limit_conn_zone using $http_ variable not working?

[Sergey Kandaurov]

> On 6 May 2022, at 03:54, Alan Jackson <alan.jackson at netvalue.nz> 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 127.0.0.1 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: 127.0.0.1, server: _, request: "GET /mail_auth.php HTTP/1.0" 
> 
> which doesn't look like the variable is being instantiated properly (client is still 127.0.0.1).
> 

The "client: 127.0.0.1" part is the above log represents client address
you previously claimed to contain "127.0.0.1", which is fine.
The limit_conn_zone key evaluated content is logged at the debug level.

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

Yes, it is.