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[thirdparty/squid.git] / doc / release-notes / release-3.5.sgml

<!doctype linuxdoc system>
<article>
<title>Squid 3.5.0.4 release notes</title>
<author>Squid Developers</author>

<abstract>
This document contains the release notes for version 3.5 of Squid.
Squid is a WWW Cache application developed by the National Laboratory
for Applied Network Research and members of the Web Caching community.
</abstract>

<toc>

<sect>Notice
<p>
The Squid Team are pleased to announce the release of Squid-3.5.0.4 for testing.

This new release is available for download from <url url="http://www.squid-cache.org/Versions/v3/3.5/"> or the
 <url url="http://www.squid-cache.org/Mirrors/http-mirrors.html" name="mirrors">.

<p>Some interesting new features adding system flexibility have been added along with general improvements all around.
   While this release is not fully bug-free we believe it is ready for use in production on many systems.

<p>We welcome feedback and bug reports. If you find a bug, please see <url url="http://wiki.squid-cache.org/SquidFaq/BugReporting">
   for how to submit a report with a stack trace.

<sect1>Known issues
<p>
Although this release is deemed good enough for use in many setups, please note the existence of 
<url url="http://bugs.squid-cache.org/buglist.cgi?query_format=advanced&amp;product=Squid&amp;bug_status=UNCONFIRMED&amp;bug_status=NEW&amp;bug_status=ASSIGNED&amp;bug_status=REOPENED&amp;version=3.5" name="open bugs against Squid-3.5">.

<sect1>Changes since earlier releases of Squid-3.5
<p>
The 3.5 change history can be <url url="http://www.squid-cache.org/Versions/v3/3.5/changesets/" name="viewed here">.

<sect1>Copyright disclaimer adjustments
<p>Squid sources are now administered by the Squid Software Foundation on
   behalf of the Squid Project and community.

<p>This version of Squid contains initial changes to streamline copyright
   declarations in Squid sources and related metafiles. No functionality
   or licensing changes are intended.

<p>Once completed, the changes will consistently declare Squid contributors
   (listed in CONTRIBUTORS and represented by the Squid Software Foundation) as
   Squid copyright owners while referring the reader to the COPYING file for GPL
   licensing details. The boilerplate with the above information is provided.

<p>These changes do not affect copyright rights of individuals or organizations.
   We are simply confirming the fact that there are many Squid copyright owners,
   just like there are many Linux kernel copyright owners. We are also providing
   a simple, consistent way to document that fact.


<sect>Major new features since Squid-3.4
<p>Squid 3.5 represents a new feature release above 3.4.

<p>The most important of these new features are:
<itemize>
	<item>Support libecap v1.0
	<item>Authentication helper query extensions
	<item>Support named services
	<item>Upgraded squidclient tool
	<item>Helper support for concurrency channels
	<item>Native FTP Relay
	<item>Receive PROXY protocol, Versions 1 & 2
	<item>Basic authentication MSNT helper changes
</itemize>

Most user-facing changes are reflected in squid.conf (see below).


<sect1>Support libecap v1.0
<p>Details at <url url="http://wiki.squid-cache.org/Features/eCAP">.

<p>The new libecap version allows Squid to better check the version of
  the eCAP adapter being loaded as well as the version of the eCAP library
  being used.

<p>Squid-3.5 can support eCAP adapters built with libecap v1.0,
   but no longer supports adapters built with earlier libecap versions
   due to API changes.


<sect1>Authentication helper query extensions
<p>Details at <url url="http://www.squid-cache.org/Doc/config/auth_param/">.

<p>The new <em>key_extras</em> parameter allows sending of additional
  details to the authentication helper beyond the minimum required for
  the HTTP authentication. This is primarily intended to allow switching
  of authentication databases based on criteria such as client IP subnet,
  Squid receiving port, or in reverse-proxy the requested domain name.

<p>In theory any <em>logformat</em> code may be used, however only the
  codes which have available details at the time of authentication
  will send any meaningful detail.


<sect1>Support named services
<p>Details at <url url="http://wiki.squid-cache.org/MultipleInstances">.
<p>Terminology details at <url url="http://wiki.squid-cache.org/Features/SmpScale#Terminology">.

<p>The command line option <em>-n</em> assigns a name to the Squid service
   instance to be used as a unique identifier for all SMP processes run as
   part of that instance. This allows multiple instances of Squid service to
   be run on a single machine without background SMP systems such as shared
   memory and inter-process communication becoming confused or requiring
   additional configuration.

