net/tap-linux.c

   1 /*
   2  * QEMU System Emulator
   3  *
   4  * Copyright (c) 2003-2008 Fabrice Bellard
   5  * Copyright (c) 2009 Red Hat, Inc.
   6  *
   7  * Permission is hereby granted, free of charge, to any person obtaining a copy
   8  * of this software and associated documentation files (the "Software"), to deal
   9  * in the Software without restriction, including without limitation the rights
  10  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  11  * copies of the Software, and to permit persons to whom the Software is
  12  * furnished to do so, subject to the following conditions:
  13  *
  14  * The above copyright notice and this permission notice shall be included in
  15  * all copies or substantial portions of the Software.
  16  *
  17  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  18  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  19  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  20  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  21  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  22  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  23  * THE SOFTWARE.
  24  */
  25
  26 #include "net/tap.h"
  27 #include "net/tap-linux.h"
  28
  29 #include <net/if.h>
  30 #include <sys/ioctl.h>
  31
  32 #include "sysemu.h"
  33 #include "qemu-common.h"
  34
  35 int tap_open(char *ifname, int ifname_size, int *vnet_hdr, int vnet_hdr_required)
  36 {
  37     struct ifreq ifr;
  38     int fd, ret;
  39
  40     TFR(fd = open("/dev/net/tun", O_RDWR));
  41     if (fd < 0) {
  42         fprintf(stderr, "warning: could not open /dev/net/tun: no virtual network emulation\n");
  43         return -1;
  44     }
  45     memset(&ifr, 0, sizeof(ifr));
  46     ifr.ifr_flags = IFF_TAP | IFF_NO_PI;
  47
  48     if (*vnet_hdr) {
  49         unsigned int features;
  50
  51         if (ioctl(fd, TUNGETFEATURES, &features) == 0 &&
  52             features & IFF_VNET_HDR) {
  53             *vnet_hdr = 1;
  54             ifr.ifr_flags |= IFF_VNET_HDR;
  55         }
  56
  57         if (vnet_hdr_required && !*vnet_hdr) {
  58             qemu_error("vnet_hdr=1 requested, but no kernel "
  59                        "support for IFF_VNET_HDR available");
  60             close(fd);
  61             return -1;
  62         }
  63     }
  64
  65     if (ifname[0] != '\0')
  66         pstrcpy(ifr.ifr_name, IFNAMSIZ, ifname);
  67     else
  68         pstrcpy(ifr.ifr_name, IFNAMSIZ, "tap%d");
  69     ret = ioctl(fd, TUNSETIFF, (void *) &ifr);
  70     if (ret != 0) {
  71         fprintf(stderr, "warning: could not configure /dev/net/tun: no virtual network emulation\n");
  72         close(fd);
  73         return -1;
  74     }
  75     pstrcpy(ifname, ifname_size, ifr.ifr_name);
  76     fcntl(fd, F_SETFL, O_NONBLOCK);
  77     return fd;
  78 }
  79
  80 /* sndbuf should be set to a value lower than the tx queue
  81  * capacity of any destination network interface.
  82  * Ethernet NICs generally have txqueuelen=1000, so 1Mb is
  83  * a good default, given a 1500 byte MTU.
  84  */
  85 #define TAP_DEFAULT_SNDBUF 1024*1024
  86
  87 int tap_set_sndbuf(int fd, QemuOpts *opts)
  88 {
  89     int sndbuf;
  90
  91     sndbuf = qemu_opt_get_size(opts, "sndbuf", TAP_DEFAULT_SNDBUF);
  92     if (!sndbuf) {
  93         sndbuf = INT_MAX;
  94     }
  95
  96     if (ioctl(fd, TUNSETSNDBUF, &sndbuf) == -1 && qemu_opt_get(opts, "sndbuf")) {
  97         qemu_error("TUNSETSNDBUF ioctl failed: %s\n", strerror(errno));
  98         return -1;
  99     }
 100     return 0;
 101 }
 102
 103 int tap_probe_vnet_hdr(int fd)
 104 {
 105     struct ifreq ifr;
 106
 107     if (ioctl(fd, TUNGETIFF, &ifr) != 0) {
 108         qemu_error("TUNGETIFF ioctl() failed: %s\n", strerror(errno));
 109         return 0;
 110     }
 111
 112     return ifr.ifr_flags & IFF_VNET_HDR;
 113 }