mavp2p not routing ParamExt commands about mavp2p

[sanderux]

@aler9
i dove a little deeper and it seems it does route the messages but it seems to truncate the payload.
Using an older mavp2p the message comes through with many bytes populated towards the end of the payload, on the new mavp2p on the first 20 or so are populated, the rest is 0x0

[Autonomost]

@sanderux @aler9 I have also seen that when QGC or Mission Planner does not negotiate stream rates, and mavp2p is configured with --streamreqdisable I can no longer receive parameters or send commands.

[aler9]

Hello, since #18 and #29, the router forwards messages, addressed to a certain system ID and component ID, only to the node which is broadcasting that specific system ID and component ID.

Therefore, this bug may be caused by one of the following things:

• the router inability to route PARAM_EXT_SET messages to the desired target; this might be caused by the fact that the target doesn't broadcast its system ID or component ID and therefore the router doesn't send him the message
• the router inability to correctly re-encode PARAM_EXT_SET messages. In order to obtain TargetSystem and TargetComponent of a message, the router has to decode the message, and then to re-encode it.

Unfortunately i don't have ready-to-use SITLs that support PARAM_EXT_SET, therefore i was not able to replicate the issue. In order to debug further, we need network dumps of the data exchanged between the control station and the router, and between the router and the drone. They can be generated in this way:

1. Download wireshark (https://www.wireshark.org/)
2. Start capturing on the interface used for exchanging packets (if the router and the external hardware or software are both installed on your pc, the interface is probably "loopback", otherwise it's the one of your network card)
3. Start the router and replicate the issue
4. Stop capturing, save the result in .pcap format
5. Attach

[sanderux]

024/05/03 12:34:45 mavp2p v0.0.0
2024/05/03 12:34:45 router started with 2 endpoints
2024/05/03 12:34:45 channel opened: tcp:172.20.110.10:5799
2024/05/03 12:34:45 node appeared: chan=tcp:172.20.110.10:5799 sid=2 cid=101
2024/05/03 12:34:45 node appeared: chan=tcp:172.20.110.10:5799 sid=2 cid=154
2024/05/03 12:34:45 node appeared: chan=tcp:172.20.110.10:5799 sid=2 cid=1
2024/05/03 12:34:45 node appeared: chan=tcp:172.20.110.10:5799 sid=1 cid=194
2024/05/03 12:34:45 node appeared: chan=tcp:172.20.110.10:5799 sid=1 cid=191
2024/05/03 12:34:45 node appeared: chan=tcp:172.20.110.10:5799 sid=1 cid=236
2024/05/03 12:34:46 node appeared: chan=tcp:172.20.110.10:5799 sid=1 cid=51
2024/05/03 12:34:46 node appeared: chan=tcp:172.20.110.10:5799 sid=1 cid=192
2024/05/03 12:34:46 node appeared: chan=tcp:172.20.110.10:5799 sid=1 cid=155

2024/05/03 12:32:40 &frame.V2Frame{IncompatibilityFlag:0x0, CompatibilityFlag:0x0, SequenceNumber:0xc0, SystemID:0xff, ComponentID:0xbe, Message:(*common.MessageParamExtSet)(0xc000258ba0), Checksum:0x870f, SignatureLinkID:0x0, SignatureTimestamp:0x0, Signature:(*frame.V2Signature)(nil)}, &common.MessageParamExtSet{TargetSystem:0x2, TargetComponent:0x65, ParamId:"CAM_STREAM", ParamValue:"", ParamType:0x1}

Seems like ParamValue should not be empty