RewriteRule includding only last part of REQUESTI_URI

Question

<LocationMatch /foo/>
 ProxyPreserveHost On
 RewriteEngine on
 RewriteCond %{HTTP:Upgrade} websocket [NC]
 RewriteCond %{HTTP:Connection} upgrade [NC]
 RewriteRule .* "ws://192.168.0.101:1234%{REQUEST_URI}" [P]

when client connects to

ws://www.example.com/foo/whatever_arbitrary_random

this works great, but the outcome is

ws://192.168.0.101:1234/foo/whatever_arbitrary_random

how can i get rid of the /foo/ so the outcome would be

ws://192.168.0.101:1234/whatever_arbitrary_random

client must still need to connect to /foo/ to trigger this

EDIT: I found how to do it, replace last line with

RewriteRule ([^/]+)/?$ ws://192.168.0.101:1234/$1 [P,L]

But please read the first answer suggesting not to do this in a Location

Answer 1

You shouldn't use mod_rewrite directives inside <Location> (and <LocationMatch>) containers.

UPDATE: As stated in the Apache docs for the RewriteRule directive:

Although rewrite rules are syntactically permitted in <Location> and <Files> sections (including their regular expression counterparts), this should never be necessary and is unsupported. A likely feature to break in these contexts is relative substitutions.

<Location> sections are merged very late. When used inside a <Location> section, the RewriteRule directive matches the absolute filesystem-path, not the URL-path as would ordinarily be expected.

If .htaccess overrides are disabled then you can do it like this instead inside the appropriate <Directory> container:

<Directory /path/to/foo>
    # Disable .htaccess overrides if not already
    AllowOverride None

    ProxyPreserveHost On

    RewriteEngine on
    RewriteCond %{HTTP:Upgrade} websocket [NC]
    RewriteCond %{HTTP:Connection} upgrade [NC]
    RewriteRule .* ws://192.168.0.101:1234/$0 [P]
</Directory>

The backreference $0 naturally excludes /foo/.

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UPDATE:

RewriteRule ([^/]+)/?$ ws://192.168.0.101:1234/$1 [P,L]

This only matches the last path segment, it doesn't strictly match everything after /foo/. This may or may not be OK, depending on your requests. eg. It will redirect a request for /foo/bar/baz to /baz only, not /bar/baz.

The regex should really be anchored. However, you've probably written it this way because the directive is inside a <Location> section and matches the absolute file-path, rather than the requested URL-path.

Incidentally, you don't need the L flag when used with P - it is implied.

---

An alternative to the above... you don't need to use these directvies in a directory context (ie. inside a <Directory> or <Location> section). You can instead place these rules directly in the <VirtualHost> container (a virtualhost context), in which case they should be written like this instead:

ProxyPreserveHost On

RewriteEngine on
RewriteCond %{HTTP:Upgrade} websocket [NC]
RewriteCond %{HTTP:Connection} upgrade [NC]
RewriteRule ^/foo/(.*) ws://192.168.0.101:1234/$1 [P]