diff --git a/API-README b/API-README
index ef61c81f..2829b95d 100644
--- a/API-README
+++ b/API-README
@@ -952,7 +952,9 @@ or in your cgminer.conf
 And in miner.php set $mcast = true;
 
 This will ignore the value of $rigs and overwrite it with the list of zero or
-more rigs found on the network in the timout specified
+more rigs found on the network in the timeout specified
+A rig will not reply if the API settings would mean it would also ignore an
+API request from the web server running miner.php
 
 ---------
 
@@ -1196,6 +1198,14 @@ Set $mcast to true to look for your rigs and ignore $rigs
 
 ---------
 
+Default:
+ $mcastexpect = 0;
+
+The minimum number of rigs expected to be found when $mcast is true
+If fewer are found, an error will be included at the top of the page
+
+---------
+
 Default:
  $mcastaddr = '224.0.0.75';
 
@@ -1237,6 +1247,16 @@ N.B. the accuracy of the timing used to wait for the replies is
 
 ---------
 
+Default:
+ $allowgen = false;
+
+Set $allowgen to true to allow customsummarypages to use 'gen' 
+false means ignore any 'gen' options
+This is disabled by default due to the possible security risk
+of using it, see the end of this document for an explanation
+
+---------
+
 Default:
  $rigipsecurity = true;
 
@@ -1498,6 +1518,7 @@ The example given:
 With cgminer 2.10.2 and later, miner.php includes an extension to
 the custom pages that allows you to apply SQL style commands to
 the data: where, group, and having
+cgminer 3.4.2 also includes another option 'gen'
 
 As an example, miner.php includes a more complex custom page called 'Pools'
 this includes the extension:
@@ -1513,6 +1534,7 @@ $poolsext = array(
                         'STATS.Bytes Sent' => 'sum',
                         'STATS.Times Recv' => 'sum',
                         'STATS.Bytes Recv' => 'sum'),
+        'gen' => array('AvShr', 'POOL.Difficulty Accepted/max(POOL.Accepted,1)),
         'having' => array(array('STATS.Bytes Recv', '>', 0)))
 );
 
