Does it really matter? It's all important for the Indians to be able to save face here. Through their media, we've seen exactly how touchy they are and willing to engage in self-destructive acts; it reminds me of May Fourth where the entire sequence of Japanese military imperialism was triggered by Chinese boycotts. If China wasn't a market for the Japanese, China became instead a target to conquer.
The best case scenario is still that all three sides negotiate a permanent border demarcation, perhaps with the return of Siachen to Pakistan, because the whole South India region is strategically worthless to China.
First, the border connections across the Himalayas, no matter how hard China tries, are going to be garbage. Second, India can't pose a valid threat to China because the Chinese control Tibet and have tons of ballistic missiles, including missiles that can blow up InN ships trying to interdict Chinese shipping. Third, China's main area of concern is East Asia, which has traditionally been China's sphere of influence.
I mean, you can jerk off about helping Pakistan retake Kashmir, but it's an extremely difficult matter given the Indian tank mass and the fact that except for Kashmir, the Indo-Pakistan border is tank territory.
Who's jerking off about helping Pakistan retake all of Kashmir? Who ever said that? I think the word Kashmir was dropped and you've proceeded to go off your head in wild speculations, accusations, and conclusions. Calm down. Kashmir is a Pak-India issue. Pakistan however is a close ally of China so that is the only place where it comes in to the question. However this doesn't mean China is going to take over all of Kashmir on behalf of anyone.