trying to add header field using PerlInputFilterHandler to proxy packets

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I am running an apache server 2.2.3 on CentOS 5.2. I have turned on the
proxy with the following lines from my apache.conf:
=20

ProxyRequests On

Order deny,allow
Deny from all
Allow from all


=20
I would like to add a header field to all requests going through the
proxy. After doing a bunch of reading it seemed that setting up a
PerlInputFilterHandler was the right thing to do. I added the following
lines to the apache.conf
=20
PerlModule company::AddHeader
PerlInputFilterHandler company::AddHeader=20
=20
and I wrote the following example handler
=20
package company::AddHeader;
=20
use strict;
use warnings;
=20
use Apache2::Filter ();
use Apache2::RequestRec ();
use APR::Table ();
=20
use Apache2::Const -compile =3D> qw(OK DECLINED);
=20
my $debug =3D 1;
=20
sub handler {
my $f =3D shift;
=20
# if we have already seen this do nothing
return Apache2::Const::DECLINED if $f->ctx;
=20
# get headers
my $headers_in =3D $f->r->headers_in();
=20
# add header field
$headers_in->set("Message","Hi Mom");
$f->r->headers_in($headers_in);
=20
if($debug)
{
open FILE, ">>/tmp/out.log" or die $!;
foreach my $key (keys %{$headers_in})
{
print FILE "$key =3D $headers_in->{$key}\n";
}
close FILE;
}
=20
$f->ctx(1);
=20
return Apache2::Const::OK;
}
1;

As you can see, if debugging is turned on the headers are written to the
file /tmp/out.log. The contents of out.log contains the new header, but
the requests being forwarded by the proxy don't seem to be altered. Why
is the new header not being sent?
=20
I am pretty sure I am missing something very simple, but have spent a
day trying to figure out what it is. Any ideas?
=20
cheers,
Brandon
=20



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charset=3Dus-ascii">

Re: trying to add header field using PerlInputFilterHandler to proxy packets

On Tue 30 Jun 2009, Brandon Allgood wrote:
> PerlInputFilterHandler company::AddHeader
> =A0
> and I wrote the following example handler
> =A0
> package company::AddHeader;
> =A0
> use strict;
> use warnings;
> =A0
> use Apache2::Filter ();
> use Apache2::RequestRec ();
> use APR::Table ();
> =A0
> use Apache2::Const -compile =3D> qw(OK DECLINED);
> =A0
> my $debug =3D 1;
> =A0
> sub handler {
> =A0 my $f =3D shift;
> =A0
> =A0 # if we have already seen this do nothing
> =A0 return Apache2::Const::DECLINED if $f->ctx;
> =A0
> =A0 # get headers
> =A0 my $headers_in =3D $f->r->headers_in();
> =A0
> =A0 # add header field
> =A0 $headers_in->set("Message","Hi Mom");
> =A0 $f->r->headers_in($headers_in);
> =A0
> =A0 if($debug)
> =A0 {
> =A0 =A0 open FILE, ">>/tmp/out.log" or die $!;
> =A0 =A0 foreach my $key (keys %{$headers_in})
> =A0 =A0 {
> =A0 =A0 =A0 print FILE "$key =3D $headers_in->{$key}\n";
> =A0 =A0 }
> =A0 =A0 close FILE;
> =A0 }
> =A0
> =A0 $f->ctx(1);
> =A0
> =A0 return Apache2::Const::OK;
> }
> 1;
>
> As you can see, if debugging is turned on the headers are written to
> the file /tmp/out.log. =A0The contents of out.log contains the new
> header, but the requests being forwarded by the proxy don't seem to
> be altered. =A0Why is the new header not being sent?

A request level input filter is called when the request body is read.=20
mod_proxy does this obviously *after* sending the request header to the=20
backend server. Hence, adding an input header at this time is too late.

Why do you want to do that in a filter? Why don't you add it in a=20
request phase prior to response. Fixup would be a good place for=20
example.

