doc/admin-guide/files/remap.config.en.rst

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============
remap.config
============

.. configfile:: remap.config

.. include:: ../../common.defs

.. toctree::
   :maxdepth: 2


The :file:`remap.config` file (by default, located in
``/usr/local/etc/trafficserver/``) contains mapping rules that Traffic Server
uses to perform the following actions:

-  Map URL requests for a specific origin server to the appropriate
   location on Traffic Server when Traffic Server acts as a reverse
   proxy for that particular origin server
-  Reverse-map server location headers so that when origin servers
   respond to a request with a location header that redirects the client
   to another location, the clients do not bypass Traffic Server
-  Redirect HTTP requests permanently or temporarily without Traffic
   Server having to contact any origin servers

Refer to  :ref:`reverse-proxy-and-http-redirects`, for information about
redirecting HTTP requests and using reverse proxy.

After you modify the :file:`remap.config` run the
:option:`traffic_ctl config reload` to apply the changes.

Format
======

Each line in the :file:`remap.config` file must contain a mapping rule. Empty lines,
or lines starting with ``#`` are ignored. Each line can be broken up into multiple
lines for better readability by using ``\`` as continuation marker.

Traffic Server recognizes three space-delimited fields: ``type``,
``target``, and ``replacement``. The following list describes the format of each field.

.. _remap-config-format-type:

``type``
    Enter one of the following:

    -  ``map`` --translates an incoming request URL to the appropriate
       origin server URL.

    -  ``map_with_recv_port`` --exactly like 'map' except that it uses the port at
       which the request was received to perform the mapping instead of the port present
       in the request. The regex qualifier can also be used for this type. When present,
       'map_with_recv_port' mappings are checked first. If there is a match, then it is
       chosen without evaluating the "regular" forward mapping rules.

    -  ``map_with_referer`` -- extended version of 'map', which can be used to activate
       "deep linking protection", where target URLs are only accessible when the Referer
       header is set to a URL that is allowed to link to the target.

    -  ``reverse_map`` --translates the URL in origin server redirect
       responses to point to the Traffic Server.

    -  ``redirect`` --redirects HTTP requests permanently without having
       to contact the origin server. Permanent redirects notify the
       browser of the URL change (by returning an HTTP status code 301)
       so that the browser can update bookmarks.

    -  ``redirect_temporary`` --redirects HTTP requests temporarily
       without having to contact the origin server. Temporary redirects
       notify the browser of the URL change for the current request only
       (by returning an HTTP status code 307).

       .. note:: use the ``regex_`` prefix to indicate that the line has a regular expression (regex).

.. _remap-config-format-target:

``target``
    Enter the request ("from") URL. You can enter up to four components: ::

        scheme://host:port/path_prefix

    where ``scheme`` is ``http``, ``https``, ``ws`` or ``wss``.

.. _remap-config-format-replacement:

``replacement``
    Enter the origin ("to") URL. You can enter up to four components: ::

        scheme://host:port/path_prefix

    where ``scheme`` is ``http``, ``https``, ``ws`` or ``wss``.

   .. note:: A remap rule for requests that upgrade from HTTP to WebSocket still require a remap rule with the ``ws`` or ``wss`` scheme.


.. _remap-config-precedence:

Precedence
==========

Remap rules are not processed top-down, but based on an internal
priority. Once these rules are executed we pick the first match
based on configuration file parse order.

1. ``map_with_recv_port`` and ``regex_map_with_recv_port``
#. ``map`` and ``regex_map`` and ``reverse_map``
#. ``redirect`` and ``redirect_temporary``
#. ``regex_redirect`` and ``regex_redirect_temporary``

For each precedence group the rules are checked in two phases. If the first phase fails to find a
match then the second phase is performed against the same group of rules. In the first phase the
rules are checked using the host name of the request. Only rules that specify a host name can match.
If there is no match in that phase, then the rules are checked again with no host name and only
rules without a host will match. The result is that rules with an explicit host take precedence over
rules without.

Match-All
=========

A map rule with a single ``/`` acts as a wildcard, it will match any
request. This should be use with care, and certainly only once at the
end of the remap.config file. E.g.

::

    map / http://all.example.com

Examples
--------

The following section shows example mapping rules in the
:file:`remap.config` file.