<p>A service name is always used. When the <em>-n</em> option is missing
   from the command line the default service name is <em>squid</em>.

<p>When multiple instances are being run the <em>-n</em> service name is
   required to target all other options such as <em>-z</em> or <em>-k</em>
   commands at the correct service.

<p>The squid.conf macro ${service_name} is added to provide the service name
   of the process parsing the config.


<sect1>Upgraded squidclient tool
<p>Details at <url="http://www.squid-cache.org/Versions/v3/3.5/manuals/squidclient.html">.

<p>The <em>squidclient</em> has begun the process of upgrading to support
   protocols other than HTTP.

<sect2>Debug levels
<p>The tool displays the server response message on STDOUT unless the <em>-q</em>
   command line option is used. Error messages will be output to STDERR.
   All other possible output is considered debug and output to STDERR using
   a range of debug verbosity levels (currently 1, 2 and 3).

<p>When the <em>-v</em> command line option is used debugging is enabled.
   The level of debug display is raised for each repetition of the option.

<sect2>PING
<p>When <em>--ping</em> is given the tool will send its message repeatedly
   using whichever protocol that message has been formatted for.
   Optional parameters to limit the number of pings and their frequency are
   available.

<p>Older tool versions also provide this feature but require the loop count
   parameter to be set to enable use of the feature.

<sect2>HTTPS
<p>When Squid is built with the GnuTLS encryption library the tool is able
   to open TLS (or SSL/3.0) connections to servers.

<p>The <em>--https</em> option enables TLS using default values.

<p>The <em>--cert</em> option specifies a file containing X.509 client
   certificate and private key in PEM format to be loaded for use. Multiple
   certificates are supported and the option may be used multiple times to
   load certificates.
   The default is not to use a client certificate.

<p>The <em>--params</em> option specifies a library specific set of parameters
   to be sent to the library for configuring the security context.
   See <url url="http://gnutls.org/manual/html_node/Priority-Strings.html"> for
   available GnuTLS parameters.

<p>The <em>--trusted-ca</em> option specifies a file in PEM format containing
   one or more Certificate Authority (CA) certificates used to verify the
   remote server. This option may be used multiple times to load additional
   CA certificate lists.
   The default is not to use any CA, nor trust any server.

<p>Anonymous TLS (using non-authenticated Diffi-Hellman or Elliptic Curve
   encryption) is available with the <em>--anonymous-tls</em> option.
   The default is to use X.509 certificate encryption instead.

<p>When performing TLS/SSL server certificates are always verified, the
   results shown at debug level 3. The encrypted type is displayed at debug
   level 2 and the connection is used to send and receive the messages
   regardless of verification results.


<sect1>Helper support for concurrency channels
<p>Helper concurrency greatly reduces the communication lag between Squid
   and its helpers allowing faster transaction speeds even on sequential
   helpers.

<p>The Digest authentication, Store-ID, and URL-rewrite helpers packaged
   with Squid have been updated to support concurrency channels. They will
   auto-detect the <em>channel-ID</em> field and will produce the appropriate
   response format.
   With these helpers concurrency may now be set to 0 or any higher number as desired.


<sect1>Native FTP Relay
<p>Details at <url url="http://wiki.squid-cache.org/Features/FtpRelay">.

<p>Squid is now capable of accepting native FTP commands and relaying native
   FTP messages between FTP clients and FTP servers. Native FTP commands
   accepted at ftp_port are internally converted or wrapped into HTTP-like
   messages. The same happens to Native FTP responses received from FTP origin
   servers. Those HTTP-like messages are shoveled through regular access
   control and adaptation layers between the FTP client and the FTP origin
   server. This allows Squid to examine, adapt, block, and log FTP exchanges.
   Squid reuses most HTTP mechanisms when shoveling wrapped FTP messages. For
   example, http_access and adaptation_access directives are used.

<p>FTP Relay is a new, experimental, complex feature that has seen limited
   production exposure. Some Squid modules (e.g., caching) do not currently
   work with native FTP proxying, and many features have not even been tested
   for compatibility. Test well before deploying!

<p>Native FTP proxying differs substantially from proxying HTTP requests with
   <em>ftp://</em> URIs because Squid works as an FTP server and receives
   actual FTP commands (rather than HTTP requests with FTP URLs).

