unix_route_socket_sample.c

linux下路由套接的实现

#include <stdio.h>;
#include <unistd.h>;
#include <stropts.h>;
#include <sys/types.h>;
#include <sys/socket.h>;
#include <sys/ioctl.h>;
#include <net/route.h>;
#define SEQ 8888
#define BUFLEN sizeof(struct rt_msghdr)+512
#define RTA_MAX 8



main(int argc, char **argv)
{
	char *buf;
	struct rt_msghdr *bufptr;
	struct sockaddr_in *sockptr;
	struct sockaddr_in *sa, *result[RTA_MAX]; //RTA_MAX = 8
	int sockfd, n, i;

if (argc != 2) {
       printf("Usage: %s <ip>;\n", argv[0]);
       exit(-1);
}
sockfd = socket(AF_ROUTE, SOCK_RAW, 0 ); //create route socket


buf = (char *)calloc(1, BUFLEN);
bufptr = (struct rt_msghdr *)buf;
bufptr->rtm_msglen = sizeof(struct rt_msghdr) + sizeof(struct sockaddr_in);
bufptr->rtm_version = RTM_VERSION;
bufptr->rtm_type = RTM_GET;
bufptr->rtm_addrs = RTA_DST;
bufptr->rtm_pid = getpid();
bufptr->rtm_seq = SEQ;
sockptr = (struct sockaddr_in *)(bufptr+1);
sockptr->sin_family = AF_INET;
(sockptr->sin_addr).s_addr = inet_addr(argv[1]);
write(sockfd, bufptr, bufptr->rtm_msglen);
write(sockfd, bufptr, bufptr->rtm_msglen);
/***
The route sockets may be opened by other process, so when the kernel send mess
ages to all route sockets, we must used type, pid and seq to get what we wants
***/
do {
       n = read(sockfd, bufptr, BUFLEN);
}while (bufptr->rtm_type != RTM_GET || bufptr->rtm_pid != getpid() || bufptr->;
rtm_seq != SEQ);

  for (i = 0; i < RTA_MAX; i++){
       bzero(result[i], sizeof(struct sockaddr_in));
       if (bufptr->rtm_addrs == RTA_DST)
               memcpy(result[0], sockptr, sizeof(struct sockaddr_in));
       if (bufptr->rtm_addrs == RTA_GATEWAY)
               memcpy(result[1], sockptr+1, sizeof(struct sockaddr_in));
       if (bufptr->rtm_addrs == RTA_NETMASK)
               memcpy(result[2], sockptr+2, sizeof(struct sockaddr_in));
       if (bufptr->rtm_addrs == RTA_GENMASK)
               memcpy(result[3], sockptr+3, sizeof(struct sockaddr_in));
}
printf("out for\n");
if ((sa = result[RTA_DST]) != NULL)
       printf("Dest: %s\n", inet_ntoa(sa->sin_addr));
if ((sa = result[RTA_GATEWAY]) != NULL)
       printf("Gateway: %s\n", inet_ntoa(sa->sin_addr));
if ((sa = result[RTA_NETMASK]) != NULL)
       printf("Netmask: %s\n", inet_ntoa(sa->sin_addr));
if ((sa = result[RTA_GENMASK]) != NULL)
       printf("Genmask: %s\n", inet_ntoa(sa->sin_addr));
}