Provide an option to forward packets with bad/missing CRC

[mullerch]

• [x] I have searched the issues of this repository and believe that this is not a duplicate.

Summary

Add an option, in the configuration file, to forward packets with bad/missing CRC. The same way the Semtech UDP Packet Forwarder does.

What is the use-case?

In case of device development, testing, debugging and diagnostic those packets can be useful on the server side.

Implementation description

At the check if CRC is ok, add a check on the options to see if the packet must be dropped.

Also, it seems that there is a little "bug" actually. If the CRC is missing, the log will report that there was a packet with bad crc: https://github.com/chirpstack/chirpstack-concentratord/blob/039b0b0058639f6b9365dcd60e0f0dfd9ec261e4/chirpstack-concentratord-2g4/src/handler/uplink.rs#L27

WARNING: the UDP forwarder connecting to the concentratord expects the CRC to be OK at this time and does override status. This means there must first be an adaptation of this software.

Can you implement this by yourself and make a pull request?

Yes possibly.

[brocaar]

Hi @mullerch I removed this (also from the v4 Protobuf messages), but I don't mind adding this back if there is an use-case for this.

[brocaar]

This is implemented by https://github.com/chirpstack/chirpstack-concentratord/commit/b9c36dd01e9b61b336e33f22afe6540e630624d1.

[brocaar]

This implements the filtering for the UDP forwarder: https://github.com/chirpstack/chirpstack-udp-forwarder/commit/6a7fb8ac93bd301ee9a72e2637bd572d95b599b6.