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 "tap_int.h"
  27 #include "tap-linux.h"
  28 #include "net/tap.h"
  29
  30 #include <net/if.h>
  31 #include <sys/ioctl.h>
  32
  33 #include "sysemu/sysemu.h"
  34 #include "qemu-common.h"
  35 #include "qemu/error-report.h"
  36
  37 #define PATH_NET_TUN "/dev/net/tun"
  38
  39 int tap_open(char *ifname, int ifname_size, int *vnet_hdr,
  40              int vnet_hdr_required, int mq_required)
  41 {
  42     struct ifreq ifr;
  43     int fd, ret;
  44     int len = sizeof(struct virtio_net_hdr);
  45     unsigned int features;
  46
  47     TFR(fd = open(PATH_NET_TUN, O_RDWR));
  48     if (fd < 0) {
  49         error_report("could not open %s: %m", PATH_NET_TUN);
  50         return -1;
  51     }
  52     memset(&ifr, 0, sizeof(ifr));
  53     ifr.ifr_flags = IFF_TAP | IFF_NO_PI;
  54
  55     if (ioctl(fd, TUNGETFEATURES, &features) == -1) {
  56         error_report("warning: TUNGETFEATURES failed: %s", strerror(errno));
  57         features = 0;
  58     }
  59
  60     if (features & IFF_ONE_QUEUE) {
  61         ifr.ifr_flags |= IFF_ONE_QUEUE;
  62     }
  63
  64     if (*vnet_hdr) {
  65         if (features & IFF_VNET_HDR) {
  66             *vnet_hdr = 1;
  67             ifr.ifr_flags |= IFF_VNET_HDR;
  68         } else {
  69             *vnet_hdr = 0;
  70         }
  71
  72         if (vnet_hdr_required && !*vnet_hdr) {
  73             error_report("vnet_hdr=1 requested, but no kernel "
  74                          "support for IFF_VNET_HDR available");
  75             close(fd);
  76             return -1;
  77         }
  78         /*
  79          * Make sure vnet header size has the default value: for a persistent
  80          * tap it might have been modified e.g. by another instance of qemu.
  81          * Ignore errors since old kernels do not support this ioctl: in this
  82          * case the header size implicitly has the correct value.
  83          */
  84         ioctl(fd, TUNSETVNETHDRSZ, &len);
  85     }
  86
  87     if (mq_required) {
  88         if (!(features & IFF_MULTI_QUEUE)) {
  89             error_report("multiqueue required, but no kernel "
  90                          "support for IFF_MULTI_QUEUE available");
  91             close(fd);
  92             return -1;
  93         } else {
  94             ifr.ifr_flags |= IFF_MULTI_QUEUE;
  95         }
  96     }
  97
  98     if (ifname[0] != '\0')
  99         pstrcpy(ifr.ifr_name, IFNAMSIZ, ifname);
 100     else
 101         pstrcpy(ifr.ifr_name, IFNAMSIZ, "tap%d");
 102     ret = ioctl(fd, TUNSETIFF, (void *) &ifr);
 103     if (ret != 0) {
 104         if (ifname[0] != '\0') {
 105             error_report("could not configure %s (%s): %m", PATH_NET_TUN, ifr.ifr_name);
 106         } else {
 107             error_report("could not configure %s: %m", PATH_NET_TUN);
 108         }
 109         close(fd);
 110         return -1;
 111     }
 112     pstrcpy(ifname, ifname_size, ifr.ifr_name);
 113     fcntl(fd, F_SETFL, O_NONBLOCK);
 114     return fd;
 115 }
 116
 117 /* sndbuf implements a kind of flow control for tap.
 118  * Unfortunately when it's enabled, and packets are sent
 119  * to other guests on the same host, the receiver
 120  * can lock up the transmitter indefinitely.
 121  *
 122  * To avoid packet loss, sndbuf should be set to a value lower than the tx
 123  * queue capacity of any destination network interface.
 124  * Ethernet NICs generally have txqueuelen=1000, so 1Mb is
 125  * a good value, given a 1500 byte MTU.
