clusterd: Implement standard command service

Implement new udp service 'exec.2' which accepts a list of predefined
commands to run.

Implement new command `clusterd exec CMD...`

The new usage is supposed to make `clusterd --exec` and the 'exec' UDP
service obsolete. Having all commands which might be issued after file
updates available in the same %CMD infrastructure will make the
following changes easier and the file shorter, once the obsolete command
`clusterd --exec` and the UDP services udp_rx_flush_gidcache,
udp_rx_make_automaps, udp_rx_reexport and udp_rx_exec are removed.

clusterd/clusterd

@@ -769,6 +769,7 @@ our %UDP_HANDLER = (
     'reexport'      => \&udp_rx_reexport,
     'log'  => \&udp_rx_log,
     'exec' => \&udp_rx_exec,
+    'exec.2' => \&udp_rx_exec2,
     'push' => \&udp_rx_push,
 );
 
@@ -871,8 +872,11 @@ sub push_file {
 
 }
 
-our %CMD=(
-    'mkmotd'=>'/usr/sbin/mkmotd.pl',
+our %CMD = (
+    'mkmotd' => '/usr/sbin/mkmotd.pl',
+    'flush-gidcache' => 'date -d tomorrow +%s > /proc/net/rpc/auth.unix.gid/flush',
+    'reexport' => '/usr/bin/mxmount --reexport-only',
+    'make-automaps' => '/sbin/make-automaps',
 );
 
 sub send_exec {
@@ -911,6 +915,25 @@ sub udp_rx_exec {
     wait;
 }
 
+sub udp_rx_exec2 {
+    my @cmd = @_;
+    my $pid = fork;
+    unless (defined $pid) {
+        warn "$!\n";
+        return;
+    }
+    if ($pid == 0) {
+        open STDIN,'<','/dev/null';
+        alarm(60);
+        chdir '/';
+        for my $cmd (@cmd) {
+            exists $CMD{$cmd} and warn "executing $CMD{$cmd}\n";
+            exists $CMD{$cmd} and system '/bin/sh', '-c', $CMD{$cmd};
+        }
+        exit;
+    }
+}
+
 #-------------------------------------------------------------
 
 sub normalize_seg { # [pos,len],[pos,len],...
@@ -1930,6 +1953,16 @@ sub cmd_push {
     }
 }
 
+sub cmd_exec {
+    my @cmd = @_;
+    for my $cmd (@cmd) {
+        exists $CMD{$cmd} or die "$cmd: only these commands are allowed: " . join(', ', keys %CMD) . "\n";
+    }
+    sync_cluster_pw() or die "$CLUSTER_PW_FILE: $!\n";
+    $donald_s=new My::Select::INET(Proto=>'udp') or die "$!\n";
+    udp_broadcast_message($donald_s, 'exec.2', @cmd);
+}
+
 #------------------------------------------------------------
 
 our $TRUSTCHECK_PORT=236;
@@ -1975,6 +2008,8 @@ usage: $0 [options]
   --daemon  # start a daemon
 
   push files....   # push files over tcp
+  exec CMD...      # execute CMD on all nodes
+    CMD : mkmotd | flush-gidcache | reexport | make-automaps
 
 __EOF__
 
@@ -2062,6 +2097,9 @@ if (defined $options{'push'}) {
     if ($cmd eq 'push') {
         @args>0 or die USAGE;
         cmd_push(@args);
+    } elsif ($cmd eq 'exec') {
+        @args > 0 or die USAGE;
+        cmd_exec(@args);
     } else {
         die USAGE;
     }