The third benefit of the Sentinel feat says (PHB, p. 169-170; emphasis mine):
- When a creature within 5 feet of you makes an attack against a target other than you (and that target doesn't have this feat), you can use your reaction to make a melee weapon attack against the attacking creature.
Do shoves and grapples meet the requirement of a creature "making an attack" (since they're described in the rules as "special melee attacks")?
If so, does the shove or grapple attempt need to be successful in order to trigger the reaction attack from the Sentinel feat?
I suspect that the answer to the first part of my question is yes, given this similar question about the third benefit of the Mobile feat, but I'm less sure about the second part of my question.
(I know that the reaction attack from Sentinel would only occur after the triggering attack by the enemy is resolved.)