Basically, IPDB is a transactional database, containing records, representing network stack objects. Any change in the database is not reflected immediately in OS (unless you ask for that explicitly), but waits until commit() is called.
These two modules, IPRoute and IPDB, use completely different approaches. The first one, IPRoute, is synchronous by default, and can be used in the same way, as usual Linux utilities. It doesn’t spawn any additional threads or processes, until one explicitly calls IPRoute.bind(async=True).
The latter, IPDB, is an asynchronously updated database, that starts several additional threads by default. If your project’s policy doesn’t allow implicit threads, keep it in mind.
Simple tutorial:
from pyroute2 import IPDB
# several IPDB instances are supported within on process
ip = IPDB()
# commit is called automatically upon the exit from `with`
# statement
with ip.interfaces.eth0 as i:
i.address = '00:11:22:33:44:55'
i.ifname = 'bala'
i.txqlen = 2000
# basic routing support
ip.routes.add({'dst': 'default', 'gateway': '10.0.0.1'}).commit()
IPDB uses IPRoute as a transport, and monitors all broadcast netlink messages from the kernel, thus keeping the database up-to-date in an asynchronous manner. IPDB inherits dict class, and has two keys:
>>> from pyroute2 import IPDB
>>> ip = IPDB()
>>> ip.by_name.keys()
['bond0', 'lo', 'em1', 'wlan0', 'dummy0', 'virbr0-nic', 'virbr0']
>>> ip.by_index.keys()
[32, 1, 2, 3, 4, 5, 8]
>>> ip.interfaces.keys()
[32,
1,
2,
3,
4,
5,
8,
'lo',
'em1',
'wlan0',
'bond0',
'dummy0',
'virbr0-nic',
'virbr0']
>>> ip.interfaces['em1']['address']
'f0:de:f1:93:94:0d'
>>> ip.interfaces['em1']['ipaddr']
[('10.34.131.210', 23),
('2620:52:0:2282:f2de:f1ff:fe93:940d', 64),
('fe80::f2de:f1ff:fe93:940d', 64)]
>>>
One can address objects in IPDB not only with dict notation, but with dot notation also:
>>> ip.interfaces.em1.address
'f0:de:f1:93:94:0d'
>>> ip.interfaces.em1.ipaddr
[('10.34.131.210', 23),
('2620:52:0:2282:f2de:f1ff:fe93:940d', 64),
('fe80::f2de:f1ff:fe93:940d', 64)]
```
It is up to you, which way to choose. The former, being more flexible, is better for developers, the latter, the shorter form – for system administrators.
The library has also IPDB module. It is a database synchronized with the kernel, containing some of the information. It can be used also to set up IP settings in a transactional manner:
>>> from pyroute2 import IPDB
>>> from pprint import pprint
>>> ip = IPDB()
>>> pprint(ip.by_name.keys())
['bond0',
'lo',
'vnet0',
'em1',
'wlan0',
'macvtap0',
'dummy0',
'virbr0-nic',
'virbr0']
>>> ip.interfaces.lo
{'promiscuity': 0,
'operstate': 'UNKNOWN',
'qdisc': 'noqueue',
'group': 0,
'family': 0,
'index': 1,
'linkmode': 0,
'ipaddr': [('127.0.0.1', 8), ('::1', 128)],
'mtu': 65536,
'broadcast': '00:00:00:00:00:00',
'num_rx_queues': 1,
'txqlen': 0,
'ifi_type': 772,
'address': '00:00:00:00:00:00',
'flags': 65609,
'ifname': 'lo',
'num_tx_queues': 1,
'ports': [],
'change': 0}
>>>
IPDB has several operating modes:
- ‘direct’ – any change goes immediately to the OS level
- ‘implicit’ (default) – the first change starts an implicit transaction, that have to be committed
- ‘explicit’ – you have to begin() a transaction prior to make any change
- ‘snapshot’ – no changes will go to the OS in any case
The default is to use implicit transaction. This behaviour can be changed in the future, so use ‘mode’ argument when creating IPDB instances.
