xref: /openbmc/qemu/net/tap-linux.c (revision 80adf54e) 
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 "tap_int.h"
28 #include "tap-linux.h"
29 #include "net/tap.h"
30 
31 #include <net/if.h>
32 #include <sys/ioctl.h>
33 
34 #include "sysemu/sysemu.h"
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)
151 {
152     struct ifreq ifr;
153 
154     if (ioctl(fd, TUNGETIFF, &ifr) != 0) {
155         error_report("TUNGETIFF ioctl() failed: %s", strerror(errno));
156         return 0;
157     }
158 
159     return ifr.ifr_flags & IFF_VNET_HDR;
160 }
161 
162 int tap_probe_has_ufo(int fd)
163 {
164     unsigned offload;
165 
166     offload = TUN_F_CSUM | TUN_F_UFO;
167 
168     if (ioctl(fd, TUNSETOFFLOAD, offload) < 0)
169         return 0;
170 
171     return 1;
172 }
173 
174 /* Verify that we can assign given length */
175 int tap_probe_vnet_hdr_len(int fd, int len)
176 {
177     int orig;
178     if (ioctl(fd, TUNGETVNETHDRSZ, &orig) == -1) {
179         return 0;
180     }
181     if (ioctl(fd, TUNSETVNETHDRSZ, &len) == -1) {
182         return 0;
183     }
184     /* Restore original length: we can't handle failure. */
185     if (ioctl(fd, TUNSETVNETHDRSZ, &orig) == -1) {
186         fprintf(stderr, "TUNGETVNETHDRSZ ioctl() failed: %s. Exiting.\n",
187                 strerror(errno));
188         abort();
189         return -errno;
190     }
191     return 1;
192 }
193 
194 void tap_fd_set_vnet_hdr_len(int fd, int len)
195 {
196     if (ioctl(fd, TUNSETVNETHDRSZ, &len) == -1) {
197         fprintf(stderr, "TUNSETVNETHDRSZ ioctl() failed: %s. Exiting.\n",
198                 strerror(errno));
199         abort();
200     }
201 }
202 
203 int tap_fd_set_vnet_le(int fd, int is_le)
204 {
205     int arg = is_le ? 1 : 0;
206 
207     if (!ioctl(fd, TUNSETVNETLE, &arg)) {
208         return 0;
209     }
210 
211     /* Check if our kernel supports TUNSETVNETLE */
212     if (errno == EINVAL) {
213         return -errno;
214     }
215 
216     error_report("TUNSETVNETLE ioctl() failed: %s.", strerror(errno));
217     abort();
218 }
219 
220 int tap_fd_set_vnet_be(int fd, int is_be)
221 {
222     int arg = is_be ? 1 : 0;
223 
224     if (!ioctl(fd, TUNSETVNETBE, &arg)) {
225         return 0;
226     }
227 
228     /* Check if our kernel supports TUNSETVNETBE */
229     if (errno == EINVAL) {
230         return -errno;
231     }
232 
233     error_report("TUNSETVNETBE ioctl() failed: %s.", strerror(errno));
234     abort();
235 }
236 
237 void tap_fd_set_offload(int fd, int csum, int tso4,
238                         int tso6, int ecn, int ufo)
239 {
240     unsigned int offload = 0;
241 
242     /* Check if our kernel supports TUNSETOFFLOAD */
243     if (ioctl(fd, TUNSETOFFLOAD, 0) != 0 && errno == EINVAL) {
244         return;
245     }
246 
247     if (csum) {
248         offload |= TUN_F_CSUM;
249         if (tso4)
250             offload |= TUN_F_TSO4;
251         if (tso6)
252             offload |= TUN_F_TSO6;
253         if ((tso4 || tso6) && ecn)
254             offload |= TUN_F_TSO_ECN;
255         if (ufo)
256             offload |= TUN_F_UFO;
257     }
258 
259     if (ioctl(fd, TUNSETOFFLOAD, offload) != 0) {
260         offload &= ~TUN_F_UFO;
261         if (ioctl(fd, TUNSETOFFLOAD, offload) != 0) {
262             fprintf(stderr, "TUNSETOFFLOAD ioctl() failed: %s\n",
263                     strerror(errno));
264         }
265     }
266 }
267 
268 /* Enable a specific queue of tap. */
269 int tap_fd_enable(int fd)
270 {
271     struct ifreq ifr;
272     int ret;
273 
274     memset(&ifr, 0, sizeof(ifr));
275 
276     ifr.ifr_flags = IFF_ATTACH_QUEUE;
277     ret = ioctl(fd, TUNSETQUEUE, (void *) &ifr);
278 
279     if (ret != 0) {
280         error_report("could not enable queue");
281     }
282 
283     return ret;
284 }
285 
286 /* Disable a specific queue of tap/ */
287 int tap_fd_disable(int fd)
288 {
289     struct ifreq ifr;
290     int ret;
291 
292     memset(&ifr, 0, sizeof(ifr));
293 
294     ifr.ifr_flags = IFF_DETACH_QUEUE;
295     ret = ioctl(fd, TUNSETQUEUE, (void *) &ifr);
296 
297     if (ret != 0) {
298         error_report("could not disable queue");
299     }
300 
301     return ret;
302 }
303 
304 int tap_fd_get_ifname(int fd, char *ifname)
305 {
306     struct ifreq ifr;
307 
308     if (ioctl(fd, TUNGETIFF, &ifr) != 0) {
309         error_report("TUNGETIFF ioctl() failed: %s",
310                      strerror(errno));
311         return -1;
312     }
313 
314     pstrcpy(ifname, sizeof(ifr.ifr_name), ifr.ifr_name);
315     return 0;
316 }
317