<p>FTP Relay highlights:
<itemize>
    <item>Added ftp_port directive telling Squid to relay native FTP commands.
    <item>Active and passive FTP support on the user-facing side; require
	  passive connections to come from the control connection source IP
	  address.
    <item>IPv6 support (EPSV and, on the user-facing side, EPRT).
    <item>Intelligent adaptation of relayed FTP FEAT responses.
    <item>Relaying of multi-line FTP control responses using various formats.
    <item>Support relaying of FTP MLSD and MLST commands (RFC 3659).
    <item>Several Microsoft FTP server compatibility features.
    <item>ICAP/eCAP support (at individual FTP command/response level).
    <item>Optional "current FTP directory" tracking with the assistance of
	  injected (by Squid) PWD commands (cannot be 100% reliable due to
	  symbolic links and such, but is helpful in some common use cases).
    <item>No caching support -- no reliable Request URIs for that (see above).
</itemize>

<sect1>Receive PROXY protocol, Versions 1 & 2
<p>More info at <url url="http://www.haproxy.org/download/1.5/doc/proxy-protocol.txt">

<p>PROXY protocol provides a simple way for proxies and tunnels of any kind to
   relay the original client source details without having to alter or understand
   the protocol being relayed on the connection.

<p>Squid currently supports receiving HTTP traffic from a client proxy using this protocol.
   An http_port which has been configured to receive this protocol may only be used to
   receive traffic from client software sending in this protocol.
   HTTP traffic without the PROXY header is not accepted on such a port.

<p>The <em>accel</em> and <em>intercept</em> options are still used to identify the
   traffic syntax being delivered by the client proxy.

<p>Squid can be configured by adding an <em>http_port</em>
   with the <em>require-proxy-header</em> mode flag. The <em>proxy_protocol_access</em>
   must also be configured with <em>src</em> ACLs to whitelist proxies which are
   trusted to send correct client details.

<p>Forward-proxy traffic from a client proxy:
<verb>
 acl frontend src 192.0.2.1
 http_port 3128 require-proxy-header
 proxy_protocol_access allow frontend
</verb>

<p>Intercepted traffic from a client proxy or tunnel:
<verb>
 acl frontend src 192.0.2.2
 http_port 3128 intercept require-proxy-header
 proxy_protocol_access allow frontend
</verb>

<p>Reverse-proxy traffic from a frontend load balancer sending PROXY protocol:
<verb>
 acl frontend src 192.0.2.3
 http_port 3128 accel require-proxy-header
 proxy_protocol_access allow frontend
</verb>

<p><em>Known Issue:</em>
   Use of <em>require-proxy-header</em> on <em>https_port</em> and <em>ftp_port</em> is not supported.


<sect1>Basic authentication MSNT helper changes

<p>The authentication helper previously known as <em>basic_msnt_auth</em> has
   been deprecated and renamed to <em>basic_smb_lm_auth</em> to reflect that
   it only performs SMB LanMan protocol(s) instead of modern MS authentication
   protocols.

<p>The <em>basic_smb_lm_auth</em> helper has been remodelled and no longer uses
   configuration files. The Doman Controller servers are now configured via
   command line parameters and user credentials are looked up in each DC in the
   order configured until one matches or all have confirmed a non-match.

<p>The <em>MSNT-multi-domain</em> helper provides the same functionality and
   is also deprecated. It will be removed in the Squid-3.6 series.



<sect>Changes to squid.conf since Squid-3.4
<p>
There have been changes to Squid's configuration file since Squid-3.4.

<p>Squid supports reading configuration option parameters from external
   files using the syntax <em>parameters("/path/filename")</em>. For example:
<verb>
    acl whitelist dstdomain parameters("/etc/squid/whitelist.txt")
</verb>

<p>The squid.conf macro <em>${service_name}</em> is added to provide the service name
   of the process parsing the config.

<p>There have also been changes to individual directives in the config file.

This section gives a thorough account of those changes in three categories:

<itemize>
	<item><ref id="newtags" name="New tags">
	<item><ref id="modifiedtags" name="Changes to existing tags">
	<item><ref id="removedtags" name="Removed tags">
</itemize>
<p>

<sect1>New tags<label id="newtags">
<p>
<descrip>
	<tag>collapsed_forwarding</tag>
	<p>Ported from Squid-2 with no configuration or visible behaviour changes.
           Collapsing of requests is performed across SMP workers.