@@ -1564,3 +1586,21 @@ The first 4 are as expected - the numerical sum, average, minimum or maximum
  of course any valid 'DEVS.Xyz' would give the same 'count' value
 'any' is effectively random: the field value in the 1st row of the grouped data
 An unrecognised 'function' uses 'any'
+
+A 'gen' allows you to generate new fields from any php valid function of any
+of the other fields
+ e.g. 'gen' => array('AvShr', 'POOL.Difficulty Accepted/max(POOL.Accepted,1)),
+will generate a new field called GEN.AvShr that is the function shown, which
+in this case is the average difficulty of each share submitted
+
+THERE IS A SECURITY RISK WITH HOW GEN WORKS
+It simply replaces all the variables with their values and then requests PHP
+the execute the formula - thus if a field value returned from a cgminer API
+request contained PHP code, it could be executed by your web server
+Of course cgminer doesn't do this, but if you do not control the cgminer that
+returns the data in the API calls, someone could modify cgminer to return a
+PHP string in a field you use in 'gen'
+Thus use 'gen' at your own risk
+If someone feels the urge to write a mathematical interpreter in PHP to get
+around this risk, feel free to write one and submit it to the API author for
+consideration
diff --git a/miner.php b/miner.php
index 137db7ee..fdb9e52f 100644
--- a/miner.php
+++ b/miner.php
@@ -1,17 +1,20 @@
 <?php
 session_start();
 #
-global $title, $miner, $port, $readonly, $notify, $rigs;
-global $mcast, $mcastaddr, $mcastport, $mcastcode;
-global $mcastlistport, $mcasttimeout;
+global $doctype, $title, $miner, $port, $readonly, $notify, $rigs;
+global $mcast, $mcastexpect, $mcastaddr, $mcastport, $mcastcode;
+global $mcastlistport, $mcasttimeout, $allowgen;
 global $rigipsecurity, $rigtotals, $forcerigtotals;
 global $socksndtimeoutsec, $sockrcvtimeoutsec;
 global $checklastshare, $poolinputs, $hidefields;
 global $ignorerefresh, $changerefresh, $autorefresh;
 global $allowcustompages, $customsummarypages;
 global $miner_font_family, $miner_font_size;
+global $bad_font_family, $bad_font_size;
 global $colouroverride, $placebuttons, $userlist;
 #
+$doctype = "<!DOCTYPE html>\n";
+#
 # See API-README for more details of these variables and how
 # to configure miner.php
 #
@@ -48,6 +51,9 @@ $rigs = array('127.0.0.1:4028');
 # Set $mcast to true to look for your rigs and ignore $rigs
 $mcast = false;
 #
+# Set $mcastexpect to at least how many rigs you expect it to find
+$mcastexpect = 0;
+#
 # API Multicast address all cgminers are listening on
 $mcastaddr = '224.0.0.75';
 #
@@ -64,6 +70,10 @@ $mcastlistport = 4027;
 # to wait for replies to the Multicast message
 $mcasttimeout = 1.5;
 #
+# Set $allowgen to true to allow customsummarypages to use 'gen' 
+# false means ignore any 'gen' options
+$allowgen = false;
+#
 # Set $rigipsecurity to false to show the IP/Port of the rig
 # in the socket error messages and also show the full socket message
 $rigipsecurity = true;
@@ -139,7 +149,7 @@ $poolspage = array(
 			'POOL.Has GBT=GBT', 'STATS.Times Sent=TSent',
 			'STATS.Bytes Sent=BSent', 'STATS.Net Bytes Sent=NSent',
 			'STATS.Times Recv=TRecv', 'STATS.Bytes Recv=BRecv',
-			'STATS.Net Bytes Recv=NRecv'));
+			'STATS.Net Bytes Recv=NRecv', 'GEN.AvShr=AvShr'));
 #
 $poolssum = array(
  'SUMMARY' => array('MHS av', 'Found Blocks', 'Accepted',
@@ -156,7 +166,9 @@ $poolsext = array(
 	'calc' => array('POOL.Difficulty Accepted' => 'sum', 'POOL.Difficulty Rejected' => 'sum',
 			'STATS.Times Sent' => 'sum', 'STATS.Bytes Sent' => 'sum',
 			'STATS.Net Bytes Sent' => 'sum', 'STATS.Times Recv' => 'sum',
-			'STATS.Bytes Recv' => 'sum', 'STATS.Net Bytes Recv' => 'sum'),
+			'STATS.Bytes Recv' => 'sum', 'STATS.Net Bytes Recv' => 'sum',
+			'POOL.Accepted' => 'sum'),
+	'gen' => array('AvShr' => 'round(POOL.Difficulty Accepted/max(POOL.Accepted,1)*100)/100'),
 	'having' => array(array('STATS.Bytes Recv', '>', 0)))
 );
 
@@ -176,9 +188,12 @@ $warnfont = '<font color=red><b>';
 $warnoff = '</b></font>';
 $dfmt = 'H:i:s j-M-Y \U\T\CP';
 #
-$miner_font_family = 'verdana,arial,sans';
+$miner_font_family = 'Verdana, Arial, sans-serif, sans';
 $miner_font_size = '13pt';
 #
+$bad_font_family = '"Times New Roman", Times, serif';
+$bad_font_size = '18pt';
+#
 # Edit this or redefine it in myminer.php to change the colour scheme
 # See $colourtable below for the list of names
 $colouroverride = array();
@@ -198,7 +213,7 @@ if (file_exists('myminer.php'))
 # This is the system default that must always contain all necessary
 # colours so it must be a constant
 # You can override these values with $colouroverride
-# The only one missing is in $warnfont
+# The only one missing is $warnfont
 # - which you can override directly anyway
 global $colourtable;
 $colourtable = array(
@@ -210,6 +225,8 @@ $colourtable = array(
 	'td.h background'	=> '#c4ffff',
 	'td.err color'		=> 'black',
 	'td.err background'	=> '#ff3050',
+	'td.bad color'		=> 'black',
+	'td.bad background'	=> '#ff3050',
 	'td.warn color'		=> 'black',
 	'td.warn background'	=> '#ffb050',
 	'td.sta color'		=> 'green',
@@ -269,9 +286,10 @@ function getdom($domname)
  return getcss($domname, true);
 }
 #
-function htmlhead($checkapi, $rig, $pg = null, $noscript = false)
+function htmlhead($mcerr, $checkapi, $rig, $pg = null, $noscript = false)
 {
- global $title, $miner_font_family, $miner_font_size;
+ global $doctype, $title, $miner_font_family, $miner_font_size;
+ global $bad_font_family, $bad_font_size;
  global $error, $readonly, $poolinputs, $here;
  global $ignorerefresh, $autorefresh;
 
