OK, actually, it is beeeeeeeeeeeeeeeeeeeeeeeeeeep.
The SIP code is making progress! It is not the target I wanted - which was a working phone call, but it is a good deal of progress. I have calls to the FireBrick being answered and feeding a 1KHz alaw tone nicely to the caller. When the call is ended the tone generation also stops (phew!).
I still have a lot of general call control to do, but the audio handling should be simple from now on - either relay from another RTP, or generate silence or tones. Plan is to have the standard tones, possibly with configuration. I also want to sort the telephone-event stuff when one end does out-of-band DTMF and the other does not, but mapping events to proper DTMF tones in-band.
The audio will need the call recording and monitoring logic at some point - that will be fun :-)
But getting close now. So maybe one day next week I'll have something we can issue for testing. Sorry it is taking so long.
I even fitted in watching the F1 this morning - but I think I have had enough coding for today.