The old idea was to take a msgb from gbprox_rcvmsg() and then
modify it and finally send it all the way down to nsip_sendmsg()
to the remote peer.
However, this introduces memory management difficulties, as we then
have to distinguish three cases:
* msgb was sent to a remote peer
* we sent some error message and need to free the msgb
* we need to make n-1 copies in case of a BSSVC-RESET from the SGSN
So instead we now simply always copy the message if we pass it on.
All messages received by gbprox_rcvmsg() are msgb_free()d in the very
same routine
All messages allocated by tx2peer() or tx2sgsn() are freed after
nsip_sendmsg()
Harald Welte
39d0bb5f7c