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 #include "qemu-error.h"
  35
  36 #define PATH_NET_TUN "/dev/net/tun"
  37
  38 int tap_open(char *ifname, int ifname_size, int *vnet_hdr, int vnet_hdr_required)
  39 {
  40     struct ifreq ifr;
  41     int fd, ret;
  42
  43     TFR(fd = open(PATH_NET_TUN, O_RDWR));
  44     if (fd < 0) {
  45         error_report("could not open %s: %m", PATH_NET_TUN);
  46         return -1;
  47     }
  48     memset(&ifr, 0, sizeof(ifr));
  49     ifr.ifr_flags = IFF_TAP | IFF_NO_PI;
  50
  51     if (*vnet_hdr) {
  52         unsigned int features;
  53
  54         if (ioctl(fd, TUNGETFEATURES, &features) == 0 &&
  55             features & IFF_VNET_HDR) {
  56             *vnet_hdr = 1;
  57             ifr.ifr_flags |= IFF_VNET_HDR;
  58         } else {
  59             *vnet_hdr = 0;
  60         }
  61
  62         if (vnet_hdr_required && !*vnet_hdr) {
  63             error_report("vnet_hdr=1 requested, but no kernel "
  64                          "support for IFF_VNET_HDR available");
  65             close(fd);
  66             return -1;
  67         }
  68     }
  69
  70     if (ifname[0] != '\0')
  71         pstrcpy(ifr.ifr_name, IFNAMSIZ, ifname);
  72     else
  73         pstrcpy(ifr.ifr_name, IFNAMSIZ, "tap%d");
  74     ret = ioctl(fd, TUNSETIFF, (void *) &ifr);
  75     if (ret != 0) {
  76         error_report("could not configure %s (%s): %m", PATH_NET_TUN, ifr.ifr_name);
  77         close(fd);
  78         return -1;
  79     }
  80     pstrcpy(ifname, ifname_size, ifr.ifr_name);
  81     fcntl(fd, F_SETFL, O_NONBLOCK);
  82     return fd;
  83 }
  84
  85 /* sndbuf should be set to a value lower than the tx queue
  86  * capacity of any destination network interface.
  87  * Ethernet NICs generally have txqueuelen=1000, so 1Mb is
  88  * a good default, given a 1500 byte MTU.
  89  */
  90 #define TAP_DEFAULT_SNDBUF 1024*1024
  91
  92 int tap_set_sndbuf(int fd, QemuOpts *opts)
  93 {
  94     int sndbuf;
  95
  96     sndbuf = qemu_opt_get_size(opts, "sndbuf", TAP_DEFAULT_SNDBUF);
  97     if (!sndbuf) {
  98         sndbuf = INT_MAX;
  99     }
 100
 101     if (ioctl(fd, TUNSETSNDBUF, &sndbuf) == -1 && qemu_opt_get(opts, "sndbuf")) {
 102         error_report("TUNSETSNDBUF ioctl failed: %s", strerror(errno));
 103         return -1;
 104     }
 105     return 0;
 106 }
 107
 108 int tap_probe_vnet_hdr(int fd)
 109 {
 110     struct ifreq ifr;
 111
 112     if (ioctl(fd, TUNGETIFF, &ifr) != 0) {
 113         error_report("TUNGETIFF ioctl() failed: %s", strerror(errno));
 114         return 0;
 115     }
 116
 117     return ifr.ifr_flags & IFF_VNET_HDR;
 118 }
 119
 120 int tap_probe_has_ufo(int fd)
 121 {
 122     unsigned offload;
 123
 124     offload = TUN_F_CSUM | TUN_F_UFO;
 125
 126     if (ioctl(fd, TUNSETOFFLOAD, offload) < 0)
 127         return 0;
 128
 129     return 1;
 130 }
 131
 132 void tap_fd_set_offload(int fd, int csum, int tso4,
 133                         int tso6, int ecn, int ufo)
 134 {
 135     unsigned int offload = 0;
 136
 137     /* Check if our kernel supports TUNSETOFFLOAD */
 138     if (ioctl(fd, TUNSETOFFLOAD, 0) != 0 && errno == EINVAL) {
 139         return;
 140     }
 141
 142     if (csum) {
 143         offload |= TUN_F_CSUM;
 144         if (tso4)
 145             offload |= TUN_F_TSO4;
 146         if (tso6)
 147             offload |= TUN_F_TSO6;
 148         if ((tso4 || tso6) && ecn)
 149             offload |= TUN_F_TSO_ECN;
 150         if (ufo)
 151             offload |= TUN_F_UFO;
 152     }
 153
 154     if (ioctl(fd, TUNSETOFFLOAD, offload) != 0) {
 155         offload &= ~TUN_F_UFO;
 156         if (ioctl(fd, TUNSETOFFLOAD, offload) != 0) {
 157             fprintf(stderr, "TUNSETOFFLOAD ioctl() failed: %s\n",
 158                     strerror(errno));
 159         }
 160     }
 161 }