	<tag>ftp_client_idle_timeout</tag>
	<p>This new configuration directive controls how long Squid should
	   wait for an FTP request on a connection to an ftp_port.  Many FTP
	   clients do not deal with idle connection closures well,
	   necessitating a longer default timeout (30 minutes) than
	   client_idle_pconn_timeout used for incoming HTTP requests (2
	   minutes). The current default may be changed as we get more
	   experience with FTP relaying.

	<tag>ftp_client_idle_timeout</tag>
	<p>New directive controlling how long to wait for an FTP request on a
	   client connection to Squid <em>ftp_port</em>.

	<tag>ftp_port</tag>
	<p>New configuration directive to accept and relay native FTP
	   commands. Typically used for port 21 traffic.  By default, native
	   FTP commands are not accepted.

	<tag>proxy_protocol_access</tag>
	<p>New directive to control which clients are permitted to open PROXY
	   protocol connections on a port flagged with <em>require-proxy-header</em>.

	<tag>send_hit</tag>
	<p>New configuration directive to enable/disable sending cached content
	   based on ACL selection. ACL can be based on client request or cached
	   response details.

	<tag>sslproxy_cert_sign_hash</tag>
	<p>New directive to set the hashing algorithm to use when signing generated certificates.

	<tag>sslproxy_session_cache_size</tag>
	<p>New directive which sets the cache size to use for TLS/SSL sessions cache.

	<tag>sslproxy_session_ttl</tag>
	<p>New directive to specify the time in seconds the TLS/SSL session is valid.

	<tag>store_id_extras</tag>
	<p>New directive to send additional lookup parameters to the configured
	   Store-ID helper program. It takes a string which may contain logformat %macros.
	<p>The Store-ID helper input format is now:
	<verb>
         [channel-ID] url [extras]
	</verb>
	<p>The default value for extras is: "%&gt;a/%&gt;A %un %&gt;rm myip=%la myport=%lp"

	<tag>store_miss</tag>
	<p>New configuration directive to enable/disable caching of MISS responses.
	   ACL can be based on any request or response details.

	<tag>url_rewrite_extras</tag>
	<p>New directive to send additional lookup parameters to the configured
	   URL-rewriter/redirector helper program. It takes a string which may
	   contain logformat %macros.
	<p>The url rewrite and redirector helper input format is now:
	<verb>
         [channel-ID] url [extras]
	</verb>
	<p>The default value for extras is: "%&gt;a/%&gt;A %un %&gt;rm myip=%la myport=%lp"

</descrip>

<sect1>Changes to existing tags<label id="modifiedtags">
<p>
<descrip>
	<tag>acl</tag>
	<p>Deprecated type <em>tag</em>. Use type <em>note</em> with 'tag' key
	   name instead.
	<p>New type <em>adaptation_service</em> to match the name of any
	   icap_service, ecap_service, adaptation_service_set, or
	   adaptation_service_chain that Squid has used (or attempted to use)
	   for the HTTP transaction so far.
	<p>New type <em>at_step</em> to match the current SSL-Bump processing step.
	   Never matches and should not be used outside of <em>ssl_bump</em>.

	<tag>auth_param</tag>
	<p>New parameter <em>key_extras</em> to send additional parameters to
	   the authentication helper.

	<tag>cache_dir</tag>
	<p>New support for larger than 32KB objects in both <em>rock</em> type
	   cache and shared memory cache.
	<p>New <em>slot-size=N</em> option for rock cache to specify the database
	   slot/page size when small slot sizes are desired. The default and
	   maximum slot size is 32KB.
	<p>Removal of old rock cache dir followed by <em>squid -z</em> is required
	   when upgrading from earlier versions of Squid.
	<p><em>COSS</em> storage type is formally replaced by Rock storage type.
	   COSS storage type and all COSS specific options are removed.

	<tag>cache_peer</tag>
	<p>New <em>standby=N</em> option to retain a set of N open and unused
	   connections to the peer at virtually all times to reduce TCP handshake
	   delays.
	<p>These connections differ from HTTP persistent connections in that they
	   have not been used for HTTP messaging (and may never be). They may be
	   turned into persistent connections after their first use subject to the
	   same keep-alive critera any HTTP connection is checked for.
	<p>Squid-2 option <em>idle=</em> replaced by <em>standby=</em>.
	<p>NOTE that standby connections are started earlier and available in
	   more circumstances than squid-2 idle connections were. They are
	   also spread over all IPs of the peer.

