[Libguestfs] [PATCH nbdkit filters-v3 7/7] filters: Add nbdkit-partition-filter.
Richard W.M. Jones
rjones at redhat.com
Fri Jan 19 22:36:28 UTC 2018
This can be used to filter a single partition from a disk image. It
supports MBR and GPT, but not MBR extended partitions because those
are crazy.
---
TODO | 2 -
configure.ac | 1 +
filters/Makefile.am | 3 +-
filters/offset/nbdkit-offset-filter.pod | 17 +-
filters/partition/Makefile.am | 62 +++++
filters/partition/nbdkit-partition-filter.pod | 99 ++++++++
filters/partition/partition.c | 351 ++++++++++++++++++++++++++
7 files changed, 531 insertions(+), 4 deletions(-)
diff --git a/TODO b/TODO
index 3ec45fd..b1f922e 100644
--- a/TODO
+++ b/TODO
@@ -41,8 +41,6 @@ Suggestions for filters
* copy-on-write, a popular feature in other servers
-* export a single partition (like qemu-nbd -P)
-
Composing nbdkit
----------------
diff --git a/configure.ac b/configure.ac
index 9376a2e..fd71ca6 100644
--- a/configure.ac
+++ b/configure.ac
@@ -515,6 +515,7 @@ AC_CONFIG_FILES([Makefile
filters/Makefile
filters/delay/Makefile
filters/offset/Makefile
+ filters/partition/Makefile
src/Makefile
src/nbdkit.pc
tests/Makefile])
diff --git a/filters/Makefile.am b/filters/Makefile.am
index d4aa6c0..d918b81 100644
--- a/filters/Makefile.am
+++ b/filters/Makefile.am
@@ -32,4 +32,5 @@
SUBDIRS = \
delay \
- offset
+ offset \
+ partition
diff --git a/filters/offset/nbdkit-offset-filter.pod b/filters/offset/nbdkit-offset-filter.pod
index a94170e..25bdbb9 100644
--- a/filters/offset/nbdkit-offset-filter.pod
+++ b/filters/offset/nbdkit-offset-filter.pod
@@ -36,7 +36,7 @@ file/device.
Note it is an error if the offset and/or range specify data which lies
beyond the end of the underlying device.
-=head1 EXAMPLE
+=head1 EXAMPLES
Using L<nbdkit-file-plugin(1)>, serve the file C<disk.img> starting at
offset C<1M>. The total length served is C<100M> (the underlying file
@@ -44,11 +44,26 @@ must therefore be at least C<101M> in length):
nbdkit --filter=offset file file=disk.img offset=1M range=100M
+One way to serve a single partition from a disk is to find the start
+and length of the partition, eg using:
+
+ $ parted disk.img -- unit b print
+ ...
+ Number Start End Size Type File system Flags
+ 1 65536B 104792575B 104727040B primary ext2
+
+You can then serve the partition only using:
+
+ nbdkit --filter=offset file file=disk.img offset=65536 range=104727040
+
+An easier way to do this is with L<nbdkit-partition-filter(1)>.
+
=head1 SEE ALSO
L<nbdkit(1)>,
L<nbdkit-file-plugin(1)>,
L<nbdkit-filter(3)>.
+L<nbdkit-partition-filter(1)>.
=head1 AUTHORS
diff --git a/filters/partition/Makefile.am b/filters/partition/Makefile.am
new file mode 100644
index 0000000..0464e7c
--- /dev/null
+++ b/filters/partition/Makefile.am
@@ -0,0 +1,62 @@
+# nbdkit
+# Copyright (C) 2018 Red Hat Inc.
+# All rights reserved.
+#
+# 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.
