Use service discovery in backends

Integrate the failover improvements with our back ends. The DNS domain
used in the SRV query is always the SSSD domain name.

Please note that this patch changes the default value of ldap_uri from
"ldap://localhost" to "NULL" in order to use service discovery with no
server set.

4 files changed, 62 insertions, 3 deletions

diff --git a/src/man/include/service_discovery.xml b/src/man/include/service_discovery.xml
new file mode 100644
index 000000000..16d016eaf
--- /dev/null
+++ b/src/man/include/service_discovery.xml
@@ -0,0 +1,36 @@
+<refsect1 id='service_discovery'>
+    <title>SERVICE DISCOVERY</title>
+    <para>
+        The service discovery feature allows back ends to automatically
+        find the appropriate servers to connect to using a special DNS
+        query.
+    </para>
+    <refsect2 id='configuration'>
+        <title>Configuration</title>
+        <para>
+            If no servers are specified, the back end automatically
+            uses service discovery to try to find a server. Optionally,
+            the user may choose to use both fixed server addresses
+            and service discovery by inserting a special keyword,
+            <quote>_srv_</quote>, in the list of servers. The order
+            of preference is maintained. This feature is useful if, for
+            example, the user prefers to use service discovery whenever
+            possible, and fall back to a specific server when no servers
+            can be discovered using DNS.
+        </para>
+    </refsect2>
+    <refsect2 id='domain_name'>
+        <title>The domain name</title>
+        <para>
+            The name of the SSSD domain is used as the domain part of the
+            service discovery DNS query.
+        </para>
+    </refsect2>
+    <refsect2 id='reference'>
+        <title>See Also</title>
+        <para>
+            For more information on the service discovery mechanism,
+            refer to RFC 2782.
+        </para>
+    </refsect2>
+</refsect1>
diff --git a/src/man/sssd-ipa.5.xml b/src/man/sssd-ipa.5.xml
index d1ba1c526..103558b04 100644
--- a/src/man/sssd-ipa.5.xml
+++ b/src/man/sssd-ipa.5.xml
@@ -82,6 +82,8 @@
                             on failover and server redundancy, see the
                             <quote>FAILOVER</quote> section.
                             This is optional if autodiscovery is enabled.
+                            For more information on service discovery, refer
+                            to the the <quote>SERVICE DISCOVERY</quote> section.
                         </para>
                     </listitem>
                 </varlistentry>
@@ -120,6 +122,8 @@
 
     <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="include/failover.xml" />
 
+    <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="include/service_discovery.xml" />
+
     <refsect1 id='example'>
         <title>EXAMPLE</title>
         <para>
diff --git a/src/man/sssd-krb5.5.xml b/src/man/sssd-krb5.5.xml
index 8455790c2..732f05bac 100644
--- a/src/man/sssd-krb5.5.xml
+++ b/src/man/sssd-krb5.5.xml
@@ -72,6 +72,9 @@
                             see the <quote>FAILOVER</quote> section. An optional
                             port number (preceded by a colon) may be appended to
                             the addresses or hostnames.
+                            If empty, service discovery is enabled -
+                            for more information, refer to the
+                            <quote>SERVICE DISCOVERY</quote> section.
                         </para>
                     </listitem>
                 </varlistentry>
@@ -262,6 +265,8 @@
 
     <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="include/failover.xml" />
 
+    <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="include/service_discovery.xml" />
+
     <refsect1 id='example'>
         <title>EXAMPLE</title>
         <para>
diff --git a/src/man/sssd-ldap.5.xml b/src/man/sssd-ldap.5.xml
index b79cbbc9a..c119e7f3f 100644
--- a/src/man/sssd-ldap.5.xml
+++ b/src/man/sssd-ldap.5.xml
@@ -61,9 +61,8 @@
                             Specifies the list of URIs of the LDAP servers to which
                             SSSD should connect in the order of preference. Refer to the
                             <quote>FAILOVER</quote> section for more information on failover and server redundancy.
-                        </para>
-                        <para>
-                            Default: ldap://localhost
+                            If not specified, service discovery is enabled. For more information, refer
+                            to the <quote>SERVICE DISCOVERY</quote> section.
                         </para>
                     </listitem>
                 </varlistentry>
@@ -632,12 +631,27 @@
                     </listitem>
                 </varlistentry>
 
+                <varlistentry>
+                    <term>ldap_dns_service_name (string)</term>
+                    <listitem>
+                        <para>
+                            Specifies the service name to use when service
+                            discovery is enabled.
+                        </para>
+                        <para>
+                            Default: ldap
+                        </para>
+                    </listitem>
+                </varlistentry>
+
             </variablelist>
         </para>
     </refsect1>
 
     <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="include/failover.xml" />
 
+    <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="include/service_discovery.xml" />
+
     <refsect1 id='example'>
         <title>EXAMPLE</title>
         <para>