On 8/8/13 9:36 PM, "Dan Hordern" <[email protected]> wrote:
>Hi, > >I have a dual interface I350 card, which uses the igb driver, that I am >using as a poor mans DAG card. The idea is to receive packets on both >interfaces and use tcpdump to capture the packets for later analysis; >where >the the timestamp information in the analysis is important. > >I am using the 'adapter unsynced' input for tcpdump (arg -j), which tells >the card to use the raw hardware timestamps. The problem I am having is >that there is a very large offset between the timestamps on each >interface; >from memory it was 3600.xxx seconds. > >I am thinking that this may be caused by differing initial or >uninitialised >timestamp counter values? If there is any other possible reason than any >info would be appreciated. Assuming this is the cause, is there a way to >synchronously reset the timestamp counters for each interface? > >Thanks, >Dan Dan, Sorry to hear you're having an issue with timestamping on the I350! Can you please specify which driver/kernel you're on? If you're using the driver from SourceForge, how are you compiling and loading the driver? If you grab the latest version of igb from SourceForge, we initialize the clock on the I350 to the kernel time. It's important to note that each port on the I350 receives its own clock. Depending on board design and other factors, the clocks will naturally drift over time, but I wouldn't expect to be that far off. I'm not familiar with using tcpdump -j with adapter unsynced, but you can try a fresh rmmod/modprobe to force the clocks to re-initialize and see if you still see a big delta. You can also set the clocks to whatever you desire via a small app that opens an ioctl to each interface and calls settime on each interface. Cheers, Matthew Matthew Vick Linux Development Networking Division Intel Corporation ------------------------------------------------------------------------------ Get 100% visibility into Java/.NET code with AppDynamics Lite! It's a free troubleshooting tool designed for production. Get down to code-level detail for bottlenecks, with <2% overhead. Download for free and get started troubleshooting in minutes. http://pubads.g.doubleclick.net/gampad/clk?id=48897031&iu=/4140/ostg.clktrk _______________________________________________ E1000-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/e1000-devel To learn more about Intel® Ethernet, visit http://communities.intel.com/community/wired
