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#include <unistd.h>
#include <stdio.h>
#include <string.h>
#include <netdb.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <stdlib.h>
#include <sys/ioctl.h>
#include <net/if.h>
#include <net/if_gre.h>
/*great = gre auto tunnel*/
int main(int argc,char *argv[]) {
struct sockaddr_in sa;
struct sockaddr_in from;
char in;
socklen_t sl=sizeof(struct sockaddr_in);
int so_inet=socket(AF_INET,SOCK_DGRAM,0);
int so=socket(AF_INET,SOCK_DGRAM,IPPROTO_UDP);
memset(&sa,0,(size_t)sizeof(struct sockaddr_in));
memset(&from,0,(size_t)sizeof(struct sockaddr_in));
if(argc < 4) {
printf("usage: %s interface address port\n",argv[0]);
printf("example: %s gre0 192.168.0.2 1013\n",argv[0]);
return 1;
}
sa.sin_addr.s_addr=inet_addr(argv[2]);
sa.sin_port=htons(atoi(argv[3]));
sa.sin_family=PF_INET;
bind(so,(struct sockaddr *)&sa,sizeof(sa));
recvfrom(so,&in,1,0,(struct sockaddr *)&from,&sl);
struct in_addr addr = {from.sin_addr.s_addr};
printf("setting remote end to %s:%d\n",inet_ntoa(addr),ntohs(from.sin_port));
connect(so,(struct sockaddr *)&from,sl);
struct ifreq *data;
data=malloc(sizeof(struct ifreq));
memset(data,0,sizeof(struct ifreq));
strcpy(data->ifr_name,argv[1]);
data->ifr_value=so;
printf("gressock: %d\n",ioctl(so_inet,GRESSOCK,data));//set socket
free(data);
return 0;
}
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