+
+EXTRA_DIST = nbdkit-partition-filter.pod
+
+CLEANFILES = *~
+
+filterdir = $(libdir)/nbdkit/filters
+
+filter_LTLIBRARIES = nbdkit-partition-filter.la
+
+nbdkit_partition_filter_la_SOURCES = \
+ partition.c \
+ $(top_srcdir)/include/nbdkit-filter.h
+
+nbdkit_partition_filter_la_CPPFLAGS = \
+ -I$(top_srcdir)/include
+nbdkit_partition_filter_la_CFLAGS = \
+ $(WARNINGS_CFLAGS)
+nbdkit_partition_filter_la_LDFLAGS = \
+ -module -avoid-version -shared
+
+if HAVE_POD2MAN
+
+man_MANS = nbdkit-partition-filter.1
+CLEANFILES += $(man_MANS)
+
+nbdkit-partition-filter.1: nbdkit-partition-filter.pod
+ $(POD2MAN) $(POD2MAN_ARGS) --section=1 --name=`basename $@ .1` $< $@.t && \
+ if grep 'POD ERROR' $@.t; then rm $@.t; exit 1; fi && \
+ mv $@.t $@
+
+endif
diff --git a/filters/partition/nbdkit-partition-filter.pod b/filters/partition/nbdkit-partition-filter.pod
new file mode 100644
index 0000000..8ba2776
--- /dev/null
+++ b/filters/partition/nbdkit-partition-filter.pod
@@ -0,0 +1,99 @@
+=encoding utf8
+
+=head1 NAME
+
+nbdkit-partition-filter - nbdkit partition filter
+
+=head1 SYNOPSIS
+
+ nbdkit --filter=partition plugin partition=PART [plugin-args...]
+
+=head1 DESCRIPTION
+
+C<nbdkit-partition-filter> is a filter that limits requests to a
+single partition within a disk image that is served by another plugin.
+
+Partition numbers are specified by the required C<partition>
+parameter, and count from 1.
+
+This works like the C<qemu-nbd -P> option.
+
+=head1 NOTE
+
+Only MBR primary partitions and GPT partition tables are supported.
+MBR logical partitions are B<not> supported.
+
+=head1 PARAMETERS
+
+=over 4
+
+=item B<partition=PART>
+
+The partition number to serve, counting from 1.
+
+This parameter is required.
+
+=back
+
+=head1 EXAMPLE
+
+F<disk.img> is a partitioned disk image (eg. a virtual machine disk
+image). To serve the first partition only use:
+
+ nbdkit --filter=partition file file=disk.img partition=1
+
+=head1 SEE ALSO
+
+L<nbdkit(1)>,
+L<nbdkit-file-plugin(1)>,
+L<nbdkit-filter(3)>.
+L<nbdkit-offset-filter(1)>,
+L<parted(8)>.
+
+=head1 AUTHORS
+
+Richard W.M. Jones
+
+=head1 COPYRIGHT
+
+Copyright (C) 2018 Red Hat Inc.
+
+=head1 LICENSE
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+=over 4
+
+=item *
+
+Redistributions of source code must retain the above copyright
+notice, this list of conditions and the following disclaimer.
+
+=item *
+
+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.
+
+=item *
+
+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.
+
+=back
+
+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.
diff --git a/filters/partition/partition.c b/filters/partition/partition.c
new file mode 100644
index 0000000..ddf6f93
--- /dev/null
+++ b/filters/partition/partition.c
@@ -0,0 +1,351 @@
+/* nbdkit
+ * Copyright (C) 2018 Red Hat Inc.
+ * All rights reserved.
+ *
+ * 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 <stdint.h>
+#include <string.h>
+#include <inttypes.h>
+#include <endian.h>
+
+#include <nbdkit-filter.h>
+
+static int partnum = -1;
+
+/* Called for each key=value passed on the command line. */
+static int
+partition_config (nbdkit_next_config *next, void *nxdata,
+ const char *key, const char *value)
+{
+ if (strcmp (key, "partition") == 0) {
+ if (sscanf (value, "%d", &partnum) != 1 || partnum <= 0) {
+ nbdkit_error ("invalid partition number");
+ return -1;
+ }
+ return 0;
+ }
+ else
+ return next (nxdata, key, value);
+}
+
+/* Check the user did pass partition number. */
+static int
+partition_config_complete (nbdkit_next_config_complete *next, void *nxdata)
+{
+ if (partnum == -1) {
+ nbdkit_error ("you must supply the partition parameter on the command line");
+ return -1;
+ }
+
+ return next (nxdata);
+}
+
+#define partition_config_help \
+ "partition=<PART> (required) The partition number (counting from 1)."
