tcpdump mailing list archives
Re: Add Sigfox support to libpcap
From: Guy Harris <gharris () sonic net>
Date: Thu, 10 Jan 2019 10:44:22 -0800
On Jan 10, 2019, at 10:17 AM, Jeija <jeija () jeija net> wrote:
1) Would the link-layer header include any radio metadata? For 802.11, there are various forms of radio metadata headers, such as the radiotap header: http://www.radiotap.org If so, what would the format of the radio metadata be?I would suggest something similar to what the LoRa people did with LoRaTap: https://github.com/eriknl/LoRaTap For the uplink, except for version / padding / length of course, I don't think we need anything other than the uplink frequency (Sigfox uses a continuous uplink band) and an RSSI value. For the downlink we should again have frequency and RSSI, but maybe also some metadata (sequence number / device ID) about the corresponding uplink (Sigfox is an uplink-initiated protocol, i.e. downlinks are only transmitted after they have been requested by a corresponding uplink and their scrambling depends on the uplink metadata, something that is described in patent EP3259864A1). But I'm not sure whether the link-layer header is the correct place for this kind of information?
Where *else* would it go in a pcap file? There *could* be additional metadata in the form of options in a pcapng file, but there's no such option for pcap. 802.11 has multiple link-layer header extensions for radio information, such as radiotap.
2) The 2.2.2 "Implementation by Sigfox" section of the spec shows, on page 14, a frame structure. In the captures, is the first byte of frame data (following the radio metadata, if there is radio metadata, or at the beginning of the packet, if there is no radio metadata), the first byte of the Preamble/Type?IMO the first byte of frame data should be the first byte of the "Type", since the "Preamble" is constant and just something that is used to detect the presence of a Sigfox uplink inside the uplink band and to synchronize the receiver.
So are you saying that the first byte of frame data should have the first 8 bits of the Type, with the next byte having 4 bits of Type and 4 bits of Flags?
Thank you two for your work, I'd be very happy to see this being integrated into libpcap :) !
"Integrated into libpcap" or "integrated into the link-layer header types page on tcpdump.org"? If you're just specifying a link-layer header type, the key part is "integrated into the link-layer header types page on tcpdump.org". Putting into pcap/dlt.h and pcap-common.c just acknowledges the addition to the link-layer header type page. _______________________________________________ tcpdump-workers mailing list tcpdump-workers () lists tcpdump org https://lists.sandelman.ca/mailman/listinfo/tcpdump-workers
Current thread:
- Add Sigfox support to libpcap jannisohms (Jan 08)
- Re: Add Sigfox support to libpcap Guy Harris (Jan 08)
- <Possible follow-ups>
- Re: Add Sigfox support to libpcap jannisohms (Jan 08)
- Re: Add Sigfox support to libpcap Guy Harris (Jan 08)
- Re: Add Sigfox support to libpcap Jeija (Jan 10)
- Re: Add Sigfox support to libpcap Guy Harris (Jan 10)
- Re: Add Sigfox support to libpcap Guy Harris (Jan 08)