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From Chen Chien-Yu <honer...@gmail.com>
Subject Re: [users@httpd] Re: HTTP doesn't work after upgrading from 2.0.55 to 2.2.15
Date Tue, 01 Jun 2010 08:25:25 GMT
Hi All,

After using the strace tools, there's a new find. It will stop at the
function call read()....
A infinite loop happens in server/core_filters.c ap_core_input_filter().


    if (mode == AP_MODE_EATCRLF) {
        apr_bucket *e;
        const char *c;

        while (1) {
            if (APR_BRIGADE_EMPTY(ctx->b)) {
                return APR_EOF;
       }

            e = APR_BRIGADE_FIRST(ctx->b);

            rv = apr_bucket_read(e, &str, &len, APR_NONBLOCK_READ);
*<---------------
I guess this is the place gets stuck...*

            if (rv != APR_SUCCESS) {
                return rv;                *<---- successful case will exit
via this place with the value of rv = 11. (APR_ENOSOCKET ??)*
    }

            c = str;
            while (c < str + len) {
                if (*c == APR_ASCII_LF)
                    c++;
                else if (*c == APR_ASCII_CR && *(c + 1) == APR_ASCII_LF)
                    c += 2;
                else
                    return APR_SUCCESS;
            }

            /* If we reach here, we were a bucket just full of CRLFs, so
             * just toss the bucket. */
            /* FIXME: Is this the right thing to do in the core? */
            apr_bucket_delete(e);
        }

I don't know why it's stuck here, and does it relate to the zero-chunk
packet that doesn't see in the client?

Thanks

Best regards,
honercek

On Mon, May 31, 2010 at 8:14 AM, Chen Chien-Yu <honercek@gmail.com> wrote:

> Hi William,
>
> I'm sorry to confuse you.
> Please let me reorganize the problem and my observations.
>
> Client ---- HTTP ---- Apache ---- Mod-CGI ---- xxx.cgi ---- login.html
>
>
> A client(browser) access the URI, http://xxx.xxx.xxx/xxx.cgi which is
> located on the Apache 2.2.15, but finally what it got was only the content
> of page and lack of the last chunk, which made the browser stuck and
> loading continually.
>
> xxx.cgi is written with the GNU library looks like this<http://mail-archives.apache.org/mod_mbox/httpd-users/201005.mbox/%3CAANLkTikTxKb8CV-ezRKfmaN0GZS4c3-Mw7V8kN1vYW51@mail.gmail.com%3E>.
> It will read the file login.html and put it on the network stream to the
> client.
> I've also tried to return a string only "Hello" instead of the file
> content, the result is the same stuck.
>
> If the directive HTTPS exists (Listen 443), the HTTP will not work
> correctly(Case A). But if I comment out the directives HTTPS, the HTTP will
> work without any problem(Case B). So I compared them by adding some debug
> messages in Apache.
> There is another case that is workable as well, even the HTTP and HTTPS
> exist at the same time.(disable the KeepAlive mechanism, but it a must
> option for us in the performance point of view)
>
> All the output filters are the built in ones, I didn't insert any one I
> write. (There are the filters I found, byterange, content length,
> http_header, http_outerror, core)
>
>
> ============================================================================================
>
> Client ---- HTTP ---- Apache ---- Mod-CGI ---- xxx.cgi ---- login.html
>
> In Mod-CGI, there's a function called cgi_bucket_read(). It's a read method
> of CGI bucket: polls on stdout of the child. I found it read 806 bytes via a
> function call cgi_read_stdout() from stdout followed by a 0 byte read.
>
> Then in Apache core filter, a function called ap_core_output_filter(), in
> the case of EOS, the function apr_bucket_read() inside it reads two times in
> a row, a 0 byte followed by a 5 bytes(0\r\n\r\n). Seems that, the 5 bytes
> bucket is the one the client expect.
>
> Until now, there's no difference between Case A and Case B.
>
> After this, I found the successful one(Case B) will flush out a 5 bytes
> bucket in the core filter. I have no idea who triggers this event. But
> nothing happens in Case A.
>
> Thanks
>
> Best regards,
> honercek
>
>
> On Fri, May 28, 2010 at 8:58 PM, William A. Rowe Jr. <wrowe@rowe-clan.net>wrote:
>
>> On 5/28/2010 3:08 AM, Chen Chien-Yu wrote:
>> > Hi William,
>> >
>> > I gave you the incorrect information in the previous post.
>> >
>> > cgi_read_stdout() in cgi_bucket_read() in mod_cgi.c, the data length is
>> > 806 followed by 0. (Not the 0 and 5 buckets)
>> > then ap_core_output_filter() found a 0 length bucket, and appended a
>> > last-chunk bucket?
>>
>> What you describe sounds like correct HTTP behavior.  The last-chunk
>> bucket is being correctly transmitted after the 806 byte bucket?
>>
>> I'm losing track of what the exact problem is.
>>
>> Also do you insert any additional filters for the output of this filter?
>>
>
>

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