+void (*snoop_recv_hook)(unsigned char *p, int len)
+void (*snoop_send_hook)(unsigned char *p, int len)
+
+These hooks are called whenever pppd receives or sends a packet. The
+packet is in p; its length is len. This allows plugins to "snoop in"
+on the pppd conversation. The hooks may prove useful in implmenting
+L2TP.