Nginx servers on both *:80 and <ip>:80? also duplicate listen parameters error when binding by just specific ips

[CJ Ess]

Francis,

Sorry it took so long, I've finally come back to this question.

The example you gave works great:

    server {
        listen 127.0.0.1:8088;
        return 200 "listen 127.0.0.1:8088\n";
    }
    server {
        listen 10.0.1.2:8088;
        return 200 "listen 10.0.1.2:8088\n";
    }
    server {
        listen 8088;
        return 200 "listen 8088\n";
    }

Where I get into problem is if I do something like this:

    server {
        listen 127.0.0.1:8088 backlog=65536 deferred;
        return 200 "listen 127.0.0.1:8088\n";
    }
    server {
        listen 10.0.1.2:8088 backlog=65536 deferred;
        return 200 "listen 10.0.1.2:8088\n";
    }
    server {
        listen 8088;
        return 200 "listen 8088\n";
    }

In that case I get errors like "nginx: [emerg] bind() to 0.0.0.0:8088
failed (98: Address already in use)". So the workaround is obviously not to
use those options - I could patch the source to use a backlog larger then
511.

This example also works well:

   server {
     listen *:80;
     server_name "test_a";
     return 200 "listen test_a";
   }

   server {
     listen *:80;
     server_name "test_b";
     return 200 "listen test_b";
   }

   server {
     listen *:80 default_server;
     return 200 "listen *";
   }

But if I change it to this:

   server {
     listen *:80 backlog=65536 deferred;
     server_name "test_a";
     return 200 "listen test_a";
   }

   server {
     listen *:80 backlog=65536 deferred;
     server_name "test_b";
     return 200 "listen test_b";
   }

   server {
     listen *:80  backlog=65536 deferred default_server;
     return 200 "listen *";
   }

Then I get the error message "nginx: [emerg] duplicate listen options for
0.0.0.0:80 in /etc/nginx/nginx.conf". I can fix it by doing something like
this:

   server {
     listen *:80;
     server_name "test_a";
     return 200 "listen test_a";
   }

   server {
     listen *:80;
     server_name "test_b";
     return 200 "listen test_b";
   }

   server {
     listen *:80 backlog=65536 deferred default_server;
     return 200 "listen *";
   }

>From the ss -l output I am picking up the larger listen queue which I'm
happy about, though its confusing why nginx is picking them from that last
server stanza (it has the same behavior without the default_server
keyword). If I'm doing a virtual hosting type setup and I'm including all
of my server definitions from individual files in a subdirectory, it
appears that any one of them could bump up the backlog, but if any two
server stanzas have options to do it then it causes an error. Maybe the
best way to do it is to have some sort of dummy entry that sets the options
- if its always the last server stanza that sets the listen options then
maybe include all the other server stanzas  and have the dummy at the end
that sets the backlog and deferred options?


On Thu, Mar 31, 2016 at 4:29 PM, Francis Daly <francis at daoine.org> wrote:

> On Thu, Mar 31, 2016 at 01:21:02PM -0400, CJ Ess wrote:
>
> Hi there,
>
> > I would like to have an Nginx setup where I have specific logic depending
> > on which interface (ip) the request arrived on.
>
> multiple server{} with different "listen"; possibly with an "include
> common-config" entry.
>
> Note: "listen" is on an ip, not an interface.
>
> > I was able to make this work by having a server stanza for each ip on the
> > server, but was't able to do a combination of a specific ip and a
> wildcard
> > ip (as a catchall) - is there a way to do that with some option
> combination
> > (i.e. nginx listens on *:80, but matches the server stanza by ip?)
>
> I don't understand what you are describing. Could you try again, perhaps
> with a config example?
>
> When I use
>
> ===
>     server {
>         listen 127.0.0.1:8088;
>         return 200 "listen 127.0.0.1:8088\n";
>     }
>     server {
>         listen 10.0.1.2:8088;
>         return 200 "listen 10.0.1.2:8088\n";
>     }
>     server {
>         listen 8088;
>         return 200 "listen 8088\n";
>     }
> ===
>
> I get the following output, which is what I expect:
>
> $ curl http://127.0.0.1:8088/
> listen 127.0.0.1:8088
> $ curl http://127.0.0.2:8088/
> listen 8088
>
> > The scenario I'm playing towards is that I have a dedicated connection
> to a
> > CDN and I want to pass thru certain headers if they arrive via the
> > dedicated interface, strip them if they arrive on other interface.
>
> As above, if "interface" is replaced with "ip", this can work with two
> server{} blocks.
>
> > When I did the server{} per IP approach nginx complained about duplicate
> > listen settings for the second IP even though both server stanzas were
> > bound to a specific port/interface. Is this a bug per chance?
>
> What short server{} config can I use to reproduce the complaint?
>
>         f
> --
> Francis Daly        francis at daoine.org
>
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>
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