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.. _conntrack-sync:
##############
Conntrack Sync
##############
One of the important features built on top of the Netfilter framework is
connection tracking. Connection tracking allows the kernel to keep track of all
logical network connections or sessions, and thereby relate all of the packets
which may make up that connection. NAT relies on this information to translate
all related packets in the same way, and iptables can use this information to
act as a stateful firewall.
The connection state however is completely independent of any upper-level
state, such as TCP's or SCTP's state. Part of the reason for this is that when
merely forwarding packets, i.e. no local delivery, the TCP engine may not
necessarily be invoked at all. Even connectionless-mode transmissions such as
UDP, IPsec (AH/ESP), GRE and other tunneling protocols have, at least, a pseudo
connection state. The heuristic for such protocols is often based upon a preset
timeout value for inactivity, after whose expiration a Netfilter connection is
dropped.
Each Netfilter connection is uniquely identified by a (layer-3 protocol, source
address, destination address, layer-4 protocol, layer-4 key) tuple. The layer-4
key depends on the transport protocol; for TCP/UDP it is the port numbers, for
tunnels it can be their tunnel ID, but otherwise is just zero, as if it were
not part of the tuple. To be able to inspect the TCP port in all cases, packets
will be mandatorily defragmented.
It is possible to use either Multicast or Unicast to sync conntrack traffic.
Most examples below show Multicast, but unicast can be specified by using the
"peer" keywork after the specificed interface, as in the following example:
:cfgcmd:`set service conntrack-sync interface eth0 peer 192.168.0.250`
*************
Configuration
*************
.. cfgcmd:: set service conntrack-sync accept-protocol
Accept only certain protocols: You may want to replicate the state of flows
depending on their layer 4 protocol.
Protocols are: tcp, sctp, udp and icmp.
.. note:: When using multiple protocols they must be separated by comma.
.. cfgcmd:: set service conntrack-sync event-listen-queue-size <size>
The daemon doubles the size of the netlink event socket buffer size if it
detects netlink event message dropping. This clause sets the maximum buffer
size growth that can be reached.
Queue size for listening to local conntrack events in MB.
.. cfgcmd:: set service conntrack-sync expect-sync <all|ftp|h323|nfs|sip|sqlnet>
Protocol for which expect entries need to be synchronized.
.. cfgcmd:: set service conntrack-sync failover-mechanism vrrp sync-group <group>
Failover mechanism to use for conntrack-sync.
Only VRRP is supported. Required option.
.. cfgcmd:: set service conntrack-sync ignore-address ipv4 <x.x.x.x>
IP addresses or networks for which local conntrack entries will not be synced
.. cfgcmd:: set service conntrack-sync interface <name>
Interface to use for syncing conntrack entries.
.. cfgcmd:: set service conntrack-sync mcast-group <x.x.x.x>
Multicast group to use for syncing conntrack entries.
Defaults to 225.0.0.50.
.. cfgcmd:: set service conntrack-sync interface <name> peer <address>
Peer to send unicast UDP conntrack sync entires to, if not using Multicast
configuration from above above.
.. cfgcmd:: set service conntrack-sync sync-queue-size <size>
Queue size for syncing conntrack entries in MB.
*********
Operation
*********
.. opcmd:: show conntrack table ipv4
Make sure conntrack is enabled by running and show connection tracking table.
