xref: /openbmc/qemu/net/tap-linux.c (revision c6bd8c70) 
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,
40              int vnet_hdr_required, int mq_required, Error **errp)
41 {
42     struct ifreq ifr;
43     int fd, ret;
44     int len = sizeof(struct virtio_net_hdr);
45     unsigned int features;
46 
47     TFR(fd = open(PATH_NET_TUN, O_RDWR));
48     if (fd < 0) {
49         error_setg_errno(errp, errno, "could not open %s", PATH_NET_TUN);
50         return -1;
51     }
52     memset(&ifr, 0, sizeof(ifr));
53     ifr.ifr_flags = IFF_TAP | IFF_NO_PI;
54 
55     if (ioctl(fd, TUNGETFEATURES, &features) == -1) {
56         error_report("warning: TUNGETFEATURES failed: %s", strerror(errno));
57         features = 0;
58     }
59 
60     if (features & IFF_ONE_QUEUE) {
61         ifr.ifr_flags |= IFF_ONE_QUEUE;
62     }
63 
64     if (*vnet_hdr) {
65         if (features & IFF_VNET_HDR) {
66             *vnet_hdr = 1;
67             ifr.ifr_flags |= IFF_VNET_HDR;
68         } else {
69             *vnet_hdr = 0;
70         }
71 
72         if (vnet_hdr_required && !*vnet_hdr) {
73             error_setg(errp, "vnet_hdr=1 requested, but no kernel "
74                        "support for IFF_VNET_HDR available");
75             close(fd);
76             return -1;
77         }
78         /*
79          * Make sure vnet header size has the default value: for a persistent
80          * tap it might have been modified e.g. by another instance of qemu.
81          * Ignore errors since old kernels do not support this ioctl: in this
82          * case the header size implicitly has the correct value.
83          */
84         ioctl(fd, TUNSETVNETHDRSZ, &len);
85     }
86 
87     if (mq_required) {
88         if (!(features & IFF_MULTI_QUEUE)) {
89             error_setg(errp, "multiqueue required, but no kernel "
90                        "support for IFF_MULTI_QUEUE available");
91             close(fd);
92             return -1;
93         } else {
94             ifr.ifr_flags |= IFF_MULTI_QUEUE;
95         }
96     }
97 
98     if (ifname[0] != '\0')
99         pstrcpy(ifr.ifr_name, IFNAMSIZ, ifname);
100     else
101         pstrcpy(ifr.ifr_name, IFNAMSIZ, "tap%d");
102     ret = ioctl(fd, TUNSETIFF, (void *) &ifr);
103     if (ret != 0) {
104         if (ifname[0] != '\0') {
105             error_setg_errno(errp, errno, "could not configure %s (%s)",
106                              PATH_NET_TUN, ifr.ifr_name);
107         } else {
108             error_setg_errno(errp, errno, "could not configure %s",
109                              PATH_NET_TUN);
110         }
111         close(fd);
112         return -1;
113     }
114     pstrcpy(ifname, ifname_size, ifr.ifr_name);
115     fcntl(fd, F_SETFL, O_NONBLOCK);
116     return fd;
117 }
118 
119 /* sndbuf implements a kind of flow control for tap.
120  * Unfortunately when it's enabled, and packets are sent
121  * to other guests on the same host, the receiver
122  * can lock up the transmitter indefinitely.
123  *
124  * To avoid packet loss, sndbuf should be set to a value lower than the tx
125  * queue capacity of any destination network interface.
126  * Ethernet NICs generally have txqueuelen=1000, so 1Mb is
127  * a good value, given a 1500 byte MTU.
