Adds mssfix support including optional
transport overhead. Some code has been ported
from openvpn2.
mssfix sets MSS option in TCP SYN to
a calculated value which guarantees that
size of UDP/TCP packet (which may or may not
include headers, see below) encapsulating
TCP segments won't exceed mssfix value.
If mssfix is used with optional "mtu" parameter,
then IP and UDP/TCP headers are also taken into account.
It is set in config like this:
mssfix 1300 mtu
Signed-off-by: Lev Stipakov <lev@openvpn.net>
