title: Send packet and change its source IP
body: <p>Lets say I have an application written in python to send a ping or e-mail. How can I change the source IP address of the sent packet to a fake one, using, e.g., Scapy?</p>
  
  <p>Consider that that the IP address assigned to my eth0 is 192.168.0.100. My e-mail application will send messages using this IP. However, I want to manipulate this packet, as soon as it is ready to be sent, so its source IP is not 192.168.0.100 but 192.168.0.101 instead.</p>
  
  <p>I'd like to do this without having to implement a MITM.</p>