Reverse Proxy Mapping Rules
~~~~~~~~~~~~~~~~~~~~~~~~~~~

The following example shows a map rule that does not specify a path
prefix in the target or replacement: ::

    map http://www.x.com/ http://server.hoster.com/
    reverse_map http://server.hoster.com/ http://www.x.com/

This rule results in the following translations:

================================================ ========================================================
Client Request                                   Translated Request
================================================ ========================================================
``http://www.x.com/Widgets/index.html``          ``http://server.hoster.com/Widgets/index.html``
``http://www.x.com/cgi/form/submit.sh?arg=true`` ``http://server.hoster.com/cgi/form/submit.sh?arg=true``
================================================ ========================================================

The following example shows a map rule with path prefixes specified in
the target: ::

    map http://www.y.com/marketing/ http://marketing.y.com/
    reverse_map http://marketing.y.com/ http://www.y.com/marketing/
    map http://www.y.com/sales/ http://sales.y.com/
    reverse_map http://sales.y.com/ http://www.y.com/sales/
    map http://www.y.com/engineering/ http://engineering.y.com/
    reverse_map http://engineering.y.com/ http://www.y.com/engineering/
    map http://www.y.com/stuff/ http://info.y.com/
    reverse_map http://info.y.com/ http://www.y.com/stuff/

These rules result in the following translations:

=============================================================== ==========================================================
Client Request                                                  Translated Request
=============================================================== ==========================================================
``http://www.y.com/marketing/projects/manhattan/specs.html``    ``http://marketing.y.com/projects/manhattan/specs.html``
``http://www.y.com/stuff/marketing/projects/boston/specs.html`` ``http://info.y.com/marketing/projects/boston/specs.html``
``http://www.y.com/engineering/marketing/requirements.html``    ``http://engineering.y.com/marketing/requirements.html``
=============================================================== ==========================================================

The following example shows that the order of the rules matters: ::

    map http://www.g.com/ http://external.g.com/
    reverse_map http://external.g.com/ http://www.g.com/
    map http://www.g.com/stuff/ http://stuff.g.com/
    reverse_map http://stuff.g.com/ http://www.g.com/stuff/

These rules result in the following translation.

================================ =====================================
Client Request                   Translated Request
================================ =====================================
``http://www.g.com/stuff/a.gif`` ``http://external.g.com/stuff/a.gif``
================================ =====================================

In the above examples, the second rule is never applied because all URLs
that match the second rule also match the first rule. The first rule
takes precedence because it appears earlier in the :file:`remap.config`
file.

This is different if one rule does not have a host. For example consider these rules using the `Match-All`_ rule::

   map / http://127.0.0.1:8001/
   map http://example.com/dist_get_user http://127.0.0.1:8001/denied.html

These rules are set up to redirect requests to another local process. Using them will result in

==================================== =====================================
Client Request                       Translated Request
==================================== =====================================
``http://example.com/a.gif``         ``http://127.0.0.1:8001/a.gif``
``http://example.com/dist_get_user`` ``http://127.0.0.1:8001/denied.html``
==================================== =====================================

For the first request the second rule host matches but the path does not and so the second rule is
not selected. The first rule is then matched in the second phase when the rules are checked without
a host value.

The second request is matched by the second rule even though the rules have the same base
precedence. Because the first rule does not have a host it will not match in the first phase. The
second rule does have a host that matches the host in the second request along with the other parts
of the URL and is therefore selected in the first phase.

This will yield the same results if the rules are reversed because the rule selection happens in
different phases making the order irrelevant. ::

   map http://example.com/dist_get_user http://127.0.0.1:8001/denied.html
   map / http://127.0.0.1:8001/

The following example shows a mapping with a path prefix specified in
the target and replacement::

   map http://www.h.com/a/b/ http://server.h.com/customers/x/y
   reverse_map http://server.h.com/customers/x/y/ http://www.h.com/a/b/

This rule results in the following translation.

===================================== ==================================================
Client Request                        Translated Request
===================================== ==================================================
``http://www.h.com/a/b/c/d/doc.html`` ``http://server.h.com/customers/x/y/c/d/doc.html``
``http://www.h.com/a/index.html``     ``Translation fails``
===================================== ==================================================

The following example shows reverse-map rules::

    map http://www.x.com/ http://server.hoster.com/x/
    reverse_map http://server.hoster.com/x/ http://www.x.com/

These rules result in the following translations.

================================ =====================================
Client Request                   Translated Request
================================ =====================================
``http://www.x.com/Widgets``     ``http://server.hoster.com/x/Widgets``
================================ =====================================

 

================================ ======================================= =============================
Client Request                   Origin Server Header                    Translated Request
================================ ======================================= =============================
``http://www.x.com/Widgets``     ``http://server.hoster.com/x/Widgets/`` ``http://www.x.com/Widgets/``
================================ ======================================= =============================

When acting as a reverse proxy for multiple servers, Traffic Server is
unable to route to URLs from older browsers that do not send the
``Host:`` header. As a solution, set the variable :ts:cv:`proxy.config.header.parse.no_host_url_redirect`
in the :file:`records.config` file to the URL to which Traffic Server will redirect
requests without host headers.

Redirect Mapping Rules
~~~~~~~~~~~~~~~~~~~~~~