+
+struct handle {
+ int64_t offset;
+ int64_t range;
+};
+
+/* Open a connection. */
+static void *
+partition_open (nbdkit_next_open *next, void *nxdata, int readonly)
+{
+ struct handle *h;
+
+ if (next (nxdata, readonly) == -1)
+ return NULL;
+
+ h = malloc (sizeof *h);
+ if (h == NULL) {
+ nbdkit_error ("malloc: %m");
+ return NULL;
+ }
+
+ /* These are set in the prepare method. */
+ h->offset = h->range = -1;
+ return h;
+}
+
+static void
+partition_close (void *handle)
+{
+ struct handle *h = handle;
+
+ free (h);
+}
+
+/* Inspect the underlying partition table. partition_prepare is
+ * called before data processing.
+ */
+struct mbr_partition {
+ uint8_t part_type_byte;
+ uint32_t start_sector;
+ uint32_t nr_sectors;
+};
+
+static void
+get_mbr_partition (uint8_t *sector, int i, struct mbr_partition *part)
+{
+ int offset = 0x1BE + i*0x10;
+
+ part->part_type_byte = sector[offset+4];
+ memcpy (&part->start_sector, §or[offset+8], 4);
+ part->start_sector = le32toh (part->start_sector);
+ memcpy (&part->nr_sectors, §or[offset+0xC], 4);
+ part->nr_sectors = le32toh (part->nr_sectors);
+}
+
+static int
+find_mbr_partition (struct nbdkit_next_ops *next_ops, void *nxdata,
+ struct handle *h, int64_t size, uint8_t *mbr)
+{
+ int i;
+ struct mbr_partition partition;
+
+ if (partnum > 4) {
+ nbdkit_error ("MBR logical partitions are not supported");
+ return -1;
+ }
+
+ for (i = 0; i < 4; ++i) {
+ get_mbr_partition (mbr, i, &partition);
+ if (partition.nr_sectors > 0 &&
+ partition.part_type_byte != 0 &&
+ partnum == i+1) {
+ h->offset = partition.start_sector * 512;
+ h->range = partition.nr_sectors * 512;
+ return 0;
+ }
+ }
+
+ nbdkit_error ("MBR partition %d not found", partnum);
+ return -1;
+}
+
+struct gpt_header {
+ uint32_t nr_partitions;
+ uint32_t partition_entry_size;
+};
+
+static void
+get_gpt_header (uint8_t *sector, struct gpt_header *header)
+{
+ memcpy (&header->nr_partitions, §or[0x50], 4);
+ header->nr_partitions = le32toh (header->nr_partitions);
+ memcpy (&header->partition_entry_size, §or[0x54], 4);
+ header->partition_entry_size = le32toh (header->partition_entry_size);
+}
+
+struct gpt_partition {
+ uint8_t partition_type_guid[16];
+ uint64_t first_lba;
+ uint64_t last_lba;
+};
+
+static void
+get_gpt_partition (uint8_t *bytes, struct gpt_partition *part)
+{
+ memcpy (&part->partition_type_guid, &bytes[0], 16);
+ memcpy (&part->first_lba, &bytes[0x20], 8);
+ part->first_lba = le64toh (part->first_lba);
+ memcpy (&part->last_lba, &bytes[0x28], 8);
+ part->last_lba = le64toh (part->last_lba);
+}
+
+static int
+find_gpt_partition (struct nbdkit_next_ops *next_ops, void *nxdata,
+ struct handle *h, int64_t size, uint8_t *header_bytes)
+{
+ uint8_t partition_bytes[128];
+ struct gpt_header header;
+ struct gpt_partition partition;
+ int i;
+
+ if (partnum > 128) {
+ out_of_range:
+ nbdkit_error ("GPT partition number out of range");
+ return -1;
+ }
+ get_gpt_header (header_bytes, &header);
+ if (partnum > header.nr_partitions)
+ goto out_of_range;
+
+ if (header.partition_entry_size != 128) {
+ nbdkit_error ("GPT partition entry is not 128 bytes");
+ return -1;
+ }
+
+ for (i = 0; i < 128; ++i) {
+ /* We already checked these are within bounds in the
+ * partition_prepare call above.
