xref: /qemu/net/tap-linux.c (revision abff1abf) 
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 "qemu/osdep.h"
27 #include "qemu-common.h"
28 #include "tap_int.h"
29 #include "tap-linux.h"
30 #include "net/tap.h"
31 
32 #include <net/if.h>
33 #include <sys/ioctl.h>
34 
35 #include "qapi/error.h"
36 #include "qemu/error-report.h"
37 #include "qemu/cutils.h"
38 
39 #define PATH_NET_TUN "/dev/net/tun"
40 
41 int tap_open(char *ifname, int ifname_size, int *vnet_hdr,
42              int vnet_hdr_required, int mq_required, Error **errp)
43 {
44     struct ifreq ifr;
45     int fd, ret;
46     int len = sizeof(struct virtio_net_hdr);
47     unsigned int features;
48 
49     TFR(fd = open(PATH_NET_TUN, O_RDWR));
50     if (fd < 0) {
51         error_setg_errno(errp, errno, "could not open %s", PATH_NET_TUN);
52         return -1;
53     }
54     memset(&ifr, 0, sizeof(ifr));
55     ifr.ifr_flags = IFF_TAP | IFF_NO_PI;
56 
57     if (ioctl(fd, TUNGETFEATURES, &features) == -1) {
58         warn_report("TUNGETFEATURES failed: %s", strerror(errno));
59         features = 0;
60     }
61 
62     if (features & IFF_ONE_QUEUE) {
63         ifr.ifr_flags |= IFF_ONE_QUEUE;
64     }
65 
66     if (*vnet_hdr) {
67         if (features & IFF_VNET_HDR) {
68             *vnet_hdr = 1;
69             ifr.ifr_flags |= IFF_VNET_HDR;
70         } else {
71             *vnet_hdr = 0;
72         }
73 
74         if (vnet_hdr_required && !*vnet_hdr) {
75             error_setg(errp, "vnet_hdr=1 requested, but no kernel "
76                        "support for IFF_VNET_HDR available");
77             close(fd);
78             return -1;
79         }
80         /*
81          * Make sure vnet header size has the default value: for a persistent
82          * tap it might have been modified e.g. by another instance of qemu.
83          * Ignore errors since old kernels do not support this ioctl: in this
84          * case the header size implicitly has the correct value.
85          */
86         ioctl(fd, TUNSETVNETHDRSZ, &len);
87     }
88 
89     if (mq_required) {
90         if (!(features & IFF_MULTI_QUEUE)) {
91             error_setg(errp, "multiqueue required, but no kernel "
92                        "support for IFF_MULTI_QUEUE available");
93             close(fd);
94             return -1;
95         } else {
96             ifr.ifr_flags |= IFF_MULTI_QUEUE;
97         }
98     }
99 
100     if (ifname[0] != '\0')
101         pstrcpy(ifr.ifr_name, IFNAMSIZ, ifname);
102     else
103         pstrcpy(ifr.ifr_name, IFNAMSIZ, "tap%d");
104     ret = ioctl(fd, TUNSETIFF, (void *) &ifr);
105     if (ret != 0) {
106         if (ifname[0] != '\0') {
107             error_setg_errno(errp, errno, "could not configure %s (%s)",
108                              PATH_NET_TUN, ifr.ifr_name);
109         } else {
110             error_setg_errno(errp, errno, "could not configure %s",
111                              PATH_NET_TUN);
112         }
113         close(fd);
114         return -1;
115     }
116     pstrcpy(ifname, ifname_size, ifr.ifr_name);
117     fcntl(fd, F_SETFL, O_NONBLOCK);
118     return fd;
119 }
120 
121 /* sndbuf implements a kind of flow control for tap.
122  * Unfortunately when it's enabled, and packets are sent
123  * to other guests on the same host, the receiver
124  * can lock up the transmitter indefinitely.
125  *
126  * To avoid packet loss, sndbuf should be set to a value lower than the tx
127  * queue capacity of any destination network interface.
128  * Ethernet NICs generally have txqueuelen=1000, so 1Mb is
129  * a good value, given a 1500 byte MTU.
