From: Tim Vaughan <tgvaughan@gmail.com>
Date: Wed, 4 Sep 2019 21:50:18 +0000 (+0200)
Subject: Outgoing delivery working!
X-Git-Url: https://thelambdalab.xyz/gitweb/index.cgi?a=commitdiff_plain;h=68469a9c497a0a6f2b1c4715c26d0d6665f60391;p=lambdamail.git

Outgoing delivery working!

Although there's infrastruture for retrying messages
with delivery failures, this only occurs after another
connection has been made. I.e. there's no support for
retrying after a certain period, which is needed.
---

diff --git a/lambdamail.scm b/lambdamail.scm
index bcd7a7e..90c186f 100644
--- a/lambdamail.scm
+++ b/lambdamail.scm
@@ -14,9 +14,10 @@
         (chicken process-context)
         (chicken process-context posix)
         (chicken condition)
+        (chicken sort)
         srfi-1 srfi-13 matchable base64)
 
-(define lambdamail-version "LambdaMail v0.0.1")
+(define lambdamail-version "LambdaMail v1.0.0")
 
 (define-record config host port spool-dir user group)
 (define-record message to from text user password)
@@ -61,6 +62,7 @@
 
 (define (receive-messages listener config)
   (let ((messages '()))
+    (print "*** Waiting for incoming mail")
     (let-values (((in-port out-port) (tcp-accept listener)))
       (let-values (((local-ip remote-ip) (tcp-addresses in-port)))
         (print "Accepted connection from " remote-ip " on " (time-stamp)))
@@ -163,41 +165,38 @@
 ;;
 
 (define (deliver-messages config messages)
-  (print "\n"
-         "**** Attempting delivery of " (length messages) " mail items.")
+  (print "**** Attempting delivery of " (length messages) " mail items.")
   (filter (lambda (msg) (not (deliver-message msg config)))
           messages))
 
 (define (deliver-message msg config)
+  (print "From: " (message-from msg))
+  (print "To: " (message-to msg))
   (condition-case
-      (begin
-        (let* ((local-addresses (get-local-addresses config))
-               (dest (assoc (message-to msg) local-addresses))
-               (orig (assoc (message-from msg) local-addresses)))
-          (cond
-           (dest
-            (let ((dest-dir (cadr dest)))
-              (deliver-message-local msg dest-dir))
-            (print "Message DELIVERED (local):"))
-           (orig
-            (let ((password (caddr orig)))
-              (if (and
-                   (string=? (conc "<" (message-user msg) "@" (config-host config) ">")
-                             (message-from msg))
-                   password
-                   (string=? (message-password msg) password))
-                  (begin
-                    (deliver-message-remote msg config)
-                    (print "Message DELIVERED (remote):"))
-                  (print "Message REMOTE DELIVERY REJECTED (auth failure):"))))
-           (else
-            (print "Message REMOTE DELIVERY REJECTED (relay forbidden):"))))
-        (print " * From: " (message-from msg))
-        (print " * To: " (message-to msg))
-        #t)
+      (let* ((local-addresses (get-local-addresses config))
+             (dest (assoc (message-to msg) local-addresses))
+             (orig (assoc (message-from msg) local-addresses)))
+        (cond
+         (dest
+          (let ((dest-dir (cadr dest)))
+            (deliver-message-local msg dest-dir)))
+         (orig
+          (let ((password (caddr orig)))
+            (if (and (string=? (conc "<" (message-user msg) "@" (config-host config) ">")
+                               (message-from msg))
+                     password
+                     (string=? (message-password msg) password))
+                (deliver-message-remote msg config)
+                (begin
+                  (print "* REMOTE DELIVERY NOT ALLOWED (auth failure)")
+                  #t))))
+         (else
+          (print "* REMOTE DELIVERY REJECTED (relay forbidden)")
+          #t)))
     (o (exn)
-       (print "Message delivery failed.")
-       (print-error-message o))))
+       (print "* DELIVERY FAILED")
+       (print-error-message o)
+       #t)))
 
 ;; Local delivery
 
@@ -217,18 +216,35 @@
 (define (deliver-message-local msg dest-dir)
   (with-output-to-file (conc dest-dir "/" (current-seconds))
     (lambda ()
-      (print (message-text msg)))))
-
+      (print (message-text msg))))
+  (print "* MESSAGE DELIVERED (local)")
+  #t)
 
 ;; Remote delivery
 
-(define (get-host-from-email email-string)
+(define (get-domain-from-email email-string)
   (car (string-split (cadr (string-split email-string "@")) ">")))
 
+;; This is a hack - there's no built-in interface to res_query()
+;; in chicken, so we have to resort to a system call to dig...
+(define (get-mail-server-for-domain domain)
+  (let* ((mx-lines (let-values (((in out id) (process (conc "dig " domain " mx +short"))))
+                     (with-input-from-port in read-lines)))
+         (mx-entries (map (lambda (l)
+                            (let ((s (string-split l)))
+                              (list (string->number (car s)) 
+                                    (string-drop-right (cadr s) 1)))) ; remove trailing "."
+                          mx-lines))
+         (sorted-mx-entries (sort mx-entries (lambda (e f) (< (car e) (car f))))))
+    (if (null? sorted-mx-entries)
+        domain ; fall-back to email address domain if no mx entries
+        (cadar sorted-mx-entries)))) ; otherwise pick the highest priority server
+
 (define (deliver-message-remote msg config)
-  (let ((host (get-host-from-email (message-to msg))))
-    (print "Attempting delivery to host " host)
-    (let-values (((tcp-in tcp-out) (tcp-connect host 25)))
+  (let* ((domain (get-domain-from-email (message-to msg)))
+         (mail-server (get-mail-server-for-domain domain)))
+    (print "Attempting delivery to " mail-server)
+    (let-values (((tcp-in tcp-out) (tcp-connect mail-server 25)))
       (let ((smtp-session (make-outgoing-smtp-session tcp-in tcp-out)))
         (let ((result (and
                        (smtp-session 'expect "220")
@@ -246,6 +262,10 @@
                        (smtp-session 'send "quit"))))
           (close-input-port tcp-in)
           (close-output-port tcp-out)
+          (print "Connection closed.")
+          (if result
+              (print "* MESSAGE DELIVERED (remote)")
+              (print "* REMOTE DELIVERY FAILED (unexpected server response)"))
           result)))))
 
 (define ((make-outgoing-smtp-session tcp-in tcp-out) . command)