###########################################################################
# Net::SIP::StatelessProxy
# implements a simple stateless proxy
# all packets will be forwarded between Leg#1 to Leg#2. If there is
# only one leg it will use only this leg.
###########################################################################
use strict;
use warnings;
package Net::SIP::StatelessProxy;
use fields qw( dispatcher rewrite_contact nathelper force_rewrite );
use Net::SIP::Util ':all';
use Digest::MD5 'md5_hex';
use Carp 'croak';
use List::Util 'first';
use Net::SIP::Debug;
###########################################################################
# creates new stateless proxy
# Args: ($class,%args)
# %args
# dispatcher: the Net::SIP::Dispatcher object managing the proxy
# rewrite_contact: callback to rewrite contact header. If called with from header
# it should return a string of form \w+. If called
# again with this string it should return the original header back.
# if called on a string without @ which cannot rewritten back it
# should return undef. If not given a reasonable default will be
# used.
# nathelper: Net::SIP::NAT::Helper used for rewrite SDP bodies.. (optional)
# force_rewrite: if true rewrite contact even if incoming and outgoing
# legs are the same
# Returns: $self
###########################################################################
sub new {
my ($class,%args) = @_;
my $self = fields::new( $class );
my $disp = $self->{dispatcher} =
delete $args{dispatcher} || croak 'no dispatcher given';
$self->{rewrite_contact} = delete $args{rewrite_contact}
|| [ \&_default_rewrite_contact, $self ];
$self->{nathelper} = delete $args{nathelper};
$self->{force_rewrite} = delete $args{force_rewrite};
return $self;
}
# default handler for rewriting, does simple XOR only,
# this is not enough if you need to hide internal addresses
sub _default_rewrite_contact {
my ($self,$contact) = @_;
my $secret = md5_hex(
sort { $a cmp $b }
map { $_->{proto}.':'.$_->{addr}.':'.$_->{port} }
$self->{dispatcher}->get_legs
);
my $new;
if ( $contact =~m{\@} ) {
# needs to be rewritten
$contact .= "MARKER";
my $lc = length($contact);
$secret = substr( $secret x int( $lc/length($secret) +1 ), 0,$lc );
# add 'r' in front of hex so it does not look like phone number
$new = 'r'.unpack( 'H*',( $contact ^ $secret ));
DEBUG( 100,"rewrite $contact -> $new" );
} elsif ( $contact =~m{^r([0-9a-f]+)$}i ) {
# needs to be written back
$new = pack( 'H*',$1 );
my $lc = length($new);
$secret = substr( $secret x int( $lc/length($secret) +1 ), 0,$lc );
$new = $new ^ $secret;
$new =~s{MARKER$}{} || return;
DEBUG( 100,"rewrite back $contact -> $new" );
} else {
# invalid format
DEBUG( 100,"no rewriting of $contact" );
}
return $new;
}
###########################################################################
# handle incoming requests
# Args: ($self,$packet,$leg,$from)
# $packet: Net::SIP::Request
# $leg: incoming leg
# $from: ip:port where packet came from
# Returns: TRUE if packet was fully handled
###########################################################################
sub receive {
my Net::SIP::StatelessProxy $self = shift;
my ($packet,$incoming_leg,$from) = @_;
DEBUG( 10,"received ".$packet->dump );
# Prepare for forwarding, e.g adjust headers
# (add record-route)
if ( my $err = $incoming_leg->forward_incoming( $packet )) {
my ($code,$text) = @$err;
DEBUG( 10,"ERROR while forwarding: $code, $text" );
return;
}
my $rewrite_contact = $self->{rewrite_contact};
my $disp = $self->{dispatcher};
# find out how to forward packet
my %entry = (
packet => $packet,
incoming_leg => $incoming_leg,
from => $from,
outgoing_leg => [],
dst_addr => [],
);
if ( $packet->is_response ) {
