Although there are more bunny chow (see picture for a visual) locations more approximate to where you'll probably be staying, the district of Chatsworth is home to the most legitimate Indian food in Durban simply because the majority of its population is still Indian. You won't find too many establishments on modern restaurant finders (foursquare, tripadvisor), a fact that lends the area an authenticity you don't often find nowadays. A half an hour drive from downtown Durban, it may work best to start at the Chatsworth Centre on Joyhurst Street, a mall with a good variety of restaurants that feature a lot of Indian before setting out into unknown territory. Also, the Bangladesh Market on Fridays and Saturdays is an excellent place to grab a kebab or a fried snack item; check it out behind the Westcliff Shopping Centre on Florence Nightingale Drive.
Note:If you aren't into taking the pilgrimage to Chatsworth, just check out Dadoo Street in downtown Durban.