modules_k/presence_xml: Modified pres_check_activities() to return -2 when part of the XML tree is not present

- This is needed because some presence UAs (such as pua_usrloc) only
  fill in the basic part of the tree.  This change enables you to
  distinguish between not having a particular activity set (by a client
  that supports that) and not having any activities at all (by clients
  that only support basic presence).

modules_k/presence_xml/README

@@ -320,11 +320,13 @@ modparam("presence_xml", "passive_mode", 1)
    Return code:
      * 1 - if a match is found.
      * -1 - if a match is not found.
+     * -2 - if /presence/person or /presence/person/activity do not exist.
 
    Example 1.12. pres_check_activities usage
 ...
     if (pres_check_basic("$ru", "open")) {
-        if (pres_check_activities("$ru", "unknown") || !is_method("INVITE"))
+        pres_check_activities("$ru", "unknown");
+        if ($retcode || $retcode == -2 || !is_method("INVITE"))
             t_relay();
         else
             send_reply("486", "Busy Here");

modules_k/presence_xml/doc/presence_xml_admin.xml

@@ -381,6 +381,12 @@ modparam("presence_xml", "passive_mode", 1)
 				<emphasis> -1 - if a match is not found</emphasis>.
 			</para>
 			</listitem>
+			<listitem>
+			<para>
+				<emphasis> -2 - if /presence/person or /presence/person/activity do not exist</emphasis>.
+			</para>
+			</listitem>
+	
 		</itemizedlist>
 		</para>
 		<example>
@@ -388,7 +394,8 @@ modparam("presence_xml", "passive_mode", 1)
 		<programlisting format="linespecific">
 ...
     if (pres_check_basic("$ru", "open")) {
-        if (pres_check_activities("$ru", "unknown") || !is_method("INVITE"))
+	pres_check_activities("$ru", "unknown");
+	if ($retcode || $retcode == -2 || !is_method("INVITE"))
             t_relay();
 	else
             send_reply("486", "Busy Here");

modules_k/presence_xml/pres_check.c

@@ -98,7 +98,7 @@ int presxml_check_basic(struct sip_msg *msg, char *presentity_uri, char *status)
 		goto error;
 	}
 
-	while (tuple->next != NULL)
+	while (tuple != NULL)
 	{
 		if (xmlStrcasecmp(tuple->name, (unsigned char *) "tuple") == 0)
 		{
@@ -189,17 +189,19 @@ int presxml_check_activities(struct sip_msg *msg, char *presentity_uri, char *ac
 
 	if ((person = xmlDocGetNodeByName(xmlDoc, "person", NULL)) == NULL)
 	{
-		LM_ERR("unable to extract 'person'\n");
+		LM_DBG("unable to extract 'person'\n");
+		retval = -2;
 		goto error;
 	}
 
-	while (person->next != NULL)
+	while (person != NULL)
 	{
 		if (xmlStrcasecmp(person->name, (unsigned char *) "person") == 0)
 		{
 			if ((activitiesNode = xmlNodeGetNodeByName(person, "activities", NULL)) == NULL)
 			{
-				LM_ERR("while extracting 'actvities' node\n");
+				LM_DBG("unable to extract 'actvities' node\n");
+				retval = -2;
 				goto error;
 			}