[rhelv6-list] weird behaviour of an application when a network interface has 2 ip-addresses

[Masopust, Christian]

Hi all,

I've a configuration here where one of my interfaces has 2 ip-addresses (added by "ip addr add ...").

Now I'm running a proprietary license-daemon (no source available here) that should respond to
request to that additional address.
The license-daemon will receive the requests (UDP-packets), but any answer is sent out with the
wrong source-address!!  (see tcpdump below).

So, do you know any method to force/change/filter (whatever :)) that packets have correct source address?


Configuration:

Server has: "host-ip", additional ip is "license-ip" (see output of "ip addr show eth0")

2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN qlen 1000
    link/ether 00:0c:29:xx:xx:xx brd ff:ff:ff:ff:ff:ff
    inet host-ip/23 brd xxx.xxx.xxx.255 scope global eth0
    inet license-ip/23 scope global secondary eth0
Client connects with: "client-ip"

Here's the tcpdump:

11:41:12.140606 IP client-ip.38668 > license-ip.371: UDP, length 108
11:41:12.140879 IP host-ip.371 > client-ip.38668: UDP, length 36
11:41:12.141121 IP client-ip.38668 > license-ip.371: UDP, length 112
11:41:12.141183 IP host-ip.371 > client-ip.38668: UDP, length 336


As said, the license-daemon cannot be modified (and I'm not sure whether the vendor will be willing to do...)

Thanks a lot,
Christian


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