Flavio,
Thank you for the clarification. You explained it very well.
I don't want to wait for the miniflow_extraction, so I am left with parsing
packet myself.
Here is what I am doing now:
for(numb=0;numb<cnt; numb++)
{
uint8_t nw_proto;
const char *frame;
packet=packets->packets[numb];
const void *data = dp_packet_data(packet);
frame = data;
*dp_packet_reset_offsets(packet);*
* packet->l3_ofs = (char *)data - frame;*
* const struct ip_header *ip = dp_packet_l3(packet);*
nw_proto = ip->ip_proto;
VLOG_DBG("IP proto---> %d ", nw_proto); // This is 0
}
I followed almost the same approach of what is going in miniflow_extract.
nw_proto(ip protocol) is printing out to be 0.
I am using this code just before emc_processing and inside
dp_netdev_input__.
Can you please help me here?
Thanks
Krish
On Mon, Feb 18, 2019 at 8:11 PM Flavio Leitner <f...@sysclose.org> wrote:
> On Mon, Feb 18, 2019 at 11:05:53AM +0800, Krish wrote:
> > Thanks for reply Ben.
> > Does it mean that *miniflow_extract* will also initialize the L3 header
> > pointer?
>
> If you look at the miniflow_extract(), you will see that it calls
> dp_packet_reset_offsets(packet) which will set all the header pointers
> to their defaults meaning that they are not pointing to anything real.
>
> These pointers are used by dp_packet_l3 (or 4) functions to locate
> the header.
>
> Then if you continue following the function, you will notice that
> the code parses the packet from the outer header to the inner header
> and as the parser goes, it updates the header offsets, like this line:
>
> packet->l3_ofs = (char *)data - frame;
>
> At this point, you have the pointer to the l3 header and you could use
> dp_packet_l3().
>
>
> > But I am getting the correct values for *nw_proto* from the L3 header.
> > struct ip_header *ip = dp_packet_l3(packet);
> > nw_proto = ip->ip_proto;
> >
> > Any comments on this? Whether its right or wrong?
>
> When using DPDK, the packet is represented by two parts. One if the
> rte buffer (packet data) that comes from DPDK library and the second
> part is the packet's metadata (the offsets you need). This offsets
> are allocated in the stack at dp_netdev_process_rxq_port(), so most
> probably you are seeing old values from previous packets which
> happens to work, but they are not correct.
>
> As I said above miniflow_extract() initializes those offsets to a
> known state and then parse the packet to update with the correct
> values.
>
> In summary, you will need to either wait for miniflow_extract() or
> parse the packet yourself if you need the tcp port.
>
> HTH,
> fbl
>
>
>
> >
> > Thanks a lot for your patience and response.
> >
> > Regards
> >
> > Krish
> >
> > On Sat, Feb 16, 2019 at 10:09 AM Ben Pfaff <b...@ovn.org> wrote:
> >
> > > You are almost certainly dereferencing a null pointer.
> > >
> > > On Sat, Feb 16, 2019 at 09:02:17AM +0800, Krish wrote:
> > > > That code I showed before. It is working fine and crashing only when
> I
> > > > enable debugging.
> > > >
> > > > As *sruct tcp_header's tcp_src* has ovs_be16 type. How to store and
> print
> > > > this value ?
> > > >
> > > > Thanks
> > > >
> > > > On Sat, Feb 16, 2019, 08:43 Ben Pfaff <b...@ovn.org> wrote:
> > > >
> > > > > Then you're going to have to work harder since miniflow_extract()
> is
> > > > > what initializes the L4 header pointer.
> > > > >
> > > > > On Sat, Feb 16, 2019 at 08:39:08AM +0800, Krish wrote:
> > > > > > I am sorry, but I am trying not to use extracted flow. I want
> to use
> > > > > this
> > > > > > information before it goes to EMC.
> > > > > >
> > > > > >
> > > > > >
> > > > > > On Sat, Feb 16, 2019, 03:44 Ben Pfaff <b...@ovn.org> wrote:
> > > > > >
> > > > > > > On Fri, Feb 15, 2019 at 03:48:22PM +0800, Krish wrote:
> > > > > > > > Hi
> > > > > > > >
> > > > > > > > I want to store tcp_src, dst port in a variable.
> > > > > > > > This is what I am doing:
> > > > > > > > 1. Retrieve packet from dp_packet_batch one by one.
> > > > > > > > 2. Retrieving field values by extracting packets headers:
> > > > > > > >
> > > > > > > > struct ip_header *ip = dp_packet_l3(packet);
> > > > > > > > nw_proto = ip->ip_proto;
> > > > > > > > if(nw_proto == 6)
> > > > > > > > {
> > > > > > > > struct tcp_header *th = dp_packet_l4(packet);
> > > > > > > > // The following are the 2 different ways I am trying to
> print
> > > the
> > > > > > > tcp_src.
> > > > > > > > I have tried it 1 and 2 separately not at the same time.
> > > > > > > > //1 . Ovs crash at the below statement
> > > > > > > > uint16_t src = (uint16_t) ntohs(th->tcp_src);
> > > > > > > > VLOG_DBG( "tcp_src ---> %d", src );
> > > > > > > > //2. When I enable logging ovs crashes at
> this
> > > point
> > > > > > > > VLOG_DBG( "tcp_src ---> %d",
> ntohs(th->tcp_src)
> > > );
> > > > > > > >
> > > > > > > >
> > > > > > > > }
> > > > > > > >
> > > > > > > > Can anyone please help how to store tcp_src port value in a
> > > variable
> > > > > and
> > > > > > > > print it in vlogs?
> > > > > > > > Statement 2 is working fine if vlogs are disabled, but I
> want the
> > > > > port
> > > > > > > > value to be stored in a variable and then print.
> > > > > > >
> > > > > > > I'd just get it from the extracted flow instead of inventing
> new
> > > code
> > > > > to
> > > > > > > extract it.
> > > > > > >
> > > > >
> > >
>
> > _______________________________________________
> > discuss mailing list
> > disc...@openvswitch.org
> > https://mail.openvswitch.org/mailman/listinfo/ovs-discuss
>
>
>
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