mod_limitipconn模块限制

这个模块对于连接数的限制，我在linux下测试结果显示：
是统计跟某个IP建立的连接数作为限制依据，其实就是ESTABLISHED状态数，如果限制为2，则只能建立2个ESTABLISHED状态的连接。对于资源下载限制的线程数即为2线程。

参考文档、下载：
http://dominia.org/djao/limitipconn2.html

limitipconn-README：http://dominia.org/djao/limitipconn2-README

# Only needed if the module is compiled as a DSO
LoadModule limitipconn_module lib/apache/mod_limitipconn.so

<IfModule mod_limitipconn.c>

    # Set a server-wide limit of 10 simultaneous downloads per IP,
    # no matter what.
    MaxConnPerIP 10
    <Location /somewhere>
    # This section affects all files under http://your.server/somewhere
    MaxConnPerIP 3
    # exempting images from the connection limit is often a good
    # idea if your web page has lots of inline images, since these
    # pages often generate a flurry of concurrent image requests
    NoIPLimit image/*
    </Location>

    <Directory /home/*/public_html>
    # This section affects all files under /home/*/public_html
    MaxConnPerIP 1
    # In this case, all MIME types other than audio/mpeg and video*
    # are exempt from the limit check
    OnlyIPLimit audio/mpeg video
    </Directory>
</IfModule>

---------------------------------------------------------------------------

Notes:

1) This module will not function unless mod_status is loaded and the
   "ExtendedStatus On" directive is set.

2) Server-wide access restrictions and per-directory access restrictions
   are computed separately.  In the above example, if someone is
   downloading 11 images from http://your.server/somewhere
   simultaneously, they WILL be denied on the 11th download, because the
   server-wide limit of 10 downloads is not affected by the per-directory
   NoIPLimit.  If you want to set global settings which can be overruled
   by per-directory settings, you will need something like

    <Location />
    # global per-directory settings here

        <Location /somewhere>
        # local per-directory settings here

        </Location>

    </Location>

3) If you are using any module based upon a quick handler hook (such as
   mod_cache), mod_limitipconn will not be able to process any
   per-directory configuration directives in time to affect the return
   result of the other module.  This is a technical limitation imposed
   by Apache.  In such a situation, you will have to use server-wide
   configuration directives only.

   Note that previous versions of mod_limitipconn did not allow any
   server-wide configuration directives, and hence could not be used
   with mod_cache at all.  In other words, the present situation still
   represents an improvement over previous versions.

4) The limits defined by mod_limitipconn.c apply to all IP addresses
   connecting to your Apache server. Currently there is no way to set
   different limits for different IP addresses.

5) Connections in excess of the limit result in a stock 503 Service
   Temporarily Unavailable response. The job of returning a more useful
   error message to the client is left as an exercise for the reader.

6) mod_limitipconn sets the LIMITIP environment variable to 1 whenever a
   download is denied on the basis of too high an IP count. You can use
   this variable to distinguish accesses that have been denied by this
   module. For example, a line like

      CustomLog /var/log/httpd/access_log common env=!LIMITIP

   in httpd.conf can be used to suppress logging of denied connections
   from /var/log/httpd/access_log. (Note that, if you really want to
   suppress logging, you'll probably also want to comment out the
   ap_log_rerror lines from mod_limitipconn.c as well.)

7) By default, all clients behind a proxy are treated as coming from the
   proxy server's IP address. If you wish to alter this behavior,
   consider installing mod_extract_forwarded from
   http://web.warhound.org/mod_extract_forwarded/

测试举例：

[root@node02 ~]# cat /etc/httpd/conf.d/limitipconn.conf
LoadModule limitipconn_module modules/mod_limitipconn.so
ExtendedStatus On
<IfModule mod_limitipconn.c>
    <Location />                   
##--/这个地方请使用相对路径，因为我测试时如果使用了绝对路径/var/www/html/便不生效了。
        MaxConnPerIP 2
        NoIPLimit image/*
    </Location>

    <Location /mp3>
        MaxConnPerIP 1
        # In this case, all MIME types other than audio/mpeg and video*
        # are exempt from the limit check
        OnlyIPLimit audio/mpeg video
    </Location>
</IfModule>
配好好放了大文件到/var/www/html/目录下，用迅雷下载，只能2线程，此时你在去打开网页会提示服务不可用。Service Temporarily Unavailable

但是用浏览器来测试线程数限制的话，效果难以看出，因为你刷新一下页面，在服务器端看不到ESTABLISHED