* Provide access to the GSM0808 TLV attributes so we can use it in
the nat code.
* Read the PAGING message, if it is paged by LAC we go through each
LAC and then attempt to find the proper BSC connection and then
send the message to that BSC.
Based on the token the NAT/MUX is capable of figuring out
which LAC this BSC is supposed to satisfy. This will be
needed for messages like paging that can be done by LAC.
* Create struct bsc_nat and move the various lists into this structure
* Create the VTY code
* Call the VTY init and parsing code
* Create functions to create the types..
* Add some stuff into the bsc_connection to be used for the NAT with
proper config files. E.g. to close the connection if the BSC does not
respond to a given command.
For the one MSC and n BSC case we need to patch the SCCP source
local reference on connection orientated links to avoid a clash.
For simple UDT packages we just let them pass and for SCCP connection
we have to:
1.) Create an entry on Connection Request
2.) Patch the entry on Connection Confirm, Connection Refuse,
Connection Release, DT1, Connect Release Complete
3.) Remove the entry on Connection Release Complete
The current code is blocking CRs, Release Complete from the MSC, and
creates the connection state only from the BSC side. The code to
assign a source reference is taken from sccp.c and handles wrap
arounds and such properly. We rely on the SCCP parser to fill out the
place to the source reference correctly so we can easily fix it.
The whole code is young and might contain bugs we need to resolve..
Introduce a bsc_nat_parse method to parse a IP Access method
into various parts. Write out the IPA Proto, in case SCCP is used,
store the msg type, pointers to the source/dest local reference and
other information.
Use the result of bsc_nat_parse inside the bsc_nat_filter method
to decide if the message should be dropped or not.
In the future the bsc_nat_parse result will be used for patching
SCCP references and other parts of the message.
The filter language should be able to filter the msg type of SCCP
messages and gain the "NOT" word in the filter language.
The first part is to analyze the IP Access Header and only forward
SCCP messages for now. In the future we might want to do MGCP
signalling through this protocol and connection as well and need to
update this then.
Harald actually pointed out that this feature is just NAT. We want
to connect n-real BSCs to one BSC Mux. We will talk the ip.access
protocol and SCCP over of this link.
The mux will drop certain GSM messages (like the reset), it will
replace source local reference (NAT functionality) and it will handle
some GSM08.08 specially.
Get the thing started...
Holger Hans Peter Freyther