Russia has no alliance with any nation. The talk of Russia coming to the aid of India, China, etc is not only pragmatic but prehensile-- especially to waste energy debating about it. The Russian Federation, through historical precedent, has enacted foreign policy that are to benefit Russia proper, only.
The 1976 Soviet Union - Viet Nam military pact proved futile. China, which had then undergone the Sino-Soviet Split, had invaded Vietnam in 1979 with pretense to punish Viet Nam for the latter's military intervention in Khmer Rouge-controlled Kampuchea (Cambodia). Did the Soviet Union intervene in behalf of Viet Nam? No, it did not. In fact, it was the United States that eventually enticed the Chinese side to withdraw the offensive.
Why didn't the Soviet Union intervene? Because by intervening, it would have meant a land war with the Chinese in their own Sino-Soviet frontier. It was best not to entagle itself in Viet Nam's situation. It would not serve Russian interest.