br_sigio.c

实现vpn网关用来建立 IP虚拟隧道

#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/time.h>
#include <sys/types.h>
#include <signal.h>
#include <errno.h>

#include <linux/if_tun.h>

extern int errno;

int bridge_term = 0;
int f1, f2;

void sig_io(int sig) 
{
   static char buf[1600];
   register int r;

   while( (r=read(f1, buf, sizeof(buf))) > 0 )
      write(f2, buf, r);
   if( r < 0 && (errno != EAGAIN && errno != EINTR) ) {
      bridge_term = 1;
      return;
   }

   while( (r=read(f2, buf, sizeof(buf))) > 0 )
      write(f1, buf, r);
   if( r < 0 && (errno != EAGAIN && errno != EINTR) ) {
      bridge_term = 1;
      return;
   }
}

int main(int argc, char *argv[])
{
   struct sigaction sa;
   char buf[20];

   if(argc < 2) {
      printf("Usage: bridge tap|tun\n");
      exit(1);
   }

   sprintf(buf,"/dev/%s%d",argv[1],0);
   f1 = open(buf, O_RDWR);

   sprintf(buf,"/dev/%s%d",argv[1],1);
   f2 = open(buf, O_RDWR);

   ioctl(f1, TUNSETNOCSUM, 1);
   ioctl(f2, TUNSETNOCSUM, 1);

   fcntl(f1, F_SETFL, O_NONBLOCK | O_ASYNC);
   fcntl(f2, F_SETFL, O_NONBLOCK | O_ASYNC);

   memset(&sa, 0, sizeof(sa));
   sa.sa_handler = sig_io;
   sigaction(SIGIO, &sa, NULL); 

   while( !bridge_term )
      sleep(1000); 
}