dh.c: change format to binary from decimal string (without introducing
endianness problems)
+log.c: implement a file-descriptor-to-log module
+
netlink.c: test the 'allow_route' option properly.
Add fragmentation code. Check that we comply with RFC1812.
plug in different block ciphers, invent an authenticity-only mode,
etc. (similar to udptunnel)
-tun.c: Solaris support, and configuring the interface and
-creating/deleting routes using ioctl()
-
udp.c: option for path-MTU discovery (once fragmentation support is
implemented in netlink)