Even though China formally sign trade agreement

to sell arms to Iran for oil. That kind of transaction is very hard to be executed logistically. From where can you transfer sold arms to Iran from China? In war time, blockade is all legal. US and NATO force will block it from both land and sea. Let's take it further and say that China declare that if US bombs Chinese arm trasport fleets in sea, China will involve directly. Once again, the same question remain: how