	<tag>configuration_includes_quoted_values</tag>
	<p>Regex pattern values cannot be parsed in parts of squid.conf when this
	   directive is configured to <em>ON</em>. Instead of quoted strings Squid
	   now accepts regex \-escaped characters (including escaped spaces) in all
	   regex patterns.

	<tag>external_acl_type</tag>
	<p>New format code <em>%ssl::&gt;sni</em> to send SSL client SNI.
	<p>New format code <em>%ssl::&lt;cert_subject</em> to send SSL server certificate DN.
	<p>New format code <em>%ssl::&lt;cert_issuer</em> to send SSL server certificate issuer DN.
	<p>New response kv-pair <em>clt_conn_tag=</em> to associates a given tag with the client TCP connection.

	<tag>forward_max_tries</tag>
	<p>Default value increased to <em>25 destinations</em> to allow better
	   contact and IPv4 failover with domains using long lists of IPv6
	   addresses.

	<tag>ftp_epsv</tag>
	<p>Converted into an Access List with allow/deny value driven by ACLs
	   using Squid standard first line wins matching basis.
	<p>The old values of <em>on</em> and <em>off</em> imply <em>allow all</em>
	    and <em>deny all</em> respectively and are now deprecated.
	   Do not combine use of on/off values with ACL configuration.

	<tag>http_port</tag>
	<p><em>protocol=</em> option altered to accept protocol version details.
	   Currently supported values are: HTTP, HTTP/1.1, HTTPS, HTTPS/1.1
	<p>New option <em>require-proxy-header</em> to mark ports receiving PROXY
	   protocol version 1 or 2 traffic.

	<tag>https_port</tag>
	<p><em>protocol=</em> option altered to accept protocol version details.
	   Currently supported values are: HTTP, HTTP/1.1, HTTPS, HTTPS/1.1

	<tag>logformat</tag>
	<p>New format code <em>%credentials</em> to log the client credentials token.
	<p>New format code <em>%ssl::&gt;sni</em> to TLS client SNI sent to Squid.
	<p>New format code <em>%tS</em> to log transaction start time in
	   "seconds.milliseconds" format, similar to the existing access.log
	   "current time" field (%ts.%03tu) which logs the corresponding
	   transaction finish time.
	<p>New format codes <em>%&lt;rs</em> and <em>%&gt;rs</em> to log request URL
	   scheme from client or sent to server/peer respectively.
	<p>New format codes <em>%&lt;rd</em> and <em>%&gt;rd</em> to log request URL
	   domain from client or sent to server/peer respectively.
	<p>New format codes <em>%&lt;rP</em> and <em>%&gt;rP</em> to log request URL
	   port from client or sent to server/peer respectively.

	<tag>ssl_bump</tag>
	<p>Bumping 'modes' redesigned as 'actions' and ACLs evaluated repeatedly in a number of steps.
	<p>Renamed <em>server-first</em> as <em>bump</em> action.
	<p>Renamed <em>none</em> as <em>splice</em> action.
	<p>New actions <em>peek</em> and <em>stare</em> to receive client or server
	   certificate while preserving the ability to later decide between bumping
	   or splicing the connections later.
	<p>New action <em>terminate</em> to close the client and server connections.

	<tag>url_rewrite_program</tag>
	<p>New response kv-pair <em>clt_conn_tag=</em> to associates a given tag with the client TCP connection.

</descrip>

<sect1>Removed tags<label id="removedtags">
<p>
<descrip>
	<tag>cache_dns_program</tag>
	<p>DNS external helper interface has been removed. It was no longer
	   able to provide high performance service and the internal DNS
	   client library with multicast DNS cover all modern use-cases.

	<tag>dns_children</tag>
	<p>DNS external helper interface has been removed.

	<tag>hierarchy_stoplist</tag>
	<p>Removed. The old directive values prohibiting CGI and dynamic content
	   going to cache_peer are no longer relevant.
	<p>The functionality provided by this directive can be configured
	   using <em>always_direct allow</em> if still needed.

</descrip>


<sect>Changes to ./configure options since Squid-3.4
<p>
There have been some changes to Squid's build configuration since Squid-3.4.

This section gives an account of those changes in three categories:

<itemize>
	<item><ref id="newoptions" name="New options">
	<item><ref id="modifiedoptions" name="Changes to existing options">
	<item><ref id="removedoptions" name="Removed options">
</itemize>


<sect1>New options<label id="newoptions">
<p>
<descrip>
	<tag>BUILDCXX=</tag>
	<p>Used when cross-compiling Squid.
	<p>The path and name of a compiler for building cf_gen and related
	   tools used in the compile process.

