Attempt to find the message by transaction id, then patch
the response and use the IP/PORT of the local network, update
the ci with the one from the BSC.
This is currently not tracking any state of the MGCP and will
not handle two bsc's... this will need to happen later.
With this in we should be feature complete and now enter the
mode of making all of this work reliable and fixing thinko's
and other bugs.
* Forward a rewritten msg to the BSS. We change the IP and port
to point to the NAT instead of the core network. We also keep
track of the BSC and the transacition id.
* Handle the case where we have not found a SCCP connection and
need to send a response ourselves.
Add code to change the ip and port for audio data inside
MGCP messages. This is needed because the BSS might be
behind the NAT and can not reach the network directly and
might be behind a nat so the announced sourceport is not
the one as we see it.
When losing the SCCP connection make sure that we free all
endpoints. The disconnection of the BSC should already make
sure they are closed but this makes sure everything is
properly reset.
For the nat we will have NAT and MGCP in the same process
and this commit starts with that. We are linking in the MGCP
code and one can embed MGCP config snippets...
* Return the SCCP connection. This will be needed to store the
assigned timeslot in there.
* Update code to work with this change
* This uncovered a bug in the CC handling, at the time the BSC was
passed it was still a null pointer and the code would have failed.
Moving it here means we can more easily test this code, there is one
behaviour change with the code that we only support paging messages
with one LAC and will silently ignore the others.
When sending a message to the MSC in the case of DT1
messages we only have the address of the MSC, so we
need to go with that, otherwise (e.g. in case of a CR, RLC)
we do have the source address and need to patch it.
When forwarding a message to the BSC we do receive
a msg that should contain the patched address, we need
to unpatch it...
On a CC message we will need to remeber where the source local
reference of the network belonged so we can properly identify
the connection when receiving UDT messages.
When we disconnect from the MSC handle it by pushing the problem
to our connected clients. We will simply close all connections,
reject all new BSC connections and attempt to reconnect to the MSC.
Create a BSC<->MSC interface and use it for the BSC MSC IP and the
BSC NAT to reduce code duplication on handling reconnects to the MSC
and cleaning up the local state. The code is only partially tested
and will contain bugs. Currently both the BSC and the NAT will just
exit on connection loss and this way have the current behavior.
The latency of setting up of the TCP connection can be quite high,
it is better to connect in a non blocking way. This code is working
by setting the socket nonblocking and temporarily replacing the
bfd callback with the connect handling.
Once the OS has connected our socket we switch back to normal operation.
In case we disconnect with some pending operations we will need to
signal the MSC that something is wrong. This could be by sending a
RLSD directly, or a clear command. Another part of the fix is to
respond with a RLC on unknown RLSD messages.
* 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.