LibBSD Network Drivers

17.2.2.1. LibBSD Network Drivers#

17.2.2.1.1. Tips for Testing a driver#

If you ported or wrote a driver and it does not work, try the following steps:

  1. Connect the target to a separate network interface on a PC via a switch. Configure a fixed IP address on that interface. If possible: Disable checksum offload for the network interface (ethtool on Linux, driver settings on Windows). Otherwise, Wireshark can not detect checksum errors. Start Wireshark on that interface on the PC.

  2. Start LibBSD ftpd01 test on the target.

  3. Configure a fixed IP address on the target using ifconfig on the RTEMS shell.

  4. Ping the IP of your PC from the target and the target from the PC.

  5. Check on the Wireshark if your PC receives packets from the target. If yes: Check if the PC responds to them. - If it responds, the target can send correctly formatted packets. - If your PC does not respond, check the packet content and checksums for

    errors like endianness, missing bytes, wrong bytes (can be a cache issue), wrong checksum (only works if checksum offloading has been disabled).

  6. Check interface statistics. Some drivers offer statistics via sysctl. Some basic information can also be printed using netstat independent of the driver.

  7. ftpd01 also provides a tcpdump that you can use to dump received packets on the target. With that it is possible to check whether the target receives packets but can not send them.

17.2.2.1.2. Cache Issues#

If you have problems with cache (wrong data sent or received, old data sent or received), check whether CPU_DATA_CACHE_ALIGNMENT is correctly defined for your target. Otherwise the bus_dma* functions will not work correctly.