HTTP/0.9 and mod_proxy

Hi,

I have to reverse proxy a beast which speaks HTTP/0.9. The documentation
to mod_proxy says:

This module implements a proxy/gateway for Apache. It implements
proxying capability for FTP, CONNECT (for SSL), HTTP/0.9,
HTTP/1.0, and HTTP/1.1.

The configuration simply is:

ProxyPass / http://backend:9110/

But all I get is error 502. The log says:

error reading status line from remote server backend

The tcpdump between Apache and the backend looks like this:

GET /test HTTP/1.0
Host: backend:9110
User-Agent: curl/7.15.1 (x86_64-suse-linux) libcurl/7.15.1
OpenSSL/0.9.8a zlib/1.2.3 libidn/0.6.0
Accept: */*
Max-Forwards: 10
X-Forwarded-For: 127.0.0.1
X-Forwarded-Host: localhost:4080
X-Forwarded-Server: localhost

AS2 Adapter is alive.

Also I've looked into the code:

while (received_continue) {
apr_brigade_cleanup(bb);

len = ap_getline(buffer, sizeof(buffer), rp, 0);
if (len == 0) {
/* handle one potential stray CRLF */
len = ap_getline(buffer, sizeof(buffer), rp, 0);
}
if (len <= 0) {
apr_socket_close(p_conn->sock);
backend->connection = NULL;
ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r,
"proxy: error reading status line from remote "
"server %s", p_conn->name);
return ap_proxyerror(r, HTTP_BAD_GATEWAY,
"Error reading from remote server");
}

So, the error is raised when len is <= 0. So, why is len <= 0 with the input
above?

-Danijel

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Re: HTTP/0.9 and mod_proxy

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Hi,

On Oct 1, 2009, at 4:25 PM, Danijel wrote:

> I have to reverse proxy a beast which speaks HTTP/0.9. The =20
> documentation
> to mod_proxy says:
>
> This module implements a proxy/gateway for Apache. It implements
> proxying capability for FTP, CONNECT (for SSL), HTTP/0.9,
> HTTP/1.0, and HTTP/1.1.
>
> The configuration simply is:
>
> ProxyPass / http://backend:9110/
>
> But all I get is error 502. The log says:
>
> error reading status line from remote server backend
>
> The tcpdump between Apache and the backend looks like this:
>
> GET /test HTTP/1.0
> Host: backend:9110
> User-Agent: curl/7.15.1 (x86_64-suse-linux) libcurl/7.15.1
> OpenSSL/0.9.8a zlib/1.2.3 libidn/0.6.0
> Accept: */*
> Max-Forwards: 10
> X-Forwarded-For: 127.0.0.1
> X-Forwarded-Host: localhost:4080
> X-Forwarded-Server: localhost
>
> AS2 Adapter is alive.

This isn't the right part of the tcpdump. The back end must reply with =20=

something like:
HTTP/1.1 200 OK
Content-length: ... whatever

and some content
You're looking at the request that goes to the back end, not the back =20=

ends' response.

If you've used the trick "follow tcp stream" in your Wireshark, and =20
have only seen the above, then indeed there is no back end response to =20=

be found, so the proxy rightfully says: error reading status line from =20=

remote server backend.
- --
Best regards / met vriendelijke groet, Karel Kubat
Mob +31 6 2956 4861

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Re: HTTP/0.9 and mod_proxy

Karel Kubat wrote:
> On Oct 1, 2009, at 4:25 PM, Danijel wrote:
> > GET /test HTTP/1.0
> > Host: backend:9110
> > User-Agent: curl/7.15.1 (x86_64-suse-linux) libcurl/7.15.1
> > OpenSSL/0.9.8a zlib/1.2.3 libidn/0.6.0
> > Accept: */*
> > Max-Forwards: 10
> > X-Forwarded-For: 127.0.0.1
> > X-Forwarded-Host: localhost:4080
> > X-Forwarded-Server: localhost
> >
> > AS2 Adapter is alive.
>
> This isn't the right part of the tcpdump. The back end must reply with
> something like:
> HTTP/1.1 200 OK
> Content-length: ... whatever
>
> and some content

Well, The thing above the empty line is what was sent (the
request). The HTML part is the thing that was received (the response).
I'm talking about HTTP/0.9 as specified here:

http://www.w3.org/Protocols/HTTP/AsImplemented.html

There are no Response Headers in HTTP/0.9. The Answer simply contains
the contents of the requested resource.

The question is: Apache receives the following line:

AS2 Adapter is alive.

So why is "len" <= 0? (Only when len is <= 0 the error is triggered).
Btw, this is Apache 2.0.63.

Danijel

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Re: HTTP/0.9 and mod_proxy

On Thu, Oct 1, 2009 at 4:25 PM, Danijel wrote:
> Hi,
>
> I have to reverse proxy a beast which speaks HTTP/0.9. The documentation
> to mod_proxy says:
>
> =A0 =A0 =A0 =A0This module implements a proxy/gateway for Apache. It impl=
ements
> =A0 =A0 =A0 =A0proxying capability for FTP, CONNECT (for SSL), HTTP/0.9,
> =A0 =A0 =A0 =A0HTTP/1.0, and HTTP/1.1.
>
> The configuration simply is:
>
> =A0 =A0 =A0 =A0ProxyPass / http://backend:9110/
>
> But all I get is error 502. The log says:
>
> =A0 =A0 =A0 =A0error reading status line from remote server backend

You get this error because the backend didn't send a status line.
Apache is behaving exactly as designed here.


