limit_conn_zone using $http_ variable not working?

Alan Jackson alan.jackson at
Mon May 9 21:27:46 UTC 2022

Thanks for the reply. Helped me along the right path - debug logging was very useful.

In the end I used real_ip module to rewrite with Client-IP:

                real_ip_header Client-IP;

And now the $binary_remote_addr contains the original remote client IP.

                limit_conn_zone $binary_remote_addr zone=perip:10m;

Log lines are also now useful, and display the original remote client IP :)


> The "client:" part is the above log represents client address
> you previously claimed to contain "", which is fine.
> The limit_conn_zone key evaluated content is logged at the debug level.

----- Original Message -----
From: "Sergey Kandaurov" <pluknet at>
To: "nginx" <nginx at>
Sent: Friday, 6 May, 2022 10:18:00 PM
Subject: Re: limit_conn_zone using $http_ variable not working?

> On 6 May 2022, at 03:54, Alan Jackson <alan.jackson at> wrote:
> Hi,
> I'm trying to use rate limiting on an nginx mail proxy->nginx fastcgi backend to restrict the number of concurrent connections from a client's IP. Unfortunately, I can't use proxy_protocol on the mail proxy side due to the nginx version not supporting it. 
> Using debug logging, I know that the nginx mail proxy is passing through an http header 'Client-IP' which contains the originating client IP.
> I've confirmed that in the http backend, the variable $http_client_ip contains the originating request's client ip ($binary_remote_addr just contains due to the proxy), and that setting a return http header using this variable works just fine.
> However, when I try to use limit_conn_zone with the $http_client_ip variable, it is not behaving as I expect:
> "limit_conn_zone $http_client_ip zone=perip:10m;" 
> Results in log lines like:
> "limiting connections, dry run, by zone "perip", client:, server: _, request: "GET /mail_auth.php HTTP/1.0" 
> which doesn't look like the variable is being instantiated properly (client is still

> Is using an $http_ variable expected to work in a limit_conn_zone config like this?

Yes, it is.

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