pbot-vm: vm-exec can now select VM; can be configured by vm-exec.json file

The vm-exec command now recognizes the following options:

    -vm-serial -vm-heart -vm-cid -vm-vport -vm

The -vm option accepts a name and configures the serial,
heart, cid and vport appropriately.

The vm-exec command can be configured by /host/config/vm-exec.json.

applets/pbot-vm/README.md

@@ -1,3 +1,3 @@
 PBot can interact with a virtual machine to safely execute arbitrary user-submitted system commands and code.
 
-For installation and usage instructions, see [the documentation.](../../doc/VirtualMachine.md)
+For installation and usage instructions, see [the PBot Virtual Machine documentation.](../../doc/VirtualMachine.md)

applets/pbot-vm/host/bin/vm-exec

@@ -108,9 +108,11 @@ sub make_context_from_args(@args_in) {
         }
     }
 
-    # parse -lang option
+    # parse options specific to vm-exec
-    if ($context->{code} =~ s/^-lang=([^ ]+)\s+//) {
+    while ($context->{code} =~ s/^-(lang|vm-cid|vm-vport|vm-serial|vm)=([^ ]+)\s+//) {
-        $context->{lang} = lc $1;
+        my ($option, $value) = ($1, $2);
+        print STDERR "Overriding `$option` to `$value`.\n";
+        $context->{$option} = lc $value;
     }
 
     return $context;
@@ -148,9 +150,90 @@ sub load_language($context) {
     return "Languages::$language"->new(%$context);
 }
 
+sub load_config($file) {
+    open my $fh, '<', $file or die "load config: could not open $file: $!\n";
+    local $/ = undef;
+    my $json = <$fh>;
+    close $fh;
+    return decode_json($json);
+}
+
+sub config_get_machine($config, $machine) {
+    # check if machine is an alias and update to actual machine
+    if (exists $config->{aliases}->{$machine}) {
+        $machine = $config->{aliases}->{$machine};
+    }
+
+    # return pointer to config entry
+    return $config->{machines}->{$machine};
+}
+
+sub list_machines($config) {
+    my @machines;
+
+    # quick-and-easy: just list the aliases
+    foreach my $alias (keys %{$config->{aliases}}) {
+        push @machines, $alias;
+    }
+
+    return join ', ', sort @machines;
+}
+
+sub configure_context($context, $config) {
+    if (exists $context->{vm}) {
+        # -vm option was passed, forcibly override machine
+        my $machine = $context->{vm};
+
+        # point at config entry
+        my $entry = config_get_machine($config, $machine);
+
+        if (not defined $entry) {
+            my $machines = list_machines($config);
+            print "Unknown machine '$machine'; available machines are: $machines\n";
+            exit 1;
+        }
+
+        # override values
+        $context->{'vm-serial'} = $entry->{'serial'};
+        $context->{'vm-heart'}  = $entry->{'heart'};
+        $context->{'vm-cid'}    = $entry->{'cid'};
+        $context->{'vm-vport'}  = $entry->{'vport'};
+    } else {
+        # otherwise configure any undefined values as default machine
+        my $machine = $config->{'default-machine'};
+
+        # point at config entry
+        my $entry = config_get_machine($config, $machine);
+
+        if (not defined $entry) {
+            my $machines = list_machines($config);
+            print "Unknown machine '$machine'; available machines are: $machines\n";
+            exit 1;
+        }
+
+        # update any undefined values, preserving any existing values
+        $context->{'vm-serial'} //= $entry->{'serial'};
+        $context->{'vm-heart'}  //= $entry->{'heart'};
+        $context->{'vm-cid'}    //= $entry->{'cid'};
+        $context->{'vm-vport'}  //= $entry->{'vport'};
+    }
+
+    # set any undefined values to default values
+    $context->{nick}        //= 'vm';
+    $context->{channel}     //= 'vm';
+    $context->{lang}        //= 'c11';
+    $context->{'vm-serial'} //= SERIAL;
+    $context->{'vm-cid'}    //= CID;
+    $context->{'vm-vport'}  //= VPORT;
+}
+
 sub main() {
     my $context = make_context_from_args(@ARGV);
 
+    my $config = load_config("$RealBin/../config/vm-exec.json");
+
+    configure_context($context, $config);
+
     if (not length $context->{code}) {
         if (exists $context->{usage}) {
             print "$context->{usage}\n";
@@ -160,14 +243,6 @@ sub main() {
         exit 1;
     }
 
-    # set any missing fields to default values
-    $context->{nick}        //= 'vm';
-    $context->{channel}     //= 'vm';
-    $context->{lang}        //= 'c11';
-    $context->{'vm-serial'} //= SERIAL;
-    $context->{'vm-cid'}    //= CID;
-    $context->{'vm-vport'}  //= VPORT;
-
     my $lang = load_language($context);
 
     $lang->process_interactive_edit;

applets/pbot-vm/host/config/vm-exec.json

@@ -0,0 +1,21 @@
+{
+   "machines" : {
+      "pbot-vm" : {
+         "serial" : 5555,
+         "heart" : 5556,
+         "cid" : 7,
+         "vport" : 5555
+      },
+      "pbot-test-vm" : {
+         "serial" : 7777,
+         "heart" : 7778,
+         "cid" : 42,
+         "vport" : 5555
+      }
+   },
+   "aliases" : {
+      "fedora-amd64" : "pbot-vm",
+      "test" : "pbot-test-vm"
+   },
+   "default-machine" : "fedora-amd64"
+}