 126  */
 127 #define TAP_DEFAULT_SNDBUF 0
 128
 129 int tap_set_sndbuf(int fd, const NetdevTapOptions *tap)
 130 {
 131     int sndbuf;
 132
 133     sndbuf = !tap->has_sndbuf       ? TAP_DEFAULT_SNDBUF :
 134              tap->sndbuf > INT_MAX  ? INT_MAX :
 135              tap->sndbuf;
 136
 137     if (!sndbuf) {
 138         sndbuf = INT_MAX;
 139     }
 140
 141     if (ioctl(fd, TUNSETSNDBUF, &sndbuf) == -1 && tap->has_sndbuf) {
 142         error_report("TUNSETSNDBUF ioctl failed: %s", strerror(errno));
 143         return -1;
 144     }
 145     return 0;
 146 }
 147
 148 int tap_probe_vnet_hdr(int fd)
 149 {
 150     struct ifreq ifr;
 151
 152     if (ioctl(fd, TUNGETIFF, &ifr) != 0) {
 153         error_report("TUNGETIFF ioctl() failed: %s", strerror(errno));
 154         return 0;
 155     }
 156
 157     return ifr.ifr_flags & IFF_VNET_HDR;
 158 }
 159
 160 int tap_probe_has_ufo(int fd)
 161 {
 162     unsigned offload;
 163
 164     offload = TUN_F_CSUM | TUN_F_UFO;
 165
 166     if (ioctl(fd, TUNSETOFFLOAD, offload) < 0)
 167         return 0;
 168
 169     return 1;
 170 }
 171
 172 /* Verify that we can assign given length */
 173 int tap_probe_vnet_hdr_len(int fd, int len)
 174 {
 175     int orig;
 176     if (ioctl(fd, TUNGETVNETHDRSZ, &orig) == -1) {
 177         return 0;
 178     }
 179     if (ioctl(fd, TUNSETVNETHDRSZ, &len) == -1) {
 180         return 0;
 181     }
 182     /* Restore original length: we can't handle failure. */
 183     if (ioctl(fd, TUNSETVNETHDRSZ, &orig) == -1) {
 184         fprintf(stderr, "TUNGETVNETHDRSZ ioctl() failed: %s. Exiting.\n",
 185                 strerror(errno));
 186         abort();
 187         return -errno;
 188     }
 189     return 1;
 190 }
 191
 192 void tap_fd_set_vnet_hdr_len(int fd, int len)
 193 {
 194     if (ioctl(fd, TUNSETVNETHDRSZ, &len) == -1) {
 195         fprintf(stderr, "TUNSETVNETHDRSZ ioctl() failed: %s. Exiting.\n",
 196                 strerror(errno));
 197         abort();
 198     }
 199 }
 200
 201 void tap_fd_set_offload(int fd, int csum, int tso4,
 202                         int tso6, int ecn, int ufo)
 203 {
 204     unsigned int offload = 0;
 205
 206     /* Check if our kernel supports TUNSETOFFLOAD */
 207     if (ioctl(fd, TUNSETOFFLOAD, 0) != 0 && errno == EINVAL) {
 208         return;
 209     }
 210
 211     if (csum) {
 212         offload |= TUN_F_CSUM;
 213         if (tso4)
 214             offload |= TUN_F_TSO4;
 215         if (tso6)
 216             offload |= TUN_F_TSO6;
 217         if ((tso4 || tso6) && ecn)
 218             offload |= TUN_F_TSO_ECN;
 219         if (ufo)
 220             offload |= TUN_F_UFO;
 221     }
 222
 223     if (ioctl(fd, TUNSETOFFLOAD, offload) != 0) {
 224         offload &= ~TUN_F_UFO;
 225         if (ioctl(fd, TUNSETOFFLOAD, offload) != 0) {
 226             fprintf(stderr, "TUNSETOFFLOAD ioctl() failed: %s\n",
 227                     strerror(errno));
 228         }
 229     }
 230 }
 231
 232 /* Enable a specific queue of tap. */
 233 int tap_fd_enable(int fd)
 234 {
 235     struct ifreq ifr;
 236     int ret;
 237
 238     memset(&ifr, 0, sizeof(ifr));
 239
 240     ifr.ifr_flags = IFF_ATTACH_QUEUE;
 241     ret = ioctl(fd, TUNSETQUEUE, (void *) &ifr);
 242
 243     if (ret != 0) {
 244         error_report("could not enable queue");
 245     }
 246
 247     return ret;
 248 }
 249
 250 /* Disable a specific queue of tap/ */
 251 int tap_fd_disable(int fd)
 252 {
 253     struct ifreq ifr;
 254     int ret;
 255
 256     memset(&ifr, 0, sizeof(ifr));
 257
 258     ifr.ifr_flags = IFF_DETACH_QUEUE;
 259     ret = ioctl(fd, TUNSETQUEUE, (void *) &ifr);
 260
 261     if (ret != 0) {
 262         error_report("could not disable queue");
 263     }
 264
 265     return ret;
 266 }
 267
 268 int tap_fd_get_ifname(int fd, char *ifname)
 269 {
 270     struct ifreq ifr;
 271
 272     if (ioctl(fd, TUNGETIFF, &ifr) != 0) {
 273         error_report("TUNGETIFF ioctl() failed: %s",
 274                      strerror(errno));
 275         return -1;
 276     }
 277
 278     pstrcpy(ifname, sizeof(ifr.ifr_name), ifr.ifr_name);
 279     return 0;
 280 }