> The tcpdump between Apache and the backend looks like this:
>
> =A0 =A0 =A0 =A0GET /test HTTP/1.0
> =A0 =A0 =A0 =A0Host: backend:9110
> =A0 =A0 =A0 =A0User-Agent: curl/7.15.1 (x86_64-suse-linux) libcurl/7.15.1
> =A0 =A0 =A0 =A0OpenSSL/0.9.8a zlib/1.2.3 libidn/0.6.0
> =A0 =A0 =A0 =A0Accept: */*
> =A0 =A0 =A0 =A0Max-Forwards: 10
> =A0 =A0 =A0 =A0X-Forwarded-For: 127.0.0.1
> =A0 =A0 =A0 =A0X-Forwarded-Host: localhost:4080
> =A0 =A0 =A0 =A0X-Forwarded-Server: localhost
>
> =A0 =A0 =A0 =A0AS2 Adapter is alive.

Your problem is that apache expects a http/1.0 response to an HTTP/1.0
request. Because the response does not conform to HTTP/1.0 it is
rejected. Thus the 502 error.

Apache will proxy HTTP/0.9 just fine. Just repeat your test with a
HTTP/0.9 client and you'll see. Apache does not translate between
HTTP/1.0 and HTTP/0.9. It would anyway not be easy to do this. So if
you send a HTTP/1.0 request to your forward proxy it will forward a
HTTP/1.0 request to the backend.

Krist

--=20
krist.vanbesien@gmail.com
krist@vanbesien.org
Bremgarten b. Bern, Switzerland
--
A: It reverses the normal flow of conversation.
Q: What's wrong with top-posting?
A: Top-posting.
Q: What's the biggest scourge on plain text email discussions?

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Re: HTTP/0.9 and mod_proxy

Krist van Besien wrote:
> > The tcpdump between Apache and the backend looks like this:
> >
> >        GET /test HTTP/1.0
> >        Host: backend:9110
> >        User-Agent: curl/7.15.1 (x86_64-suse-linux) libcurl/7.15.1
> >        OpenSSL/0.9.8a zlib/1.2.3 libidn/0.6.0
> >        Accept: */*
> >        Max-Forwards: 10
> >        X-Forwarded-For: 127.0.0.1
> >        X-Forwarded-Host: localhost:4080
> >        X-Forwarded-Server: localhost
> >
> >        AS2 Adapter is alive.
>
> Your problem is that apache expects a http/1.0 response to an HTTP/1.0
> request. Because the response does not conform to HTTP/1.0 it is
> rejected. Thus the 502 error.
>
> Apache will proxy HTTP/0.9 just fine. Just repeat your test with a
> HTTP/0.9 client and you'll see. Apache does not translate between
> HTTP/1.0 and HTTP/0.9. It would anyway not be easy to do this. So if
> you send a HTTP/1.0 request to your forward proxy it will forward a
> HTTP/1.0 request to the backend.

I've done that today. The error is the same.

Danijel

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Re: HTTP/0.9 and mod_proxy

On Mon, Oct 5, 2009 at 8:30 PM, Danijel wrote:
> Krist van Besien wrote:
>> > The tcpdump between Apache and the backend looks like this:
>> >
>> > =A0 =A0 =A0 =A0GET /test HTTP/1.0
>> > =A0 =A0 =A0 =A0Host: backend:9110
>> > =A0 =A0 =A0 =A0User-Agent: curl/7.15.1 (x86_64-suse-linux) libcurl/7.1=
5.1
>> > =A0 =A0 =A0 =A0OpenSSL/0.9.8a zlib/1.2.3 libidn/0.6.0
>> > =A0 =A0 =A0 =A0Accept: */*
>> > =A0 =A0 =A0 =A0Max-Forwards: 10
>> > =A0 =A0 =A0 =A0X-Forwarded-For: 127.0.0.1
>> > =A0 =A0 =A0 =A0X-Forwarded-Host: localhost:4080
>> > =A0 =A0 =A0 =A0X-Forwarded-Server: localhost
>> >
>> > =A0 =A0 =A0 =A0AS2 Adapter is alive.
>>
>> Your problem is that apache expects a http/1.0 response to an HTTP/1.0
>> request. Because the response does not conform to HTTP/1.0 it is
>> rejected. Thus the 502 error.
>>
>> Apache will proxy HTTP/0.9 just fine. Just repeat your test with a
>> HTTP/0.9 client and you'll see. Apache does not translate between
>> HTTP/1.0 and HTTP/0.9. It would anyway not be easy to do this. So if
>> you send a HTTP/1.0 request to your forward proxy it will forward a
>> HTTP/1.0 request to the backend.
>
> I've done that today. The error is the same.

What does the TCP dump show now?

Krist


--=20
krist.vanbesien@gmail.com
krist@vanbesien.org
Bremgarten b. Bern, Switzerland
--
A: It reverses the normal flow of conversation.
Q: What's wrong with top-posting?
A: Top-posting.
Q: What's the biggest scourge on plain text email discussions?

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