Catch ctrl-c call

[ethandmd]

#11

[ethandmd]

Use struct sigaction sa with a handler, and sig action flags to complete cleanup on a ctrl-c call.

[TCCQ]

read pcap_breakloop for how to break the pcap_loop call to end early and return to our code to rename the interface etc.

It warns that if called from a sig_handler, it may cause the OS to restart the syscall, causing the loop to not stop. Not sure how to indicate a preference to that. Stack Overflow seems to suggest man 7 signal includes some info, but I don't see it from a quick look.