	<tag>BUILDCXXFLAGS=</tag>
	<p>Used when cross-compiling Squid.
	<p>C++ compiler flags used for building cf_gen and related
	   tools used in the compile process.

	<tag>--without-gnutls</tag>
	<p>New option to explicitly disable use of GnuTLS encryption library.
	   Use of this library is auto-enabled if v3.1.5 or later is available.
	<p>It is currently only used by the squidclient tool.

	<tag>--without-mit-krb5</tag>
	<p>New option to explicitly disable use of MIT Kerberos library.
	   Default is to auto-detect and use if possible.
	<p>Only one Kerberos library may be built against.

	<tag>--without-heimdal-krb5</tag>
	<p>New option to explicitly disable use of Hiemdal Kerberos library.
	   Default is to auto-detect and use if possible.
	<p>Only one Kerberos library may be built against.

	<tag>--without-gnugss</tag>
	<p>New option to explicitly disable use of GNU GSSAPI library for Kerberos.
	   Default is to auto-detect and use if possible.
	<p>Only one Kerberos library may be built against.

</descrip>

<sect1>Changes to existing options<label id="modifiedoptions">
<p>
<descrip>
	<tag>--enable-icap-client</tag>
	<p>Deprecated. ICAP client is now auto-enabled.
	   Use --disable-icap-client to disable if you need to.

</descrip>
</p>

<sect1>Removed options<label id="removedoptions">
<p>
<descrip>
	<tag>--disable-internal-dns</tag>
	<p>DNS external helper interface has been removed. It was no longer
	   able to provide high performance service and the internal DNS
	   client library with multicast DNS cover all modern use-cases.

	<tag>--enable-ssl</tag>
	<p>Removed. Use <em>--with-openssl</em> to enable OpenSSL library support.

	<tag>--with-coss-membuf-size</tag>
	<p>The COSS cache type has been removed.
	   It has been replaced by <em>rock</em> cache type.

	<tag>--with-krb5-config</tag>
	<p>Removed. The Kerberos library is auto-detected now.
	<p>Use <em>--with/--without-mit-krb5</em>, <em>--with/--without-heimdal-krb5</em>, or
	   <em>--with/--without-gnugss</em> options for specific library selection if necesary.

</descrip>


<sect>Regressions since Squid-2.7

<p>Some squid.conf options which were available in Squid-2.7 are not yet available in Squid-3.5

<p>If you need something to do then porting one of these from Squid-2 to Squid-3 is most welcome.

<sect1>Missing squid.conf options available in Squid-2.7
<p>
<descrip>
	<tag>broken_vary_encoding</tag>
	<p>Not yet ported from 2.6

	<tag>cache_peer</tag>
	<p><em>monitorinterval=</em> not yet ported from 2.6
	<p><em>monitorsize=</em> not yet ported from 2.6
	<p><em>monitortimeout=</em> not yet ported from 2.6
	<p><em>monitorurl=</em> not yet ported from 2.6

	<tag>cache_vary</tag>
	<p>Not yet ported from 2.6

	<tag>error_map</tag>
	<p>Not yet ported from 2.6

	<tag>external_refresh_check</tag>
	<p>Not yet ported from 2.7

	<tag>location_rewrite_access</tag>
	<p>Not yet ported from 2.6

	<tag>location_rewrite_children</tag>
	<p>Not yet ported from 2.6

	<tag>location_rewrite_concurrency</tag>
	<p>Not yet ported from 2.6

	<tag>location_rewrite_program</tag>
	<p>Not yet ported from 2.6

	<tag>refresh_pattern</tag>
	<p><em>stale-while-revalidate=</em> not yet ported from 2.7
	<p><em>ignore-stale-while-revalidate=</em> not yet ported from 2.7
	<p><em>negative-ttl=</em> not yet ported from 2.7

	<tag>refresh_stale_hit</tag>
	<p>Not yet ported from 2.7

	<tag>update_headers</tag>
	<p>Not yet ported from 2.7

</descrip>

<sect>Copyright
<p>
Copyright (C) 1996-2015 The Squid Software Foundation and contributors
<p>
Squid software is distributed under GPLv2+ license and includes
contributions from numerous individuals and organizations.
Please see the COPYING and CONTRIBUTORS files for details.

</article>