+ */
+ if (next_ops->pread (nxdata, partition_bytes, sizeof partition_bytes,
+ 2*512 + i*128) == -1)
+ return -1;
+ get_gpt_partition (partition_bytes, &partition);
+ if (memcmp (partition.partition_type_guid,
+ "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0", 16) != 0 &&
+ partnum == i+1) {
+ h->offset = partition.first_lba * 512;
+ h->range = (1 + partition.last_lba - partition.first_lba) * 512;
+ return 0;
+ }
+ }
+
+ nbdkit_error ("GPT partition %d not found", partnum);
+ return -1;
+}
+
+static int
+partition_prepare (struct nbdkit_next_ops *next_ops, void *nxdata,
+ void *handle)
+{
+ struct handle *h = handle;
+ int64_t size;
+ uint8_t lba01[1024]; /* LBA 0 and 1 */
+ int r;
+
+ size = next_ops->get_size (nxdata);
+ if (size == -1)
+ return -1;
+ if (size < 1024) {
+ nbdkit_error ("disk is too small to be a partitioned disk");
+ return -1;
+ }
+
+ nbdkit_debug ("disk size=%" PRIi64, size);
+
+ if (next_ops->pread (nxdata, lba01, sizeof lba01, 0) != 0)
+ return -1;
+
+ /* Is it GPT? */
+ if (size >= 2 * 34 * 512 && memcmp (&lba01[512], "EFI PART", 8) == 0)
+ r = find_gpt_partition (next_ops, nxdata, h, size, &lba01[512]);
+ /* Is it MBR? */
+ else if (lba01[0x1fe] == 0x55 && lba01[0x1ff] == 0xAA)
+ r = find_mbr_partition (next_ops, nxdata, h, size, lba01);
+ else {
+ nbdkit_error ("disk does not contain MBR or GPT partition table signature");
+ r = -1;
+ }
+ if (r == -1)
+ return -1;
+
+ /* The find_*_partition functions set h->offset & h->range in the
+ * handle to point to the partition boundaries. However we
+ * additionally check that they are inside the underlying disk.
+ */
+ if (h->offset < 0 || h->range < 0 || h->offset + h->range > size) {
+ nbdkit_error ("partition is outside the disk");
+ return -1;
+ }
+
+ nbdkit_debug ("partition offset=%" PRIi64 " range=%" PRIi64,
+ h->offset, h->range);
+
+ return 0;
+}
+
+/* Get the file size. */
+static int64_t
+partition_get_size (struct nbdkit_next_ops *next_ops, void *nxdata,
+ void *handle)
+{
+ struct handle *h = handle;
+
+ return h->range;
+}
+
+/* Read data. */
+static int
+partition_pread (struct nbdkit_next_ops *next_ops, void *nxdata,
+ void *handle, void *buf, uint32_t count, uint64_t offs)
+{
+ struct handle *h = handle;
+
+ return next_ops->pread (nxdata, buf, count, offs + h->offset);
+}
+
+/* Write data. */
+static int
+partition_pwrite (struct nbdkit_next_ops *next_ops, void *nxdata,
+ void *handle,
+ const void *buf, uint32_t count, uint64_t offs)
+{
+ struct handle *h = handle;
+
+ return next_ops->pwrite (nxdata, buf, count, offs + h->offset);
+}
+
+/* Trim data. */
+static int
+partition_trim (struct nbdkit_next_ops *next_ops, void *nxdata,
+ void *handle, uint32_t count, uint64_t offs)
+{
+ struct handle *h = handle;
+
+ return next_ops->trim (nxdata, count, offs + h->offset);
+}
+
+/* Zero data. */
+static int
+partition_zero (struct nbdkit_next_ops *next_ops, void *nxdata,
+ void *handle, uint32_t count, uint64_t offs, int may_trim)
+{
+ struct handle *h = handle;
+
+ return next_ops->zero (nxdata, count, offs + h->offset, may_trim);
+}
+
+static struct nbdkit_filter filter = {
+ .name = "partition",
+ .longname = "nbdkit partition filter",
+ .version = PACKAGE_VERSION,
+ .config = partition_config,
+ .config_complete = partition_config_complete,
+ .config_help = partition_config_help,
+ .open = partition_open,
+ .prepare = partition_prepare,
+ .close = partition_close,
+ .get_size = partition_get_size,
+ .pread = partition_pread,
+ .pwrite = partition_pwrite,
+ .trim = partition_trim,
+ .zero = partition_zero,
+};
+
+NBDKIT_REGISTER_FILTER(filter)
--
2.15.1
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