Re: [ath5k-devel] Ath5k Hardware Timestamping of Transmitted Packets
On Mon, Mar 19, 2012 at 10:50 PM, Qasim Javed qas...@gmail.com wrote: Hi Alexander, As Adrian mentioned, indeed there is a timestamp field in the transmit status descriptor which could be used for your purpose. This timestamp is basically the last 16-bits of a snapshot of the TSF counter. Since you are using a card based on AR5213 chipset, the TX status descriptor has 4 32-bit words. The function used to process the TX status descriptor for your card is then: ath5khw_proc_4word_tx_status (in desc.c) This is ath5k_hw_proc_4word_tx_status You will notice that within this function, the TX timestamp is recorded: Just a correction, the timestamp is not recorded here, but copied from the TX status descriptor. It is recorded at the last transmission attempt when the frame is put on air. ts-ts_tstamp = AR5K_REG_MS(txstat0, AR5K_DESC_TX_STATUS0_SEND_TIMESTAMP); where ts is of type struct ath5k_tx_status. Having described this, I should mention that I have had mixed experience when using this field. Some cards such as (Ubiquiti XR9) do not fill the value properly (or there is some bug in the firmware running on the card), for others such as AR5212 based cards, it works fine. From what little I know, in case there are multiple retransmissions, the reported TX timestamp is recorded when the frame is finally transmitted, that is at the last successful transmission attempt. I hope that helps. -Qasim On Wed, Mar 14, 2012 at 6:42 PM, Adrian Chadd adr...@freebsd.org wrote: I'd ignore wireshark for now. Look through the TX and TX completion code. There's a timestamp field somewhere that should be populated for all TXed frames. Verify first that the TSF is being written into that timestamp field upon completion, and then verify that it's pushed all the way back up through radiotap. Adrian ___ ath5k-devel mailing list ath5k-devel@lists.ath5k.org https://lists.ath5k.org/mailman/listinfo/ath5k-devel ___ ath5k-devel mailing list ath5k-devel@lists.ath5k.org https://lists.ath5k.org/mailman/listinfo/ath5k-devel
[ath5k-devel] Ath5k Hardware Timestamping of Transmitted Packets
Hello, I am working on a project where I need to be able to accurately timestamp both transmitted and received packets from an Atheros NIC. I am aware that in its normal mode of operation and that Ath5k only timestamps received packets and beacons. To get around this, I have tried running two NICs (Atheros based Ubiquiti SR2s, wlan0 and wlan1), where wlan0 transmits data frames and the second NIC wlan1 is in monitor mode. My intent was that the second NIC in monitor mode would receive the transmitted packets from wlan0 and time stamp them as well as other incoming packets. Unfortunately, there appears to be some level of filtering at the driver or possibly kernel level that prevents the second NIC from seeing the packets that have been sent out by the first NIC. Notes: ** I have read about some people flagging outgoing packets in Ath5k as beacons, which are timestamped by hardware, but am not sure where to look or implement this in the driver. ** I am not concerned about providing normal 802.11 operation with this system, just being able to transmit packets and accurately timestamp the associated transmit and receive times. Any suggestions about how to successfully timestamp transmitted and received packets using Ath5k would be much appreciated. Preferably, I'd like to do this with one NIC, but if there is an easier way to do this with two NICs that will work as well. Thanks -Alex ___ ath5k-devel mailing list ath5k-devel@lists.ath5k.org https://lists.ath5k.org/mailman/listinfo/ath5k-devel
Re: [ath5k-devel] Ath5k Hardware Timestamping of Transmitted Packets
Hi! On 14 March 2012 13:57, Alexander Watson zredli...@gmail.com wrote: Hello, I am working on a project where I need to be able to accurately timestamp both transmitted and received packets from an Atheros NIC. I am aware that in its normal mode of operation and that Ath5k only timestamps received packets and beacons. I believe all AR5212 and later NICs have a TX and RX timestamp in the completion descriptor. Does it not do what you want? Adrian ___ ath5k-devel mailing list ath5k-devel@lists.ath5k.org https://lists.ath5k.org/mailman/listinfo/ath5k-devel
Re: [ath5k-devel] Ath5k Hardware Timestamping of Transmitted Packets
Adrian, I am currently running a 5413, details attached below which does not appear to attach timestamps to packets that have been transmitted from the same interface. When I run wireshark (or tshark) on the wlan0 interface, I can see timestamps associated with all received packets. However, when I inject packets to the interface, I can see the packet payload but there is no timestamp information associated with packets transmitted from that interface. On the second (monitor) interface, I can only see the responses to the packets that I injected from wlan0, no payload or timestamp data for the injected packets. I know that the packets were sent correctly, because I can see the response from the client computer as well as monitor the whole interaction from a 2nd computer that is also running a 5413. Unfortunately, requiring a second computer will not work for my project. As for why I am unable to see packets injected from wlan0 on wlan1, it appears that some level of filtering (perhaps at the ath5k driver level) is preventing me from seeing the packets injected from wlan0 on wlan1. Also- to be clear, i am interested in the radiotap mactime (TSF counter), not the system time field. Example tshark command: tshark -i mon0 -R wlan.fc.type_subtype == 0x1b || wlan.fc.type_subtype == 0x1c -T fields -e frame.time -e radiotap.mactime -e radiotap.datarate -e radiotap.dbm_antsignal -e wlan.channel.freq -e wlan.fc.subtype -e wlan.ta -e wlan.ra Wireless card: 00:0e.0 Ethernet controller: Atheros Communications Inc. AR5413 802.11abg NIC (rev 01) Subsystem: Device 0777:3009 Flags: bus master, medium devsel, latency 168, IRQ 11 Memory at e008 (32-bit, non-prefetchable) [size=64K] Capabilities: [44] Power Management version 2 Kernel driver in use: ath5k Thanks Alex On Wed, Mar 14, 2012 at 5:09 PM, Adrian Chadd adr...@freebsd.org wrote: Hi! On 14 March 2012 13:57, Alexander Watson zredli...@gmail.com wrote: Hello, I am working on a project where I need to be able to accurately timestamp both transmitted and received packets from an Atheros NIC. I am aware that in its normal mode of operation and that Ath5k only timestamps received packets and beacons. I believe all AR5212 and later NICs have a TX and RX timestamp in the completion descriptor. Does it not do what you want? Adrian ___ ath5k-devel mailing list ath5k-devel@lists.ath5k.org https://lists.ath5k.org/mailman/listinfo/ath5k-devel
