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, int vnet_hdr_required) 40 { 41 struct ifreq ifr; 42 int fd, ret; 43 int len = sizeof(struct virtio_net_hdr); 44 45 TFR(fd = open(PATH_NET_TUN, O_RDWR)); 46 if (fd < 0) { 47 error_report("could not open %s: %m", PATH_NET_TUN); 48 return -1; 49 } 50 memset(&ifr, 0, sizeof(ifr)); 51 ifr.ifr_flags = IFF_TAP | IFF_NO_PI; 52 53 if (*vnet_hdr) { 54 unsigned int features; 55 56 if (ioctl(fd, TUNGETFEATURES, &features) == 0 && 57 features & IFF_VNET_HDR) { 58 *vnet_hdr = 1; 59 ifr.ifr_flags |= IFF_VNET_HDR; 60 } else { 61 *vnet_hdr = 0; 62 } 63 64 if (vnet_hdr_required && !*vnet_hdr) { 65 error_report("vnet_hdr=1 requested, but no kernel " 66 "support for IFF_VNET_HDR available"); 67 close(fd); 68 return -1; 69 } 70 /* 71 * Make sure vnet header size has the default value: for a persistent 72 * tap it might have been modified e.g. by another instance of qemu. 73 * Ignore errors since old kernels do not support this ioctl: in this 74 * case the header size implicitly has the correct value. 75 */ 76 ioctl(fd, TUNSETVNETHDRSZ, &len); 77 } 78 79 if (ifname[0] != '\0') 80 pstrcpy(ifr.ifr_name, IFNAMSIZ, ifname); 81 else 82 pstrcpy(ifr.ifr_name, IFNAMSIZ, "tap%d"); 83 ret = ioctl(fd, TUNSETIFF, (void *) &ifr); 84 if (ret != 0) { 85 if (ifname[0] != '\0') { 86 error_report("could not configure %s (%s): %m", PATH_NET_TUN, ifr.ifr_name); 87 } else { 88 error_report("could not configure %s: %m", PATH_NET_TUN); 89 } 90 close(fd); 91 return -1; 92 } 93 pstrcpy(ifname, ifname_size, ifr.ifr_name); 94 fcntl(fd, F_SETFL, O_NONBLOCK); 95 return fd; 96 } 97 98 /* sndbuf implements a kind of flow control for tap. 99 * Unfortunately when it's enabled, and packets are sent 100 * to other guests on the same host, the receiver 101 * can lock up the transmitter indefinitely. 102 * 103 * To avoid packet loss, sndbuf should be set to a value lower than the tx 104 * queue capacity of any destination network interface. 105 * Ethernet NICs generally have txqueuelen=1000, so 1Mb is 106 * a good value, given a 1500 byte MTU. 107 */ 108 #define TAP_DEFAULT_SNDBUF 0 109 110 int tap_set_sndbuf(int fd, const NetdevTapOptions *tap) 111 { 112 int sndbuf; 113 114 sndbuf = !tap->has_sndbuf ? TAP_DEFAULT_SNDBUF : 115 tap->sndbuf > INT_MAX ? INT_MAX : 116 tap->sndbuf; 117 118 if (!sndbuf) { 119 sndbuf = INT_MAX; 120 } 121 122 if (ioctl(fd, TUNSETSNDBUF, &sndbuf) == -1 && tap->has_sndbuf) { 123 error_report("TUNSETSNDBUF ioctl failed: %s", strerror(errno)); 124 return -1; 125 } 126 return 0; 127 } 128 129 int tap_probe_vnet_hdr(int fd) 130 { 131 struct ifreq ifr; 132 133 if (ioctl(fd, TUNGETIFF, &ifr) != 0) { 134 error_report("TUNGETIFF ioctl() failed: %s", strerror(errno)); 135 return 0; 136 } 137 138 return ifr.ifr_flags & IFF_VNET_HDR; 139 } 140 141 int tap_probe_has_ufo(int fd) 142 { 143 unsigned offload; 144 145 offload = TUN_F_CSUM | TUN_F_UFO; 146 147 if (ioctl(fd, TUNSETOFFLOAD, offload) < 0) 148 return 0; 149 150 return 1; 151 } 152 153 /* Verify that we can assign given length */ 154 int tap_probe_vnet_hdr_len(int fd, int len) 155 { 156 int orig; 157 if (ioctl(fd, TUNGETVNETHDRSZ, &orig) == -1) { 158 return 0; 159 } 160 if (ioctl(fd, TUNSETVNETHDRSZ, &len) == -1) { 161 return 0; 162 } 163 /* Restore original length: we can't handle failure. */ 164 if (ioctl(fd, TUNSETVNETHDRSZ, &orig) == -1) { 165 fprintf(stderr, "TUNGETVNETHDRSZ ioctl() failed: %s. Exiting.\n", 166 strerror(errno)); 167 assert(0); 168 return -errno; 169 } 170 return 1; 171 } 172 173 void tap_fd_set_vnet_hdr_len(int fd, int len) 174 { 175 if (ioctl(fd, TUNSETVNETHDRSZ, &len) == -1) { 176 fprintf(stderr, "TUNSETVNETHDRSZ ioctl() failed: %s. Exiting.\n", 177 strerror(errno)); 178 assert(0); 179 } 180 } 181 182 void tap_fd_set_offload(int fd, int csum, int tso4, 183 int tso6, int ecn, int ufo) 184 { 185 unsigned int offload = 0; 186 187 /* Check if our kernel supports TUNSETOFFLOAD */ 188 if (ioctl(fd, TUNSETOFFLOAD, 0) != 0 && errno == EINVAL) { 189 return; 190 } 191 192 if (csum) { 193 offload |= TUN_F_CSUM; 194 if (tso4) 195 offload |= TUN_F_TSO4; 196 if (tso6) 197 offload |= TUN_F_TSO6; 198 if ((tso4 || tso6) && ecn) 199 offload |= TUN_F_TSO_ECN; 200 if (ufo) 201 offload |= TUN_F_UFO; 202 } 203 204 if (ioctl(fd, TUNSETOFFLOAD, offload) != 0) { 205 offload &= ~TUN_F_UFO; 206 if (ioctl(fd, TUNSETOFFLOAD, offload) != 0) { 207 fprintf(stderr, "TUNSETOFFLOAD ioctl() failed: %s\n", 208 strerror(errno)); 209 } 210 } 211 } 212