@@ -300,14 +318,16 @@ function htmlhead($checkapi, $rig, $pg = null, $noscript = false)
 		$readonly = true;
  }
  $miner_font = "font-family:$miner_font_family; font-size:$miner_font_size;";
+ $bad_font = "font-family:$bad_font_family; font-size:$bad_font_size;";
 
- echo "<html><head>$refreshmeta
+ echo "$doctype<html><head>$refreshmeta
 <title>$title</title>
 <style type='text/css'>
 td { $miner_font ".getcss('td')."}
 td.two { $miner_font ".getcss('td.two')."}
 td.h { $miner_font ".getcss('td.h')."}
 td.err { $miner_font ".getcss('td.err')."}
+td.bad { $bad_font ".getcss('td.bad')."}
 td.warn { $miner_font ".getcss('td.warn')."}
 td.sta { $miner_font ".getcss('td.sta')."}
 td.tot { $miner_font ".getcss('td.tot')."}
@@ -339,6 +359,14 @@ echo "</script>\n";
 <tr><td align=center valign=top>
 <table border=0 cellpadding=4 cellspacing=0 summary='Mine'>
 <?php
+ echo $mcerr;
+}
+#
+function minhead($mcerr = '')
+{
+ global $readonly;
+ $readonly = true;
+ htmlhead($mcerr, false, null, null, true);
 }
 #
 global $haderror, $error;
@@ -643,9 +671,14 @@ function newrow()
  echo '<tr>';
 }
 #
+function othrow($row)
+{
+ return "<tr>$row</tr>";
+}
+#
 function otherrow($row)
 {
- echo "<tr>$row</tr>";
+ echo othrow($row);
 }
 #
 function endrow()
@@ -1810,8 +1843,6 @@ function doOne($rig, $preprocess)
  global $haderror, $readonly, $notify, $rigs;
  global $placebuttons;
 
- htmlhead(true, $rig);
-
  if ($placebuttons == 'top' || $placebuttons == 'both')
 	pagebuttons($rig, null);
 
@@ -2324,8 +2355,55 @@ function processcompare($which, $ext, $section, $res)
  return $res;
 }
 #
-function processext($ext, $section, $res)
+function ss($a, $b)
+{
+ $la = strlen($a);
+ $lb = strlen($b);
+ if ($la != $lb)
+	return $la - $lb;
+ return strcmp($a, $b);
+}
+#
+function genfld($row, $calc)
+{
+ uksort($row, "ss");
+
+ foreach ($row as $name => $value)
+	if (strstr($calc, $name) !== FALSE)
+		$calc = str_replace($name, $value, $calc);
+
+ eval("\$val = $calc;");
+
+ return $val;
+}
+#
+function dogen($ext, $section, &$res, &$fields)
+{
+ $gen = $ext[$section]['gen'];
+
+ foreach ($gen as $fld => $calc)
+	$fields[] = "GEN.$fld";
+
+ foreach ($res as $rig => $result)
+	foreach ($result as $sec => $row)
+	{
+		$secname = preg_replace('/\d/', '', $sec);
+		if (secmatch($section, $secname))
+			foreach ($gen as $fld => $calc)
+			{
+				$name = "GEN.$fld";
+
+				$val = genfld($row, $calc);
+
+				$res[$rig][$sec][$name] = $val;
+			}
+	}
+}
+#
+function processext($ext, $section, $res, &$fields)
 {
+ global $allowgen;
+
  $res = processcompare('where', $ext, $section, $res);
 
  if (isset($ext[$section]['group']))
@@ -2393,6 +2471,10 @@ function processext($ext, $section, $res)
 	}
  }
 
+ // Generated fields (functions of other fields)
+ if ($allowgen === true && isset($ext[$section]['gen']))
+	dogen($ext, $section, $res, $fields);
+
  return processcompare('having', $ext, $section, $res);
 }
 #
@@ -2451,6 +2533,8 @@ function processcustompage($pagename, $sections, $sum, $ext, $namemap)
 				$results[$cmd][$num] = $process;
 		}
 	}
+	else
+		otherrow('<td class=bad>Bad "$rigs" array</td>');
  }
 