# find out outgoing leg by checking (and removing) top via
if ( my ($via) = $packet->get_header( 'via' )) {
my ($data,$param) = sip_hdrval2parts( via => $via );
my $branch = $param->{branch};
if ( $branch ) {
my @legs = $self->{dispatcher}->get_legs( sub => sub {
my $lb = shift->{branch};
$lb eq substr($branch,0,length($lb));
});
if (@legs) {
$entry{outgoing_leg} = \@legs;
# remove top via, see Leg::forward_incoming
my $via;
$packet->scan_header( via => [ sub {
my ($vref,$hdr) = @_;
if ( !$$vref ) {
$$vref = $hdr->{value};
$hdr->remove;
}
}, \$via ]);
}
}
}
__forward_response( $self, \%entry );
} else {
# check if the URI was handled by rewrite_contact
# this is the case where the Contact-Header was rewritten
# (see below) and a new request came in using the new
# contact header. In this case we need to rewrite the URI
# to reflect the original contact header
my ($to) = sip_hdrval2parts( uri => $packet->uri );
$to = $1 if $to =~m{<(\w+:\S+)>};
my ($pre,$name) = $to =~m{^(sips?:)(\S+)?\@};
if ( $name && ( my $back = invoke_callback( $rewrite_contact,$name ) )) {
$to = $pre.$back;
DEBUG( 10,"rewrote URI from '%s' back to '%s'", $packet->uri, $to );
$packet->set_uri( $to )
}
$self->__forward_request_getleg( \%entry );
}
}
###########################################################################
# Get destination address from Via: header in response
# Calls __forward_response_1 either directly or after resolving hostname
# of destination to IP
###########################################################################
sub __forward_response {
my Net::SIP::StatelessProxy $self = shift;
my $entry = shift;
my $packet = $entry->{packet};
# find out where to send packet by parsing the upper via
# which should contain the addr of the next hop
my ($via) = $packet->get_header( 'via' ) or do {
DEBUG( 10,"no via header in packet. DROP" );
return;
};
my ($first,$param) = sip_hdrval2parts( via => $via );
my ($addr,$port) = $first =~m{([\w\-\.]+)(?::(\d+))?\s*$};
$port ||= 5060; # FIXME default for sip, not sips!
$addr = $param->{maddr} if $param->{maddr};
$addr = $param->{received} if $param->{received}; # where it came from
$port = $param->{rport} if $param->{rport}; # where it came from
@{ $entry->{dst_addr}} = ( "$addr:$port" );
DEBUG( 50,"get dst_addr from via header: $first -> $addr:$port" );
if ( $addr !~m{^[0-9\.]+$} ) {
$self->{dispatcher}->dns_host2ip(
$addr,
[ \&__forward_response_1,$self,$entry ]
);
} else {
__forward_response_1($self,$entry);
}
}
###########################################################################
# Called from _forward_response directly or indirectly after resolving
# hostname of destination.
# Calls __forward_packet_final at the end to deliver packet
###########################################################################
sub __forward_response_1 {
my Net::SIP::StatelessProxy $self = shift;
my $entry = shift;
if ( @_ ) {
my ($errno,$ip) = @_;
unless ( $ip ) {
DEBUG( 10,"cannot resolve address $entry->{dst_addr}[0]" );
return;
}
# replace host part in dst_addr with ip
$entry->{dst_addr}[0] =~s{^(udp:|tcp:)?([^:]+)}{$1$ip};
}
__forward_packet_final( $self,$entry );
}
###########################################################################
# Forwards request
# try to find outgoing_leg from Route header
# if there are more Route headers it picks the destination address from next
###########################################################################
sub __forward_request_getleg {
my Net::SIP::StatelessProxy $self = shift;
my $entry = shift;
return $self->__forward_request_getdaddr($entry)
if @{$entry->{outgoing_leg}};
my $packet = $entry->{packet};
my $disp = $self->{dispatcher};
# if the top route header points to a local leg we use this as outgoing leg
if ( my @route = $packet->get_header( 'route' ) ) {
