Comment 5 for bug 1352809

Analysis of the upstream patch that fixes the problem
================================
The new _cupsSetDefaults() in cups v2.1 has been refactored to use a _cups_client_conf_t structure that holds the user defined value. This structure gets populated first by cups_init_client_conf(), that reads the /etc/cups/client.conf and ~/.cups/client.conf if present.

It then runs cups_finalize_client_conf() that reads in the environment variables in the _cups_client_conf_t structure.

A new check is added to verify if a value already exists in cg->server before calling cupsSetServer() on the ENV variable collected value which is stored in the structure.

The original patch is :
  if (!cg->server[0] || !cg->ipp_port)
    cupsSetServer(cc.server_name);

  if (!cg->ipp_port)
  {
    const char *ipp_port; /* IPP_PORT environment variable */

    if ((ipp_port = getenv("IPP_PORT")) != NULL)
    {
      if ((cg->ipp_port = atoi(ipp_port)) <= 0)
        cg->ipp_port = CUPS_DEFAULT_IPP_PORT;
    }
    else
      cg->ipp_port = CUPS_DEFAULT_IPP_PORT;
  }

This portion of code is found in 1.7.2 in the cups_read_client_conf() starting at line 1027. The server name given to cupsSetServer() is conditional to the value set in cups_server :

  if ((!cg->server[0] || !cg->ipp_port) && cups_server)
    cupsSetServer(cups_server);

So in order to correctly trigger the server name definition, the following patch is needed :

Index: cups-1.7.5/cups/usersys.c
===================================================================
--- cups-1.7.5.orig/cups/usersys.c 2015-02-04 12:58:39.000000000 +0100
+++ cups-1.7.5/cups/usersys.c 2015-02-04 13:10:54.062431647 +0100
@@ -891,6 +891,12 @@
     }

    /*
+ * Check if values have been provided as CLI options
+ */
+ if (cg->server[0])
+ cups_server = cg->server;
+
+ /*
     * Read the configuration file and apply any environment variables; both
     * functions handle NULL cups_file_t pointers...
     */
~