Hi, Mark, Sounds like progress!
> On May 25, 2020, at 13:56, Mark Ruzindana <ruziem...@gmail.com> wrote: > > I have been able to capture data with the first round of frames of the > circular buffer i.e. if I have 160 frames, I am able to capture packets of > frames 0 to 159 at which point right at the memcpy() in the process_packet() > function of the net thread, I get a segmentation fault. The fact that you get a the segfault right at the memcpy of the final frame of the ring buffer suggests that there is problem with the parameters passed to memcpy. Most likely src+length-1 exceeds the end of the frame so you get a segfault when memcpy tries to read from beyond the allocated memory. This would explain why it segfaults on the final frame and not the previous frames because reading beyond a previous frame still reads from "legal" (though incorrect) memory locations. It's also possible that the segfault happens due to a bad address on the destination side of the memcpy(), but unless the destination buffer is also 160 frames in size that seems less likely. The release_frame function is not likely to be a culprit here unless the pointer you are passing it differs from the pointer that the pktsock_recv function returned. For debugging, I suggest logging dst, src, len before calling memcpy. Normally you wouldn't generate a log message for every packet because that would ruin your throughput, but since you know it's going to crash after the first 160 packets there's not much throughout to ruin. :) One thing to remember is that PKT_UDP_DATA() evaluates to a pointer to the UDP payload of the packet, but PKT_UDP_SIZE() evaluates to the total UDP size (i.e. 8 bytes for the UDP header plus the length of the UDP payload). Passing PKT_UDP_SIZE() as "len" to memcpy without subtracting 8 for the header bytes is not correct and could potentially cause this problem. HTH, Dave -- You received this message because you are subscribed to the Google Groups "casper@lists.berkeley.edu" group. To unsubscribe from this group and stop receiving emails from it, send an email to casper+unsubscr...@lists.berkeley.edu. To view this discussion on the web visit https://groups.google.com/a/lists.berkeley.edu/d/msgid/casper/297C1709-AE9C-488D-9110-FD0832BF5951%40berkeley.edu.
