NAME
IO::Socket::IP - Family-neutral IP socket supporting both IPv4 and IPv6
SYNOPSIS
use IO::Socket::IP;
my $sock = IO::Socket::IP->new(
PeerHost => "www.google.com",
PeerPort => "http",
Type => SOCK_STREAM,
) or die "Cannot construct socket - $@";
my $familyname = ( $sock->sockdomain == PF_INET6 ) ? "IPv6" :
( $sock->sockdomain == PF_INET ) ? "IPv4" :
"unknown";
printf "Connected to google via %s\n", $familyname;
DESCRIPTION
This module provides a protocol-independent way to use IPv4 and IPv6
sockets, intended as a replacement for IO::Socket::INET. Most
constructor arguments and methods are provided in a backward-compatible
way. For a list of known differences, see the IO::Socket::INET
INCOMPATIBILITES section below.
It uses the getaddrinfo(3) function to convert hostnames and service
names or port numbers into sets of possible addresses to connect to or
listen on. This allows it to work for IPv6 where the system supports
it, while still falling back to IPv4-only on systems which don't.
REPLACING IO::Socket DEFAULT BEHAVIOUR
By placing -register in the import list to IO::Socket::IP, it will
register itself with IO::Socket as the class that handles PF_INET. It
will also ask to handle PF_INET6 as well, provided that constant is
available.
Changing IO::Socket's default behaviour means that calling the
IO::Socket constructor with either PF_INET or PF_INET6 as the Domain
parameter will yield an IO::Socket::IP object.
use IO::Socket::IP -register;
my $sock = IO::Socket->new(
Domain => PF_INET6,
LocalHost => "::1",
Listen => 1,
) or die "Cannot create socket - $@\n";
print "Created a socket of type " . ref($sock) . "\n";
Note that -register is a global setting that applies to the entire
program; it cannot be applied only for certain callers, removed, or
limited by lexical scope.
CONSTRUCTORS
new
$sock = IO::Socket::IP->new( %args )
Creates a new IO::Socket::IP object, containing a newly created socket
handle according to the named arguments passed. The recognised
arguments are:
PeerHost => STRING
PeerService => STRING
Hostname and service name for the peer to connect() to. The service
name may be given as a port number, as a decimal string.
PeerAddr => STRING
PeerPort => STRING
For symmetry with the accessor methods and compatibility with
IO::Socket::INET, these are accepted as synonyms for PeerHost and
PeerService respectively.
PeerAddrInfo => ARRAY
Alternate form of specifying the peer to connect() to. This should be
an array of the form returned by Socket::getaddrinfo.
This parameter takes precedence over the Peer*, Family, Type and
Proto arguments.
LocalHost => STRING
LocalService => STRING
Hostname and service name for the local address to bind() to.
LocalAddr => STRING
LocalPort => STRING
For symmetry with the accessor methods and compatibility with
IO::Socket::INET, these are accepted as synonyms for LocalHost and
LocalService respectively.
LocalAddrInfo => ARRAY
Alternate form of specifying the local address to bind() to. This
should be an array of the form returned by Socket::getaddrinfo.
This parameter takes precedence over the Local*, Family, Type and
Proto arguments.
Family => INT
The address family to pass to getaddrinfo (e.g. AF_INET, AF_INET6).
Normally this will be left undefined, and getaddrinfo will search
using any address family supported by the system.
Type => INT
The socket type to pass to getaddrinfo (e.g. SOCK_STREAM,
SOCK_DGRAM). Normally defined by the caller; if left undefined
getaddrinfo may attempt to infer the type from the service name.
Proto => STRING or INT
The IP protocol to use for the socket (e.g. 'tcp', IPPROTO_TCP,
'udp',IPPROTO_UDP). Normally this will be left undefined, and either
getaddrinfo or the kernel will choose an appropriate value. May be
given either in string name or numeric form.
GetAddrInfoFlags => INT
More flags to pass to the getaddrinfo() function. If not supplied, a
default of AI_ADDRCONFIG will be used.
These flags will be combined with AI_PASSIVE if the Listen argument
is given. For more information see the documentation about
getaddrinfo() in the Socket module.
