"The trade of Chinese goods underpins its neighbour’s economic survival, while decades of Beijing political support have provided Pyongyang with vital cover in international affairs." And, "But it has been difficult to discern Beijing’s willingness to bring its actions into line with its rhetoric. North Korean trade has continued at a steady pace and its economy has continued to grow."

Okay. But, China's involvement may go far beyond typical "trade." Missing here is the ominous possibility that...

 "North Korea’s launch of a nuclear-capable intercontinental ballistic missile on July 4, ... was likely supported by Chinese technology and expertise [and] include Chinese transport trucks used for multiple North Korean missiles, the biconic warhead design of the Hwasong-14, and other Chinese missile components."  Read more, on-line, in Forbes, July 5 2017. 

Doubt this if you will, but ask yourself "If not from China...then from where??"

A potential "proxy war" in the making, perhaps?