kernel - userspace communication, ng_socket

[serena zanetta]

I have a question involving the userspace and kernel communication.

I need to get a point where I can exchange data between netgraph nodes and a
program in the userland.

I have a netgraph node which receives network packets and sends them to the
program to be processed. The modified packets are then sent back to the same
node.



I thought to do it with the ng_socket node type. I’ve written a program that
creates two sockets (data and control) as reported in “All about netgraph”.
Then I’ve tried to assign the node a name with bind(), as follow:



#include <stdio.h>

#include <errno.h>

#include <netdb.h>

#include <stdlib.h>

#include <string.h>

#include <unistd.h>

#include <ctype.h>

#include <err.h>

#include <stddef.h>

#include <sys/types.h>

#include <sys/socket.h>

#include <netinet/in.h>

#include <arpa/inet.h>



#include <netgraph/ng_socket.h>



#define NGSA_OVERHEAD   (offsetof(struct sockaddr_ng, sg_data))



int

main()

{

      int s_control = -1, s_data = -1;

      struct sockaddr_ng *sg;



      s_control = socket(PF_NETGRAPH,SOCK_DGRAM,NG_CONTROL);



      strcpy(sg->sg_data,"SOCKET");

      sg->sg_family = AF_NETGRAPH;

      sg->sg_len = strlen(sg->sg_data) + 1 + NGSA_OVERHEAD;

      bind(s_control,(struct sockaddr *)sg,sg->sg_len)<0);

       …



      return 0;

}


If I look at ngctl to verify the ng_socket creation, no trace of it can be
found.

So I don't know how to proceed .. any suggestion?

Thank you,

Serena