[RADIATOR] Multi-homed, Virtual IP and source IP

[Thomas Guthmann]

Hi Hugh,

> Radiator does not have access to the UDP packet headers - it simply gives the packet to the operating system to send.
Indeed.

But I looked into the code and it took me a whole morning to remember my 
sockets knowledge and to understand Radiator's low layers. And then it 
was so obvious and so simple that I wonder why I haven't thought about 
that before. That's maybe why you didn't understand my question, because 
it was a dumb one :)

*Solution*
You bind a socket to an interface. And therefore you will reply with 
this interface. So instead using the default bind to 0.0.0.0. You just 
have to listen to the interfaces you are interested in with BindAddress. 
Radiator will create different sockets per IP aka interfaces and Bob's 
your uncle.

*Example*
[..]
BindAddress VIP1,VIP2,VIP3,RIP,127.0.0.1
[..]
# Listen to everything for SNMP queries
<SNMPAgent>
     BindAddress 0.0.0.0
</SNMPAgent>

*Contrib*
If you add the following code after the variable definitions in your 
init.d script it will generate the BindAddress parameter automatically 
in a sub config. So you need to tell radiator to include this file or 
the directory containing this file 
(/etc/radiator/conf.d/bindaddresses.cfg). This code will parse ifconfig 
and add all IPs in BindAddress. This is a quick hack, feel free to improve.

/etc/init.d/radiator
[..]

# LVS support so Radiator will use the good VIP to reply to requests
# Indeed if Radiator listens to 0.0.0.0 it will use eth0's IP to reply
# which will break the dialogue (the client may complain that he's
# receiving an answer of an unknown server).
# Tom - 26/5/10
grep -q '^net.ipv4.conf.eth0.arp_ignore' /etc/sysctl.conf
if [[ $? == 0 ]]
then
         LOCALIPS="`/sbin/ifconfig |grep 'inet addr:' |cut -d ':' -f2 
|cut -d ' ' -f1`"
         BINDADDRESSES=`echo $LOCALIPS |tr ' ' ','`
         echo "BindAddress $BINDADDRESSES" > 
/etc/radiator/conf.d/bindaddresses.cfg
else
         if [ -f /etc/radiator/conf.d/bindaddresses.cfg ]
         then
                 /bin/rm -f /etc/radiator/conf.d/bindaddresses.cfg
         fi
fi
# End Tom
[..]

Thanks guys for your time and hope it will help lost mind like mine :)
Thomas