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.

MacOS provides an older version of bison which results in
macro redifinitions for CMSG_LEN and CMSG_DATA. Renaming
them resolves this.

Use the IANA assigned option number for the TCP Fast Open option.
Use EXP-FO instead of TO for using the deprecate experimental option.

This is based on https://github.com/freebsd-net/packetdrill/pull/15
but adds support for af_arg, getsockopt() and clearing the
acceptfilter.

Sponsored by:	Netlix, Inc.