add scripts and tuntap.c

Blatt02/tuntap.c

@@ -0,0 +1,87 @@
+#include <assert.h>
+#include <sys/ioctl.h>
+#include <net/if.h>
+#include <linux/if_tun.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <stdint.h>
+
+#define CLEAR(x) memset(&(x), 0x00, sizeof(x))
+
+#define IFNAME "tap0"
+
+#define BUFLEN 1600
+
+static int tun_alloc(char *dev)
+{
+    struct ifreq ifr;
+    int fd, err;
+
+    if( (fd = open("/dev/net/tun", O_RDWR)) < 0 ) {
+        perror("Cannot open TUN/TAP dev\n"
+                    "Make sure one exists with "
+                    "'$ mknod /dev/net/tun c 10 200'");
+        exit(1);
+    }
+
+    CLEAR(ifr);
+
+    /* Flags: IFF_TUN   - TUN device (no Ethernet headers)
+     *        IFF_TAP   - TAP device
+     *
+     *        IFF_NO_PI - Do not provide packet information
+     */
+    ifr.ifr_flags = IFF_TAP | IFF_NO_PI;
+    if( *dev ) {
+        strncpy(ifr.ifr_name, dev, IFNAMSIZ);
+    }
+
+    if( (err = ioctl(fd, TUNSETIFF, (void *) &ifr)) < 0 ){
+        perror("ERR: Could not ioctl tun");
+        close(fd);
+        return err;
+    }
+
+    strcpy(dev, ifr.ifr_name);
+    return fd;
+}
+
+int main(int argc, char** argv) {
+
+  char dev[IFNAMSIZ];
+  int tun_fd;
+
+  if (argc > 1) {
+    assert(strlen(argv[1]) < IFNAMSIZ);
+    strcpy(dev, argv[1]);
+  } else {
+    strcpy(dev, IFNAME);
+  }
+
+  printf("device name: %s\n", dev);
+
+  tun_fd = tun_alloc(dev);
+
+  int running = 1;
+
+  uint8_t buf[BUFLEN];
+  while (running) {
+    int nread;
+
+    if ((nread = read(tun_fd, buf, BUFLEN)) < 0) {
+      perror("ERR: Read from tun_fd");
+      break;
+    }
+
+    printf("Read %d bytes from device %s\n", nread, dev);
+  }
+
+  close(tun_fd);
+
+  return EXIT_SUCCESS;
+}