LVS routers under any topology require extra configuration when creating
multi-port LVS services. Multi-port services can be created artificially
by using firewall marks to bundle together different, but related
protocols, such as HTTP (port 80) and HTTPS (port 443), or when LVS is
used to cluster true multi-port protocols, such as FTP. In either case,
the LVS router uses firewall marks to recognize that packets destined
for different ports, but bearing the same firewall mark, should be
handled identically. Also, when combined with persistence, firewall
marks ensure connections from the client machine are routed to the same
host, as long as the connections occur within the length of time
specified by the persistence parameter. For more on assigning
persistence to a virtual server, see Section 10.6.1 The VIRTUAL SERVER Subsection.
Unfortunately, the mechanism used to balance the loads on the real
servers — IPVS — can recognize the firewall marks assigned
to a packet, but cannot itself assign firewall marks. The job of
assigning firewall marks must be performed by the
network packet filter, iptables, outside of
Piranha Configuration Tool.
To assign firewall marks to a packet destined for a particular port,
the administrator must use iptables.
This section illustrates how to bundle HTTP and HTTPS as an
example, however FTP is another commonly clustered multi-port
protocol. If an LVS cluster is used for FTP services, see Section 9.4 FTP In an LVS Cluster for details on how to best configure the
cluster.
The basic rule to remember when using firewall marks is that for every
protocol using a firewall mark in Piranha Configuration Tool
there must be a commensurate iptables rule to
assign marks to the network packets.
Before creating network packet filter rules, make sure there are no
rules already in place. To do this, open a shell prompt, login as root, and type:
/sbin/service iptables status |
If iptables is not running, the prompt will
instantly reappear.
If iptables is active, it displays a set of
rules. If rules are present, type the following command:
/sbin/service iptables stop |
If the rules already in place are important, check the contents of
/etc/sysconfig/iptables and copy any rules worth
keeping to a safe place before proceeding.
Below are rules which assign the same firewall mark, 80, to incoming
traffic destined for the floating IP address,
n.n.n.n, on ports 80 and 443. For
instructions on assigning the VIP to the public network interface, see
Section 10.6.1 The VIRTUAL SERVER Subsection. Also note that you must log
in as root and load the module for iptables before
issuing rules for the first time.
/sbin/modprobe ip_tables
/sbin/iptables -t mangle -A PREROUTING -p tcp \
-d n.n.n.n/32 --dport 80 -j MARK --set-mark 80
/sbin/iptables -t mangle-A PREROUTING -p tcp \
-d n.n.n.n/32 --dport 443 -j MARK --set-mark 80 |
In the above iptables commands,
n.n.n.n should be replaced with the
floating IP for your HTTP and HTTPS virtual servers. These commands
have the net effect of assigning any traffic addressed to the VIP on
the appropriate ports a firewall mark of 80, which in turn is
recognized by IPVS and forwarded appropriately.
