I live in Brazil, I don’t know this university.
I put this url in the reverse proxy because it is quoted here https://vault.centos.org/6.10/os/x86_64/repodata/repomd.xml
And I thought that might be part of the problem he was trying to solve using Caddy.
Because I have no control over the content of yum.oracle.com or vault.centos.org, and this caddy server is not listening on a public ip.
I was just trying to get around a situation.
Anyway this was not the reason for my problem but a bug in curl which was resolved in Centos 6.10