  $shownsomething = false;
@@ -2487,7 +2571,8 @@ function processcustompage($pagename, $sections, $sum, $ext, $namemap)
 
 		if (isset($results[$sectionmap[$section]]))
 		{
-			$rigresults = processext($ext, $section, $results[$sectionmap[$section]]);
+			$rigresults = processext($ext, $section, $results[$sectionmap[$section]], $fields);
+
 			$showfields = array();
 			$showhead = array();
 			foreach ($fields as $field)
@@ -2566,21 +2651,19 @@ function showcustompage($pagename)
  global $customsummarypages;
  global $placebuttons;
 
- htmlhead(false, null, $pagename);
-
  if ($placebuttons == 'top' || $placebuttons == 'both')
 	pagebuttons(null, $pagename);
 
  if (!isset($customsummarypages[$pagename]))
  {
-	otherrow("<td colspan=100>Unknown custom summary page '$pagename'</td>");
+	otherrow("<td colspan=100 class=bad>Unknown custom summary page '$pagename'</td>");
 	return;
  }
 
  $c = count($customsummarypages[$pagename]);
  if ($c < 2 || $c > 3)
  {
-	$rw = "<td colspan=100>Invalid custom summary page '$pagename' (";
+	$rw = "<td colspan=100 class=bad>Invalid custom summary page '$pagename' (";
 	$rw .= count($customsummarypages[$pagename]).')</td>';
 	otherrow($rw);
 	return;
@@ -2625,7 +2708,7 @@ function showcustompage($pagename)
 
  if (count($page) <= 1)
  {
-	otherrow("<td colspan=100>Invalid custom summary page '$pagename' no content </td>");
+	otherrow("<td colspan=100 class=bad>Invalid custom summary page '$pagename' no content </td>");
 	return;
  }
 
@@ -2639,7 +2722,7 @@ function onlylogin()
 {
  global $here;
 
- htmlhead(false, null, null, true);
+ htmlhead('', false, null, null, true);
 
 ?>
 <tr height=15%><td>&nbsp;</td></tr>
@@ -2739,6 +2822,7 @@ function checklogin()
 function display()
 {
  global $miner, $port;
+ global $mcast, $mcastexpect;
  global $readonly, $notify, $rigs;
  global $ignorerefresh, $autorefresh;
  global $allowcustompages, $customsummarypages;
@@ -2750,11 +2834,24 @@ function display()
  if ($pagesonly === 'login')
 	return;
 
+ $mcerr = '';
+
  if ($rigs == null or count($rigs) == 0)
  {
-	otherrow("<td>No rigs defined</td>");
+	if ($mcast === true)
+		$action = 'found';
+	else
+		$action = 'defined';
+
+	minhead();
+	otherrow("<td class=bad>No rigs $action</td>");
 	return;
  }
+ else
+ {
+	if ($mcast === true && count($rigs) < $mcastexpect)
+		$mcerr = othrow('<td class=bad>Found '.count($rigs)." rigs but expected at least $mcastexpect</td>");
+ }
 
  if ($ignorerefresh == false)
  {
@@ -2811,7 +2908,8 @@ function display()
 
 	if ($pg !== null && $pg !== '')
 	{
-		showcustompage($pg);
+		htmlhead($mcerr, false, null, $pg);
+		showcustompage($pg, $mcerr);
 		return;
 	}
  }
@@ -2830,10 +2928,14 @@ function display()
 		$miner = $parts[0];
 		$port = $parts[1];
 
+		htmlhead($mcerr, true, 0);
 		doOne(0, $preprocess);
 	}
 	else
-		otherrow('<td>Invalid "$rigs" array</td>');
+	{
+		minhead($mcerr);
+		otherrow('<td class=bad>Invalid "$rigs" array</td>');
+	}
 
 	return;
  }
@@ -2846,15 +2948,19 @@ function display()
 		$miner = $parts[0];
 		$port = $parts[1];
 
+		htmlhead($mcerr, true, 0);
 		doOne($rig, $preprocess);
 	}
 	else
-		otherrow('<td>Invalid "$rigs" array</td>');
+	{
+		minhead($mcerr);
+		otherrow('<td class=bad>Invalid "$rigs" array</td>');
+	}
 
 	return;
  }
 
- htmlhead(false, null);
+ htmlhead($mcerr, false, null);
 
  if ($placebuttons == 'top' || $placebuttons == 'both')
 	pagebuttons(null, null);
@@ -2880,7 +2986,7 @@ function display()
 	pagebuttons(null, null);
 }
 #
-if (isset($mcast) && $mcast === true)
+if ($mcast === true)
  getrigs();
 display();
 #