This commit adds support for UDPLite as specified in RFC 3828
and the corresponding socket options.
It is tested on FreeBSD 10.1 and Linux, the platforms supporting
UDPLite.

Signed-off-by: Michael Tuexen <tuexen@fh-muenster.de>

This patch makes sure that all heaaders start at a four byte
boundary. This is done by not having the ethernet header, which
is 14 bytes long, in the packet buffer.
This fixes the remote mode for platforms having strict alignment
restrictions, like ARM. Without this patch you can't use the remote
mode on a Rasperry Pi running FreeBSD.
This patch has been tested on Linux (Intel) in local and remote mode
and one FreeBSD (Intel and ARM) in local and remote mode.

Signed-off-by: Michael Tuexen <tuexen@fh-muenster.de>

Fix the packet header location calculations in packet_append_header()
forgot to account for the fact that there might be layer 2 headers.

Remote mode has been broken since the addition of encapsulation
support, partly due to this issue.

Change-Id: Idfb0670da8799e11fe1b72771ed13d52d8e991fe

Add a little helper for accessing the inner-most header of a
packet. In preparation for a patch to support parsing ICMP packets on
the wire.

The main engine for handling encapsualted packets in packetdrill,
including:

- parsing scripts with encapsulation
- parsing packets with encapsulation
- injecting packets with encapsulation

Encapsulated packets look like the following, which has an IP header,
GRE header, and then regular IP/TCP header:

+0 > ipv4 1.1.1.1 > 2.2.2.2: gre: . 1:1001(1000) ack 1

See other patches in the series for more detailed examples.


Change-Id: Ia8c7580e268f5b0347bd9d3fdc73b096f751a79d

Initial commit for the packetdrill network stack testing tool:

  https://code.google.com/p/packetdrill/



Signed-off-by: Neal Cardwell <ncardwell@google.com>