Transit permit required or not

I have to go to Seoul(S.Korea) i have booked ticket in china eastern. travel plan is

Kolkatta to Kunming

Kunming to Shanghai

Shanghai to Seoul.

and the return is

Seoul to Nanking/Nangunj

Nanking/Nangunj to Kunming

Kunming to Kolkatta

All the travel is by china eastern. do i require transit Visa

if required. how to apply to it and in how many days i can get it.