upstream on OpenBSD not executing requests

[roman_mir]

Hello everybody!
I am a new and excited nginx user and I just had to hit a problem complex
enough for me to post a message here hoping to get some help.

OS: OpenBSD 5.5 amd64
nginx -v:   nginx version: nginx/1.4.7

nginx.conf:

user  www;
worker_processes  10;
error_log /var/log/nginx/error.log  error;
worker_rlimit_nofile 1024;
events {
    worker_connections  800;
}
http {
  include       mime.types;
  default_type  application/octet-stream;
  index         index.jsp;
  keepalive_timeout  4;
  upstream shipmaticacluster {
    server 10.0.0.10:8080;
    server 10.0.0.11:8080;
  }
  server {
    server_tokens off;
    access_log /var/log/nginx/proxy.log;
    location / {
      proxy_pass http://shipmaticacluster;
    }
  }
}


Here is the problem: if the following is used:
proxy_pass http://10.1.1.10:8080;
or this is used:
proxy_pass http://10.1.1.11:8080;
then the requests are executed and the proxy log has this in it:

192.168.0.13 - - [16/Jun/2014:21:22:56 -0400] "GET /Shipmatica/ HTTP/1.1"
200 11118 "-" "Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:16.0)
Gecko/20100101 Firefox/16.0"

and that is great!

However when I use upstream cluster settings:

proxy_pass http://shipmaticacluster;

then the request executes a long time until it expires or until I hit escape
in the browser and then these lines are printed into the proxy log:

192.168.0.13 - - [16/Jun/2014:23:03:26 -0400] "GET /Shipmatica HTTP/1.1" 499
0 "-" "Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:16.0) Gecko/20100101
Firefox/16.0"

and info log:

2014/06/16 23:03:26 [info] 29349#0: *1 kevent() reported that client
prematurely closed connection, so upstream connection is closed too while
connecting to upstream, client: 192.168.0.13, server: , request: "GET
/Shipmatica HTTP/1.1", upstream: "http://10.0.0.10:8080/Shipmatica", host:
"192.168.0.28"


I have gone through about 5 or 6 hours of internet searches and experiments
by now, looked at the system log files and payed attention to pflog, no
results anywhere, nothing is found in the OS log files, pf doesn't block any
traffic.  I switch back to the specific IP address in the proxy_pass and the
requests flow through just fine.

This is as far as I can go without some help, I hope somebody has insights
on this issue.

Thank you!
Roman

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,250904,250904#msg-250904