perform cheap checks first
[tinc] / src / linux / device.c
1 /*
2     device.c -- Interaction with Linux ethertap and tun/tap device
3     Copyright (C) 2001-2005 Ivo Timmermans,
4                   2001-2014 Guus Sliepen <guus@tinc-vpn.org>
5
6     This program is free software; you can redistribute it and/or modify
7     it under the terms of the GNU General Public License as published by
8     the Free Software Foundation; either version 2 of the License, or
9     (at your option) any later version.
10
11     This program is distributed in the hope that it will be useful,
12     but WITHOUT ANY WARRANTY; without even the implied warranty of
13     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14     GNU General Public License for more details.
15
16     You should have received a copy of the GNU General Public License along
17     with this program; if not, write to the Free Software Foundation, Inc.,
18     51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
19 */
20
21 #include "../system.h"
22
23 #include <linux/if_tun.h>
24 #define DEFAULT_DEVICE "/dev/net/tun"
25
26 #include "../conf.h"
27 #include "../device.h"
28 #include "../logger.h"
29 #include "../names.h"
30 #include "../net.h"
31 #include "../route.h"
32 #include "../utils.h"
33 #include "../xalloc.h"
34 #include "../device.h"
35
36 typedef enum device_type_t {
37         DEVICE_TYPE_TUN,
38         DEVICE_TYPE_TAP,
39 } device_type_t;
40
41 int device_fd = -1;
42 static device_type_t device_type;
43 char *device = NULL;
44 char *iface = NULL;
45 static char *type = NULL;
46 static char ifrname[IFNAMSIZ];
47 static const char *device_info;
48
49 static bool setup_device(void) {
50         if(!get_config_string(lookup_config(config_tree, "Device"), &device)) {
51                 device = xstrdup(DEFAULT_DEVICE);
52         }
53
54         if(!get_config_string(lookup_config(config_tree, "Interface"), &iface))
55                 if(netname) {
56                         iface = xstrdup(netname);
57                 }
58
59         device_fd = open(device, O_RDWR | O_NONBLOCK);
60
61         if(device_fd < 0) {
62                 logger(DEBUG_ALWAYS, LOG_ERR, "Could not open %s: %s", device, strerror(errno));
63                 return false;
64         }
65
66 #ifdef FD_CLOEXEC
67         fcntl(device_fd, F_SETFD, FD_CLOEXEC);
68 #endif
69
70         struct ifreq ifr = {0};
71
72         get_config_string(lookup_config(config_tree, "DeviceType"), &type);
73
74         if(type && strcasecmp(type, "tun") && strcasecmp(type, "tap")) {
75                 logger(DEBUG_ALWAYS, LOG_ERR, "Unknown device type %s!", type);
76                 return false;
77         }
78
79         if((type && !strcasecmp(type, "tun")) || (!type && routing_mode == RMODE_ROUTER)) {
80                 ifr.ifr_flags = IFF_TUN;
81                 device_type = DEVICE_TYPE_TUN;
82                 device_info = "Linux tun/tap device (tun mode)";
83         } else {
84                 if(routing_mode == RMODE_ROUTER) {
85                         overwrite_mac = true;
86                 }
87
88                 ifr.ifr_flags = IFF_TAP | IFF_NO_PI;
89                 device_type = DEVICE_TYPE_TAP;
90                 device_info = "Linux tun/tap device (tap mode)";
91         }
92
93 #ifdef IFF_ONE_QUEUE
94         /* Set IFF_ONE_QUEUE flag... */
95
96         bool t1q = false;
97
98         if(get_config_bool(lookup_config(config_tree, "IffOneQueue"), &t1q) && t1q) {
99                 ifr.ifr_flags |= IFF_ONE_QUEUE;
100         }
101
102 #endif
103
104         if(iface) {
105                 strncpy(ifr.ifr_name, iface, IFNAMSIZ);
106                 ifr.ifr_name[IFNAMSIZ - 1] = 0;
107         }
108
109         if(!ioctl(device_fd, TUNSETIFF, &ifr)) {
110                 strncpy(ifrname, ifr.ifr_name, IFNAMSIZ);
111                 ifrname[IFNAMSIZ - 1] = 0;
112                 free(iface);
