[Sks-devel] Add new check to pool: HKP connect with only IP (no Host)

[Shengjing Zhu]

Hi,

Recently I find those keys send to my key server are never synced to others.

Finally I found the reason, I configured my HTTP proxy to only accept
requests with whitelist domains(on 11371 port too). See
https://github.com/zhsj/sks-ustc/commit/8920c4e

However in recon, the peer will connect without Host value in the HTTP
request(which is `POST /pks/hashquery`).

So the peers can't fetch new changes from my server. But my server is
included in the pool, so I think the pool inclusion checks should add
this one.

-- 
Regards,
Shengjing Zhu