Provided by: libnet-sip-perl_0.838-1_all 
NAME
Net::SIP::NATHelper::Base - rewrite SDP and transport RTP for NAT
DESCRIPTION
This module helps with doing NAT. It is implicitly used in do_nat from Net::SIP::StatelessProxy.
It cares about the rewriting the SDP bodies, forwarding RTP data for active sessions and expiring
sessions.
CONSTRUCTOR
new ( %ARGS )
Creates a new object. %ARGS can be of:
max_sockets N
Restricts the maximum number of sockets allocated inside the object to N.
max_sockets_in_group N
Restricts the maximum number of sockets allocated for a single socket group (e.g. a single
call to get_rtp_sockets) to N.
METHODS
allocate_sockets ( NAT_BASIC,SIDE,ADDR,MEDIA )
This is called to allocate new local sockets for MEDIA. MEDIA is a \@list of specifications like you
get from get_media in Net::SIP::SDP. ADDR is the local address, where the sockets should be
allocated.
NAT_BASIC consists of "<[ CALLID, CSEQ, IDFROM, IDTO, URI_FROM, URI_TO ]">.
IDFROM and IDTO represent the sides of the session, while SIDE helps to pick the right side for
allocation, e.g. if SIDE is 0 the sockets will be allocated on the IDFROM side, if it is 1 it will be
on the IDTO side. Thus for Requests SIDE will be 0, while for responses it will be 1.
CALLID and CSEQ are used to identify the SIP transaction, for which the NAT will be done, while
IDSIDE is either IDFROM or IDTO (see below) depending on the side, where the packet came in.
URI_FROM and URI_TO are primarily for information.
The methode will return the \@list of new media in the format needed by replace_media_listen in
Net::SIP::SDP, e.g tuples of "[ip,base_port]".
If the allocation of sockets failed (because of resource constraints) it will return undef. This will
usually cause the caller do simply not forward the packet and wait for the reetransmit (at least for
UDP).
activate_session ( NAT_BASIC ,[\%PARAM] )
NAT_BASIC is as described in "allocate_sockets" Activates a session in the transaction defined by
CALLID,CSEQ. This will cause all sessions for older transactions in the same call (identified by
CALLID) to shut down.
IDFROM and IDTO represent the sides of the session, e.g. for the activation to succeed there had to
be an allocate_sockets call for each of these sides.
PARAM is an optional hash reference. If given it will be added as user information to the new session
and given back in the information hash returned by close_session etc. URI_FROM and URI_TO will be
added to PARAM as "uri_from" and "uri_to".
The method returns two items: The first is information about the session like returned in
close_session, the second is a flag, which is true, if the activation was for an already astablished
session.
The method is usually called whenever a SDP body is given and on ACK requests.
close_session ( NAT_BASIC )
NAT_BASIC is as described before.
This will cause the close of the session described by the arguments (which have the same meaning like
in activate_session). Usually called for BYE or CANCEL requests. For CANCEL it will be called with
CSEQ (because it should cancel a specific transaction) while for BYE it will called with CSEQ undef,
because it should end all sessions in this call.
It will return a list with infos about all closed sessions. Each of these infos is a reference to a
hash with the following items:
callid
cseq
idfrom
idto
bytes_from - number of bytes received on the 'from' side
bytes_to - number of bytes received on the 'to' side
from - space delimited list of "ip:port/range" for the media on the 'from' side
to - same for the 'to' side
created - "time_t" when the session was created
Stateless proxies should forward the packet even if the session did not exist, because the packet
might be a retransmit referring to an already closed session.
expire ( [ %ARGS ] )
This causes the sessions and sockets to expire. It will return a list with a hash for each expired
session. See close_session for details on the returned information.
With %ARGS the behavior can be customized:
time Current time, can be given to save system call for getting current time.
unused Expire time for unused sockets. Default ist 180, e.g. 3 minutes.
active Expire time for active sessions. Default to 30 seconds. If no data gets transferred through
the session for "active" seconds the session will be closed.
closed Expire time for closed sessions, i.e. the time after which the sockets from a closed
(replaced) session will be closed too. They are usually kept open a short time in case
packets are still in transit. Default to 1 second.
callbacks
This will return a list (not a reference) of "[cbid,fd,callback]" pairs, where fd is the file
descriptor of the socket and callback is a callback for invoke_callback in Net::SIP::Util. cbid is a
uniq id for each callback so that one get compare the result from different calls to callbacks and
see, what changed.
Each of these callbacks should be invoked once the file descriptor gets readable and the callback
will then forward the received packet to the other side of the session.
sessions ( [ CALLBACK ] )
This will call CALLBACK on all sessions and return an array containing the results of the callbacks
together. If no CALLBACK is given it will return all session objects.
To use this function you might need to know the interna of the session objects (see source code), but
in most cases it is enough to know, that session objects have a method info_as_hash which will return
infos about the session as hash like described in close_session.
get_rtp_sockets ( NEW_ADDR, @MEDIA )
Allocates sockets for on address NEW_ADDR for @MEDIA. @MEDIA is in the format given by get_media in
Net::SIP::SDP.
Returns reference to array of allocated media, each item in the array is "[
ADDR,BASE_PORT,\@SOCKS,\@TARGETS ]", where ADDR is NEW_ADDR, BASE_PORT the base port for the
allocated sockets, @SOCKS the allocated sockets and @TARGETS the "sockaddr" of the original targets,
e.g. where it needs to forward the data received on the sockets.
If not all necssary sockets could be allocated it will allocate none and return "()".
This method might be redefined to better control resource allocation or to cache temporally unused
resources together with unget_rtp_sockets.
unget_rtp_sockets ( NEW_MEDIA )
Will take resources back. NEW_MEDIA is the result from get_rtp_sockets. Returns nothing.
Together with get_rtp_sockets it could be redefined to not destroy resources but to cache them for
future use.
dump
This method is used for debugging only. It will return a string with information about all calls
within this nathelper and all sessions and allocated sockets within the calls.
number_of_calls
Returns the number of calls within the nathelper. This vaalue has not much association with the
result of callbacks because there might be inactive sockets (not yet or no longer in active session)
which don't affect the result of callbacks.
This value can be used to determine if expire needs to be called at all.
perl v5.40.0 2024-09-08 Net::SIP::NATHelper::Base(3pm)