With LD_PRELOAD and bindp, you can do:

• For server application
  • Assign ip and port for listening
  • Add SO_REUSEADDR/SO_REUSEPORT for existing application
• For socket client
  • Assign special ip and port for connection
  • Add SO_REUSEPORT for reuse the ip add port

Compile on Linux with:

make

How to use it:

REUSE_ADDR=1 REUSE_PORT=1 BIND_ADDR="your ip" BIND_PORT="your port" LD_PRELOAD=/your_path/libindp.so The_Command_Here ...

Example in bash to make inetd only listen to the localhost lo interface, thus disabling remote connections and only enable to/from localhost:

BIND_ADDR="127.0.0.1" BIND_PORT="49888" LD_PRELOAD=/your_path/libindp.so curl http://192.168.190.128

OR:

BIND_ADDR="127.0.0.1" LD_PRELOAD=/your_path/libindp.so curl http://192.168.190.128

Just want to change the nginx's listen port:

BIND_PORT=8888 LD_PRELOAD=/your_path/libindp.so /usr/sbin/nginx -c /etc/nginx/nginx.conf

Example in bash to use your virtual IP as your outgoing sourceaddress for ircII:

BIND_ADDR="your-virt-ip" LD_PRELOAD=/your_path/bind.so ircII

Note that you have to set up your server's virtual IP first.

Now, I add the SO_REUSEADDR/SO_REUSEPORT support within Centos7 or Linux OS with kernel >= 3.9, for the old applictions with multi-process just listen the same port now:

REUSE_ADDR=1 REUSE_PORT=1 LD_PRELOAD=./libindp.so python server.py &

OR

REUSE_ADDR=1 REUSE_PORT=1 BIND_PORT=9999 LD_PRELOAD=./libindp.so java -server -jar your.jar &

With libindp.so's support, you can run your app multi-instance just for you need.

And, for socket client's connect you can also reuse the same client's ip and port:

REUSE_PORT=1 BIND_ADDR="10.10.10.10" BIND_PORT=49999 LD_PRELOAD=/the_path/libindp.so nc 10.10.10.11 10001
REUSE_PORT=1 BIND_ADDR="10.10.10.10" BIND_PORT=49999 LD_PRELOAD=/the_path/libindp.so nc 10.10.10.11 10011

With IP_TRANSPARENT support, we can bind more nonlocal IP address, some one called "AnyIP".

IP_TRANSPARENT=1 REUSE_PORT=1 BIND_ADDR="NONLOCAL_IP" BIND_PORT=Your_Bind_Port LD_PRELOAD=/the_path/libindp.so nc The_Target_Address The_Target_Port

The IP_TRANSPARENT operation need root right

And don't forget, you should have set the ip roule before, as below example:

ip rule add iif eth0 tab 100
ip route add local 0.0.0.0/0 dev lo tab 100

Enjoy it :))