File Coverage

blib/lib/IO/Async/OS.pm

Criterion	Covered	Total	%
statement	219	229	95.6
branch	73	104	70.1
condition	39	57	68.4
subroutine	41	42	97.6
pod			n/a
total	372	432	86.1

#  You may distribute under the terms of either the GNU General Public License
#  or the Artistic License (the same terms as Perl itself)
#
#  (C) Paul Evans, 2012-2019 -- [e-mail]

package IO::Async::OS;

use strict;
use warnings;

our $VERSION = '0.79';

our @ISA = qw( IO::Async::OS::_Base );

if( eval { require "IO/Async/OS/$^O.pm" } ) {
   @ISA = "IO::Async::OS::$^O";
}

package # hide from CPAN
   IO::Async::OS::_Base;

use Carp;

use Socket 1.95 qw(
   AF_INET AF_INET6 AF_UNIX INADDR_LOOPBACK SOCK_DGRAM SOCK_RAW SOCK_STREAM
   pack_sockaddr_in inet_aton
   pack_sockaddr_in6 inet_pton
   pack_sockaddr_un
);

use POSIX qw( sysconf _SC_OPEN_MAX );

# Win32 [and maybe other places] don't have an _SC_OPEN_MAX. About the best we
# can do really is just make up some largeish number and hope for the best.
use constant OPEN_MAX_FD => eval { sysconf(_SC_OPEN_MAX) } || 1024;

# Some constants that define features of the OS

use constant HAVE_SOCKADDR_IN6 => defined eval { pack_sockaddr_in6 0, inet_pton( AF_INET6, "2001::1" ) };
use constant HAVE_SOCKADDR_UN  => defined eval { pack_sockaddr_un "/foo" };

# Do we have to fake S_ISREG() files read/write-ready in select()?
use constant HAVE_FAKE_ISREG_READY => 0;

# Do we have to select() for for evec to get connect() failures
use constant HAVE_SELECT_CONNECT_EVEC => 0;
# Ditto; do we have to poll() for POLLPRI to get connect() failures
use constant HAVE_POLL_CONNECT_POLLPRI => 0;

# Does connect() yield EWOULDBLOCK for nonblocking in progress?
use constant HAVE_CONNECT_EWOULDBLOCK => 0;

# Can we rename() files that are open?
use constant HAVE_RENAME_OPEN_FILES => 1;

# Can we reliably watch for POSIX signals, including SIGCHLD to reliably
# inform us that a fork()ed child has exit()ed?
use constant HAVE_SIGNALS => 1;

# Do we support POSIX-style true fork()ed processes at all?
use constant HAVE_POSIX_FORK => !$ENV{IO_ASYNC_NO_FORK};
# Can we potentially support threads? (would still need to 'require threads')
use constant HAVE_THREADS => !$ENV{IO_ASYNC_NO_THREADS} &&
   eval { require Config && $Config::Config{useithreads} };

# Preferred trial order for built-in Loop classes
use constant LOOP_BUILTIN_CLASSES => qw( Poll Select );

# Should there be any other Loop classes we try before the builtin ones?
use constant LOOP_PREFER_CLASSES => ();

=head1 NAME

C - operating system abstractions for C

=head1 DESCRIPTION

This module acts as a class to provide a number of utility methods whose exact
behaviour may depend on the type of OS it is running on. It is provided as a
class so that specific kinds of operating system can override methods in it.

As well as these support functions it also provides a number of constants, all
with names beginning C which describe various features that may or may
not be available on the OS or perl build. Most of these are either hard-coded
per OS, or detected at runtime.

The following constants may be overridden by environment variables.

=over 4

=item * HAVE_POSIX_FORK

True if the C call has full POSIX semantics (full process separation).
This is true on most OSes but false on MSWin32.

This may be overridden to be false by setting the environment variable
C.

=item * HAVE_THREADS

True if C are available, meaning that the C module can be
used. This depends on whether perl was built with threading support.

This may be overridable to be false by setting the environment variable
C.

=back

=cut

=head2 getfamilybyname

   $family = IO::Async::OS->getfamilybyname( $name )

Return a protocol family value based on the given name. If C<$name> looks like
a number it will be returned as-is. The string values C, C and
C will be converted to the appropriate C constant.

