diginet-probe: the first test on a real desk

diginet-probe wakes a Control|24 or ProControl, drives a few controls, logs everything the desk sends, and prints what it found. It is built on libdiginet and its transport and needs one capability, cap_net_raw, to open the packet socket. Nothing else on the machine is involved: no mixer, no DAW.

Before the probe: a passive capture (M0)

Cable the desk to a NIC of its own (directly, or through a 10/100 switch; never a network that carries anything else), power it on, and record two minutes without sending anything:

cat /sys/class/net/<if>/speed /sys/class/net/<if>/duplex
sudo tcpdump -i <if> -w c24-boot.pcap 'ether proto 0x885f'

Expected: e0 frames from 00:a0:7e:…, length 50, the name CNTRL|24 and a version, about 7 s apart.

Running it (M1)

make
sudo setcap cap_net_raw=ep ./tools/diginet-probe
./tools/diginet-probe -i <if>

Run tcpdump beside it to keep a capture of the whole session. The probe:

1. waits for the desk's e0 announce and prints its MAC, name, version and personality; if the desk is in a session with another host (e1 naming another MAC) it stops there;
2. sends e2;
3. requires an a0 and then an e1 naming this host, and prints where the host MAC sits in the e1 body;
4. keeps the session alive every 10 s (--keepalive);
5. moves fader 1 to mid-travel (B0 00 40 20 00) and says whether the desk ACKed it;
6. lights strip 1 MUTE (90 08 40), then turns it off;
7. writes OMX1 to strip 1's scribble at address 0x00, asks what the desk shows (type a word and Enter), then writes it at 0x20 and asks again;
8. logs and decodes every command from the desk for 60 s (--listen): press keys, touch and move fader 1, turn V-Pot 1 and the jog wheel;
9. sends e3 on exit (also on Ctrl-C).

It ends with a summary, one line per open question it can answer.

Exit status: 0 when every step was acknowledged; 2 for a usage error; 3 when the desk is in another host's session; 4 when no desk answered; 5 when the desk did not ACK our data.

setcap has to be repeated after every rebuild: a new binary carries no capability.

Every interface, with no capability (--any)

diginet-probe --any needs no interface name. It opens one packet socket bound to no interface, so it hears a desk on any NIC, a NIC plugged in after it started included, and talks to the desk from the MAC of the interface the desk appeared on. Where the probe holds no cap_net_raw, the socket comes from diginet-packet-helper (installed with that capability by the packages, or sudo setcap cap_net_raw=ep ./tools/diginet-packet-helper in the tree), and the probe says so:

./tools/diginet-probe --any --helper ./tools/diginet-packet-helper --listen 60

It logs desk <mac> appeared on <if> for every desk it hears and desk <mac> gone from <if> when one falls silent for 30 s, and ends with SUMMARY any interface: desks appeared on .... To see that an interface added later is heard: start the probe with the desk unplugged, plug in the USB NIC, then cable the desk to it; the desk appears on the new interface.

Which interface the desk is on is the probe's to report, not to choose: the socket hears EtherType 0x885F on every interface, a REAC link included.