SuperScript::Software::shttpd

The redir-httpd program

Interface

  redir-httpd

redir-httpd reads an HTTP request message from standard input, looks up the URI in a cdb-format database, and prints a redirection command or error message to standard output.

Before reading any input, redir-httpd changes the working directory to that named in the $ROOT environment variable, performs chroot to the current directory, and then sets its group id and user id to the numeric values given in the environment variables $GID and $UID, typically set with envdir. If it cannot carry out these operations, redir-httpd complains to standard error and exits 111.

If it encounters an error in processing a request, redir-httpd exits 21. Otherwise, it exits 0.

The redir-httpd program accepts HTTP/0.9, HTTP/1.0, and HTTP/1.1 requests. For a request with the host name host, redir-httpd replaces /. with /: and // with / in ./host, and looks for redirection commands in the file ./host/data.cdb, created by redir-data. For a valid request lacking a host name, redir-httpd uses 0 as the host name.

Request path parsing

redir-httpd replaces /. with /: and // with / in the request path before looking for a match.

Starting immediately to the left of any query string in the request path, and moving from right to left, redir-httpd splits the request path at each / character to obtain head/tail, and and attempts a cdb lookup using head/ as the key. Upon sucess, redir-httpd replaces head/ with the lookup result, appends tail, and redirects the client to the resultant URL. When redir-httpd receives a request with an empty path, it uses / instead. If the full request path (sans query string) ends with a character other than /, then redir-httpd first attempts a lookup using the full request path as the key.

Logging

When it processes a request without error, redir-httpd prints to standard error a line with the form 

  host ref match key value
The string host is the request host name. The string ref is the value of the first Referer: header, or 0 if there is no such header. The string match is unknown if no match is found, partial for a partial path match, or exact for an exact path match. The string key is the portion of the request path that matched a redirection command, or the full request path when match is unknown. The string value is the replacement for key in the relevant redirection command, or the empty string when match is unknown.

Within each component of the log line, redir-httpd replaces control characters with '?' and spaces with '_'. If a component exceeds 100 characters in length, redir-httpd truncates it to 100 characters and appends ellipses.

Redirection examples

Commands specifying the following substitutions 
  /shttpd  --> http://www.superscript.com/shttpd/intro.html
  /shttpd/ --> http://www.superscript.com/shttpd/
result in the following redirections: 
  /shttpd --> http://www.superscript.com/shttpd/intro.html
  /shttpd/cgi-httpd.html --> http://www.superscript.com/shttpd/cgi-httpd.html