Net::SIP::StatelessProxy(3) Simple implementation of a stateless proxy




This package implements a simple stateless SIP proxy. Basic idea is that the proxy has either a single or two legs and that the packets are exchanged between those legs, e.g. packets incoming on one leg will be forwarded through the other leg.

Because this is a stateless proxy no retransmits will be done by the proxy.

If the proxy should work as a registrar too it should be put after a Net::SIP::Registrar in a Net::SIP::ReceiveChain.

While forwarding the proxy will be insert itself into the packet, e.g. it will add Via and Record-Route header while forwarding requests.

Additionally it will rewrite the Contact header while forwarding packets (see below), e.g. if the Contact header points to some client it will rewrite it, so that it points to the proxy and if it already points to the proxy it will rewrite it back so that it again points to the client.


new ( %ARGS )
Creates a new stateless proxy. With %ARGS the behavior can be influenced:
The Net::SIP::Dispatcher object managing the proxy.
Callback which is used in rewriting Contact headers. If one puts user@host in it should rewrite it and if one puts something without '@' it should try to rewrite it back (and return () if it cannot rewrite it back).

A working default implementation is provided. If you want to implement your own: the callbacks gets the arguments contact, incoming_leg and outgoing_leg. For rewriting a contact of user@host the legs will be Net::SIP::Leg objects. For rewriting the contact back outgoing_leg can be either a leg object and you should check if it is the expected leg. Or it is a scalar reference which you should fill with the leg extracted from the contact. The function should return the new contact or nothing if there was nothing to rewrite or the rewrite failed.

If you want to have your own encryption for the rewritten contact you should defined a subroutine here, which gets "data" as the first and "dir" as the second parameter and should return the de/encrypted data. If "dir" is +1 it should encrypt and on -1 it should decrypt.

If not defined, then RC4 will be used with a (pseudo)random key, 4 byte (pseudo)random seed and 4 byte ``checksum'' (md5) over seed and data.

Optional Net::SIP::NATHelper::* object. When given it will be used to do NAT, e.g. if the incoming and outgoing legs are different it will rewrite the SDP bodies to use local sockets and the nathelper will transfer the RTP data between the local and the original sockets.
Usually the contact header will only be rewritten, if the incoming and outgoing leg are different. With this option one can force the rewrite, even if they are the same.


receive ( PACKET, LEG, FROM )
PACKET is the incoming packet, LEG is the Net::SIP::Leg where the packet arrived and FROM is the "ip:port" of the sender.

Called from the dispatcher on incoming packets. The packet will be rewritten ("Via" and "Record-Route" headers added, Contact modified) and then the packet will be forwarded.

For requests it can determine the target of the forwarded packet by looking at the route or if no route it looks at the URI. For responses it looks at the next Via header.

This will be called from receive while forwarding data. If nathelper is defined it will be used to rewrite SDP bodies and update nathelpers internal states to forward RTP data.

Return values are like forward_outgoing in Net::SIP::Leg, e.g. it will return "[code,text]" on error or "()" on success, where success can be that the packet was rewritten or that there was no need to touch it.