128  */
129 #define TAP_DEFAULT_SNDBUF 0
130 
131 void tap_set_sndbuf(int fd, const NetdevTapOptions *tap, Error **errp)
132 {
133     int sndbuf;
134 
135     sndbuf = !tap->has_sndbuf       ? TAP_DEFAULT_SNDBUF :
136              tap->sndbuf > INT_MAX  ? INT_MAX :
137              tap->sndbuf;
138 
139     if (!sndbuf) {
140         sndbuf = INT_MAX;
141     }
142 
143     if (ioctl(fd, TUNSETSNDBUF, &sndbuf) == -1 && tap->has_sndbuf) {
144         error_setg_errno(errp, errno, "TUNSETSNDBUF ioctl failed");
145     }
146 }
147 
148 int tap_probe_vnet_hdr(int fd)
149 {
150     struct ifreq ifr;
151 
152     if (ioctl(fd, TUNGETIFF, &ifr) != 0) {
153         error_report("TUNGETIFF ioctl() failed: %s", strerror(errno));
154         return 0;
155     }
156 
157     return ifr.ifr_flags & IFF_VNET_HDR;
158 }
159 
160 int tap_probe_has_ufo(int fd)
161 {
162     unsigned offload;
163 
164     offload = TUN_F_CSUM | TUN_F_UFO;
165 
166     if (ioctl(fd, TUNSETOFFLOAD, offload) < 0)
167         return 0;
168 
169     return 1;
170 }
171 
172 /* Verify that we can assign given length */
173 int tap_probe_vnet_hdr_len(int fd, int len)
174 {
175     int orig;
176     if (ioctl(fd, TUNGETVNETHDRSZ, &orig) == -1) {
177         return 0;
178     }
179     if (ioctl(fd, TUNSETVNETHDRSZ, &len) == -1) {
180         return 0;
181     }
182     /* Restore original length: we can't handle failure. */
183     if (ioctl(fd, TUNSETVNETHDRSZ, &orig) == -1) {
184         fprintf(stderr, "TUNGETVNETHDRSZ ioctl() failed: %s. Exiting.\n",
185                 strerror(errno));
186         abort();
187         return -errno;
188     }
189     return 1;
190 }
191 
192 void tap_fd_set_vnet_hdr_len(int fd, int len)
193 {
194     if (ioctl(fd, TUNSETVNETHDRSZ, &len) == -1) {
195         fprintf(stderr, "TUNSETVNETHDRSZ ioctl() failed: %s. Exiting.\n",
196                 strerror(errno));
197         abort();
198     }
199 }
200 
201 int tap_fd_set_vnet_le(int fd, int is_le)
202 {
203     int arg = is_le ? 1 : 0;
204 
205     if (!ioctl(fd, TUNSETVNETLE, &arg)) {
206         return 0;
207     }
208 
209     /* Check if our kernel supports TUNSETVNETLE */
210     if (errno == EINVAL) {
211         return -errno;
212     }
213 
214     error_report("TUNSETVNETLE ioctl() failed: %s.\n", strerror(errno));
215     abort();
216 }
217 
218 int tap_fd_set_vnet_be(int fd, int is_be)
219 {
220     int arg = is_be ? 1 : 0;
221 
222     if (!ioctl(fd, TUNSETVNETBE, &arg)) {
223         return 0;
224     }
225 
226     /* Check if our kernel supports TUNSETVNETBE */
227     if (errno == EINVAL) {
228         return -errno;
229     }
230 
231     error_report("TUNSETVNETBE ioctl() failed: %s.\n", strerror(errno));
232     abort();
233 }
234 
235 void tap_fd_set_offload(int fd, int csum, int tso4,
236                         int tso6, int ecn, int ufo)
237 {
238     unsigned int offload = 0;
239 
240     /* Check if our kernel supports TUNSETOFFLOAD */
241     if (ioctl(fd, TUNSETOFFLOAD, 0) != 0 && errno == EINVAL) {
242         return;
243     }
244 
245     if (csum) {
246         offload |= TUN_F_CSUM;
247         if (tso4)
248             offload |= TUN_F_TSO4;
249         if (tso6)
250             offload |= TUN_F_TSO6;
251         if ((tso4 || tso6) && ecn)
252             offload |= TUN_F_TSO_ECN;
253         if (ufo)
254             offload |= TUN_F_UFO;
255     }
256 
257     if (ioctl(fd, TUNSETOFFLOAD, offload) != 0) {
258         offload &= ~TUN_F_UFO;
259         if (ioctl(fd, TUNSETOFFLOAD, offload) != 0) {
260             fprintf(stderr, "TUNSETOFFLOAD ioctl() failed: %s\n",
261                     strerror(errno));
262         }
263     }
264 }
265 
266 /* Enable a specific queue of tap. */
267 int tap_fd_enable(int fd)
268 {
269     struct ifreq ifr;
270     int ret;
271 
272     memset(&ifr, 0, sizeof(ifr));
273 
274     ifr.ifr_flags = IFF_ATTACH_QUEUE;
275     ret = ioctl(fd, TUNSETQUEUE, (void *) &ifr);
276 
277     if (ret != 0) {
278         error_report("could not enable queue");
279     }
280 
281     return ret;
282 }
283 
284 /* Disable a specific queue of tap/ */
285 int tap_fd_disable(int fd)
286 {
287     struct ifreq ifr;
288     int ret;
289 
290     memset(&ifr, 0, sizeof(ifr));
291 
292     ifr.ifr_flags = IFF_DETACH_QUEUE;
293     ret = ioctl(fd, TUNSETQUEUE, (void *) &ifr);
294 
295     if (ret != 0) {
296         error_report("could not disable queue");
297     }
298 
299     return ret;
300 }
301 
302 int tap_fd_get_ifname(int fd, char *ifname)
303 {
304     struct ifreq ifr;
305 
306     if (ioctl(fd, TUNGETIFF, &ifr) != 0) {
307         error_report("TUNGETIFF ioctl() failed: %s",
308                      strerror(errno));
309         return -1;
310     }
311 
312     pstrcpy(ifname, sizeof(ifr.ifr_name), ifr.ifr_name);
313     return 0;
314 }
315