PerlFixupHandler "sub { \
use Apache2::RequestRec; \
use Apache2::Const -compile=3D>'DECLINED'; \
$_[0]->headers_in->{Message}=3D'Hi, Mom'; \
return Apache2::Const::DECLINED; \
}"

Another word to your filter, did you know you can remove a filter on=20
first invocation? This way you can avoid the useless

return Apache2::Const::DECLINED if $f->ctx;

sub filter {
my ($f)=3D@_;
# do something
$f->remove;
return Apache2::Const::DECLINED;
}

I haven't benchmarked it but I believe this is faster than return if=20
$f->ctx. But it only makes a difference of course if the filter is=20
called more than once.

Torsten

=2D-=20
Need professional mod_perl support?
Just hire me: torsten.foertsch@gmx.net

Re: trying to add header field using PerlInputFilterHandler to proxy

On Mon, Jun 29, 2009 at 8:07 PM, Brandon Allgood wrote:
> I am running an apache server 2.2.3 on CentOS 5.2. I have turned on the
> proxy with the following lines from my apache.conf:
>
>
> ProxyRequests On
>
> Order deny,allow
> Deny from all
> Allow from all
>
>
>
> I would like to add a header field to all requests going through the proxy.

If your adding a static header you can just use the Apache directive
'Header'. Using mod_perl to add a static header is somewhat overkil.

-wjt

RE: trying to add header field using PerlInputFilterHandler to proxy packets

FYI, this answered my question and everything is working.

thanks,
Brandon

-----Original Message-----
From: Torsten Foertsch [mailto:torsten.foertsch@gmx.net]=20
Sent: Tuesday, June 30, 2009 1:00 AM
To: modperl@perl.apache.org
Cc: Brandon Allgood
Subject: Re: trying to add header field using PerlInputFilterHandler to =
proxy packets

On Tue 30 Jun 2009, Brandon Allgood wrote:
> PerlInputFilterHandler company::AddHeader
> =A0
> and I wrote the following example handler
> =A0
> package company::AddHeader;
> =A0
> use strict;
> use warnings;
> =A0
> use Apache2::Filter ();
> use Apache2::RequestRec ();
> use APR::Table ();
> =A0
> use Apache2::Const -compile =3D> qw(OK DECLINED);
> =A0
> my $debug =3D 1;
> =A0
> sub handler {
> =A0 my $f =3D shift;
> =A0
> =A0 # if we have already seen this do nothing
> =A0 return Apache2::Const::DECLINED if $f->ctx;
> =A0
> =A0 # get headers
> =A0 my $headers_in =3D $f->r->headers_in();
> =A0
> =A0 # add header field
> =A0 $headers_in->set("Message","Hi Mom");
> =A0 $f->r->headers_in($headers_in);
> =A0
> =A0 if($debug)
> =A0 {
> =A0 =A0 open FILE, ">>/tmp/out.log" or die $!;
> =A0 =A0 foreach my $key (keys %{$headers_in})
> =A0 =A0 {
> =A0 =A0 =A0 print FILE "$key =3D $headers_in->{$key}\n";
> =A0 =A0 }
> =A0 =A0 close FILE;
> =A0 }
> =A0
> =A0 $f->ctx(1);
> =A0
> =A0 return Apache2::Const::OK;
> }
> 1;
>
> As you can see, if debugging is turned on the headers are written to=20
> the file /tmp/out.log. =A0The contents of out.log contains the new=20
> header, but the requests being forwarded by the proxy don't seem to be =

> altered. =A0Why is the new header not being sent?

A request level input filter is called when the request body is read.=20
mod_proxy does this obviously *after* sending the request header to the =
backend server. Hence, adding an input header at this time is too late.

Why do you want to do that in a filter? Why don't you add it in a =
request phase prior to response. Fixup would be a good place for =
example.

PerlFixupHandler "sub { \
use Apache2::RequestRec; \
use Apache2::Const -compile=3D>'DECLINED'; \
$_[0]->headers_in->{Message}=3D'Hi, Mom'; \
return Apache2::Const::DECLINED; \
}"

Another word to your filter, did you know you can remove a filter on =
first invocation? This way you can avoid the useless

return Apache2::Const::DECLINED if $f->ctx;

sub filter {
my ($f)=3D@_;
# do something
$f->remove;
return Apache2::Const::DECLINED;
}

I haven't benchmarked it but I believe this is faster than return if =
$f->ctx. But it only makes a difference of course if the filter is =
called more than once.

Torsten

--
Need professional mod_perl support?
Just hire me: torsten.foertsch@gmx.net