Is there a Freebsd equivalent to this Linux header file

[Ray Seals]

I'm not a programmer, but I trying to learn a few things.  I have a
Niagara 2261 pass through nic and I need to change it's operating mode.
It came with the source code and header files for a command line utility
which allows me to change operation modes on the card.  Along with the
documentation.

The card is recognized under the 'em' network driver.

I have all the errors down except for one.  The error is
'SIOCDEVPRIVATE' undeclared (first use in this function).

Doing some research I found that the linux header file sockios.h defines
this.

Is there a FreeBSD equivalent to this or am I so far out of my league
with this question that I should probably just stop right now?