Kubernetes: get real client source IP of incoming packet - iptables

Question

I want to get the actual IP using which the client sent out the packet in my app sitting in a kubernetes pod.
I did some searches and found that this was not supported earlier but supported later.
I ungraded my setup and here is the current setup version:
$ kubectl version
Client Version: version.Info{Major:"1", Minor:"1", GitVersion:"v1.1.3", GitCommit:"6a81b50c7e97bbe0ade075de55ab4fa34f049dc2", GitTreeState:"clean"}
Server Version: version.Info{Major:"1", Minor:"1", GitVersion:"v1.1.3", GitCommit:"6a81b50c7e97bbe0ade075de55ab4fa34f049dc2", GitTreeState:"clean"}
$ kubectl api-versions
extensions/v1beta1
v1
I also ran:
$ for node in $(kubectl get nodes -o name); do kubectl annotate $node net.beta.kubernetes.io/proxy-mode=iptables; done
This now gives:
error: --overwrite is false but found the following declared
annotation(s): 'net.beta.kubernetes.io/proxy-mode' already has a value
(iptables)
error: --overwrite is false but found the following declared
annotation(s): 'net.beta.kubernetes.io/proxy-mode' already has a value
(iptables)
I also rebooted all the boxes.
However, I still get IP of docker0 interface of the worker node when the packet is received inside my application.
Here, I read:
But that will not expose external client IPs, just intra cluster IPs.
So, the question is how to get the real, external client IP when I get a packet.
The packets are not http/websocket packets, but plain TCP packets if this is relevant to get an answer.
I also tried following this comment but did not get lucky. App continued to get packets with docker0 interface IP as source IP. May be I could not copy-paste the stuff. I don't know how to get kube-proxy IP and just used worker machine IP there. I am just getting started with Kubernetes and CoreOS.