Request_nodes from close dht node, which closest to the chatid (however, we do not inform this node about chatid in any way). Probably, there is already similar function in dht.c
Send announce request to nodes closes to chat id (choose from received nodes). However, we encrypt packet with our peerid in the chat, not dhtid. Most probably those nodes do not have us in dht list -> don't have our ip, so they will get packet from unknown ip with unknown pk.