Everything that North Korea is, is due to China, their technology, materials, rocket fuel, etc. Everything.
China created the North Korean threat as the long arm of Chinese military capabilities against America. The equivalent would be America propping up Mexico or Cuba as a possible nuclear deterrent against South America or Africa, we would own them but they'd technically be their own govern country acting on their own.
China could stop all their NK bullshit with a phone call, not sure what's going on, unless Kim Kong Un has gone rogue, which should be just as easy for China to take care of.