The following rule permanently redirects all HTTP requests for
``www.company.com`` to ``www.company2.com``: ::

    redirect http://www.company.com/ http://www.company2.com/

The following rule *temporarily* redirects all HTTP requests for
``www.company1.com`` to ``www.company2.com``: ::

    redirect_temporary http://www.company1.com/ http://www.company2.com/

.. _remap-config-regex:

Regular Expression (regex) Remap Support
========================================

Regular expressions can be specified in remapping rules, with the
limitations below:

-  Only the ``host`` field can contain a regex; the ``scheme``,
   ``port``, and other fields cannot. For path manipulation via regexes,
   use the :ref:`admin-plugins-regex-remap`.
-  The number of capturing subpatterns is limited to 9. This means that
   ``$0`` through ``$9`` can be used as subtraction placeholders (``$0``
   will be the entire input string).
-  The number of substitutions in the expansion string is limited to 10.
-  There is no ``regex_`` equivalent to ``reverse_remap``, so when using
   ``regex_map`` you should make sure the reverse path is clear by
   setting (:ts:cv:`proxy.config.url_remap.pristine_host_hdr`)

Examples
--------

::

    regex_map http://x([0-9]+).z.com/ http://real-x$1.z.com/
    regex_redirect http://old.(.*).z.com http://new.$1.z.com

.. _map_with_referer:

map_with_referer
================

the format of is the following::

    map_with_referer client-URL origin-server-URL redirect-URL regex1 [regex2 ...]

'redirect-URL' is a redirection URL specified according to RFC 2616 and can
contain special formatting instructions for run-time modifications of the
resulting redirection URL.  All regexes Perl compatible  regular expressions,
which describes the content of the "Referer" header which must be
verified. In case an actual request does not have "Referer" header or it
does not match with referer regular expression, the HTTP request will be
redirected to 'redirect-URL'.

At least one regular expressions must be specified in order to activate
'deep linking protection'.  There are limitations for the number of referer
regular expression strings - 2048.  In order to enable the 'deep linking
protection' feature in Traffic Server, configure records.config with::

    CONFIG proxy.config.http.referer_filter INT 1

In order to enable run-time formatting for redirect URL, configure::

    CONFIG proxy.config.http.referer_format_redirect INT 1

When run-time formatting for redirect-URL was enabled the following format
symbols can be used::

    %r - to substitute original "Referer" header string
    %f - to substitute client-URL from 'map_with_referer' record
    %t - to substitute origin-server-URL from 'map_with_referer' record
    %o - to substitute request URL to origin server, which was created a
         the result of a mapping operation

Note: There is a special referer type "~*" that can be used in order to
specify that the Referer header is optional in the request.  If "~*" referer
was used in map_with_referer mapping, only requests with Referer header will
be verified for validity.  If the "~" symbol was specified before referer
regular expression, it means that the request with a matching referer header
will be redirected to redirectURL. It can be used to create a so-called
negative referer list.  If "*" was used as a referer regular expression -
all referers are allowed.  Various combinations of "*" and "~" in a referer
list can be used to create different filtering rules.

map_with_referer Examples
-------------------------

::

   map_with_referer http://y.foo.bar.com/x/yy/  http://foo.bar.com/x/yy/ http://games.bar.com/new_games .*\.bar\.com www.bar-friends.com

Explanation: Referer header must be in the request, only ".*\.bar\.com" and "www.bar-friends.com" are allowed.

::

   map_with_referer http://y.foo.bar.com/x/yy/  http://foo.bar.com/x/yy/ http://games.bar.com/new_games * ~.*\.evil\.com

Explanation: Referer header must be in the request but all referers are allowed except ".*\.evil\.com".

::

    map_with_referer http://y.foo.bar.com/x/yy/  http://foo.bar.com/x/yy/ http://games.bar.com/error ~* * ~.*\.evil\.com

Explanation: Referer header is optional. However, if Referer header exists, only request from ".*\.evil\.com" will be redirected to redirect-URL.


.. _remap-config-plugin-chaining:

Plugin Chaining
===============

Plugins can be configured to be evaluated in a specific order, passing
the results from one in to the next (unless a plugin returns 0, then the
"chain" is broken).

