[vpp-dev] plugin to filter packets

[Alex Syrnikov]

Hello, VPP developers.


I need to hook on some feature graph, check every packet and remove matched.

I bound required IP for interface, hooked arc "ip4-local" (it can also
be "ip4-unicast") with my node "checker" and do not understand how to
write node function. My node function work if I enable plugin for interface.

If I use node with next nodes as created by extras/emacs/make-plugin.sh
VLIB_REGISTER_NODE (checker_node) =
{
  // ...
  .n_next_nodes = CHECKER_N_NEXT,
  .next_nodes = {
        [CHECKER_NEXT_DROP] = "error-drop",
  },
};


- so all packets dropped because next[0] = 0;


or "ip4-unicast" arc will be after my node to pass buffer there. So I do not

packets to further processing.


but how to drop matched buffers?

The best solution I found is to use vlib_buffer_free() or code like this

  vlib_node_t* drop_node = vlib_get_node_by_name (vm, (u8 *)"error-drop");
  vlib_frame_t* f = vlib_get_frame_to_node (vm, drop_node->index );
  f->n_vectors = 1;
  u32* to_next = vlib_frame_vector_args( f );
  to_next[0] = buffer_index;

  vlib_put_frame_to_node( vm, drop_node->index, f );

and remove matched buffer indexes from vlib_buffer_enqueue_to_next().


there is better way (this looks like hack).



vlib_buffer_enqueue_to_next (vm, node, from, nexts, frame->n_vectors)

but I do not understand how to get it.


next node on arc unmatched. What do I need to write in

.next_nodes of VLIB_REGISTER_NODE



Alex

I can't understand how to write plugin to filter some packets and passing others. I do not understand how to pass buffer to further nodes on arc in node function Also as I understand feature arc can have many features enabled and all packets will be processed by all nodes on arc, so I do not know which node on "ip4-local" understand what to write in .next_nodes except "error-drop" to pass unfiltered If I use .n_next_nodes = 0, all packets will pass to next node on feature arc, (I know vlib_get_node_by_name() can be moved out of loop - this is not important.) But this solution will break batch processing architecture of vpp and I think As I understand I just need to assign some index to next[0] which is nexts for Please help to write node function which will drop matched packets and pass to and how to drop matched buffers and pass others to next nodes on feature arc in node function.

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