SPD: Automatically Test Unmodified Network Programs with Symbolic Packet Dynamics

Network programs are difficult to test, especially under the large space of network program behavior defined by packet dynamics such as packet delay and packet loss. It is unlikely for common approaches using testbeds with random packet dynamics to cover the prohibitively large number of packet dynamics possibilities in a limited time. In this paper, we leverage symbolic execution to find the equivalence classes of packet dynamics which lead to exactly the same network program behavior, in order to efficiently check the large space of network program behavior. Specifically, we propose and develop a network program test platform, called Symbolic Packet Dynamics (SPD), to automatically and transparently test unmodified network programs for low- probability bugs and extreme-case performance under packet dynamics. SPD uses symbolic representation of packet dynamics, instead of random packet dynamics. Our experiments show that SPD can achieve significantly much higher packet dynamics coverage than random packet dynamics within the same amount of time, and thus it is much easier and takes much shorter time for SPD to detect low-probability bugs and extreme-case performance.