Examples
--------

::

    map http://url/path http://url/path \
        @plugin=/etc/traffic_server/config/plugins/plugin1.so @pparam=1 @pparam=2 \
        @plugin=/etc/traffic_server/config/plugins/plugin2.so @pparam=3

will pass "1" and "2" to plugin1.so and "3" to plugin2.so.

This will pass "1" and "2" to plugin1.so and "3" to plugin2.so

.. _remap-config-named-filters:

Acl Filters
===========

Acl filters can be created to control access of specific remap lines. The markup
is very similar to that of :file:`ip_allow.yaml`, with slight changes to
accommodate remap markup

Examples
--------

::

    map http://foo.example.com/neverpost  http://foo.example.com/neverpost @action=deny @method=post
    map http://foo.example.com/onlypost  http://foo.example.com/onlypost @action=allow @method=post

    map http://foo.example.com/  http://foo.example.com/ @action=deny @src_ip=1.2.3.4
    map http://foo.example.com/  http://foo.example.com/ @action=allow @src_ip=127.0.0.1

    map http://foo.example.com/  http://foo.example.com/ @action=allow @src_ip=10.5.2.1 @in_ip=72.209.23.4

    map http://foo.example.com/  http://foo.example.com/ @action=allow @src_ip=127.0.0.1 @method=post @method=get @method=head

Note that these Acl filters will return a 403 response if the resource is restricted.

The difference between ``@src_ip`` and ``@in_ip`` is that the ``@src_ip`` is the client
ip and the ``in_ip`` is the ip address the client is connecting to (the incoming address).

Named Filters
=============

Named filters can be created and applied to blocks of mappings using
the ``.definefilter``, ``.activatefilter``, and ``.deactivatefilter``
directives. Named filters must be defined using ``.definefilter`` before
being used. Once defined, ``.activatefilter`` can used to activate a
filter for all mappings that follow until deactivated with
``.deactivatefilter``.

The ``@internal`` operator can be used to filter on whether a request
is generated by |TS| itself, usually by a plugin.  This operator
is helpful for remapping internal requests without allowing access
to external users. By default both internal and external requests
are allowed.


Examples
--------

::

    .definefilter disable_delete_purge @action=deny @method=delete @method=purge
    .definefilter local_only @action=allow @src_ip=192.168.0.1-192.168.0.254 @src_ip=10.0.0.1-10.0.0.254

    .activatefilter disable_delete_purge

    map http://foo.example.com/ http://bar.example.com/

    .activatefilter local_only
    map http://www.example.com/admin http://internal.example.com/admin
    .deactivatefilter local_only

    map http://www.example.com/ http://internal.example.com/
    map http://auth.example.com/ http://auth.internal.example.com/ @action=allow @internal

The filter `disable_delete_purge` will be applied to all of the
mapping rules. (It is activated before any mappings and is never
deactivated.) The filter `local_only` will only be applied to the
second mapping.

NextHop Selection Strategies
============================

You may configure Nexthop or Parent hierarchical caching rules by remap using the
**@strategy** tag.  See :doc:`../configuration/hierarchical-caching.en` and :doc:`strategies.yaml.en`
for configuration details and examples.

Including Additional Remap Files
================================

The ``.include`` directive allows mapping rules to be spread across
multiple files. The argument to the ``.include`` directive is a
list of file names to be parsed for additional mapping rules. Unless
the names are absolute paths, they are resolved relative to the
Traffic Server configuration directory.

The effect of the ``.include`` directive is as if the contents of
the listed files is included in the parent and parsing restarted
at the point of inclusion. This means that and filters named in the
included files are global in scope, and that additional ``.include``
directives are allowed.

.. note::

  Included remap files are not currently tracked by the configuration
  subsystem. Changes to included remap files will not be noticed
  by online configuration changes applied by :option:`traffic_ctl config reload`
  unless :file:`remap.config` has also changed.

Examples
--------

In this example, a top-level :file:`remap.config` file simply
references additional mapping rules files ::

  .include filters.config
  .include one.example.com.config two.example.com.config

The file `filters.config` contains ::

  .definefilter deny_purge @action=deny @method=purge
  .definefilter allow_purge @action=allow @method=purge

The file `one.example.com.config` contains::

  .activatefilter deny_purge
  map http://one.example.com http://origin-one.example.com
  .deactivatefilter deny_purge

The file `two.example.com.config` contains::

  .activatefilter allow_purge
  map http://two.example.com http://origin-two.example.com
  .deactivatefilter allow_purge