Thanks for the suggestions. I neglected to mention that I'm printing out the PKT_UDP_SIZE() and PKT_UDP_DST() right before the memcpy(), I take into account the 8 byte UDP header and the size and port are correct. When performing the memcpy(), I am taking into account that PKT_UDP_DATA() returns a pointer of the payload and excludes the UDP header. However, I also have an 8 byte packet header within that payload (this gives me the mcnt, f-engine, and x-engine indices) and I exclude it when performing the memcpy(). This is what it looks like:
uint8_t * dest_p = db->block[idx].data + input_databuf_idx(m, f, 0,0,0); // This macro index shifts every mcnt and f-engine index const uint8_t * payload = (uint8_t *)(PKT_UDP_DATA(frame)+8); // Ignore packet header fprintf(...); // prints PKT_UDP_SIZE() and PKT_UDP_DST() memcpy(dest_p, payload, PKT_UDP_SIZE(frame) - 16) // Ignore both UDP (8 bytes) and packet header (8 bytes) I will look into the other possible issues that you suggested, but as far as I can tell, it doesn't seem like there should be a segfault given what I'm doing before that memcpy(). I will let you know what else I find. Thanks again, I really appreciate the help. Mark On Mon, May 25, 2020 at 4:30 PM David MacMahon <dav...@berkeley.edu> wrote: > 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 > <https://groups.google.com/a/lists.berkeley.edu/d/msgid/casper/297C1709-AE9C-488D-9110-FD0832BF5951%40berkeley.edu?utm_medium=email&utm_source=footer> > . > -- 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/CA%2B41hpxVHhDiD6RT6qK86ub3Tq3aQaTFxrGitKFMaNnRh3rKRw%40mail.gmail.com.
