--- loncom/auth/switchserver.pm	2018/07/04 16:58:19	1.41
+++ loncom/auth/switchserver.pm	2018/11/24 16:19:04	1.42
@@ -1,7 +1,7 @@
 # The LearningOnline Network
 # Switch Servers Handler
 #
-# $Id: switchserver.pm,v 1.41 2018/07/04 16:58:19 raeburn Exp $
+# $Id: switchserver.pm,v 1.42 2018/11/24 16:19:04 raeburn Exp $
 #
 # Copyright Michigan State University Board of Trustees
 #
@@ -32,6 +32,7 @@ use strict;
 use Apache::Constants qw(:common);
 use Apache::lonnet;
 use Apache::lonmenu;
+use Digest::MD5 qw(md5_hex);
 use CGI::Cookie();
 use Apache::lonlocal;
 use LONCAPA qw(:DEFAULT :match);
@@ -49,7 +50,7 @@ sub init_env {
     }
     my $lonidsdir=$r->dir_config('lonIDsDir');
     &Apache::lonnet::transfer_profile_to_env($lonidsdir,$handle);
-    
+
     return $r->dir_config('lonIDsDir')."/$handle.id";
 }
 
@@ -101,7 +102,7 @@ sub handler {
         if ($Apache::lonnet::protocol{$env{'form.otherserver'}} eq 'https') {
             $protocol = $Apache::lonnet::protocol{$env{'form.otherserver'}};
         }
-    } 
+    }
 
     if ($env{'user.name'} eq 'public'
 	&& $env{'user.domain'} eq 'public') {
@@ -176,7 +177,8 @@ sub handler {
             }
         }
     }
-    my %temp=('switchserver' => time.':'.$env{'form.otherserver'},
+    my $now = time;
+    my %temp=('switchserver' => $now.':'.$env{'form.otherserver'},
 	      $env{'form.role'});
     &Apache::lonnet::put('email_status',\%temp);
     my $logmsg = "Switch Server to $env{'form.otherserver'}";
@@ -212,13 +214,42 @@ sub handler {
 	   
 # ---------------------------------------------------------------- Get handover
 
-    my ($is_balancer) = &Apache::lonnet::check_loadbalancing($env{'user.name'},$env{'user.domain'});
+    my $newcookieid;
+    (my $is_balancer,undef,my $setcookie) =
+        &Apache::lonnet::check_loadbalancing($env{'user.name'},$env{'user.domain'});
+    if ($is_balancer && $setcookie && $env{'form.otherserver'}) {
+
+        # Set a balancer cookie unless browser already sent LON-CAPA load balancer
+        # cookie which points at the target server
+        my ($found_server,$balancer_cookie) = &Apache::lonnet::check_for_balancer_cookie($r,1);
+
+        unless (($found_server eq $env{'form.otherserver'}) &&
+                ($balancer_cookie =~ /^\Q$env{'user.domain'}\E_\Q$env{'user.name'}\E_/)) {
+            my @hosts = &Apache::lonnet::current_machine_ids();
+            my $desthost = $env{'form.otherserver'};
+            unless (grep(/^\Q$desthost\E$/,@hosts)) {
+                my $balancedir=$r->dir_config('lonBalanceDir');
+                $newcookieid = &md5_hex(&md5_hex($now.{}.rand().$$));
+                my $cookie = $env{'user.domain'}.'_'.$env{'user.name'}.'_'.$newcookieid;
+                my $balcookie = "balanceID=$cookie; path=/; HttpOnly;";
+                if (open(my $fh,'>',"$balancedir/$cookie.id")) {
+                    print $fh $env{'form.otherserver'};
+                    close($fh);
+                }
+                $r->headers_out->add('Set-cookie' => $balcookie);
+            }
+        }
+    }
+
     my %info=('ip'       => $ENV{'REMOTE_ADDR'},
 	      'domain'   => $env{'user.domain'},
 	      'username' => $env{'user.name'},
 	      'role'     => $env{'form.role'},
 	      'server'   => $r->dir_config('lonHostID'),
 	      'balancer' => $is_balancer);
+    if ($newcookieid) {
+        $info{'balcookie'} = $newcookieid;
+    }
     if ($env{'form.origurl'}) {
         $info{'origurl'} = $env{'form.origurl'};
     }