Listen => INT
If defined, puts the socket into listening mode where new connections
can be accepted using the accept method. The value given is used as
the listen(2) queue size.
ReuseAddr => BOOL
If true, set the SO_REUSEADDR sockopt
ReusePort => BOOL
If true, set the SO_REUSEPORT sockopt (not all OSes implement this
sockopt)
Broadcast => BOOL
If true, set the SO_BROADCAST sockopt
Sockopts => ARRAY
An optional array of other socket options to apply after the three
listed above. The value is an ARRAY containing 2- or 3-element
ARRAYrefs. Each inner array relates to a single option, giving the
level and option name, and an optional value. If the value element is
missing, it will be given the value of a platform-sized integer 1
constant (i.e. suitable to enable most of the common boolean
options).
For example, both options given below are equivalent to setting
ReuseAddr.
Sockopts => [
[ SOL_SOCKET, SO_REUSEADDR ],
[ SOL_SOCKET, SO_REUSEADDR, pack( "i", 1 ) ],
]
V6Only => BOOL
If defined, set the IPV6_V6ONLY sockopt when creating PF_INET6
sockets to the given value. If true, a listening-mode socket will
only listen on the AF_INET6 addresses; if false it will also accept
connections from AF_INET addresses.
If not defined, the socket option will not be changed, and default
value set by the operating system will apply. For repeatable
behaviour across platforms it is recommended this value always be
defined for listening-mode sockets.
Note that not all platforms support disabling this option. Some, at
least OpenBSD and MirBSD, will fail with EINVAL if you attempt to
disable it. To determine whether it is possible to disable, you may
use the class method
if( IO::Socket::IP->CAN_DISABLE_V6ONLY ) {
...
}
else {
...
}
If your platform does not support disabling this option but you still
want to listen for both AF_INET and AF_INET6 connections you will
have to create two listening sockets, one bound to each protocol.
MultiHomed
This IO::Socket::INET-style argument is ignored, except if it is
defined but false. See the IO::Socket::INET INCOMPATIBILITES section
below.
However, the behaviour it enables is always performed by
IO::Socket::IP.
Blocking => BOOL
If defined but false, the socket will be set to non-blocking mode.
Otherwise it will default to blocking mode. See the NON-BLOCKING
section below for more detail.
Timeout => NUM
If defined, gives a maximum time in seconds to block per connect()
call when in blocking mode. If missing, no timeout is applied other
than that provided by the underlying operating system. When in
non-blocking mode this parameter is ignored.
Note that if the hostname resolves to multiple address candidates,
the same timeout will apply to each connection attempt individually,
rather than to the operation as a whole. Further note that the
timeout does not apply to the initial hostname resolve operation, if
connecting by hostname.
This behviour is copied inspired by IO::Socket::INET; for more fine
grained control over connection timeouts, consider performing a
nonblocking connect directly.
If neither Type nor Proto hints are provided, a default of SOCK_STREAM
and IPPROTO_TCP respectively will be set, to maintain compatibility
with IO::Socket::INET. Other named arguments that are not recognised
are ignored.
If neither Family nor any hosts or addresses are passed, nor any
*AddrInfo, then the constructor has no information on which to decide a
socket family to create. In this case, it performs a getaddinfo call
with the AI_ADDRCONFIG flag, no host name, and a service name of "0",
and uses the family of the first returned result.
If the constructor fails, it will set $@ to an appropriate error
message; this may be from $! or it may be some other string; not every
failure necessarily has an associated errno value.
new (one arg)
$sock = IO::Socket::IP->new( $peeraddr )
As a special case, if the constructor is passed a single argument (as
opposed to an even-sized list of key/value pairs), it is taken to be
the value of the PeerAddr parameter. This is parsed in the same way,
according to the behaviour given in the PeerHost AND LocalHost PARSING
section below.
METHODS
As well as the following methods, this class inherits all the methods
in IO::Socket and IO::Handle.
sockhost_service
( $host, $service ) = $sock->sockhost_service( $numeric )
Returns the hostname and service name of the local address (that is,
the socket address given by the sockname method).
If $numeric is true, these will be given in numeric form rather than
being resolved into names.
