HTTP.SYS(8) XR32 REFERENCE MANUAL 29/1/2013
NAME
HTTP.SYS -- HTTP Rewrite / Proxy Control File (Optional).
DESCRIPTION
HTTP.SYS is an optional file. If present, it contains
REWRITE rules for the HTTP server, and settings for the
HTTP proxy server.
URL rewriting modifies the URL's of incoming requests,
according to a set of REWRITE rules. This can be used to
organise widely-dispersed resources into a logical
directory tree.
The resources may be located on the same PC or even on
different servers, but can be made to look as if they are
all in the same tree on your server. This is done by
replacing parts of the requested URL with alternative
strings of characters.
The PROXY commands configure XR32's HTTP proxy to use a
"downstream" proxy to reach certain IP address ranges.
FORMAT
Each command or rule must be on a separate line, and may be
up to 255 characters long. Lines beginning with ';' or '#'
are ignored, and may be used for comments. Commands and
rules are not case sensitive, and their fields must be
separated by one or more spaces or tabs. Blank lines are
ignored.
The commands and rules are as follows:
REWRITE <old_string> <new_string>
PROXY <ipaddr> <port> <subnet_mask>
PROXYTIMEOUT <secs>
These are discussed in more detail below...
REWRITE
The REWRITE rules have the following syntax:
REWRITE <old_string> <new_string>
<old_string> is a template which is compared with an equal
number of characters from the start of the
requested URL when an HTTP request is received.
The comparison is case-insensitive.
<new string> is the character sequence which replaces
<old_string> if there is a match.
Example: REWRITE /bbs /systems/gb7pzt
This would replace "/bbs" at the start of the URL with
"/systems/gb7pzt". Thus a request for "/bbs/msgs.htm" would
be rewritten to "/systems/gb7pzt/msgs.htm".
There are no validity checks, so you must be careful not to
inadvertently remove / characters from the rewritten string.
e.g. the entry "rewrite /bbs/ http://192.168.0.4" would cause
"/bbs/index.htm" to rewrite as "http://192.168.0.4index.htm",
which will clearly fail.
You can use rewriting to organise your resources into a neat,
logical and compact directory tree, regardless of where they
are actually located.
<new_string> may also contain a URL, which invisibly invokes
the HTTP proxy. For example:
REWRITE /bbs http://192.168.0.4:85
This would replace "/bbs" at the start of the URL with
"http://192.168.0.4:85", so that a URL like:
/bbs/cgi-bin/menu.pz becomes:
http://192.168.0.4:85/cgi-bin/menu.pz
The resulting URL then treated as if it was a proxy request.
When rewriting to proxy another system, the new URL must
begin with "http://<address>[:port]" where <address> can be
either a hostname or IP address.
rewrite http://g8pzt.ath.cx/bbs http://192.168.0.4
PROXY
The PROXY command allows XR32's HTTP proxy to pass certain
traffic to a downstream proxy. The format of the command is:
PROXY <ipaddr> <port> <subnet_mask>
e.g. "proxy 44.131.91.245 80 255.0.0.0"
<ipaddr> is the IP address of the downstream proxy.
<port> is the TCP port number of the downstream proxy.
<subnet_mask> when combined with the proxy address specifies
the range of addresses which are on the same
subnet as the proxy. These addressess will
bypass the proxy, i.e. XR32's proxy will
connect directly to them instead of via the
next proxy.
This kludge allows 44-net systems to use a further proxy to
gain a public (Internet) IP address when connecting non-44
websites. This is necessary because 44-net routing is
unreliable at best, i.e. if a 44-net browser tries to
connect directly to Google, the reply probably won't get
routed back.
For example, imagine a mobile station, consisting of a web
browser and XR32, with an IP/AX25 link to a nearby gateway,
but no Internet connection. The IP address used over the
radio link is 44.131.91.3. The browser has been configured
to use XR32's HTTP proxy, which means the IP source address
for all HTTP traffic from this station is 44.131.91.3.
Via the nearby gateway, whose IP address is 44.131.91.245,
the mobile station can happily browse 44-net (amprnet)
websites. But when it tries to use Google, the replies
aren't routed back.
However, if the local gateway has been set up with the
above PROXY command, the 44.x.x.x sites will be connected
directly by the mobile XR32's proxy, whilst the non-44 sites
will be passed to the gateway's HTTP proxy, where they will
gain a 62.31.206.176 source address, which is reliably
routable and doesn't rely on the co-operation of others in
the amprnet.
The PROXYTIMEOUT command specifies the maximum time in
seconds to wait for a proxied connection. If a connection
takes longer than this to establish, an error is returned.
The default is 30 secs, but may need to be longer on a
slow radio channel.
FILES
If required, HTTP.SYS must be located in the same
directory as XR32.EXE.
SEE ALSO
HTTP.ACL(8) -- HTTP Proxy Egress Control File
HTTPBAN.SYS(8) -- Blocks Malicious HTTP Requests
HTTP.SYS(8) END OF DOCUMENT
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