Nginx proxy_pass with $remote_addr

Question

I'm trying to include $remote_addr or $http_remote_addr on my proxy_pass without success.

The rewrite rule works

location ^~ /freegeoip/ {  
  rewrite ^ http://freegeoip.net/json/$remote_addr last;
}

The proxy_pass without the $remote_addr works, but freegeoip does not read the x-Real-IP

location ^~ /freegeoip/ {
  proxy_pass http://freegeoip.net/json/;
  proxy_set_header X-Real-IP $remote_addr;
  proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
  proxy_set_header Host $host;
}

Then, I'm adding the ip to the end of the request, like this:

location ^~ /freegeoip/ {
  proxy_pass http://freegeoip.net/json/$remote_addr;
}

but nginx report this error: no resolver defined to resolve freegeoip.net

Answer 1

If the proxy_pass statement has no variables in it, then it will use the "gethostbyaddr" system call during start-up or reload and will cache that value permanently.

if there are any variables, such as using either of the following:

set $originaddr http://origin.example.com;
proxy_pass $originaddr;
# or even
proxy_pass http://origin.example.com$request_uri;

Then nginx will use a built-in resolver, and the "resolver" directive must be present. "resolver" is probably a misnomer; think of it as "what DNS server will the built-in resolver use". Since nginx 1.1.9 the built-in resolver will honour DNS TTL values. Before then it used a fixed value of 5 minutes.

Answer 2

It seems a bit strange that nginx is failing to resolve the domain name at runtime rather than at configuration time (since the domain name is hard coded). Adding a resolver declaration to the location block usually fixes dns issues experienced at runtime. So your location block might look like:

location ^~ /freegeoip/ {
  #use google as dns
  resolver 8.8.8.8;
  proxy_pass http://freegeoip.net/json/$remote_addr;
}

This solution is based on an article I read a while back - Proxy pass and resolver. Would be worth a read.

Answer 3

You could also mention your nginx server port in the proxy_pass uri. This solved the issue for me.

Answer 4

If anyone is stll experiencing trouble, for me it helped to move the proxy_pass host to a seperate upstream, so I come up with something like this

upstream backend-server {
  server backend.service.consul;
}

server {
  listen       80;
  server_name  frontend.test.me;

  location ~/api(.*)$  {
    proxy_pass http://backend-server$1;
  }
  location / {
    # this works mystically! backend doesn't...
    proxy_pass http://frontend.service.consul/;
  }
}