120 lines
5.3 KiB
Python
120 lines
5.3 KiB
Python
# -*- coding: utf-8 -*-
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import fcntl
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import os
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import shutil
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import subprocess
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from . import flock
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from .paths import HOSTS_FILE, HOSTS_LOCK, LXC_LOGS, LXC_ROOT, LXC_STORAGE_DIR
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from .templates import LXC_CONTAINER
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def prepare_container(container, layers):
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# Remove ephemeral layer data
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clean_ephemeral_layer(container)
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# Prepare and mount overlayfs. This needs to be done before handing over control to LXC as we use unprivileged containers
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# which don't have the capability to mount overlays - https://www.spinics.net/lists/linux-fsdevel/msg105877.html
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rootfs = os.path.join(LXC_ROOT, container, 'rootfs')
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# Unmount rootfs in case it remained mounted for whatever reason
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unmount_rootfs(rootfs)
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layers = layers.split(',')
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mount_rootfs(container, layers, rootfs)
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def mount_rootfs(container, layers, mountpoint):
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if len(layers) == 1:
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# We have only single layer, no overlay needed
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subprocess.run(['mount', '--bind', layers[0], mountpoint])
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else:
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olwork = os.path.join(LXC_ROOT, container, 'olwork')
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subprocess.run(['mount', '-t', 'overlay', '-o', 'upperdir={},lowerdir={},workdir={}'.format(layers[0], ':'.join(layers[1:]), olwork), 'none', mountpoint])
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def unmount_rootfs(mountpoint):
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if os.path.exists(mountpoint):
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subprocess.run(['umount', '--quiet', mountpoint])
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def clean_ephemeral_layer(container):
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# Cleans containers ephemeral layer. Called in lxc.hook.post-stop and lxc.hook.pre-start in case of unclean shutdown
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# This is done early in the container start process, so the inode of the ephemeral directory must remain unchanged
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ephemeral = os.path.join(LXC_ROOT, container, 'ephemeral')
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for item in os.scandir(ephemeral):
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shutil.rmtree(item.path) if item.is_dir() else os.unlink(item.path)
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def cleanup_container(container):
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# Unmount rootfs
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rootfs = os.path.join(LXC_ROOT, container, 'rootfs')
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unmount_rootfs(rootfs)
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# Remove ephemeral layer data
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clean_ephemeral_layer(container)
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def create_container(container, image):
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# Create directories after container installation
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rootfs = os.path.join(LXC_ROOT, container, 'rootfs')
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olwork = os.path.join(LXC_ROOT, container, 'olwork')
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ephemeral = os.path.join(LXC_ROOT, container, 'ephemeral')
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os.makedirs(rootfs, 0o755, True)
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os.makedirs(olwork, 0o755, True)
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os.makedirs(ephemeral, 0o755, True)
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os.chown(ephemeral, 100000, 100000)
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# Create container configuration file
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layers = ','.join([os.path.join(LXC_STORAGE_DIR, layer) for layer in image['layers']])
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# Add ephemeral layer if the container is not created as part of build process
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if 'build' not in image:
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layers = '{},{}'.format(layers, ephemeral)
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mounts = '\n{}'.format('\n'.join(['lxc.mount.entry = {} {} none bind,create={} 0 0'.format(m[1], m[2].lstrip('/'), m[0].lower()) for m in image['mounts']])) if 'mounts' in image else ''
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env = '\n{}'.format('\n'.join(['lxc.environment = {}={}'.format(e[0], e[1]) for e in image['env']])) if 'env' in image else ''
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uid = image['uid'] if 'uid' in image else '0'
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gid = image['gid'] if 'gid' in image else '0'
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cmd = image['cmd'] if 'cmd' in image else '/bin/sh'
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cwd = image['cwd'] if 'cwd' in image else '/root'
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halt = image['halt'] if 'halt' in image else 'SIGINT'
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# Lease the first unused IP to the container
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ipv4 = update_hosts_lease(container, True)
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# Create the config file
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with open(os.path.join(LXC_ROOT, container, 'config'), 'w') as f:
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f.write(LXC_CONTAINER.format(name=container, ipv4=ipv4, layers=layers, mounts=mounts, env=env, uid=uid, gid=gid, cmd=cmd, cwd=cwd, halt=halt))
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def destroy_container(container):
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# Remove container configuration and directories
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rootfs = os.path.join(LXC_ROOT, container, 'rootfs')
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unmount_rootfs(rootfs)
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try:
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shutil.rmtree(os.path.join(LXC_ROOT, container))
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except FileNotFoundError:
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pass
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try:
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os.unlink(os.path.join(LXC_LOGS, '{}.log'.format(container)))
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except FileNotFoundError:
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pass
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# Release the IP address
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update_hosts_lease(container, False)
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@flock.flock_ex(HOSTS_LOCK)
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def update_hosts_lease(container, is_request):
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# This is a poor man's DHCP server which uses /etc/hosts as lease database
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# Leases the first unused IP from range 172.17.0.0/16
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# Uses file lock as interprocess mutex
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ip = None
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# Load all existing records
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with open(HOSTS_FILE, 'r') as f:
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leases = [l.strip().split(' ', 1) for l in f]
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# If this call is a request for lease, find if there isn't already existing lease for the container
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if is_request:
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already_leased = [l[0] for l in leases if l[1] == container]
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if already_leased:
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return already_leased[0]
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# Otherwise assign the first unassigned IP
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used_ips = [l[0] for l in leases]
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for i in range(2, 65278): # Reserve last /24 subnet for VPN
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ip = '172.17.{}.{}'. format(i // 256, i % 256)
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if ip not in used_ips:
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leases.append([ip, container])
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break
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# Otherwise it is a release in which case we just delete the record
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else:
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leases = [l for l in leases if l[1] != container]
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# Write the contents back to the file
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with open(HOSTS_FILE, 'w') as f:
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for lease in leases:
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f.write('{} {}\n'.format(lease[0], lease[1]))
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return ip
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