Spell casting while grappled

[Devcat]

In Combat rules said: you must make a concentration check (DC 10 + the grappler’s CMB + the level of the spell you’re casting) or lose the spell.

But what is the grappler’s CMB include? Just initial CMB(Base attack bonus + Strength modifier + special size modifier)?
OR
Is initial CMB + feats and abilities bonus?

[avr]

CMB includes most attack modifiers, and here grappling-specific modifiers like improved grapple will certainly apply. BAB + Str mod + size mod is a starting place, not the whole thing.

[RAWmonger]

Most creatures will have their CMB listed in their entry and any bonuses they get for specific maneuvers.