The CAA requires you to use an agent to apply for permits here. No permit is required for overflying water routes within the Indian FIR.
Overfly permits over landmass need one day’s notice. Landings need three days’ notice.
However, if you are registered in a Chinese country you need to give three days for an overflight and seven for a landing. Plus, be aware landing at a military airport here takes a lot of time to arrange, at least four weeks.