$route[0] =~s{.*<}{} && $route[0] =~s{>.*}{};
my ($data,$param) = sip_hdrval2parts( route => $route[0] );
my ($addr,$port) = $data =~m{([\w\-\.]+)(?::(\d+))?\s*$};
$port ||= 5060; # FIXME sips
my @legs = $disp->get_legs( addr => $addr, port => $port );
if ( ! @legs ) {
$addr = $param->{maddr} if $param->{maddr};
@legs = $disp->get_legs( addr => $addr, port => $port );
}
if ( @legs ) {
DEBUG( 50,"setting leg from our route header: $data -> ".$legs[0]->dump );
$entry->{outgoing_leg} = \@legs;
shift(@route);
} else {
DEBUG( 50,"no legs which can deliver to $addr:$port (route)" );
}
if ( @route ) {
# still routing infos. Use next route as dst_addr
$route[0] =~s{.*<}{} && $route[0] =~s{>.*}{};
my ($data,$param) = sip_hdrval2parts( route => $route[0] );
my ($addr,$port) = $data =~m{([\w\-\.]+)(?::(\d+))?\s*$};
$port ||= 5060; # FIXME sips
if ( my $m = $param->{maddr} ) {
$addr = $m;
DEBUG( 50, "setting dst_addr from route $data;maddr=$m to $addr:$port" );
} else {
DEBUG( 50, "setting dst_addr from route $data to $addr:$port" );
}
@{ $entry->{dst_addr} } = ( "$addr:$port" );
}
} else {
DEBUG( 50,'no route header' );
}
$self->__forward_request_getdaddr($entry);
}
###########################################################################
# Forwards request
# try to find dst addr
# if it does not have destination address tries to resolve URI and then
# calls __forward_request_1
###########################################################################
sub __forward_request_getdaddr {
my Net::SIP::StatelessProxy $self = shift;
my $entry = shift;
return __forward_request_1( $self,$entry )
if @{ $entry->{dst_addr}};;
my $proto = $entry->{incoming_leg}{proto} eq 'tcp' ? [ 'tcp','udp' ]:undef;
my $packet = $entry->{packet};
my $disp = $self->{dispatcher};
DEBUG( 50,"need to resolve ".$packet->uri." proto=".( $proto ||'') );
return $disp->resolve_uri(
$packet->uri,
$entry->{dst_addr},
$entry->{outgoing_leg},
[ \&__forward_request_1,$self,$entry ],
$proto,
);
}
###########################################################################
# should have dst_addr now, but this might be still with non-IP hostname
# resolve it and go to __forward_request_2 or directly to __forward_packet_final
###########################################################################
sub __forward_request_1 {
my Net::SIP::StatelessProxy $self = shift;
my $entry = shift;
my $dst_addr = $entry->{dst_addr};
if ( ! @$dst_addr ) {
DEBUG( 10,"cannot find dst for uri ".$entry->{packet}->uri );
return;
}
my %hostnames;
foreach (@$dst_addr) {
my ($addr) = m{^(?:udp:|tcp:)?([^:]+)};
$hostnames{$addr} = undef if $addr !~m{^[0-9\.]+$};
}
if ( %hostnames ) {
$self->{dispatcher}->dns_host2ip(
\%hostnames,
[ \&__forward_request_2,$self,$entry ]
);
} else {
__forward_packet_final($self,$entry);
}
}
###########################################################################
# called after hostname for destination address got resolved
# calls __forward_packet_final
###########################################################################
sub __forward_request_2 {
my Net::SIP::StatelessProxy $self = shift;
my ($entry,$errno,$host2ip) = @_;
my $dst_addr = $entry->{dst_addr};
while ( my ($host,$ip) = each %$host2ip ) {
unless ( $ip ) {
DEBUG( 10,"cannot resolve address $host" );
@$dst_addr = grep { !m{^(?:\w*:)?\Q$host\E(?::)?} } @$dst_addr;
next;
} else {
DEBUG( 50,"resolved $host -> $ip" );
s{^(\w*:)?\Q$host\E(:)?}{$1$ip$2} for (@$dst_addr);
}
}
return unless @$dst_addr; # nothing could be resolved
__forward_packet_final( $self,$entry );
}
###########################################################################
