That's the Fantasy Variation, but it can transpose into a Blackmore-Diemer gambit. It's a very sharp line.
Gambit vs caro kann
Ahoy!
Vecana is correct but I wouldn't just limit myself to the Fantasy variation alone. If you have the time, patience and skill, there is an excellent book by Uwe Bekemann called "Gambits Gegen Caro-Kann" by Schachverlag Manfred Madler out there. It is in German but fear not, as long as you have a grasp of algebraic notation then there are more than a few good ideas to try.
(a basic grasp of German phrases is a help but not required)
How about the Hillbilly Attack gambit used against the Caro Kann in the book Grandmaster Gambits 1 e4:
1 e4 c6 2 Bc4 d5 3 Bb3
isnt the hillbilly bad after d5 if you try qh5 stuff if black knows what they are doing you are gone
For what it's worth, the Alterman Gambit Guide, which tries to create a complete repertoire based on gambits, winds up acknowledging that there isn't really a gambit against the Caro-Kann that's reputable enough to recommend seriously. Instead Alterman covers the Panov Attack, which isn't really a gambit (unless you treat the creation of an IQP as some sort of vague material loss, which almost nobody does), but which he considers closest in style to what gambiteers are looking for in terms of quick development and open lines.
E4 C6 NC3 D5 F3? dxe4 bc4