This allows the usage of
--ip_version=ipv4_mapped_ipv6
at the beginning of a script.

You can use -Dproto=IPPROTO_SCTP or --define proto=IPPROTO_SCTP
and run the script
```
 0.0 socket(..., SOCK_STREAM, proto) = 3
+0.0 close (3)
```
to control the protocol being used from the command line.

On *BSD platforms the original version always used the tun0 device
in local mode and never deleted it, except on NetBSD. This was
handy when using for example Wireshark for capturing trafic.
The last commit removed this possibility, since it removes the
interface. Add the --persistent_tun_dev command line option
to bring it back.

To get the behaviour of the original version, use on *BSD
platforms --tun-dev=tun0 --persistent_tun_dev.

When using local mode on *BSD, using the tun0 device was hard
coded in contrast to Linux, where the next unused tun device
was used.
This patch changes the behaviour on *BSD to use the next unused
tun device. This also requires that the device is removed when
packetdrill terminates. This was the case on Linux, but not on
*BSD.
On *BSD there is also a new command line option (--tun-dev) to
set the device name and not select an ephemerial one.

This adds support for SCTP/UDP and TCP/UDP including ICMP
support.

Sponsored by:	Netflix, Inc.

Sponsored by:	Netflix

When using remote mode, eth0 only makes sense for Linux. So don't
use it on non-Linux platforms. Additionally, check for an interface
being specified and, when acting as a client, that a server address
is specified.

Sponsored by:	Netflix

Using the explicit local IP address instead of the wildcard
address doesn't change the behavior for UDP/TCP, but for
SCTP it forces the SUT to be single homed.

On FreeBSD python is installed in /usr/local. So use that as the
default.

Fixed typos in the 'usage' message: a few ']' were missing

Signed-off-by: Matthieu Baerts <matttbe@gmail.com>

The --dry_run command line flag causes packetdrill to verify command
line args, load and parse the given script, but not execute it. If any
errors are found during these steps, packetdrill will print an error
as before.  Otherwise, it will exit(0) and produce no output.

Change-Id: Ibf4502c6ea326539346a58b58d7feb29d4b3da69

Allow the --remote_ip config parameter to be a prefix, not just a
single address. The entire remote prefix is routed to the tun device
or remote packetdrill machine.

The goal here is to all tests to use more than one remote IP. The
immediate motivation is testing GRE, where there is a remote IP for
the TCP endpoint and a separate remote IP for the GRE decapsulator.
But eventually we'll also want to allow testing multiple concurrent
TCP connections from multiple remote IPs addresses as well.

Here are examples of the remote prefix you get for various values of
the --remote_ip field. These are chosen for convenience and backwards
compatibility with existing tests that are already using the
--remote_ip parameter.

o Default:

configuration                      remote prefix
------------------------------     -----------------
IPv4, no --remote_ip            -> 192.0.2.0/24   (default)
v4/6, no --remote_ip            -> 192.0.2.0/24   (default)
IPv6, no --remote_ip            -> 2001:DB8::0/32 (default)

o Explicit IP without prefix length (prefix includes all bits):

configuration                      remote prefix
------------------------------     -----------------
IPv4 --remote_ip=10.248.0.3     -> 10.248.0.3/32
v4/6 --remote_ip=10.248.0.3     -> 10.248.0.3/32
IPv6 --remote_ip=2001:db8::3    -> 2001:db8::3/128

o Explicit with prefix length:

configuration                      remote prefix
------------------------------     -----------------
IPv4 --remote_ip=10.248.0.3/16  -> 10.248.0.0/16
v4/6 --remote_ip=10.248.0.3/16  -> 10.248.0.0/16
IPv6 --remote_ip=2001:db8::3/16 -> 2001::0/16

Change-Id: Ibc95c3419d66bcf1bbfd8a1fc7650d0003345ef2

Initial commit for the packetdrill network stack testing tool:

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



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