# dst_addr is known and IP
# if no legs given use the one which can deliver to dst_addr
# if there are more than one try to pick best based on protocol
# but finally pick simply the first
# rewrite contact header
# call forward_outgoing on the outgoing_leg
# and finally deliver the packet
###########################################################################
sub __forward_packet_final {
my ($self,$entry) = @_;
my $dst_addr = $entry->{dst_addr};
my $legs = $entry->{outgoing_leg};
if ( !@$legs == @$dst_addr ) {
# get legs from dst_addr
my @all_legs = $self->{dispatcher}->get_legs;
@$legs = ();
my @addr;
foreach my $addr (@$dst_addr) {
my $leg = first { $_->can_deliver_to( $addr ) } @all_legs;
if ( ! $leg ) {
DEBUG( 50,"no leg for $addr" );
next;
}
push @addr,$addr;
push @$legs,$leg
}
@$dst_addr = @addr;
@$legs or do {
DEBUG( 10,"cannot find any legs" );
return;
};
}
my $incoming_leg = $entry->{incoming_leg};
if ( @$legs > 1 ) {
if ( $incoming_leg->{proto} eq 'tcp' ) {
# prefer tcp legs
my @tcp_legs = grep { $_->{proto} eq 'tcp' } @$legs;
@$legs = @tcp_legs if @tcp_legs;
}
}
# pick first
my $outgoing_leg = $legs->[0];
$dst_addr = $dst_addr->[0];
my $packet = $entry->{packet};
# rewrite contact header if outgoing leg is different to incoming leg
if ( ( $outgoing_leg != $incoming_leg or $self->{force_rewrite} ) and
(my @contact = $packet->get_header( 'contact' ))) {
my $rewrite_contact = $self->{rewrite_contact};
foreach my $c (@contact) {
# rewrite all sip(s) contacts
my ($data,$p) = sip_hdrval2parts( contact => $c );
my ($pre,$addr,$post) =
$data =~m{^(.*<sips?:)([^>\s]+)(>.*)}i ? ($1,$2,$3) :
$data =~m{^(sips?:)([^>\s]+)$}i ? ($1,$2,'') :
next;
# if contact was rewritten rewrite back
if ( $addr =~m{^(\w+)(\@.*)} &&
( my $back = $1 && invoke_callback($rewrite_contact,$1))) {
$addr = $back;
my $cnew = sip_parts2hdrval( 'contact', $pre.$addr.$post, $p );
DEBUG( 50,"rewrote back '$c' to '$cnew'" );
$c = $cnew;
# otherwise rewrite it
} else {
$addr = invoke_callback( $rewrite_contact,$addr);
$addr .= '@'.$outgoing_leg->{addr}.':'.$outgoing_leg->{port};
my $cnew = sip_parts2hdrval( 'contact', $pre.$addr.$post, $p );
DEBUG( 50,"rewrote '$c' to '$cnew'" );
$c = $cnew;
}
}
$packet->set_header( contact => \@contact );
}
if ( $outgoing_leg != $incoming_leg and $packet->is_request ) {
$incoming_leg->add_via($packet);
}
# prepare outgoing packet
if ( my $err = $outgoing_leg->forward_outgoing( $packet,$incoming_leg )) {
my ($code,$text) = @$err;
DEBUG( 10,"ERROR while forwarding: ".( defined($code) ? "$code, $text" : $text ));
return;
}
if ( my $err = $self->do_nat( $packet,$incoming_leg,$outgoing_leg ) ) {
my ($code,$text) = @$err;
DEBUG( 10,"ERROR while doing NAT: $code, $text" );
return;
}
# Just forward packet via the outgoing_leg
$self->{dispatcher}->deliver( $packet,
leg => $outgoing_leg,
dst_addr => $dst_addr,
do_retransmits => 0
);
}
############################################################################
# If a nathelper is given try to rewrite SDP bodies. If this fails
# (not enough resources) just drop packet, the sender will retry later
# (FIXME: this is only true in case of UDP, but not TCP)
#
# Args: ($self,$packet,$incoming_leg,$outgoing_leg)
# $packet: packet to forward
# $incoming_leg: where packet came in
# $outgoing_leg: where packet will be send out
# Returns: $error
# $error: undef | [ $code,$text ]
############################################################################
sub do_nat {
my Net::SIP::StatelessProxy $self = shift;
my ($packet,$incoming_leg,$outgoing_leg) = @_;
my $nathelper = $self->{nathelper} || do {
DEBUG( 100, "no nathelper" );
return;
};
# no NAT if outgoing leg is same as incoming leg
if ( $incoming_leg == $outgoing_leg ) {
DEBUG( 100,"no NAT because incoming leg is outgoing leg" );
return;
}
my $body = eval { $packet->sdp_body };