=cut

sub getfamilybyname
{
   shift;
   my ( $name ) = @_;

   return undef unless defined $name;

   return $name if $name =~ m/^\d+$/;

   return AF_INET    if $name eq "inet";
   return AF_INET6() if $name eq "inet6" and defined &AF_INET6;
   return AF_UNIX    if $name eq "unix";

   croak "Unrecognised socket family name '$name'";
}

=head2 getsocktypebyname

   $socktype = IO::Async::OS->getsocktypebyname( $name )

Return a socket type value based on the given name. If C<$name> looks like a
number it will be returned as-is. The string values C, C and
C will be converted to the appropriate C constant.

=cut

sub getsocktypebyname
{
   shift;
   my ( $name ) = @_;

   return undef unless defined $name;

   return $name if $name =~ m/^\d+$/;

   return SOCK_STREAM if $name eq "stream";
   return SOCK_DGRAM  if $name eq "dgram";
   return SOCK_RAW    if $name eq "raw";

   croak "Unrecognised socktype name '$name'";
}

# This one isn't documented because it's not really overridable. It's largely
# here just for completeness
my $HAVE_IO_SOCKET_IP;

sub socket
{
   my $self = shift;
   my ( $family, $socktype, $proto ) = @_;

   require IO::Socket;
   defined $HAVE_IO_SOCKET_IP or
      $HAVE_IO_SOCKET_IP = defined eval { require IO::Socket::IP };

   croak "Cannot create a new socket without a family" unless $family;
   # PF_UNSPEC and undef are both false
   $family = $self->getfamilybyname( $family ) || AF_UNIX;

   # SOCK_STREAM is the most likely
   $socktype = $self->getsocktypebyname( $socktype ) || SOCK_STREAM;

   defined $proto or $proto = 0;

   if( $HAVE_IO_SOCKET_IP and ( $family == AF_INET || $family == AF_INET6() ) ) {
      return IO::Socket::IP->new->socket( $family, $socktype, $proto );
   }

   my $sock = eval {
      IO::Socket->new(
         Domain => $family,
         Type   => $socktype,
         Proto  => $proto,
      );
   };
   return $sock if $sock;

   # That failed. Most likely because the Domain was unrecognised. This
   # usually happens if getaddrinfo returns an AF_INET6 address but we don't
   # have a suitable class loaded. In this case we'll return a generic one.
   # It won't be in the specific subclass but that's the best we can do. And
   # it will still work as a generic socket.
   return IO::Socket->new->socket( $family, $socktype, $proto );
}

=head2 socketpair

   ( $S1, $S2 ) = IO::Async::OS->socketpair( $family, $socktype, $proto )

An abstraction of the C syscall, where any argument may be
missing (or given as C).

If C<$family> is not provided, a suitable value will be provided by the OS
(likely C on POSIX-based platforms). If C<$socktype> is not provided,
then C will be used.

Additionally, this method supports building connected C or
C pairs in the C family even if the underlying platform's
C does not, by connecting two normal sockets together.

C<$family> and C<$socktype> may also be given symbolically as defined by
C and C.

=cut

sub socketpair
{
   my $self = shift;
   my ( $family, $socktype, $proto ) = @_;

   require IO::Socket;

   # PF_UNSPEC and undef are both false
   $family = $self->getfamilybyname( $family ) || AF_UNIX;

   # SOCK_STREAM is the most likely
   $socktype = $self->getsocktypebyname( $socktype ) || SOCK_STREAM;

   $proto ||= 0;

   my ( $S1, $S2 ) = IO::Socket->new->socketpair( $family, $socktype, $proto );
   return ( $S1, $S2 ) if defined $S1;

   return unless $family == AF_INET and ( $socktype == SOCK_STREAM or $socktype == SOCK_DGRAM );

   # Now lets emulate an AF_INET socketpair call

   my $Stmp = IO::Async::OS->socket( $family, $socktype ) or return;
   $Stmp->bind( pack_sockaddr_in( 0, INADDR_LOOPBACK ) ) or return;

