i don't understand this 1. plan 9 never used a static source port for queries, and more importantly
Erm, sequential source ports are close enough.
2. who does recursive queries on external interfaces? i would have considerd this a configuration error and security problem ten years ago.
Tell that to the rest of the internet. It's not that simple, either. I am using recursive capability as an example of making an attack extremely easy. I could also send you an e-mail with HTML that loads images from a specific domain name. There are a million other vectors that are just as predictable because of the luxury of web2.0. Recursive queries obviously just make this simpler for the attacker. D