id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	uname	nginx_version
1677	nginx does not resolve hostnames if there is no route	wanneut@…		"In my configuration is the following line:
{{{proxy_pass http://localhost4:7500;}}}
Problem is, that I am using it on a host without IPv4 connectivity.
This shouldn't b a problem since 127/8 can be accessed without a route over the lo interface.
But it is. nginx fails with the following message:
{{{nginx: [emerg] host not found in upstream ""localhost4"" in}}}
This should not be happening, since localhost4 can be resolved over /etc/hosts. So gethostbyname should work properly.
There is a working DNS resolution over IPv6.
A workaround would be something like that:
{{{
ip addr add 192.0.2.1/24 dev eth0
systemctl restart nginx
ip addr del 192.0.2.1/24 dev eth0
}}}

Related:
https://trac.nginx.org/nginx/ticket/1040
https://trac.nginx.org/nginx/ticket/696
https://trac.nginx.org/nginx/ticket/1417"	defect	closed	minor		nginx-core	1.15.x	wontfix	dns		Linux 3.10.0-862.14.4.el7.x86_64 #1 SMP Wed Sep 26 15:12:11 UTC 2018 x86_64 GNU/Linux	nginx version: nginx/1.12.2