   $S1 = IO::Async::OS->socket( $family, $socktype ) or return;

   if( $socktype == SOCK_STREAM ) {
      $Stmp->listen( 1 ) or return;
      $S1->connect( getsockname $Stmp ) or return;
      $S2 = $Stmp->accept or return;

      # There's a bug in IO::Socket here, in that $S2 's ->socktype won't
      # yet be set. We can apply a horribly hacky fix here
      #   defined $S2->socktype and $S2->socktype == $socktype or
      #     ${*$S2}{io_socket_type} = $socktype;
      # But for now we'll skip the test for it instead
   }
   else {
      $S2 = $Stmp;
      $S1->connect( getsockname $S2 ) or return;
      $S2->connect( getsockname $S1 ) or return;
   }

   return ( $S1, $S2 );
}

=head2 pipepair

   ( $rd, $wr ) = IO::Async::OS->pipepair

An abstraction of the C syscall, which returns the two new handles.

=cut

sub pipepair
{
   my $self = shift;

   pipe( my ( $rd, $wr ) ) or return;
   return ( $rd, $wr );
}

=head2 pipequad

   ( $rdA, $wrA, $rdB, $wrB ) = IO::Async::OS->pipequad

This method is intended for creating two pairs of filehandles that are linked
together, suitable for passing as the STDIN/STDOUT pair to a child process.
After this function returns, C<$rdA> and C<$wrA> will be a linked pair, as
will C<$rdB> and C<$wrB>.

On platforms that support C, this implementation will be
preferred, in which case C<$rdA> and C<$wrB> will actually be the same
filehandle, as will C<$rdB> and C<$wrA>. This saves a file descriptor in the
parent process.

When creating a L or subclass of it, the C
and C parameters should always be used.

   my ( $childRd, $myWr, $myRd, $childWr ) = IO::Async::OS->pipequad;

   $loop->open_process(
      stdin  => $childRd,
      stdout => $childWr,
      ...
   );

   my $str = IO::Async::Stream->new(
      read_handle  => $myRd,
      write_handle => $myWr,
      ...
   );
   $loop->add( $str );

=cut

sub pipequad
{
   my $self = shift;

   # Prefer socketpair
   if( my ( $S1, $S2 ) = $self->socketpair ) {
      return ( $S1, $S2, $S2, $S1 );
   }

   # Can't do that, fallback on pipes
   my ( $rdA, $wrA ) = $self->pipepair or return;
   my ( $rdB, $wrB ) = $self->pipepair or return;

   return ( $rdA, $wrA, $rdB, $wrB );
}

=head2 signame2num

   $signum = IO::Async::OS->signame2num( $signame )

This utility method converts a signal name (such as "TERM") into its system-
specific signal number. This may be useful to pass to C or use
in other places which use numbers instead of symbolic names.

=cut

my %sig_num;
sub _init_signum
{
   my $self = shift;
   # Copypasta from Config.pm's documentation

   our %Config;
   require Config;
   Config->import;

   unless($Config{sig_name} && $Config{sig_num}) {
      die "No signals found";
   }
   else {
      my @names = split ' ', $Config{sig_name};
      @sig_num{@names} = split ' ', $Config{sig_num};
   }
}

sub signame2num
{
   my $self = shift;
   my ( $signame ) = @_;

   %sig_num or $self->_init_signum;

   return $sig_num{$signame};
}

=head2 extract_addrinfo

   ( $family, $socktype, $protocol, $addr ) = IO::Async::OS->extract_addrinfo( $ai )

Given an ARRAY or HASH reference value containing an addrinfo, returns a
family, socktype and protocol argument suitable for a C call and an
address suitable for C or C.

If given an ARRAY it should be in the following form:

   [ $family, $socktype, $protocol, $addr ]

If given a HASH it should contain the following keys:

   family socktype protocol addr

Each field in the result will be initialised to 0 (or empty string for the
address) if not defined in the C<$ai> value.

The family type may also be given as a symbolic string as defined by
C.

The socktype may also be given as a symbolic string; C, C or
C; this will be converted to the appropriate C constant.

Note that the C field, if provided, must be a packed socket address,
such as returned by C or C.

