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lib/Arc/Command.pod  view on Meta::CPAN

   }
 )  
 
 resp.

 $arc->{connection_vars}->{commands}

This hash describes the assignment of B<Command Name> and B<Command Class>. 
When a client has authenticated and wants to run a command, it will send 
the B<Command Name> and suitable, optional parameters. The server will look into 
the commands hash and creates an object of the B<Command Class> 
associated with B<Command Name>.

 my $perlcmd = $this->{commands}->{$cmd};
 [..]
 eval "require $perlcmd;"
 [..]
 (fork)
 my $ret = eval
 {
  my $object = new $perlcmd(
    _username => $this->{_username},
    _peeraddr => $this->{peeraddr},
    _peerport => $this->{peerport},
    _peername => $this->{peername},
    _cmd => $cmd,
    logfileprefix => "command",
  );
  $object->Execute(@a);
  $cmderr = $object->IsError();

  return -1;
 };
 
When everything went alright, the command will be executed. The command runs
in a separate process. Therefore STDIN, STDOUT and STDERR are duped to two
pipes, one for the in, one for the out direction. In the parent process data
from the encrypted network command connection is read from and written to these pipes.
Same situation on the client side, STDIN and STDOUT are used to put and get the 
data through the network.
 
                   encrypted
          /--->>---| net- |--->>-----\   
        / /---<<---| work |---<<-----\ \
      / /                              \ \
     | |     in                         | |    p2
  |--------|->>--\                  |--------|->>--\ 
  | Client | out   \                | Server | p1    \
  |--------|-<<-\    \              |--------|-<<-\    \ 
                /|\  \|/                          /|\  \|/
               |--------|                       |-----------|
               |  User  |                       |  Command  |
               |--------|                       |-----------|
 
This design makes it easy for ARCv2 Commands to get input and produce output.

B<Example>:
 sub Execute 
 {
  while ($_ = <STDIN>) { # ends on EOF
     s/a/b/g; print;
  }
 }
 
If you want to implement a new Command for ARCv2 you have to derive from 
Arc::Command and override the sub C<Execute>. See existing Arc::Command::* 
classes for examples. To get your Command recognised you have to assign a 
B<Command Name> to your command class. ARCv2 ignores the return code of
B<Execute>. If your command runs into an error use the _SetError function 
and return immediately. This is what ARCv2 will evaluate and send to the
client.

B<Example>:
 sub Execute
 {
  my $this = shift;
  my $pw = <>;
  if ($pw ne "klaus") {
	  return $this->_SetError("Wrong password.");
  }
 }
 
In ARCv2 some standard commands are already implemented: C<Arc::Command::Get>,
C<Arc::Command::Put>, C<Arc::Command::Uptime>, C<Arc::Command::Whoami>,
C<Arc::Command::Test>.

By default, these classes are mapped to B<Command Names> as follows (in the 
default arcxd.conf for arcxd):
  uptime => Arc::Command::Uptime,
  whoami => Arc::Command::Whoami,
  copy   => Arc::Command::Get,
  cp     => Arc::Command::Get,
  get    => Arc::Command::Get,
  put    => Arc::Command::Put,
  test   => Arc::Command::Test,
  help   => Arc::Command::Help,
 
B<Caution>: Especially take care of the C<Arc::Command::Get> and 
C<Arc::Command::Put> in production environment. As ARCv2 will probably
run as root and by default the Get and Put command do NOT have an access
control, everyone can get or put any files from/to your ARCv2 server.

There are some member variables, which contain information about the 
client. See 'Class VARIABLES' for a complete list of them. These values 
are filled by Arc::Connection::Server, when the client wants to run a command.


=head1 Class VARIABLES

=head3 PUBLIC MEMBERS

=over 2

=item logfileprefix I<reimplemented from Arc>

B<Default value>: "command"

=back 

=over 2

lib/Arc/Command.pod  view on Meta::CPAN

=back 

=over 2

=item _error I<inherited from Arc>

B<Description>: contains the error message

B<Default value>: undef

=item _syslog I<inherited from Arc>

B<Description>: log to syslog or to STDERR

B<Default value>: 1

=back 

=over 2

=back 

=head3 PRIVATE MEMBERS

=head1 Class METHODS

=head3 PUBLIC METHODS

=over 2

=item Execute ( ... (parameter from users request) ) 

B<Description>: execute this command.
This function is called by the ARCv2 Server when the user wants 
to execute this command. 


B<Returns:> true if the command has succeeded, false (and please set _SetError) if not.


=back 

=over 2

=item DESTROY (  ) I<inherited from Arc>

B<Description>: Destructor


=item IsError (  ) I<inherited from Arc>

B<Description>: User function to get the error msg.


B<Returns:> the error message if any otherwise undef


B<Example:>

unless (my $err = $arc->IsError()) { .. } else { print STDERR $err; }


=item Log ( $facility, ... (message) ) I<inherited from Arc>

B<Description>: Log function.
Logs messages to 'logdestination' if 'loglevel' is is set appropriatly.
loglevel behaviour has changed in the 1.0 release of ARCv2, the "Arc"-class can export
LOG_AUTH (authentication information), LOG_USER (connection information), LOG_ERR (errors), 
LOG_CMD (ARCv2 addition internal command information), LOG_SIDE (verbose client/server-specific
information), LOG_DEBUG (verbose debug information). It possible to combine the 
levels with or (resp. +) to allow a message to appear when not all loglevels are 
requested by the user.
Commonly used for logging errors from application level.


B<Returns:> always false


B<Example:>

return $arc->Log(LOG_ERR,"Message");


=item new ( %hash, key => val, ... ) I<inherited from Arc>

B<Description>: Constructor. 
Initializes the object and returns it blessed.
For all sub classes, please override C<_Init> to check the 
parameter which are passed to the C<new> function. This
is necessary because you are not able to call the the new method of a
parent class, when having a class name (new $class::SUPER::new, does not work.).


B<Returns:> blessed object of the class


B<Example:>

my $this = new Arc::Class ( key => value, key2 => value2 );


=back 

=over 2

=back 

=head3 PROTECTED METHODS

=over 2

=item _Debug ( ... (message) ) I<inherited from Arc>

B<Description>: Debug function.
Logs messages with "DEBUG" 


B<Returns:> always false