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         if (ifname[0] != '\0') {
  77             error_report("could not configure %s (%s): %m", PATH_NET_TUN, ifr.ifr_name);
  78         } else {
  79             error_report("could not configure %s: %m", PATH_NET_TUN);
  80         }
  81         close(fd);
  82         return -1;
  83     }
  84     pstrcpy(ifname, ifname_size, ifr.ifr_name);
  85     fcntl(fd, F_SETFL, O_NONBLOCK);
  86     return fd;
  87 }
  88
  89 /* sndbuf implements a kind of flow control for tap.
  90  * Unfortunately when it's enabled, and packets are sent
  91  * to other guests on the same host, the receiver
  92  * can lock up the transmitter indefinitely.
  93  *
  94  * To avoid packet loss, sndbuf should be set to a value lower than the tx
  95  * queue capacity of any destination network interface.
  96  * Ethernet NICs generally have txqueuelen=1000, so 1Mb is
  97  * a good value, given a 1500 byte MTU.
  98  */
  99 #define TAP_DEFAULT_SNDBUF 0
 100
 101 int tap_set_sndbuf(int fd, const NetdevTapOptions *tap)
 102 {
 103     int sndbuf;
 104
 105     sndbuf = !tap->has_sndbuf       ? TAP_DEFAULT_SNDBUF :
 106              tap->sndbuf > INT_MAX  ? INT_MAX :
 107              tap->sndbuf;
 108
 109     if (!sndbuf) {
 110         sndbuf = INT_MAX;
 111     }
 112
 113     if (ioctl(fd, TUNSETSNDBUF, &sndbuf) == -1 && tap->has_sndbuf) {
 114         error_report("TUNSETSNDBUF ioctl failed: %s", strerror(errno));
 115         return -1;
 116     }
 117     return 0;
 118 }
 119
 120 int tap_probe_vnet_hdr(int fd)
 121 {
 122     struct ifreq ifr;
 123
 124     if (ioctl(fd, TUNGETIFF, &ifr) != 0) {
 125         error_report("TUNGETIFF ioctl() failed: %s", strerror(errno));
 126         return 0;
 127     }
 128
 129     return ifr.ifr_flags & IFF_VNET_HDR;
 130 }
 131
 132 int tap_probe_has_ufo(int fd)
 133 {
 134     unsigned offload;
 135
 136     offload = TUN_F_CSUM | TUN_F_UFO;
 137
 138     if (ioctl(fd, TUNSETOFFLOAD, offload) < 0)
 139         return 0;
 140
 141     return 1;
 142 }
 143
 144 /* Verify that we can assign given length */
 145 int tap_probe_vnet_hdr_len(int fd, int len)
 146 {
 147     int orig;
 148     if (ioctl(fd, TUNGETVNETHDRSZ, &orig) == -1) {
 149         return 0;
 150     }
 151     if (ioctl(fd, TUNSETVNETHDRSZ, &len) == -1) {
 152         return 0;
 153     }
 154     /* Restore original length: we can't handle failure. */
 155     if (ioctl(fd, TUNSETVNETHDRSZ, &orig) == -1) {
 156         fprintf(stderr, "TUNGETVNETHDRSZ ioctl() failed: %s. Exiting.\n",
 157                 strerror(errno));
 158         assert(0);
 159         return -errno;
 160     }
 161     return 1;
 162 }
 163
 164 void tap_fd_set_vnet_hdr_len(int fd, int len)
 165 {
 166     if (ioctl(fd, TUNSETVNETHDRSZ, &len) == -1) {
 167         fprintf(stderr, "TUNSETVNETHDRSZ ioctl() failed: %s. Exiting.\n",
 168                 strerror(errno));
 169         assert(0);
 170     }
 171 }
 172
 173 void tap_fd_set_offload(int fd, int csum, int tso4,
 174                         int tso6, int ecn, int ufo)
 175 {
 176     unsigned int offload = 0;
 177
 178     /* Check if our kernel supports TUNSETOFFLOAD */
 179     if (ioctl(fd, TUNSETOFFLOAD, 0) != 0 && errno == EINVAL) {
 180         return;
 181     }
 182
 183     if (csum) {
 184         offload |= TUN_F_CSUM;
 185         if (tso4)
 186             offload |= TUN_F_TSO4;
 187         if (tso6)
 188             offload |= TUN_F_TSO6;
 189         if ((tso4 || tso6) && ecn)
 190             offload |= TUN_F_TSO_ECN;
 191         if (ufo)
 192             offload |= TUN_F_UFO;
 193     }
 194
 195     if (ioctl(fd, TUNSETOFFLOAD, offload) != 0) {
 196         offload &= ~TUN_F_UFO;
 197         if (ioctl(fd, TUNSETOFFLOAD, offload) != 0) {
 198             fprintf(stderr, "TUNSETOFFLOAD ioctl() failed: %s\n",
 199                     strerror(errno));
 200         }
 201     }
 202 }