 * write a pid file when running as a daemon
 * rewrite main() to not open any files before daemon()
 * implement --script functionality for launching vpnc
 * implement token support
 * implement main mode
 * -s sniffing option using libpcap
 * check on the nonce in phase2_hash
 * code cleanup: replace all those ugly linked lists with real, generic
   data structure implementations, and use hash maps instead of linked lists
   where appropriate (config->keys, peer_ctx->msg_iv)
 * implement full MitM (well, maybe)
