On Jan 10, 2019, at 10:17 AM, Jeija <je...@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
