Re: [dpdk-users] segmention fault while accessing mbuf

[Cliff Burdick <shaklee3@gmail.com>]

I can't tell from your code, but you assigned nb_rx to the number of
packets received, but then used vec_size, which might be larger. Does this
happen if you use nb_rx in your loops?

On Sat, Jun 6, 2020 at 5:59 AM Alex Kiselev <alex@therouter.net> wrote:

>
>
> > 1 июня 2020 г., в 19:17, Stephen Hemminger <stephen@networkplumber.org>
> написал(а):
> >
> > On Mon, 01 Jun 2020 15:24:25 +0200
> > Alex Kiselev <alex@therouter.net> wrote:
> >
> >> Hello,
> >>
> >> I've got a segmentation fault error in my data plane path.
> >> I am pretty sure the code where the segfault happened is ok,
> >> so my guess is that I somehow received a corrupted mbuf.
> >> How could I troubleshoot this? Is there any way?
> >> Is it possible that other threads of the application
> >> corrupted that mbuf?
> >>
> >> I would really appriciate any advice.
> >> Thanks.
> >>
> >> DPDK 18.11.3
> >> NIC: 82599ES
> >>
> >> Code:
> >>
> >> nb_rx = rte_eth_rx_burst(port_id, queue_id, pkts_burst,
> >>          MAX_PKT_BURST);
> >>
> >> ...
> >>
> >> for (i=0; i < vec_size; i++) {
> >>    rte_prefetch0(rte_pktmbuf_mtod(m_v[i], void *));
> >>
> >> for (i=0; i < vec_size; i++) {
> >>    m = m_v[i];
> >>    eth_hdr = rte_pktmbuf_mtod(m, struct ether_hdr *);
> >>    eth_type = rte_be_to_cpu_16(eth_hdr->ether_type);               <---
> >> Segmentation fault
> >>    ...
> >>
> >> #0  rte_arch_bswap16 (_x=<error reading variable: Cannot access memory
> >> at address 0x4d80000000053010>)
> >
> > Build with as many of the debug options turned on in the DPDK config,
> > and build with EXTRA_CFLAGS of -g.
>
> Could using an incorrect (a very big one) value of mbuf pkt_len and
> data_len while transmitting cause mbuf corruption and following
> segmentation fault on rx?
>