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Date: Tue, 15 Jul 2003 08:30:05 -0400
From: Jeff Trawick <trawick@attglobal.net>
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To: dev@httpd.apache.org
Subject: Re: [PATCH] UDP Listeners (was Re: DNS+HTTP redirection system inside
 an Apache module)
References: <Pine.GSO.4.53.0307142254390.25665@flits.cs.vu.nl>
 <3F137E1D.7040702@apache.org>
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Ian Holsman wrote:

> I would like to commit your UDP listener patch to apache 2.1's source tree.
> 
> (providing other people don't have any major objections)

I'm at a loss as to what the big picture is with the programming model 
enabled by this path.  I could go read the whole "DNS+HTTP redirection 
system" but I'd rather not :)

How does process_func field ever get set?  What type of MPM thread would 
be used to process the UDP -- the type of thread that polls on sockets 
or the type of thread that processes work.  It doesn't fit well within 
the rest of Apache to assume that the "accept"-ing thread should process 
the message.

Why does ap_old_listeners need to be externalized?

About this code below: It seems like process_func is a flag that means 
????? (I dunno; why wouldn't we be using the existing record here).  Is 
that inherently connected to having a process_func, or are those 
separate issues?

           /* Some listeners are not real so they will not have a 
bind_addr. */
           if (sa) {
               apr_sockaddr_port_get(&oldport, sa);
!             if (!strcmp(sa->hostname, addr) && port == oldport && 
!(*walk)->process_func) {
                   /* re-use existing record */
                   new = *walk;
                   *walk = new->next;

Regarding the code below:  Setting a key in a pool is not an appropriate 
way to get Apache to do some special processing on a socket.  Surely the 
problem is that Apache doesn't have quite the right hook currently and 
an existing hook needs to be modified in Apache 2.1-dev or some new hook 
is needed?

   {
       apr_status_t rv;
!     conn_rec *c;
!     ap_listen_rec * lr = NULL;
!
!     rv = apr_pool_userdata_get((void**)&lr,AP_LISTEN_REC_KEY,ptrans);
!     if (rv == APR_SUCCESS && lr && lr->process_func) {
!         apr_pool_userdata_set(NULL,AP_LISTEN_REC_KEY,NULL,ptrans);
!         lr->process_func(csd,lr,server,ptrans);
!         return NULL;
!     }