MOUNT parameter*    ==  MOUNT="vURL rURL [MountOptions]"
                    --  default: MOUNT="/* SERVER_URL*"

Map vURL to/from the rURL. URLs matches with vURL in a request message from a client are rewritten to rURL and forwarded to a server, and URLs matches with rURL in a response message from the server is rewritten to vURL and forwarded to the client. What is rewritten by MOUNT in each protocol is like follows:

HTTP -- URL or part of it appeared in header or HTML body (tags)

FTP -- file name in command and status response

NNTP -- newsgroup name in command, status response, and user data (header)

POP -- user and host name in USER,PASS,APOP command

IMAP -- user and host name in LOGIN command

SMTP -- mail address in the RCPT command

Telnet -- hostname and port number of destination server

LDAP -- base object name in requests/responses

If a vURL is terminated with "*" then partially matched path is also rewritten. If a rURL is terminated with "*" then remaining part in the partially matched path will be copied after the rURL.

Example: a MOUNT for HTTP-DeleGate

MOUNT="/abc/* http://host/*"
// rewrites "/abc/def" to/from "http://host/def"

If "=" is specified as vURL or rURL, it means mount as is without rewriting for the vURL in a request, or rewriting for rURL in a response.

The port number of the destination server (in rURL) can be prefixed with "-" or "+" to be determined dynamically by offsetting from the port number of the entransport, as in SERVER parameter.

A special host name "odst.-" in rURL (or in the SERVER parameter) represents the original destination host of the TCP connection from the client via NAT (provided by iptables on Linux). It can be used to configure a transparent proxy (or gateway) for arbitrary protocols. The original destination port number can be referred with "-" as "odst.-:-". The number can be mapped with an offset value as "-8000" or "+8000" for example. The name "odst.-" can be used in the "rserv" MountOption too.

If the rURL is of "file:path" and the path is a relative one, then the data file is searched under the DGROOT directory or directories listed in DATAPATH.

If a rURL is prefixed as "vurl:rURL", the rewritten URL (in a request message) from vURL to rURL will be rewritten by another MOUNT again. This recursive MOUNT is not applied to the rewriting a URL in response data from rURL to vURL, therefore it does not work as expected in HTTP where such reverse rewriting of URL in response is expected too.

Example: recursive MOUNT

MOUNT="/x/* vurl:/f/x/*"
MOUNT="/y/* vurl:/f/y/*"
MOUNT="/f/* ftp://server/*"
// "/x/path" is rewritten to "ftp://server/x/path"
// "ftp://server/x/path" is rewritten to "/f/x/path"


Abbreviations

To make configurations be simple and reusable, special abbreviated formats of URL can be used in MOUNT parameter. If "=" is specified as protocol-name, host-name or port-number in rURL which consists of protocol-name://host-name:port-number/url-path, then it represents that of the DeleGate itself (i.e. that of vURL). URLs beginning with "//" represents further abbreviations, "///path" for "=://=:=/path" (in the same protocol,host and port) and "//serv..." for "=://serv..." (in the same protocol).

Abbreviated host-name and port-number is substituted by that of the virtual host (given in HTTP Host: field) if exists, or by that of the real interface with the client. To explicitly specify the real interface, use "-P" for "host-name:port-number part like "http://-P/path".

Example: abbreviation in rURL of MOUNT parameter

// DeleGate's parameters: SERVER=http -Pdhost:9080 ...
// Requested URL: http://vhost:9080/x/
MOUNT="/x/* =://=:=/y/*" -> http://vhost:9080/y/
MOUNT="/x/* ///y/*" -> (the abbreviation of the above)
MOUNT="/x/* //-P/y/*" -> http://dhost:9080/y/
MOUNT="/x/* =://serv/y/*" -> http://serv:80/y/
MOUNT="/x/* //serv/y/*" -> (the abbreviation of the above)
MOUNT="/x/* //serv:=/y/*" -> http://serv:9080/y/
MOUNT="/x/* //=:9088/y/*" -> http://vhost:9088/y/
MOUNT="/x/* https://=/y/*" -> https://vhost:443/y/


Complex Matching and Rewriting

A pattern following "*%" in vURL and rURL represents a pattern for complex matching specified in the format like that of scanf(3). Each format specification consists of a specification following "%", like "%c", "%[a-z]" and so on. The extended format "%S" has variable meanings determined by its adjacent character, i.e. "%Sx" means "%[^x]x": ex. "%S." for "%[^.]." and "%S/" for "%[^/]/". "%(N)" in rURL means copying Nth element in vURL. If a vURL pattern ends with "$" character, then complete matching to the end of URL string is required.

Example: complex matching and rewriting

// Requested URL: http://dhost/x/abc/def
MOUNT="/x/*%S/%S ///y/*%S.%S" -> http://dhost/y/abc.def
MOUNT="/x/*%S/%S ///y/*%(1)/%(0)" -> http://dhost/y/def/abc
MOUNT="/x/*%1[a-z]%S http://w/*%S/%S" -> http://w/a/bc/def