The sample session with explicit transactions:
In [1]: from pyroute2 import IPDB
In [2]: ip = IPDB(mode='explicit')
In [3]: ifdb = ip.interfaces
In [4]: ifdb.tap0.begin()
Out[3]: UUID('7a637a44-8935-4395-b5e7-0ce40d31d937')
In [5]: ifdb.tap0.up()
In [6]: ifdb.tap0.address = '00:11:22:33:44:55'
In [7]: ifdb.tap0.add_ip('10.0.0.1', 24)
In [8]: ifdb.tap0.add_ip('10.0.0.2', 24)
In [9]: ifdb.tap0.review()
Out[8]:
{'+ipaddr': set([('10.0.0.2', 24), ('10.0.0.1', 24)]),
'-ipaddr': set([]),
'address': '00:11:22:33:44:55',
'flags': 4099}
In [10]: ifdb.tap0.commit()
Note, that you can review() the last() transaction, and commit() or drop() it. Also, multiple self._transactions are supported, use uuid returned by begin() to identify them.
Actually, the form like ‘ip.tap0.address’ is an eye-candy. The IPDB objects are dictionaries, so you can write the code above as that:
ip.interfaces['tap0'].down()
ip.interfaces['tap0']['address'] = '00:11:22:33:44:55'
...
Also, interface objects in transactional mode can operate as context managers:
with ip.interfaces.tap0 as i:
i.address = '00:11:22:33:44:55'
i.ifname = 'vpn'
i.add_ip('10.0.0.1', 24)
i.add_ip('10.0.0.1', 24)
On exit, the context manager will authomatically commit() the transaction.
IPDB can also create interfaces:
with ip.create(kind='bridge', ifname='control') as i:
i.add_port(ip.interfaces.eth1)
i.add_port(ip.interfaces.eth2)
i.add_ip('10.0.0.1/24') # the same as i.add_ip('10.0.0.1', 24)
Right now IPDB supports creation of dummy, bond, bridge and vlan interfaces. VLAN creation requires also link and vlan_id parameters, see example scripts.
In the case of bursts of Netlink broadcast messages, all the activity of the pyroute2-based code in the async mode becomes suppressed to leave more CPU resources to the packet reader thread. So please be ready to cope with delays in the case of Netlink broadcast storms. It means also, that IPDB state will be synchronized with OS also after some delay.
The class that maintains information about network setup of the host. Monitoring netlink events allows it to react immediately. It uses no polling.
Create an interface. Arguments ‘kind’ and ‘ifname’ are required.
Different interface kinds can require different arguments for creation.
FIXME: this should be documented.
Restart IPRoute channel, and create all the DB from scratch. Can be used when sync is lost.
IPDB callbacks are routines executed on a RT netlink message arrival. There are two types of callbacks: “post” and “pre” callbacks.
...
“Post” callbacks are executed after the message is processed by IPDB and all corresponding objects are created or deleted. Using ipdb reference in “post” callbacks you will access the most up-to-date state of the IP database.
“Post” callbacks are executed asynchronously in separate threads. These threads can work as long as you want them to. Callback threads are joined occasionally, so for a short time there can exist stopped threads.
...
“Pre” callbacks are synchronous routines, executed before the message gets processed by IPDB. It gives you the way to patch arriving messages, but also places a restriction: until the callback exits, the main event IPDB loop is blocked.
Normally, only “post” callbacks are required. But in some specific cases “pre” also can be useful.
...
The routine, register_callback(), takes two arguments: 1. callback function 2. mode (optional, default=”post”)
The callback should be a routine, that accepts three arguments:
cb(ipdb, msg, action)
E.g., to work on a new interface, you should catch action == ‘RTM_NEWLINK’ and with the interface index (arrived in msg[‘index’]) get it from IPDB:
index = msg['index']
interface = ipdb.interfaces[index]
Shutdown monitoring thread and release iproute.
Main monitoring cycle. It gets messages from the default iproute queue and updates objects in the database.
Note
Should not be called manually.
Utility function to get NLA, containing the interface address.
Incosistency in Linux IP addressing scheme is that IPv4 uses IFA_LOCAL to store interface’s ip address, and IPv6 uses for the same IFA_ADDRESS.
IPv4 sets IFA_ADDRESS to == IFA_LOCAL or to a tunneling endpoint.