Squid internals

IPC (src/ipc.c) (ctd.)
Child
Give up any SUID priviliges
If a TCP or UDP socket, wait for parent to connect and send a test HELLO
use dup() / dup2() to map STDIN/STDOUT/STDERR to the socket fds
Close all other fds
Attempt to execvp() the external program
Log an error (we should be running the program here!)