113                 iface = xstrdup(ifrname);
114         } else {
115                 logger(DEBUG_ALWAYS, LOG_ERR, "Could not create a tun/tap interface from %s: %s", device, strerror(errno));
116                 return false;
117         }
118
119         logger(DEBUG_ALWAYS, LOG_INFO, "%s is a %s", device, device_info);
120
121         if(ifr.ifr_flags & IFF_TAP) {
122                 struct ifreq ifr_mac = {0};
123
124                 if(!ioctl(device_fd, SIOCGIFHWADDR, &ifr_mac)) {
125                         memcpy(mymac.x, ifr_mac.ifr_hwaddr.sa_data, ETH_ALEN);
126                 } else {
127                         logger(DEBUG_ALWAYS, LOG_WARNING, "Could not get MAC address of %s: %s", device, strerror(errno));
128                 }
129         }
130
131         return true;
132 }
133
134 static void close_device(void) {
135         close(device_fd);
136         device_fd = -1;
137
138         free(type);
139         type = NULL;
140         free(device);
141         device = NULL;
142         free(iface);
143         iface = NULL;
144         device_info = NULL;
145 }
146
147 static bool read_packet(vpn_packet_t *packet) {
148         int inlen;
149
150         switch(device_type) {
151         case DEVICE_TYPE_TUN:
152                 inlen = read(device_fd, DATA(packet) + 10, MTU - 10);
153
154                 if(inlen <= 0) {
155                         logger(DEBUG_ALWAYS, LOG_ERR, "Error while reading from %s %s: %s",
156                                device_info, device, strerror(errno));
157
158                         if(errno == EBADFD) {  /* File descriptor in bad state */
159                                 event_exit();
160                         }
161
162                         return false;
163                 }
164
165                 memset(DATA(packet), 0, 12);
166                 packet->len = inlen + 10;
167                 break;
168
169         case DEVICE_TYPE_TAP:
170                 inlen = read(device_fd, DATA(packet), MTU);
171
172                 if(inlen <= 0) {
173                         logger(DEBUG_ALWAYS, LOG_ERR, "Error while reading from %s %s: %s",
174                                device_info, device, strerror(errno));
175                         return false;
176                 }
177
178                 packet->len = inlen;
179                 break;
180
181         default:
182                 abort();
183         }
184
185         logger(DEBUG_TRAFFIC, LOG_DEBUG, "Read packet of %d bytes from %s", packet->len,
186                device_info);
187
188         return true;
189 }
190
191 static bool write_packet(vpn_packet_t *packet) {
192         logger(DEBUG_TRAFFIC, LOG_DEBUG, "Writing packet of %d bytes to %s",
193                packet->len, device_info);
194
195         switch(device_type) {
196         case DEVICE_TYPE_TUN:
197                 DATA(packet)[10] = DATA(packet)[11] = 0;
198
199                 if(write(device_fd, DATA(packet) + 10, packet->len - 10) < 0) {
200                         logger(DEBUG_ALWAYS, LOG_ERR, "Can't write to %s %s: %s", device_info, device,
201                                strerror(errno));
202                         return false;
203                 }
204
205                 break;
206
207         case DEVICE_TYPE_TAP:
208                 if(write(device_fd, DATA(packet), packet->len) < 0) {
209                         logger(DEBUG_ALWAYS, LOG_ERR, "Can't write to %s %s: %s", device_info, device,
210                                strerror(errno));
211                         return false;
212                 }
213
214                 break;
215
216         default:
217                 abort();
218         }
219
220         return true;
221 }
222
223 const devops_t os_devops = {
224         .setup = setup_device,
225         .close = close_device,
226         .read = read_packet,
227         .write = write_packet,
228 };