If you run Jira behind a http proxy, namely https (ssl) then you need to add three options to the server.xml file in /opt/atlassian/jira/conf:
scheme=“https”
proxyName=“sub.domain.tld”
proxyPort=“443”
The only change needed to vanilla Jira. Then in something like nginx you have the line:
proxy_pass http://192.168.1.123:8080;