Implementation of sieve "redirect" action. Kept apart from other actions due to …

…the lack of API support.

+;;;; GNU mailutils - a suite of utilities for electronic mail
+;;;; Copyright (C) 1999, 2000, 2001 Free Software Foundation, Inc.
+;;;;
+;;;; This program is free software; you can redistribute it and/or modify
+;;;; it under the terms of the GNU General Public License as published by
+;;;; the Free Software Foundation; either version 2, or (at your option)
+;;;; any later version.
+;;;; 
+;;;; This program is distributed in the hope that it will be useful,
+;;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;;;; GNU General Public License for more details.
+;;;; 
+;;;; You should have received a copy of the GNU General Public License
+;;;; along with this program; if not, write to the Free Software
+;;;; Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.  
+
+;;;; This module provides sieve's "redirect" action.
+
+(use-modules (ice-9 popen))
+
+(define PATH-SENDMAIL "/usr/lib/sendmail")
+(define sieve-my-email "")
+
+;;; Bounce a message.
+;;; Current mailutils API does not provide a way to send a message
+;;; specifying its recipients (like "sendmail -t foo@bar.org" does),
+;;; hence the need for this function.
+(define (sieve-message-bounce message addr-list)
+  (catch #t
+	 (lambda ()
+	   (let ((port (open-output-pipe
+			(apply string-append
+			       (append
+				(list
+				 PATH-SENDMAIL
+				 " -oi -t ")
+				(map
+				 (lambda (addr)
+				   (string-append addr " "))
+				 addr-list))))))
+	     ;; Write headers
+	     (for-each
+	      (lambda (hdr)
+		(display (string-append (car hdr) ": " (cdr hdr)) port)
+		(newline port))
+	      (mu-message-get-header-fields message))
+	     (newline port)
+	     ;; Write body
+	     (let ((body (mu-message-get-body message)))
+	       (do ((line (mu-body-read-line body) (mu-body-read-line body)))
+		   ((eof-object? line) #f)
+		   (display line port)))
+	     (close-output-port port)))
+	 (lambda args
+	   (runtime-error LOG_ERR "redirect: Can't send message")
+	   (write args))))
+
+;;; rfc3028 says: 
+;;; "Implementations SHOULD take measures to implement loop control,"
+;;; We do this by appending an "X-Sender" header to each message
+;;; being redirected. If one of the "X-Sender" headers of the message
+;;; contains our email address, we assume it is a loop and bail out.
+
+(define (sent-from-me? msg)
+  (call-with-current-continuation
+   (lambda (x)
+     (for-each
+      (lambda (hdr)
+	(if (and (string=? (car hdr) "X-Sender")
+		 (string=? (mu-address-get-email (cdr hdr))
+			   sieve-my-email))
+	    (x #t)))
+      (mu-message-get-header-fields sieve-current-message))
+     #f)))
+
+;;; redirect action
+(define (action-redirect address)
+  (if sieve-my-email
+      (cond
+       ((sent-from-me? sieve-current-message)
+	(runtime-error LOG_ERR "redirect: Loop detected"))
+       (else
+	(let ((out-msg (mu-message-copy sieve-current-message)))
+	  (mu-message-set-header out-msg "X-Sender" sieve-my-email)
+	  (sieve-message-bounce out-msg (list address)))))
+      (sieve-message-bounce out-msg (list address))))
+
+;;; Register action
+(if sieve-parser
+    (sieve-register-action "redirect" action-redirect 'string))
+
+