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