If the HASH form is used, rather than passing a packed socket address in the
C field, certain other hash keys may be used instead for convenience on
certain named families.

=over 4

=cut

use constant ADDRINFO_FAMILY   => 0;
use constant ADDRINFO_SOCKTYPE => 1;
use constant ADDRINFO_PROTOCOL => 2;
use constant ADDRINFO_ADDR     => 3;

sub extract_addrinfo
{
   my $self = shift;
   my ( $ai, $argname ) = @_;

   $argname ||= "addr";

   my @ai;

   if( ref $ai eq "ARRAY" ) {
      @ai = @$ai;
   }
   elsif( ref $ai eq "HASH" ) {
      $ai = { %$ai }; # copy so we can delete from it
      @ai = delete @{$ai}{qw( family socktype protocol addr )};

      if( defined $ai[ADDRINFO_FAMILY] and !defined $ai[ADDRINFO_ADDR] ) {
         my $family = $ai[ADDRINFO_FAMILY];
         my $method = "_extract_addrinfo_$family";
         my $code = $self->can( $method ) or croak "Cannot determine addr for extract_addrinfo on family='$family'";

         $ai[ADDRINFO_ADDR] = $code->( $self, $ai );

         keys %$ai and croak "Unrecognised '$family' addrinfo keys: " . join( ", ", keys %$ai );
      }
   }
   else {
      croak "Expected '$argname' to be an ARRAY or HASH reference";
   }

   $ai[ADDRINFO_FAMILY]   = $self->getfamilybyname( $ai[ADDRINFO_FAMILY] );
   $ai[ADDRINFO_SOCKTYPE] = $self->getsocktypebyname( $ai[ADDRINFO_SOCKTYPE] );

   # Make sure all fields are defined
   $ai[$_] ||= 0 for ADDRINFO_FAMILY, ADDRINFO_SOCKTYPE, ADDRINFO_PROTOCOL;
   $ai[ADDRINFO_ADDR]  = "" if !defined $ai[ADDRINFO_ADDR];

   return @ai;
}

=item family => 'inet'

Will pack an IP address and port number from keys called C and C.
If C is missing it will be set to "0.0.0.0". If C is missing it will
be set to 0.

=cut

sub _extract_addrinfo_inet
{
   my $self = shift;
   my ( $ai ) = @_;

   my $port = delete $ai->{port} || 0;
   my $ip   = delete $ai->{ip}   || "0.0.0.0";

   return pack_sockaddr_in( $port, inet_aton( $ip ) );
}

=item family => 'inet6'

Will pack an IP address and port number from keys called C and C.
If C is missing it will be set to "::". If C is missing it will be
set to 0. Optionally will also include values from C and C
keys if provided.

This will only work if a C function can be found in
C

=cut

sub _extract_addrinfo_inet6
{
   my $self = shift;
   my ( $ai ) = @_;

   my $port     = delete $ai->{port}     || 0;
   my $ip       = delete $ai->{ip}       || "::";
   my $scopeid  = delete $ai->{scopeid}  || 0;
   my $flowinfo = delete $ai->{flowinfo} || 0;

   if( HAVE_SOCKADDR_IN6 ) {
      return pack_sockaddr_in6( $port, inet_pton( AF_INET6, $ip ), $scopeid, $flowinfo );
   }
   else {
      croak "Cannot pack_sockaddr_in6";
   }
}

=item family => 'unix'

Will pack a UNIX socket path from a key called C.

=cut

sub _extract_addrinfo_unix
{
   my $self = shift;
   my ( $ai ) = @_;

   defined( my $path = delete $ai->{path} ) or croak "Expected 'path' for extract_addrinfo on family='unix'";

   return pack_sockaddr_un( $path );
}

=pod

=back

=cut

=head2 make_addr_for_peer

   $connectaddr = IO::Async::OS->make_addr_for_peer( $family, $listenaddr )

Given the C and C of a listening socket. creates an
address suitable to C to it.

This method will handle specially any C address bound to
C or any C address bound to C, as some OSes
do not allow Cing to those and would instead insist on receiving
C or C respectively.

This method is used by the C<< ->connect( peer => $sock ) >> parameter of
handle and loop connect methods.