.. code-block:: none
vyos@vyos:~$ show conntrack table ipv4
TCP state codes: SS - SYN SENT, SR - SYN RECEIVED, ES - ESTABLISHED,
FW - FIN WAIT, CW - CLOSE WAIT, LA - LAST ACK,
TW - TIME WAIT, CL - CLOSE, LI - LISTEN
CONN ID Source Destination Protocol TIMEOUT
1015736576 10.35.100.87:58172 172.31.20.12:22 tcp [6] ES 430279
1006235648 10.35.101.221:57483 172.31.120.21:22 tcp [6] ES 413310
1006237088 10.100.68.100 172.31.120.21 icmp [1] 29
1015734848 10.35.100.87:56282 172.31.20.12:22 tcp [6] ES 300
1015734272 172.31.20.12:60286 239.10.10.14:694 udp [17] 29
1006239392 10.35.101.221 172.31.120.21 icmp [1] 29
.. note:: If the table is empty and you have a warning message, it means
conntrack is not enabled. To enable conntrack, just create a NAT or a firewall
rule. :cfgcmd:`set firewall state-policy established action accept`
.. opcmd:: show conntrack-sync external-cache
Show connection syncing external cache entries
.. opcmd:: show conntrack-sync internal-cache
Show connection syncing internal cache entries
.. opcmd:: show conntrack-sync statistics
Retrieve current statistics of connection tracking subsystem.
.. code-block:: none
vyos@vyos:~$ show conntrack-sync statistics
Main Table Statistics:
cache internal:
current active connections: 19606
connections created: 6298470 failed: 0
connections updated: 3786793 failed: 0
connections destroyed: 6278864 failed: 0
cache external:
current active connections: 15771
connections created: 1660193 failed: 0
connections updated: 77204 failed: 0
connections destroyed: 1644422 failed: 0
traffic processed:
0 Bytes 0 Pckts
multicast traffic (active device=eth0.5):
976826240 Bytes sent 212898000 Bytes recv
8302333 Pckts sent 2009929 Pckts recv
0 Error send 0 Error recv
message tracking:
0 Malformed msgs 263 Lost msgs
.. opcmd:: show conntrack-sync status
Retrieve current status of connection tracking subsystem.
.. code-block:: none
vyos@vyos:~$ show conntrack-sync status
sync-interface : eth0.5
failover-mechanism : vrrp [sync-group GEFOEKOM]
last state transition : no transition yet!
ExpectationSync : disabled
*******
Example
*******
The next example is a simple configuration of conntrack-sync.
.. figure:: /_static/images/service_conntrack_sync-schema.png
:scale: 60 %
:alt: Conntrack Sync Example
Now configure conntrack-sync service on ``router1`` **and** ``router2``
.. code-block:: none
set high-availablilty vrrp group internal virtual-address ... etc ...
set high-availability vrrp sync-group syncgrp member 'internal'
set service conntrack-sync accept-protocol 'tcp,udp,icmp'
set service conntrack-sync failover-mechanism vrrp sync-group 'syncgrp'
set service conntrack-sync interface 'eth0'
set service conntrack-sync mcast-group '225.0.0.50'
On the active router, you should have information in the internal-cache of
conntrack-sync. The same current active connections number should be shown in
the external-cache of the standby router
On active router run:
.. code-block:: none
$ show conntrack-sync statistics
Main Table Statistics:
cache internal:
current active connections: 10
connections created: 8517 failed: 0
connections updated: 127 failed: 0
connections destroyed: 8507 failed: 0
cache external:
current active connections: 0
connections created: 0 failed: 0
connections updated: 0 failed: 0
connections destroyed: 0 failed: 0
traffic processed:
0 Bytes 0 Pckts
multicast traffic (active device=eth0):
868780 Bytes sent 224136 Bytes recv
20595 Pckts sent 14034 Pckts recv
0 Error send 0 Error recv
message tracking:
0 Malformed msgs 0 Lost msgs
On standby router run:
.. code-block:: none
$ show conntrack-sync statistics
Main Table Statistics:
cache internal:
current active connections: 0
connections created: 0 failed: 0
connections updated: 0 failed: 0
connections destroyed: 0 failed: 0
cache external:
current active connections: 10
connections created: 888 failed: 0
connections updated: 134 failed: 0
connections destroyed: 878 failed: 0
traffic processed:
0 Bytes 0 Pckts
multicast traffic (active device=eth0):
234184 Bytes sent 907504 Bytes recv
14663 Pckts sent 21495 Pckts recv
0 Error send 0 Error recv
message tracking:
0 Malformed msgs 0 Lost msgs
|
