Couple of potential issues which I see:
1.) if this buffer is generated by vpp, it should be flagged as such
(b->flags |= VNET_BUFFER_LOCALLY_ORIGINATED;)
2.) I don't see it passed to another node - you need to create a frame
and associate the buffer with it, then pass the frame to the next node,
which would be either ip4-arp or ip4-rewrite for ipv4 case depending on
whether the arp resolution has taken place or not...
take a look at functions
bfd_udp_init() - where the next nodes are resolved
bfd_transport_udp4() - where the next node is decided and frame created
You can take a look at show error and show trace to see what happens to
the packet..
HTH,
Klement
Quoting Alessio Silvestro (2017-06-16 17:20:30)
> Dear Klement,
>
> thanks for the hint. I had a look at the code bfd_main.c and in particular
> at the function bfd_send_periodic().
>
> I wrote the function send_udp_packet() -- see below -- in order to send
> out UDP packets.
>
> The function is executed (I can see from the VPP terminal) and no
> exception is raised, however I do not see any packet out.
>
> 1 -- is the function correct or I am missing something?
>
> 2 -- if it is not correct, how I can see where the problem is?
>
> Thanks,
>
> Alessio
>
> static void send_udp_packet(vlib_main_t * vm, vlib_node_runtime_t * rt){
> u32 bi;
> vlib_buffer_alloc (vm, &bi, 1)
> vlib_buffer_t *b = vlib_get_buffer (vm, bi);
> ASSERT (b->current_data == 0);
> memset (vnet_buffer (b), 0, sizeof (*vnet_buffer (b)));
> VLIB_BUFFER_TRACE_TRAJECTORY_INIT (b);
> add_udp4_transport (vm,b);
> }
>
> int add_udp4_transport (vlib_main_t * vm, vlib_buffer_t * b)
> {
> vnet_buffer (b)->ip.adj_index[VLIB_RX] = ~0;
> vnet_buffer (b)->ip.adj_index[VLIB_TX]= ~0;
> vnet_buffer (b)->sw_if_index[VLIB_RX] = 0;
> vnet_buffer (b)->sw_if_index[VLIB_TX] = ~0;
> u8 *data;
> udp_header_t *udp;
> ip4_header_t *ip;
> data = vlib_buffer_get_current (b);
> udp = (udp_header_t *) (data - sizeof (udp_header_t));
> ip = (ip4_header_t *) ((u8 *) udp - sizeof (ip4_header_t));
> // Build packet header
> u32 src_address = 167772161; //[1]10.0.0.1 u32 version
> u32 dst_address = 167772162; // 10.0.0.2 u32 version
> ip->src_address.as_u32 = src_address;
> ip->dst_address.as_u32 = dst_address;
> ip->ip_version_and_header_length = 0x45;
> ip->ttl = 254;
> ip->protocol = IP_PROTOCOL_UDP; //0x45 == IP_PROTOCOL_UDP
> ip->length = clib_host_to_net_u16 (b->current_length + sizeof (*udp));
> ip->checksum = ip4_header_checksum (ip);
> udp->src_port = DNS_SERVER_PORT;
> udp->dst_port = DNS_DST_PORT;
> udp->length = clib_host_to_net_u16 (b->current_length);
> udp->checksum = 0;
> b->current_length = sizeof (*ip) + sizeof (*udp);
> return 1;
> }
>
> On Wed, Jun 14, 2017 at 6:56 PM, Klement Sekera -X (ksekera - PANTHEON
> TECHNOLOGIES at Cisco) <[2]ksek...@cisco.com> wrote:
>
> Hi Alessio,
>
> you can take a look at BFD code which
>
> a.) creates and sends its own UDP packets - bfd_main.c -
> bfd_send_periodic() creates, encapsulates (UDP) and sends a packet out
> b.) loops back packets received - bfd_udp.c - bfd_udp_echo_input()
>
> I'm not sure what's your use case, whether you are trying to reuse
> existing buffer, but one of these should fit it.
>
> Regards,
> Klement
>
> Quoting Alessio Silvestro (2017-06-14 17:22:14)
> > Dear all,
> > I implemented a new VPP node that receives UDP traffic using the
> following
> > function:
> >
> > udp_register_dst_port (vm, PORT, my_node.index , 1 /* is_ip4 */);
> >
> > I am able to parse the packet and I would like to be able to send
> back an
> > UDP packet.
> >
> > Looking at the source code, the only function that seems fit my
> scope is
> > the following (in ~/vpp/src/vnet/udp/udp.h)
> >
> > ip_udp_encap_one (vlib_main_t * vm, vlib_buffer_t * b0, u8 * ec0,
> word
> > ec_len,
> >
> > u8 is_ip4)
> >
> > Is that correct or there is another function for this purpose?
> >
> > Thanks in advance for any help.
> >
> > Best regards,
> >
> > Alessio
>
> References
>
> Visible links
> 1. http://10.0.0.1/
> 2. mailto:ksek...@cisco.com
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