Send nginx server port in host header to upstream only when port is non-standard.

gistfile1.txt

# Send nginx server port in host header to upstream only when port is non-standard.
# Requires nginx >= 0.9.0
map $server_port $host_port {
    default $:port;
    80 '';
    443 '';
}

server {
    ...
    set $:port :$server_port;
    location @proxy {
        ...
        proxy_set_header Host $host$host_port;
        ...
    }
    ...
}


# Requires nginx >= 1.11.0
on nginx < 1.11
map $server_port $host_port {
    default :$server_port;
    80 '';
    443 '';
}

server {
    ...
    location @proxy {
        ...
        proxy_set_header Host $host$host_port;
        ...
    }
    ...
}