代理指定dns：

    location / {
        resolver 223.6.6.6;
        set $backend "www.twitch.tv/videos/939025713/";
        #proxy_pass https://zhangxiaoqiang.top/;
        proxy_pass https://$backend;
        proxy_connect_timeout 1;
    }

connect() to connect() failed (13: Permission denied):

selinux导致,命令放行: 

setsebool httpd_can_network_connect=1

转发监听非常规http端口报错：[emerg] bind() to 0.0.0.0:xxxx failed (13: Permission denied)

1.若是端口小于1024，原因是1024以下端口启动时需要root权限

2.端口大于1024

首先，查看http允许访问的端口：

semanage port -l | grep http_port_t

结果中若没有所需端口，则执行命令放行：

semanage port -a -t http_port_t  -p tcp 8090

selinux导致502:

getsebool httpd_can_network_connect

若为off

setsebool -P httpd_can_network_connect 1

参考：https://blog.csdn.net/RunSnail2018/article/details/81185138

附：nginx的403和502:https://www.cnblogs.com/caijt/p/10982470.html