WritablePacket

[Eddie Kohler]

Hi,

I thought about this Packet cloning issue and came up with a kind of
solution that will make it harder to screw up.

There are now two kinds of packet: Packet has non-writable data, and
WritablePacket has writable data.

When you uniqueify() a Packet, you get back a WritablePacket.

When you push(), put() or take() a Packet, you also get back a
WritablePacket.

If you try to write into a Packet's data or IP header, you should get a
type error, unless you are doing a cast. If you try to write into a
WritablePacket's data or IP header, it should work fine.

This required a lot of changes. Sorry.

love,
ed