130  */
131 #define TAP_DEFAULT_SNDBUF 0
132 
133 void tap_set_sndbuf(int fd, const NetdevTapOptions *tap, Error **errp)
134 {
135     int sndbuf;
136 
137     sndbuf = !tap->has_sndbuf       ? TAP_DEFAULT_SNDBUF :
138              tap->sndbuf > INT_MAX  ? INT_MAX :
139              tap->sndbuf;
140 
141     if (!sndbuf) {
142         sndbuf = INT_MAX;
143     }
144 
145     if (ioctl(fd, TUNSETSNDBUF, &sndbuf) == -1 && tap->has_sndbuf) {
146         error_setg_errno(errp, errno, "TUNSETSNDBUF ioctl failed");
147     }
148 }
149 
150 int tap_probe_vnet_hdr(int fd, Error **errp)
151 {
152     struct ifreq ifr;
153 
154     if (ioctl(fd, TUNGETIFF, &ifr) != 0) {
155         /* TUNGETIFF is available since kernel v2.6.27 */
156         error_setg_errno(errp, errno,
157                          "Unable to query TUNGETIFF on FD %d", fd);
158         return -1;
159     }
160 
161     return ifr.ifr_flags & IFF_VNET_HDR;
162 }
163 
164 int tap_probe_has_ufo(int fd)
165 {
166     unsigned offload;
167 
168     offload = TUN_F_CSUM | TUN_F_UFO;
169 
170     if (ioctl(fd, TUNSETOFFLOAD, offload) < 0)
171         return 0;
172 
173     return 1;
174 }
175 
176 /* Verify that we can assign given length */
177 int tap_probe_vnet_hdr_len(int fd, int len)
178 {
179     int orig;
180     if (ioctl(fd, TUNGETVNETHDRSZ, &orig) == -1) {
181         return 0;
182     }
183     if (ioctl(fd, TUNSETVNETHDRSZ, &len) == -1) {
184         return 0;
185     }
186     /* Restore original length: we can't handle failure. */
187     if (ioctl(fd, TUNSETVNETHDRSZ, &orig) == -1) {
188         fprintf(stderr, "TUNGETVNETHDRSZ ioctl() failed: %s. Exiting.\n",
189                 strerror(errno));
190         abort();
191         return -errno;
192     }
193     return 1;
194 }
195 
196 void tap_fd_set_vnet_hdr_len(int fd, int len)
197 {
198     if (ioctl(fd, TUNSETVNETHDRSZ, &len) == -1) {
199         fprintf(stderr, "TUNSETVNETHDRSZ ioctl() failed: %s. Exiting.\n",
200                 strerror(errno));
201         abort();
202     }
203 }
204 
205 int tap_fd_set_vnet_le(int fd, int is_le)
206 {
207     int arg = is_le ? 1 : 0;
208 
209     if (!ioctl(fd, TUNSETVNETLE, &arg)) {
210         return 0;
211     }
212 
213     /* Check if our kernel supports TUNSETVNETLE */
214     if (errno == EINVAL) {
215         return -errno;
216     }
217 
218     error_report("TUNSETVNETLE ioctl() failed: %s.", strerror(errno));
219     abort();
220 }
221 
222 int tap_fd_set_vnet_be(int fd, int is_be)
223 {
224     int arg = is_be ? 1 : 0;
225 
226     if (!ioctl(fd, TUNSETVNETBE, &arg)) {
227         return 0;
228     }
229 
230     /* Check if our kernel supports TUNSETVNETBE */
231     if (errno == EINVAL) {
232         return -errno;
233     }
234 
235     error_report("TUNSETVNETBE ioctl() failed: %s.", strerror(errno));
236     abort();
237 }
238 
239 void tap_fd_set_offload(int fd, int csum, int tso4,
240                         int tso6, int ecn, int ufo)
241 {
242     unsigned int offload = 0;
243 
244     /* Check if our kernel supports TUNSETOFFLOAD */
245     if (ioctl(fd, TUNSETOFFLOAD, 0) != 0 && errno == EINVAL) {
246         return;
247     }
248 
249     if (csum) {
250         offload |= TUN_F_CSUM;
251         if (tso4)
252             offload |= TUN_F_TSO4;
253         if (tso6)
254             offload |= TUN_F_TSO6;
255         if ((tso4 || tso6) && ecn)
256             offload |= TUN_F_TSO_ECN;
257         if (ufo)
258             offload |= TUN_F_UFO;
259     }
260 
261     if (ioctl(fd, TUNSETOFFLOAD, offload) != 0) {
262         offload &= ~TUN_F_UFO;
263         if (ioctl(fd, TUNSETOFFLOAD, offload) != 0) {
264             fprintf(stderr, "TUNSETOFFLOAD ioctl() failed: %s\n",
265                     strerror(errno));
266         }
267     }
268 }
269 
270 /* Enable a specific queue of tap. */
271 int tap_fd_enable(int fd)
272 {
273     struct ifreq ifr;
274     int ret;
275 
276     memset(&ifr, 0, sizeof(ifr));
277 
278     ifr.ifr_flags = IFF_ATTACH_QUEUE;
279     ret = ioctl(fd, TUNSETQUEUE, (void *) &ifr);
280 
281     if (ret != 0) {
282         error_report("could not enable queue");
283     }
284 
285     return ret;
286 }
287 
288 /* Disable a specific queue of tap/ */
289 int tap_fd_disable(int fd)
290 {
291     struct ifreq ifr;
292     int ret;
293 
294     memset(&ifr, 0, sizeof(ifr));
295 
296     ifr.ifr_flags = IFF_DETACH_QUEUE;
297     ret = ioctl(fd, TUNSETQUEUE, (void *) &ifr);
298 
299     if (ret != 0) {
300         error_report("could not disable queue");
301     }
302 
303     return ret;
304 }
305 
306 int tap_fd_get_ifname(int fd, char *ifname)
307 {
308     struct ifreq ifr;
309 
310     if (ioctl(fd, TUNGETIFF, &ifr) != 0) {
311         error_report("TUNGETIFF ioctl() failed: %s",
312                      strerror(errno));
313         return -1;
314     }
315 
316     pstrcpy(ifname, sizeof(ifr.ifr_name), ifr.ifr_name);
317     return 0;
318 }
319