About server limit dos defense

Or the html "target = _ blank>Server limit dos.

The access volume of this article on my blog is the fastest growing in all my articles. It seems that everyone is interested in this article.

The reason why we need to talk about this problem again is that we have encountered difficulties in designing the repair solution.

Luoluo wrote an articleIt is difficult to fix.

In fact, the main cause of the problem is that it cannot be fixed through mod in apache. The information on luoluo's blog is incomplete. I will repeat the Technical Analysis Section of luoluo.

>In the past two days, I have investigatedApacheLevel SolutionServer limit dosThe conclusion is that

>ModifiedApacheIn addition to the source code, it cannot be solved.

>

>The following are some specific analyses to check whether there are any problems:

>

> ApacheOfServer/protocol. cAboutHttpCode related to request header processing:

>

& Gt; 837 request_rec * ap_read_request (conn_rec * conn)

>

> 838 {

>

& Gt; 839 request_rec * r;

>

>...

>

> 880 r-> status = HTTP_REQUEST_TIME_OUT;/* Until we get a request */

>

>...

>

& Gt; 917 if (! R-> assbackwards ){

>

> 918 ap_get_mime_headers_core (r, tmp_bb );

>

> 919 if (r-> status! = HTTP_REQUEST_TIME_OUT ){

>

> 920 ap_log_rerror (APLOG_MARK, APLOG_ERR, 0, r,

>

> 921 "request failed: error reading the headers ");

>

> 922 ap_send_error_response (r, 0 );

>

& Gt; 923 ap_update_child_status (conn-> sbh, SERVER_BUSY_LOG, r );

>

& Gt; 924 ap_run_log_transaction (r );

>

> 925 apr_brigade_destroy (tmp_bb );

>

& Gt; 926 return r;

>

> 927}

>

>CallAp_get_mime_headers_coreFunction ProcessingHttpHeader, ifStatus

>Not previously setHTTP_REQUEST_TIME_OUTThen, an error is returned immediately.

> Ap_get_mime_headers_coreSee:

>

> 670 AP_DECLARE (void) ap_get_mime_headers_core (request_rec * r,

> Apr_bucket_brigade * bb)