--- mailfront-1.16/plugin-clamav.c.original	2010-04-07 20:25:03.000000000 +0800
+++ mailfront-1.16/plugin-clamav.c	2010-04-07 20:26:19.000000000 +0800
@@ -13,6 +13,8 @@
 static RESPONSE(no_scan,451,"4.3.0 Could not virus scan message");
 static response resp_virus = { 554, 0 };
 
+static unsigned long failsafe;
+
 #define MAX_IPS 16
 
 static str line;
@@ -29,6 +31,12 @@
   return -1;
 }
 
+static const response *warn_sys(const char *s1)
+{
+  warn2sys("clamav skipped: ", s1);
+  return failsafe ? 0 : &resp_internal;
+}
+
 static const response* message_end(int fd)
 {
   const char* hostname;
@@ -48,6 +56,9 @@
   ibuf netin;
   obuf netout;
   struct stat st;
+
+  if ((tmp = getenv("CLAMAV_FAILSAFE")) && *tmp)
+    failsafe = strtoul(tmp, 0, 10);
   
   if ((hostname = session_getenv("CLAMAV_HOST")) != 0
       || (hostname = session_getenv("CLAMD_HOST")) != 0) {
@@ -56,7 +67,7 @@
 	&& (maxsize = strtoul(tmp, (char**)&tmp, 10)) != 0
 	&& *tmp == 0) {
       if (fstat(fd, &st) != 0)
-	return &resp_internal;
+	return warn_sys("fstat(fd, &st) != 0");
       if (st.st_size > (ssize_t)maxsize){
 	warn1("ClamAV scanning skipped: message larger than maximum");
 	return 0;
@@ -81,15 +92,19 @@
 	|| (send_timeout = strtoul(tmp, (char**)&tmp, 10)) == 0
 	|| *tmp != 0)
       send_timeout = timeout;
-    if ((ip_count = resolve_ipv4name_n(hostname, ips, MAX_IPS)) <= 0)
-      return &resp_no_hostname;
+    if ((ip_count = resolve_ipv4name_n(hostname, ips, MAX_IPS)) <= 0) {
+      if (failsafe > 0)
+        return warn_sys("Could not resolve virus scanner hostname");
+      else
+        return &resp_no_hostname;
+    }
 
     gettimeofday(&tv, 0);
     offset = (tv.tv_sec ^ tv.tv_usec) % ip_count;
     for (i = 0; i < ip_count; ++i) {
       const ipv4addr* addr = &ips[(i + offset) % ip_count];
       if (lseek(fd, 0, SEEK_SET) != 0)
-	return &resp_internal;
+	return warn_sys("lseek(fd, 0, SEEK_SET) != 0");
       if ((sock = try_connect(addr, cmdport, connect_timeout)) < 0)
 	continue;
 
@@ -128,7 +143,10 @@
 	close(sock);
     }
   }
-  return &resp_no_scan;
+  if (failsafe > 0)
+    return warn_sys("Could not virus scan message");
+  else
+    return &resp_no_scan;
 }
 
 struct plugin plugin = {
--- mailfront-1.16/plugin-clamav.html.original	2010-04-07 20:25:16.000000000 +0800
+++ mailfront-1.16/plugin-clamav.html	2010-04-07 20:26:25.000000000 +0800
@@ -20,6 +20,12 @@
 
 <dl>
 
+<dt><tt>$CLAMAV_FAILSAFE</tt></dt>
+<dd>The default behaviour of the plugin is to defer any SMTP delivery if the
+ClamAV scanner is not available, at the risk of emails being finally rejected if
+the problem is not fixed. To let any mail pass in such a case set this variable
+to a numerical value greater than 0.</dd>
+
 <dt><tt>$CLAMAV_CONNECT_TIMEOUT</tt></dt> <dd>The maximum amount of time
 to wait for a response when connecting to a ClamAV scanner, in
 milliseconds. (defaults to <tt>$CLAMAV_TIMEOUT</tt> below)</dd>