=cut

sub make_addr_for_peer
{
   shift;
   my ( $p_family, $p_addr ) = @_;

   if( $p_family == Socket::AF_INET ) {
      my @params = Socket::unpack_sockaddr_in $p_addr;
      $params[1] = Socket::INADDR_LOOPBACK if $params[1] eq Socket::INADDR_ANY;
      return Socket::pack_sockaddr_in @params;
   }
   if( HAVE_SOCKADDR_IN6 and $p_family == Socket::AF_INET6 ) {
      my @params = Socket::unpack_sockaddr_in6 $p_addr;
      $params[1] = Socket::IN6ADDR_LOOPBACK if $params[1] eq Socket::IN6ADDR_ANY;
      return Socket::pack_sockaddr_in6 @params;
   }

   # Most other cases should be fine
   return $p_addr;
}

=head1 LOOP IMPLEMENTATION METHODS

The following methods are provided on C because they are likely
to require OS-specific implementations, but are used by L to
implement its functionality. It can use the HASH reference C<< $loop->{os} >>
to store other data it requires.

=cut

=head2 loop_watch_signal

=head2 loop_unwatch_signal

   IO::Async::OS->loop_watch_signal( $loop, $signal, $code )

   IO::Async::OS->loop_unwatch_signal( $loop, $signal )

Used to implement the C / C Loop pair.

=cut

sub _setup_sigpipe
{
   my $self = shift;
   my ( $loop ) = @_;

   require IO::Async::Handle;

   my ( $reader, $sigpipe ) = $self->pipepair or croak "Cannot pipe() - $!";
   $_->blocking( 0 ) for $reader, $sigpipe;

   $loop->{os}{sigpipe} = $sigpipe;

   my $sigwatch = $loop->{os}{sigwatch};

   $loop->add( $loop->{os}{sigpipe_reader} = IO::Async::Handle->new(
      notifier_name => "sigpipe",
      read_handle => $reader,
      on_read_ready => sub {
         sysread $reader, my $buffer, 8192 or return;
         foreach my $signum ( unpack "I*", $buffer ) {
            $sigwatch->{$signum}->() if $sigwatch->{$signum};
         }
      },
   ) );

   return $sigpipe;
}

sub loop_watch_signal
{
   my $self = shift;
   my ( $loop, $signal, $code ) = @_;

   exists $SIG{$signal} or croak "Unrecognised signal name $signal";
   ref $code or croak 'Expected $code as a reference';

   my $signum = $self->signame2num( $signal );
   my $sigwatch = $loop->{os}{sigwatch} ||= {}; # {$num} = $code

   my $sigpipe = $loop->{os}{sigpipe} // $self->_setup_sigpipe( $loop );

   my $signum_str = pack "I", $signum;
   $SIG{$signal} = sub { syswrite $sigpipe, $signum_str };

   $sigwatch->{$signum} = $code;
}

sub loop_unwatch_signal
{
   my $self = shift;
   my ( $loop, $signal ) = @_;

   my $signum = $self->signame2num( $signal );
   my $sigwatch = $loop->{os}{sigwatch} or return;

   delete $sigwatch->{$signum};
   undef $SIG{$signal};
}

=head2 potentially_open_fds

   @fds = IO::Async::OS->potentially_open_fds

Returns a list of filedescriptors which might need closing. By default this
will return C<0 .. _SC_OPEN_MAX>. OS-specific subclasses may have a better
guess.

=cut

sub potentially_open_fds
{
   return 0 .. OPEN_MAX_FD;
}

sub post_fork
{
   my $self = shift;
   my ( $loop ) = @_;

   if( $loop->{os}{sigpipe} ) {
      $loop->remove( $loop->{os}{sigpipe_reader} );
      undef $loop->{os}{sigpipe};

      my $sigwatch = $loop->{os}{sigwatch};

      foreach my $signal ( keys %SIG ) {
         my $signum = $self->signame2num( $signal ) or next;
         my $code = $sigwatch->{$signum} or next;

         $self->loop_watch_signal( $loop, $signal, $code );
      }
   }
}

=head1 AUTHOR

Paul Evans

=cut

0x55AA;