The following four convenience wrappers may be used to obtain one of
the two values returned here. If both host and service names are
required, this method is preferable to the following wrappers, because
it will call getnameinfo(3) only once.
sockhost
$addr = $sock->sockhost
Return the numeric form of the local address as a textual
representation
sockport
$port = $sock->sockport
Return the numeric form of the local port number
sockhostname
$host = $sock->sockhostname
Return the resolved name of the local address
sockservice
$service = $sock->sockservice
Return the resolved name of the local port number
sockaddr
$addr = $sock->sockaddr
Return the local address as a binary octet string
peerhost_service
( $host, $service ) = $sock->peerhost_service( $numeric )
Returns the hostname and service name of the peer address (that is, the
socket address given by the peername method), similar to the
sockhost_service method.
The following four convenience wrappers may be used to obtain one of
the two values returned here. If both host and service names are
required, this method is preferable to the following wrappers, because
it will call getnameinfo(3) only once.
peerhost
$addr = $sock->peerhost
Return the numeric form of the peer address as a textual representation
peerport
$port = $sock->peerport
Return the numeric form of the peer port number
peerhostname
$host = $sock->peerhostname
Return the resolved name of the peer address
peerservice
$service = $sock->peerservice
Return the resolved name of the peer port number
peeraddr
$addr = $peer->peeraddr
Return the peer address as a binary octet string
as_inet
$inet = $sock->as_inet
Returns a new IO::Socket::INET instance wrapping the same filehandle.
This may be useful in cases where it is required, for
backward-compatibility, to have a real object of IO::Socket::INET type
instead of IO::Socket::IP. The new object will wrap the same underlying
socket filehandle as the original, so care should be taken not to
continue to use both objects concurrently. Ideally the original $sock
should be discarded after this method is called.
This method checks that the socket domain is PF_INET and will throw an
exception if it isn't.
NON-BLOCKING
If the constructor is passed a defined but false value for the Blocking
argument then the socket is put into non-blocking mode. When in
non-blocking mode, the socket will not be set up by the time the
constructor returns, because the underlying connect(2) syscall would
otherwise have to block.
The non-blocking behaviour is an extension of the IO::Socket::INET API,
unique to IO::Socket::IP, because the former does not support
multi-homed non-blocking connect.
When using non-blocking mode, the caller must repeatedly check for
writeability on the filehandle (for instance using select or IO::Poll).
Each time the filehandle is ready to write, the connect method must be
called, with no arguments. Note that some operating systems, most
notably MSWin32 do not report a connect() failure using write-ready; so
you must also select() for exceptional status.
While connect returns false, the value of $! indicates whether it
should be tried again (by being set to the value EINPROGRESS, or
EWOULDBLOCK on MSWin32), or whether a permanent error has occurred
(e.g. ECONNREFUSED).
Once the socket has been connected to the peer, connect will return
true and the socket will now be ready to use.
Note that calls to the platform's underlying getaddrinfo(3) function
may block. If IO::Socket::IP has to perform this lookup, the
constructor will block even when in non-blocking mode.
To avoid this blocking behaviour, the caller should pass in the result
of such a lookup using the PeerAddrInfo or LocalAddrInfo arguments.
This can be achieved by using Net::LibAsyncNS, or the getaddrinfo(3)
function can be called in a child process.
use IO::Socket::IP;
use Errno qw( EINPROGRESS EWOULDBLOCK );
my @peeraddrinfo = ... # Caller must obtain the getaddinfo result here
my $socket = IO::Socket::IP->new(
PeerAddrInfo => \@peeraddrinfo,
Blocking => 0,
) or die "Cannot construct socket - $@";
while( !$socket->connect and ( $! == EINPROGRESS || $! == EWOULDBLOCK ) ) {
my $wvec = '';
vec( $wvec, fileno $socket, 1 ) = 1;
my $evec = '';
vec( $evec, fileno $socket, 1 ) = 1;
select( undef, $wvec, $evec, undef ) or die "Cannot select - $!";
}
die "Cannot connect - $!" if $!;
...
