Hi, >> 2. What about FCS field in IEEE-802.15.4 header ? > > Usually FCS is stripped by the hardware or by software right after receiving > a frame. There is little point passing it down the stack.
There is one point :) For sniffing the channel (for example with wireshark) it would be nice to keep the FCS in the received frame. So one could see garbled frames in the sniffer output too, but gets a hint that there is something wrong with the frame. Actual the the monitor interfaces receive the FCS, but the implementation is somewhat odd here :/ In the rx path the FCS is removed first. Depending on the device driver this happens in hardwarem the driver (like in the rf230 driver [1]) or it will be removed in mac802154_subif_rx() [2] after checking it for correctness. Directly after this, the frame is given to mac802154_monitors_rx(), where a new FCS is calculated for this frame [3]. This FCS is somewhat useless now, because it is always correct, even if the original received frame was completely garbled :/ [1] https://github.com/torvalds/linux/blob/40706af0b246f416a35fc3e12dc695deca8da3ff/drivers/net/ieee802154/at86rf230.c#L611 [2] https://github.com/torvalds/linux/blob/32bad7e30f113a8a5cebe4704bf6519ab4383e1b/net/mac802154/rx.c#L64-L77 [3] https://github.com/torvalds/linux/blob/0606069d9ef538687957d41ed6387d665af7a643/net/mac802154/monitor.c#L76-L81 Sascha. > If the hardware handles > FCS, one can set the IEEE802154_HW_OMIT_CKSUM flag. > > > > -- Hi! I'm a .signature virus! Copy me into your ~/.signature to help me spread! ------------------------------------------------------------------------------ WatchGuard Dimension instantly turns raw network data into actionable security intelligence. It gives you real-time visual feedback on key security issues and trends. Skip the complicated setup - simply import a virtual appliance and go from zero to informed in seconds. http://pubads.g.doubleclick.net/gampad/clk?id=123612991&iu=/4140/ostg.clktrk _______________________________________________ Linux-zigbee-devel mailing list Linux-zigbee-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-zigbee-devel
