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