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         } else {
  56             *vnet_hdr = 0;
  57         }
  58
  59         if (vnet_hdr_required && !*vnet_hdr) {
  60             qemu_error("vnet_hdr=1 requested, but no kernel "
  61                        "support for IFF_VNET_HDR available");
  62             close(fd);
  63             return -1;
  64         }
  65     }
  66
  67     if (ifname[0] != '\0')
  68         pstrcpy(ifr.ifr_name, IFNAMSIZ, ifname);
  69     else
  70         pstrcpy(ifr.ifr_name, IFNAMSIZ, "tap%d");
  71     ret = ioctl(fd, TUNSETIFF, (void *) &ifr);
  72     if (ret != 0) {
  73         fprintf(stderr, "warning: could not configure /dev/net/tun: no virtual network emulation\n");
  74         close(fd);
  75         return -1;
  76     }
  77     pstrcpy(ifname, ifname_size, ifr.ifr_name);
  78     fcntl(fd, F_SETFL, O_NONBLOCK);
  79     return fd;
  80 }
  81
  82 /* sndbuf should be set to a value lower than the tx queue
  83  * capacity of any destination network interface.
  84  * Ethernet NICs generally have txqueuelen=1000, so 1Mb is
  85  * a good default, given a 1500 byte MTU.
  86  */
  87 #define TAP_DEFAULT_SNDBUF 1024*1024
  88
  89 int tap_set_sndbuf(int fd, QemuOpts *opts)
  90 {
  91     int sndbuf;
  92
  93     sndbuf = qemu_opt_get_size(opts, "sndbuf", TAP_DEFAULT_SNDBUF);
  94     if (!sndbuf) {
  95         sndbuf = INT_MAX;
  96     }
  97
  98     if (ioctl(fd, TUNSETSNDBUF, &sndbuf) == -1 && qemu_opt_get(opts, "sndbuf")) {
  99         qemu_error("TUNSETSNDBUF ioctl failed: %s\n", strerror(errno));
 100         return -1;
 101     }
 102     return 0;
 103 }
 104
 105 int tap_probe_vnet_hdr(int fd)
 106 {
 107     struct ifreq ifr;
 108
 109     if (ioctl(fd, TUNGETIFF, &ifr) != 0) {
 110         qemu_error("TUNGETIFF ioctl() failed: %s\n", strerror(errno));
 111         return 0;
 112     }
 113
 114     return ifr.ifr_flags & IFF_VNET_HDR;
 115 }
 116
 117 int tap_probe_has_ufo(int fd)
 118 {
 119     unsigned offload;
 120
 121     offload = TUN_F_CSUM | TUN_F_UFO;
 122
 123     if (ioctl(fd, TUNSETOFFLOAD, offload) < 0)
 124         return 0;
 125
 126     return 1;
 127 }
 128
 129 void tap_fd_set_offload(int fd, int csum, int tso4,
 130                         int tso6, int ecn, int ufo)
 131 {
 132     unsigned int offload = 0;
 133
 134     /* Check if our kernel supports TUNSETOFFLOAD */
 135     if (ioctl(fd, TUNSETOFFLOAD, 0) != 0 && errno == EINVAL) {
 136         return;
 137     }
 138
 139     if (csum) {
 140         offload |= TUN_F_CSUM;
 141         if (tso4)
 142             offload |= TUN_F_TSO4;
 143         if (tso6)
 144             offload |= TUN_F_TSO6;
 145         if ((tso4 || tso6) && ecn)
 146             offload |= TUN_F_TSO_ECN;
 147         if (ufo)
 148             offload |= TUN_F_UFO;
 149     }
 150
 151     if (ioctl(fd, TUNSETOFFLOAD, offload) != 0) {
 152         offload &= ~TUN_F_UFO;
 153         if (ioctl(fd, TUNSETOFFLOAD, offload) != 0) {
 154             fprintf(stderr, "TUNSETOFFLOAD ioctl() failed: %s\n",
 155                     strerror(errno));
 156         }
 157     }
 158 }