PQconnectionUsedGSSAPI(const PGconn *conn);
</synopsis>
      </para>

      <para>
       This function can be applied to detect whether the connection was
       authenticated with GSSAPI.
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>

  <para>
    The following functions return information related to SSL. This information
    usually doesn't change after a connection is established.

    <variablelist>
    <varlistentry id="libpq-PQsslInUse">
     <term><function>PQsslInUse</function><indexterm><primary>PQsslInUse</primary></indexterm></term>
     <listitem>
      <para>
        Returns true (1) if the connection uses SSL, false (0) if not.

<synopsis>
int PQsslInUse(const PGconn *conn);
</synopsis>
      </para>

     </listitem>
    </varlistentry>

    <varlistentry id="libpq-PQsslAttribute">
     <term><function>PQsslAttribute</function><indexterm><primary>PQsslAttribute</primary></indexterm></term>
     <listitem>
      <para>
        Returns SSL-related information about the connection.

<synopsis>
const char *PQsslAttribute(const PGconn *conn, const char *attribute_name);
</synopsis>
      </para>

      <para>
       The list of available attributes varies depending on the SSL library
       being used and the type of connection.  Returns NULL if the connection
       does not use SSL or the specified attribute name is not defined for the
       library in use.
      </para>

      <para>
       The following attributes are commonly available:
       <variablelist>
        <varlistentry>
         <term><literal>library</literal></term>
          <listitem>
           <para>
            Name of the SSL implementation in use. (Currently, only
            <literal>"OpenSSL"</literal> is implemented)
           </para>
          </listitem>
         </varlistentry>
        <varlistentry>
         <term><literal>protocol</literal></term>
          <listitem>
           <para>
             SSL/TLS version in use. Common values
             are <literal>"TLSv1"</literal>, <literal>"TLSv1.1"</literal>
             and <literal>"TLSv1.2"</literal>, but an implementation may
             return other strings if some other protocol is used.
           </para>
          </listitem>
         </varlistentry>
        <varlistentry>
         <term><literal>key_bits</literal></term>
          <listitem>
           <para>
            Number of key bits used by the encryption algorithm.
           </para>
          </listitem>
         </varlistentry>
        <varlistentry>
         <term><literal>cipher</literal></term>
          <listitem>
           <para>
            A short name of the ciphersuite used, e.g.,
            <literal>"DHE-RSA-DES-CBC3-SHA"</literal>. The names are specific
            to each SSL implementation.
           </para>
          </listitem>
         </varlistentry>
        <varlistentry>
         <term><literal>compression</literal></term>
          <listitem>
           <para>
            Returns "on" if SSL compression is in use, else it returns "off".
           </para>
          </listitem>
         </varlistentry>
        <varlistentry>
         <term><literal>alpn</literal></term>
          <listitem>
           <para>
            Application protocol selected by the TLS Application-Layer
            Protocol Negotiation (ALPN) extension.  The only protocol
            supported by libpq is <literal>postgresql</literal>, so this is
            mainly useful for checking whether the server supported ALPN or
            not. Empty string if ALPN was not used.
           </para>
          </listitem>
         </varlistentry>
       </variablelist>
      </para>

      <para>
       As a special case, the <literal>library</literal> attribute may be
       queried without a connection by passing NULL as
       the <literal>conn</literal> argument.  The result will be the default
       SSL library name, or NULL if <application>libpq</application> was
       compiled without