if ( $@ ) {
DEBUG( 10, "malformed SDP body" );
return [ 500,"malformed SDP body" ];
}
my ($request,$response) = $packet->is_request
? ( $packet,undef )
: ( undef,$packet )
;
my $method = $request ? $request->method : '';
# NAT for anything with SDP body
# activation and close of session will be done on ACK|CANCEL|BYE
unless ( $body
or $method eq 'ACK'
or $method eq 'CANCEL'
or $method eq 'BYE' ) {
DEBUG( 100, "no NAT because no SDP body and method is $method" );
return;
}
# find NAT data for packet:
# $idfrom and $idto are the IDs for FROM|TO which consist of
# the SIP address + (optional) Tag + Contact-Info from responsable
# Leg, delimited by "\0"
my ($idfrom,$idto);
if ( my $from = $packet->get_header( 'from' ) ) {
my ($data,$param) = sip_hdrval2parts( from => $from );
my $tag = $param->{tag} || '';
$idfrom = "$data\0$tag";
} else {
return [ 0,'no FROM header in packet' ]
}
if ( my $to = $packet->get_header( 'to' ) ) {
my ($data,$param) = sip_hdrval2parts( from => $to );
my $tag = $param->{tag} || '';
$idto = "$data\0$tag";
} else {
return [ 0,'no TO header in packet' ]
}
# side is either 0 (request) or 1 (response)
# If a request comes in 'from' points to the incoming_leg while
# 'to' points to the outgoing leg. For responses it's the other
# way around
my $side;
my $ileg = join( ':', @{ $incoming_leg }{qw(addr port)} );
my $oleg = join( ':', @{ $outgoing_leg }{qw(addr port)} );
if ( $request ) {
$idfrom .= "\0".$ileg;
$idto .= "\0".$oleg;
$side = 0;
} else {
$idfrom .= "\0".$oleg;
$idto .= "\0".$ileg;
$side = 1;
}
my ($cseq) = $packet->get_header( 'cseq' ) =~m{^(\d+)}
or return [ 0,'no CSEQ in packet' ];
my $callid = $packet->callid;
# CANCEL|BYE will be handled first to close session
# no NAT will be done, even if the packet contains SDP (which makes no sense)
if ( $method eq 'CANCEL' ) {
# keep cseq for CANCEL
DEBUG( 50,"close session $callid|$cseq because of CANCEL" );
$nathelper->close_session( $callid,$cseq,$idfrom,$idto );
return;
} elsif ( $method eq 'BYE' ) {
# no cseq for BYE, eg close all sessions in call
DEBUG( 50,"close call $callid because of BYE" );
$nathelper->close_session( $callid,undef,$idfrom,$idto );
return;
}
if ( $body ) {
DEBUG( 100,"need to NAT SDP body: ".$body->as_string );
my $new_media = $nathelper->allocate_sockets(
$callid,$cseq,$idfrom,$idto,$side,$outgoing_leg->{addr},
scalar( $body->get_media) );
if ( ! $new_media ) {
DEBUG( 10,"allocation of RTP session failed for $callid|$cseq $idfrom|$idto|$side" );
return [ 0,'allocation of RTP sockets failed' ];
}
$body->replace_media_listen( $new_media );
$packet->set_body( $body );
DEBUG( 100, "new SDP body: ".$body->as_string );
}
# Try to activate session as early as possible (for early data).
# In a lot of cases this will be too early, because I only have one
# site, but only in the case of ACK an incomplete session is invalid.
if ( ! $nathelper->activate_session( $callid,$cseq,$idfrom,$idto ) ) {
if ( $method eq 'ACK' ) {
DEBUG( 50,"session $callid|$cseq $idfrom -> $idto still incomplete in ACK" );
return [ 0,'incomplete session in ACK' ]
} else {
# ignore problem, session not yet complete
DEBUG( 100, "session $callid|$cseq $idfrom -> $idto not yet complete" );
}
} else {
DEBUG( 50,"activated session $callid|$cseq $idfrom -> $idto" )
}
return;
}
############################################################################
# convert idside (idfrom,idto) to hash
# Args: ?$class,$idside
# Returns: \%hash
# %hash: extracted info with keys address (sip address), tag, leg (ip:port)
############################################################################
sub idside2hash {
my $idside = pop;
my %hash;
@hash{qw/ address tag leg /} = split( "\0",$idside,3 );
return \%hash;
}
1;