There are two (closely-related) implementations here:
monolithic-lowlevelis the original implementation, originally written for
minimart, a language that followed our ESOP 2014 paper quite closely. Porting it to a monolithic-assertion-set Syndicate dialect helped substantially simplify the code.
incremental-highlevelis a port of
monolithic-lowlevelto the Syndicate high-level DSL ("
syndicate/actor"). Moving from the low-level Syndicate style to the high-level style also drastically simplified the code.
Linux Firewall Configuration
Imagine a setup where the machine you are running this code has IP 192.168.1.10. This code claims 192.168.1.222 for itself. Now, pinging 192.168.1.222 from some other machine, say 192.168.1.99, will cause the local kernel to receive the pings and then forward them on to 192.168.1.222, which because of the gratuitous ARP announcement, it knows to be on its own Ethernet MAC address. This causes the ping requests to repeat endlessly, each time with one lower TTL.
One approach to solving the problem is to prevent the kernel from forwarding packets addressed to 192.168.1.222. To do this,
sudo iptables -I FORWARD -d 192.168.1.222 -j DROP