3)>, L<nbdkit-loop(1)>, L<nbdkit-data-plugin(1)>, L<nbdkit-file-plugin(1)>, -L<nbdkit-info-plugin(1)>. +L<nbdkit-info-plugin(1)>, +L<nbdkit-tmpdisk-plugin(1)>. =head1 AUTHORS diff --git a/plugins/tmpdisk/nbdkit-tmpdisk-plugin.pod b/plugins/tmpdisk/nbdkit-tmpdisk-plugin.pod new file mode 100644 index 00000000..925a5091 --- /dev/null +++ b/plugins/tmpdisk/nbdkit-tmpdisk-plugin.pod @@ -0,0 +1,157 @@ +=head1 NAME + +nbdkit-tmpdisk-plugin - create a fresh temporary filesystem for each client + +=head1 SYNOPSIS + + nbdkit tmpdisk [size=]SIZE + [type=ext4|xfs|vfat|...] [label=LABEL] + [command=COMMAND] + +=head1 DESCRIPTION + +This L<nbdkit(1)> plugin is used for creating temporary filesystems +for thin clients. Each time a client connects it will see a fresh, +empty filesystem for its exclusive use. B<The filesystem is deleted> +when the client disconnects. + +When a new client connects, a blank, sparse file of the required size +is created in C<$TMPDIR> (or F</var/tmp>). L<mkfs(8)> is then run on +the file to create the empty filesystem, and this filesystem is served +to the client. Unlike L<nbdkit-linuxdisk-plugin(1)> each client of +this plugin sees a different disk. + +The size of the disk is chosen using the C<size> parameter. The +filesystem type is C<ext4> but this can be changed using the C<type> +parameter (controlling the I<-t> option of mkfs). + +Instead of running mkfs you can run an arbitrary C<command> to create +the disk. + +=head2 Example + +One use for this is to create a kind of "remote L<tmpfs(5)>" for thin +clients. On the server you would run (see L<nbdkit-service(1)>): + + nbdkit tmpdisk 16G + +and each thin client would have a file F</etc/rc.d/rc.local> +containing: + + nm-online + modprobe nbd + nbd-client server /dev/nbd0 + mount /dev/nbd0 /var/scratch + +Clients would see a fresh, empty C</var/scratch> directory after boot. + +=head2 Security considerations + +Because each client gets a new disk, the amount of disk space +required on the server can be as much as +S<<< I<number of clients> × I<size parameter> >>>. It is therefore +best to limit the number of clients using L<nbdkit-limit-filter(1)> or +take steps to limit where clients can connect from using +L<nbdkit-ip-filter(1)>, firewalls, or TLS client certificates. + +=head1 PARAMETERS + +=over 4 + +=item B<command='>COMMANDB<'> + +Instead of running L<mkfs(8)> to create the initial filesystem, run +C<COMMAND> (which usually must be quoted to protect it from the +shell). The following shell variables may be used in C<COMMAND>: + +=over 4 + +=item C<$disk> + +The absolute path of the file that the command must initialize. This +file is created by nbdkit before the command runs. + +=item C<$label> + +The filesystem label (from the C<label> parameter). + +=item C<$size> + +The virtual size in bytes, which is the same as the file size. + +=item C<$type> + +The filesystem type (from the C<type> parameter), defaulting to +C<ext4>. (Commands can ignore this if it is not relevant). + +=back + +=item B<label=>LABEL + +Select the filesystem label. The default is not set. + +=item [B<size=>]SIZE + +Specify the virtual size of the disk image. + +This parameter is required. + +C<size=> is a magic config key and may be omitted in most cases. +See L<nbdkit(1)/Magic parameters>. + +=item B<type=>FS + +Select the filesystem type. The default is C<ext4>. Most +non-networked, non-cluster filesystem types supported by the +L<mkfs(8)> command can be used here. + +=back + +=head1 ENVIRONMENT VARIABLES + +=over 4 + +=item C<TMPDIR> + +The temporary disks for this plugin are created in this directory, one +per connected client. If not set this defaults to F</var/tmp>. + +=back + +=head1 FILES + +=over 4 + +=item F<$plugindir/nbdkit-tmpdisk-plugin.so> + +The plugin. + +Use C<nbdkit --dump-config> to find the location of C<$plugindir>. + +=back + +=head1 VERSION + +C<nbdkit-tmpdisk-plugin> first appeared in nbdkit 1.20. + +=head1 SEE ALSO + +L<nbdkit(1)>, +L<nbdkit-plugin(3)>, +L<nbdkit-data-plugin(1)>, +L<nbdkit-file-plugin(1)>, +L<nbdkit-ip-filter(1)>, +L<nbdkit-limit-filter(1)>, +L<nbdkit-linuxdisk-plugin(1)>, +L<nbdkit-memory-plugin(1)>, +L<nbdkit-loop(1)>, +L<nbdkit-tls(1)>, +L<mkfs(8)>. + +=head1 AUTHORS + +Richard W.M. Jones + +=head1 COPYRIGHT + +Copyright (C) 2018-2020 Red Hat Inc. diff --git a/configure.ac b/configure.ac index dd9ca765..7b5e61e3 100644 --- a/configure.ac +++ b/configure.ac @@ -86,6 +86,7 @@ non_lang_plugins="\ ssh \ streaming \ tar \ + tmpdisk \ vddk \ zero \ " @@ -1016,6 +1017,7 @@ AC_CONFIG_FILES([Makefile plugins/streaming/Makefile plugins/tar/Makefile plugins/tcl/Makefile + plugins/tmpdisk/Makefile plugins/vddk/Makefile plugins/zero/Makefile filters/Makefile diff --git a/plugins/tmpdisk/Makefile.am b/plugins/tmpdisk/Makefile.am new file mode 100644 index 00000000..2e487e92 --- /dev/null +++ b/plugins/tmpdisk/Makefile.am @@ -0,0 +1,66 @@ +# nbdkit +# Copyright (C) 2017-2020 Red Hat Inc. +# +# Redistribution and use in source and binary forms, with or without +# modification, are permitted provided that the following conditions are +# met: +# +# * Redistributions of source code must retain the above copyright +# notice, this list of conditions and the following disclaimer. +# +# * Redistributions in binary form must reproduce the above copyright +# notice, this list of conditions and the following disclaimer in the +# documentation and/or other materials provided with the distribution. +# +# * Neither the name of Red Hat nor the names of its contributors may be +# used to endorse or promote products derived from this software without +# specific prior written permission. +# +# THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND +# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, +# THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A +# PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR +# CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, +# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT +# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF +# USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND +# ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, +# OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT +# OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF +# SUCH DAMAGE. + +include $(top_srcdir)/common-rules.mk + +EXTRA_DIST = nbdkit-tmpdisk-plugin.pod + +plugin_LTLIBRARIES = nbdkit-tmpdisk-plugin.la + +nbdkit_tmpdisk_plugin_la_SOURCES = \ + tmpdisk.c \ + $(top_srcdir)/include/nbdkit-plugin.h \ + $(NULL) + +nbdkit_tmpdisk_plugin_la_CPPFLAGS = \ + -I$(top_srcdir)/include \ + -I$(top_srcdir)/common/utils \ + $(NULL) +nbdkit_tmpdisk_plugin_la_CFLAGS = $(WARNINGS_CFLAGS) +nbdkit_tmpdisk_plugin_la_LDFLAGS = \ + -module -avoid-version -shared \ + -Wl,--version-script=$(top_srcdir)/plugins/plugins.syms \ + $(NULL) +nbdkit_tmpdisk_plugin_la_LIBADD = \ + $(top_builddir)/common/utils/libutils.la \ + $(NULL) + +if HAVE_POD + +man_MANS = nbdkit-tmpdisk-plugin.1 +CLEANFILES += $(man_MANS) + +nbdkit-tmpdisk-plugin.1: nbdkit-tmpdisk-plugin.pod + $(PODWRAPPER) --section=1 --man $@ \ + --html $(top_builddir)/html/$@.html \ + $< + +endif HAVE_POD diff --git a/plugins/tmpdisk/tmpdisk.c b/plugins/tmpdisk/tmpdisk.c new file mode 100644 index 00000000..aa3c25f9 --- /dev/null +++ b/plugins/tmpdisk/tmpdisk.c @@ -0,0 +1,426 @@ +/* nbdkit + * Copyright (C) 2017-2020 Red Hat Inc. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions are + * met: + * + * * Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * + * * Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * + * * Neither the name of Red Hat nor the names of its contributors may be + * used to endorse or promote products derived from this software without + * specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, + * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A + * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR + * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, + * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT + * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF + * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND + * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, + * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT + * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + */ + +#include <config.h> + +#include <stdio.h> +#include <stdlib.h> +#include <stdbool.h> +#include <stdint.h> +#include <inttypes.h> +#include <string.h> +#include <unistd.h> +#include <fcntl.h> +#include <errno.h> +#include <sys/types.h> +#include <sys/wait.h> + +#define NBDKIT_API_VERSION 2 +#include <nbdkit-plugin.h> + +#include "cleanup.h" +#include "utils.h" + +static int64_t size = -1; + +static const char *command = + "labelopt='-L'\n" + "case \"$type\" in\n" + " ext?)\n" + " extra='-F' ;;\n" + " *fat|msdos)\n" + " extra='-I' ;;\n" + " ntfs)\n" + " extra='-Q -F'\n" + " labelopt='-n' ;;\n" + " xfs)\n" + " extra='-f' ;;\n" + "esac\n" + "if [ \"x$label\" = \"x\" ]; then\n" + " mkfs -t \"$type\" $extra $disk >/dev/null\n" + "else\n" + " mkfs -t \"$type\" $extra $labelopt \"$label\" $disk >/dev/null\n" + "fi\n"; +static const char *label = NULL; +static const char *type = "ext4"; + +static int +tmpdisk_config (const char *key, const char *value) +{ + if (strcmp (key, "command") == 0) { + command = value; + } + else if (strcmp (key, "label") == 0) { + if (strcmp (value, "") == 0) + label = NULL; + else + label = value; + } + else if (strcmp (key, "size") == 0) { + size = nbdkit_parse_size (value); + if (size == -1) + return -1; + } + else if (strcmp (key, "type") == 0) { + type = value; + } + else { + nbdkit_error ("unknown parameter '%s'", key); + return -1; + } + + return 0; +} + +static int +tmpdisk_config_complete (void) +{ + if (size == -1) { + nbdkit_error ("size parameter is required"); + return -1; + } + + return 0; +} + +#define tmpdisk_config_help \ + "size=<SIZE> (required) Virtual filesystem size.\n" \ + "label=<LABEL> The filesystem label.\n" \ + "type=ext4|... The filesystem type.\n" \ + "command=<COMMAND> Alternate command instead of mkfs." + +struct handle { + int fd; + bool can_punch_hole; +}; + +/* Absolutely unsafe! Although this is simply returning the default + * value, provide this callback to make it clear. + */ +static int +tmpdisk_can_multi_conn (void *handle) +{ + return 0; +} + +static int +tmpdisk_can_trim (void *handle) +{ +#ifdef FALLOC_FL_PUNCH_HOLE + return 1; +#else + return 0; +#endif +} + +/* Pretend we have native FUA support, but actually because all disks + * are temporarily we will deliberately ignore flush/FUA operations. + */ +static int +tmpdisk_can_fua (void *handle) +{ + return NBDKIT_FUA_NATIVE; +} + +static int64_t +tmpdisk_get_size (void *handle) +{ + return size; +} + +/* This creates and runs the full "mkfs" (or whatever) command. */ +static int +run_command (const char *disk) +{ + FILE *fp; + CLEANUP_FREE char *cmd = NULL; + size_t len = 0; + int r; + + fp = open_memstream (&cmd, &len); + if (fp == NULL) { + nbdkit_error ("open_memstream: %m"); + return -1; + } + + /* Set the shell variables. */ + fprintf (fp, "disk="); + shell_quote (disk, fp); + putc ('\n', fp); + if (label) { + fprintf (fp, "label="); + shell_quote (label, fp); + putc ('\n', fp); + } + fprintf (fp, "size=%" PRIi64 "\n", size); + fprintf (fp, "type="); + shell_quote (type, fp); + putc ('\n', fp); + putc ('\n', fp); + fprintf (fp, "%s", command); + + if (fclose (fp) == EOF) { + nbdkit_error ("memstream failed"); + return -1; + } + + r = system (cmd); + if (r == -1) { + nbdkit_error ("failed to execute command: %m"); + return -1; + } + if (WIFEXITED (r) && WEXITSTATUS (r) != 0) { + nbdkit_error ("command exited with code %d", WEXITSTATUS (r)); + return -1; + } + else if (WIFSIGNALED (r)) { + nbdkit_error ("command killed by signal %d", WTERMSIG (r)); + return -1; + } + else if (WIFSTOPPED (r)) { + nbdkit_error ("command stopped by signal %d", WSTOPSIG (r)); + return -1; + } + + return 0; +} + +static void * +tmpdisk_open (int readonly) +{ + struct handle *h; + CLEANUP_FREE char *disk = NULL; + const char *tmpdir; + + tmpdir = getenv ("TMPDIR"); + if (!tmpdir) + tmpdir = "/var/tmp"; + + h = malloc (sizeof *h); + if (h == NULL) { + nbdkit_error ("malloc: %m"); + goto error; + } + h->fd = -1; + h->can_punch_hole = true; + + /* Create the new disk image for this connection. */ + if (asprintf (&disk, "%s/tmpdiskXXXXXX", tmpdir) == -1) { + nbdkit_error ("asprintf: %m"); + goto error; + } + + h->fd = mkstemp (disk); + if (h->fd == -1) { + nbdkit_error ("mkstemp: %m"); + goto error; + } + + /* Truncate the disk to a sparse file of the right size. */ + if (ftruncate (h->fd, size) == -1) { + nbdkit_error ("ftruncate: %s: %m", disk); + goto error; + } + + /* Now run the mkfs command. */ + if (run_command (disk) == -1) + goto error; + + /* We don't need the disk to appear in the filesystem since we hold + * a file descriptor open and access it through that, so unlink the + * disk. This also ensures it is always cleaned up. + */ + unlink (disk); + + /* Return the handle. */ + return h; + + error: + if (h) { + if (h->fd >= 0) { + close (h->fd); + unlink (disk); + } + free (h); + } + return NULL; +} + +static void +tmpdisk_close (void *handle) +{ + struct handle *h = handle; + + close (h->fd); + free (h); +} + +/* Read data from the file. */ +static int +tmpdisk_pread (void *handle, void *buf, + uint32_t count, uint64_t offset, + uint32_t flags) +{ + struct handle *h = handle; + + while (count > 0) { + ssize_t r = pread (h->fd, buf, count, offset); + if (r == -1) { + nbdkit_error ("pread: %m"); + return -1; + } + if (r == 0) { + nbdkit_error ("pread: unexpected end of file"); + return -1; + } + buf += r; + count -= r; + offset += r; + } + + return 0; +} + +/* Write data to the file. */ +static int +tmpdisk_pwrite (void *handle, const void *buf, + uint32_t count, uint64_t offset, + uint32_t flags) +{ + struct handle *h = handle; + + while (count > 0) { + ssize_t r = pwrite (h->fd, buf, count, offset); + if (r == -1) { + nbdkit_error ("pwrite: %m"); + return -1; + } + buf += r; + count -= r; + offset += r; + } + + /* Deliberately ignore FUA if present in flags. */ + + return 0; +} + +/* This plugin deliberately provides a null flush operation, because + * all of the disks created are temporary. + */ +static int +tmpdisk_flush (void *handle, uint32_t flags) +{ + return 0; +} + +#if defined (FALLOC_FL_PUNCH_HOLE) +static int +do_fallocate (int fd, int mode, off_t offset, off_t len) +{ + int r = fallocate (fd, mode, offset, len); + if (r == -1 && errno == ENODEV) { + /* kernel 3.10 fails with ENODEV for block device. Kernel >= 4.9 fails + * with EOPNOTSUPP in this case. Normalize errno to simplify callers. + */ + errno = EOPNOTSUPP; + } + return r; +} + +static bool +is_enotsup (int err) +{ + return err == ENOTSUP || err == EOPNOTSUPP; +} +#endif + +/* Punch a hole in the file. */ +static int +tmpdisk_trim (void *handle, uint32_t count, uint64_t offset, uint32_t flags) +{ +#ifdef FALLOC_FL_PUNCH_HOLE + struct handle *h = handle; + int r; + + if (h->can_punch_hole) { + r = do_fallocate (h->fd, FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE, + offset, count); + if (r == -1) { + /* Trim is advisory; we don't care if it fails for anything other + * than EIO or EPERM. + */ + if (errno == EPERM || errno == EIO) { + nbdkit_error ("fallocate: %m"); + return -1; + } + + if (is_enotsup (EOPNOTSUPP)) + h->can_punch_hole = false; + + nbdkit_debug ("ignoring failed fallocate during trim: %m"); + } + } +#endif + + /* Deliberately ignore FUA if present in flags. */ + + return 0; +} + +#define THREAD_MODEL NBDKIT_THREAD_MODEL_PARALLEL + +static struct nbdkit_plugin plugin = { + .name = "tmpdisk", + .version = PACKAGE_VERSION, + + .config = tmpdisk_config, + .config_complete = tmpdisk_config_complete, + .config_help = tmpdisk_config_help, + .magic_config_key = "size", + + .can_multi_conn = tmpdisk_can_multi_conn, + .can_trim = tmpdisk_can_trim, + .can_fua = tmpdisk_can_fua, + .get_size = tmpdisk_get_size, + + .open = tmpdisk_open, + .close = tmpdisk_close, + .pread = tmpdisk_pread, + .pwrite = tmpdisk_pwrite, + .flush = tmpdisk_flush, + .trim = tmpdisk_trim, + + .errno_is_preserved = 1, +}; + +NBDKIT_REGISTER_PLUGIN(plugin) -- 2.25.0