mirror of
https://github.com/GNS3/gns3-server
synced 2024-11-12 19:38:57 +00:00
103 lines
3.2 KiB
Python
103 lines
3.2 KiB
Python
#!/usr/bin/env python
|
|
#
|
|
# Copyright (C) 2016 GNS3 Technologies Inc.
|
|
#
|
|
# This program is free software: you can redistribute it and/or modify
|
|
# it under the terms of the GNU General Public License as published by
|
|
# the Free Software Foundation, either version 3 of the License, or
|
|
# (at your option) any later version.
|
|
#
|
|
# This program is distributed in the hope that it will be useful,
|
|
# but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
# GNU General Public License for more details.
|
|
#
|
|
# You should have received a copy of the GNU General Public License
|
|
# along with this program. If not, see <http://www.gnu.org/licenses/>.
|
|
|
|
import os
|
|
import asyncio
|
|
import struct
|
|
|
|
|
|
class Qcow2Error(Exception):
|
|
pass
|
|
|
|
|
|
class Qcow2:
|
|
"""
|
|
Allows to parse a Qcow2 file
|
|
"""
|
|
|
|
def __init__(self, path):
|
|
|
|
self._path = path
|
|
self._reload()
|
|
|
|
def _reload(self):
|
|
# Each QCOW2 file begins with a header, in big endian format, as follows:
|
|
#
|
|
# typedef struct QCowHeader {
|
|
# uint32_t magic;
|
|
# uint32_t version;
|
|
#
|
|
# uint64_t backing_file_offset;
|
|
# uint32_t backing_file_size;
|
|
#
|
|
# uint32_t cluster_bits;
|
|
# uint64_t size; /* in bytes */
|
|
# uint32_t crypt_method;
|
|
#
|
|
# uint32_t l1_size;
|
|
# uint64_t l1_table_offset;
|
|
#
|
|
# uint64_t refcount_table_offset;
|
|
# uint32_t refcount_table_clusters;
|
|
#
|
|
# uint32_t nb_snapshots;
|
|
# uint64_t snapshots_offset;
|
|
# } QCowHeader;
|
|
|
|
struct_format = ">IIQi"
|
|
with open(self._path, 'rb') as f:
|
|
content = f.read(struct.calcsize(struct_format))
|
|
self.magic, self.version, self.backing_file_offset, self.backing_file_size = struct.unpack_from(struct_format, content)
|
|
|
|
if self.magic != 1363560955: # The first 4 bytes contain the characters 'Q', 'F', 'I' followed by 0xfb.
|
|
raise Qcow2Error("Invalid magic for {}".format(self._path))
|
|
|
|
@property
|
|
def backing_file(self):
|
|
"""
|
|
When using linked clone this will return the path to the base image
|
|
|
|
:returns: None if it's not a linked clone, the path otherwise
|
|
"""
|
|
|
|
with open(self._path, 'rb') as f:
|
|
f.seek(self.backing_file_offset)
|
|
content = f.read(self.backing_file_size)
|
|
|
|
path = content.decode()
|
|
if len(path) == 0:
|
|
return None
|
|
return path
|
|
|
|
@asyncio.coroutine
|
|
def rebase(self, qemu_img, base_image):
|
|
"""
|
|
Rebase a linked clone in order to use the correct disk
|
|
|
|
:param qemu_img: Path to the qemu-img binary
|
|
:param base_image: Path to the base image
|
|
"""
|
|
|
|
if not os.path.exists(base_image):
|
|
raise FileNotFoundError(base_image)
|
|
command = [qemu_img, "rebase", "-u", "-b", base_image, self._path]
|
|
process = yield from asyncio.create_subprocess_exec(*command)
|
|
retcode = yield from process.wait()
|
|
if retcode != 0:
|
|
raise Qcow2Error("Could not rebase the image")
|
|
self._reload()
|