krt.c

Adhoc无线网络路由协议源码

/*      
 * function to communicate and make changes to tke kernel IP routing table
 * 
 */

#include"krt.h"


/* Declaration of global variable */
int krt;

/* 
 *  init_rtsocket
 *
 *  Description:
 *    Initiates the socket through which commands to the
 *    kernels routing table are given.
 * 
 *  Arguments:
 *  Return:  
 *  int - File descriptor to the kernel routing table
 *       -1 on failure
 */
int 
init_rtsocket()
{  
  int fd = 0;
  int type = SOCK_DGRAM;
  
  /* Get socket for UDP or TCP */
  if ((fd = socket(AF_INET, type, 0)) < 0)
    return -1; /* Unable to create socket */
  
  return fd;
}

/*
 * gen_krtentry
 *
 * Description:
 *   Generates an entry for the kernel's routing table to be used
 *   both att addition and deletion of routes.
 *
 * Arguments:
 *   u_int32_t dst_ip - IP address to the destination
 *   u_int32_t gw_ip  - IP address to gateway of the route
 *
 * Returns:
 *   struct rtentry* - pointer to the entry
 */
struct rtentry*
gen_krtentry(u_int32_t dst_ip, u_int32_t gw_ip, char *dev)
{
  struct rtentry *new_rtentry;
  struct sockaddr_in dst;
  struct sockaddr_in gw;
  struct sockaddr_in genmask;
  
  if((new_rtentry = malloc(sizeof(struct rtentry))) == NULL)
    return NULL; /* Malloc failed */

  dst.sin_family = AF_INET;
  gw.sin_family = AF_INET;
  genmask.sin_family = AF_INET;
  
  dst.sin_addr.s_addr = dst_ip;
  gw.sin_addr.s_addr = gw_ip;
  /* modification by vikas to enable addition of default route */
  if(dst_ip == 0)
  {
  	genmask.sin_addr.s_addr = dst_ip ;
    new_rtentry->rt_flags = RTF_UP ;
  }
  else
  {
  	genmask.sin_addr.s_addr = inet_addr("255.255.255.255");
    new_rtentry->rt_flags = RTF_UP | RTF_HOST | RTF_GATEWAY;
  }
  
  new_rtentry->rt_metric = 0;
  new_rtentry->rt_dev = dev;
  new_rtentry->rt_dst = *(struct sockaddr*) &dst;
  new_rtentry->rt_gateway = *(struct sockaddr*) &gw;
  new_rtentry->rt_genmask = *(struct sockaddr*) &genmask;

  return new_rtentry;
}

/*
 * add_kroute
 *
 * Description:
 *   Adds a route to the kernel's routing table.
 *
 * Arguments:
 *   u_int32_t dst_ip - IP address to the destination
 *   u_int32_t gw_ip  - IP address to the gateway of the route
*    char *dev	- name of the device 
 *
 * Returns:
 *   int - 0 on success
 *        -1 on failure
 */
int
add_kroute(u_int32_t dst_ip, u_int32_t gw_ip, char *dev)
{
  struct rtentry  *new_krtentry;
	
 if ((new_krtentry = gen_krtentry(dst_ip, gw_ip, dev)) == NULL)
  {
	  fprintf(stderr,"add_kroute new_krt_entry");
    return -1; 
  }
  
  if(ioctl(krt, SIOCADDRT, (char*) new_krtentry) == -1)
  {
	  perror("ioctl in add_kroute");
    return -1;
  }

#ifdef DEBUG  
 	fprintf(stdout,"added route to kernel\n");
#endif   	

  return 0;
}

/*
 * del_kroute
 *
 * Description:
 *   Deletes a route from the kernel's routing table.
 *
 * Arguments:
 *   u_int32_t dst_ip - IP address to the destination
 *
 * Return:
 *   int - 0 on success
 *        -1 on failure
 */ 
int
del_kroute(u_int32_t dst_ip, u_int32_t gw_ip, char *dev)
{
  struct rtentry  *new_krtentry;

  if ((new_krtentry = gen_krtentry(dst_ip, gw_ip, dev)) == NULL)
  {
	  fprintf(stderr,"del_kroute new_krt_entry");
    return -1; 
  }
  
  if(ioctl(krt, SIOCDELRT, (char*) new_krtentry) == -1)
    /* SIOCDELRT failed */
  {
	  perror("del_kroute : ioctl");
    return -1;
  }
  
  return 0;
}