This is part of a general policy that India has of pushing their defense perimeter forward:
India, worried about encirclement by Chinese interests in the South Asian region, has been cooperating with Vietnam since the early 1990s as part of its "Look East policy" aimed at expanding ties with its eastern neighbours.
I've noted before that India should move east to block China. But I didn't realize it was official Indian policy. In which case it is hard to understand why India doesn't seek closer defense relations with Taiwan. Taiwan is the ultimate distraction for China. If Taiwan goes down, China could turn on India.
I really should get some basic book on modern Indian foreign policy.