The example above uses select(), but any similar mechanism should work
analogously. IO::Socket::IP takes care when creating new socket
filehandles to preserve the actual file descriptor number, so such
techniques as poll or epoll should be transparent to its reallocation
of a different socket underneath, perhaps in order to switch protocol
family between PF_INET and PF_INET6.
For another example using IO::Poll and Net::LibAsyncNS, see the
examples/nonblocking_libasyncns.pl file in the module distribution.
PeerHost AND LocalHost PARSING
To support the IO::Socket::INET API, the host and port information may
be passed in a single string rather than as two separate arguments.
If either LocalHost or PeerHost (or their ...Addr synonyms) have any of
the following special forms then special parsing is applied.
The value of the ...Host argument will be split to give both the
hostname and port (or service name):
hostname.example.org:http # Host name
192.0.2.1:80 # IPv4 address
[2001:db8::1]:80 # IPv6 address
In each case, the port or service name (e.g. 80) is passed as the
LocalService or PeerService argument.
Either of LocalService or PeerService (or their ...Port synonyms) can
be either a service name, a decimal number, or a string containing both
a service name and number, in a form such as
http(80)
In this case, the name (http) will be tried first, but if the resolver
does not understand it then the port number (80) will be used instead.
If the ...Host argument is in this special form and the corresponding
...Service or ...Port argument is also defined, the one parsed from the
...Host argument will take precedence and the other will be ignored.
split_addr
( $host, $port ) = IO::Socket::IP->split_addr( $addr )
Utility method that provides the parsing functionality described above.
Returns a 2-element list, containing either the split hostname and port
description if it could be parsed, or the given address and undef if it
was not recognised.
IO::Socket::IP->split_addr( "hostname:http" )
# ( "hostname", "http" )
IO::Socket::IP->split_addr( "192.0.2.1:80" )
# ( "192.0.2.1", "80" )
IO::Socket::IP->split_addr( "[2001:db8::1]:80" )
# ( "2001:db8::1", "80" )
IO::Socket::IP->split_addr( "something.else" )
# ( "something.else", undef )
join_addr
$addr = IO::Socket::IP->join_addr( $host, $port )
Utility method that performs the reverse of split_addr, returning a
string formed by joining the specified host address and port number.
The host address will be wrapped in [] brackets if required (because it
is a raw IPv6 numeric address).
This can be especially useful when combined with the sockhost_service
or peerhost_service methods.
say "Connected to ", IO::Socket::IP->join_addr( $sock->peerhost_service );
IO::Socket::INET INCOMPATIBILITES
* The behaviour enabled by MultiHomed is in fact implemented by
IO::Socket::IP as it is required to correctly support searching for a
useable address from the results of the getaddrinfo(3) call. The
constructor will ignore the value of this argument, except if it is
defined but false. An exception is thrown in this case, because that
would request it disable the getaddrinfo(3) search behaviour in the
first place.
* IO::Socket::IP implements both the Blocking and Timeout parameters,
but it implements the interaction of both in a different way.
In ::INET, supplying a timeout overrides the non-blocking behaviour,
meaning that the connect() operation will still block despite that
the caller asked for a non-blocking socket. This is not explicitly
specified in its documentation, nor does this author believe that is
a useful behaviour - it appears to come from a quirk of
implementation.
In ::IP therefore, the Blocking parameter takes precedence - if a
non-blocking socket is requested, no operation will block. The
Timeout parameter here simply defines the maximum time that a
blocking connect() call will wait, if it blocks at all.
In order to specifically obtain the "blocking connect then
non-blocking send and receive" behaviour of specifying this
combination of options to ::INET when using ::IP, perform first a
blocking connect, then afterwards turn the socket into nonblocking
mode.
my $sock = IO::Socket::IP->new(
PeerHost => $peer,
Timeout => 20,
) or die "Cannot connect - $@";
$sock->blocking( 0 );
This code will behave identically under both IO::Socket::INET and
IO::Socket::IP.
TODO
* Investigate whether POSIX::dup2 upsets BSD's kqueue watchers, and
if so, consider what possible workarounds might be applied.
AUTHOR
Paul Evans <leonerd@leonerd.org.uk>
a51b265b43