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test-example: Provide a polypath test
[secnet.git] / tun.c
1 #include "secnet.h"
2 #include "util.h"
3 #include "netlink.h"
4 #include <stdio.h>
5 #include <string.h>
6 #include <errno.h>
7 #include <unistd.h>
8 #include <fcntl.h>
9 #include <sys/ioctl.h>
10 #include <sys/utsname.h>
11 #include <sys/socket.h>
12
13 #ifdef HAVE_NET_IF_H
14 #include <net/if.h>
15 #ifdef HAVE_LINUX_IF_H
16 #include <linux/if_tun.h>
17 #define LINUX_TUN_SUPPORTED
18 #endif
19 #endif
20
21 #ifdef HAVE_NET_ROUTE_H
22 #include <net/route.h>
23 #endif
24
25 #if defined(HAVE_STROPTS_H) && defined(HAVE_SYS_SOCKIO_H) && \
26 defined(HAVE_NET_IF_TUN_H)
27 #define HAVE_TUN_STREAMS
28 #endif
29
30 #ifdef HAVE_TUN_STREAMS
31 #include <stropts.h>
32 #include <sys/sockio.h>
33 #include <net/if_tun.h>
34 #endif
35
36 #define TUN_FLAVOUR_GUESS   0
37 #define TUN_FLAVOUR_BSD     1
38 #define TUN_FLAVOUR_LINUX   2
39 #define TUN_FLAVOUR_STREAMS 3
40
41 static struct flagstr flavours[]={
42     {"guess", TUN_FLAVOUR_GUESS},
43     {"bsd", TUN_FLAVOUR_BSD},
44     {"BSD", TUN_FLAVOUR_BSD},
45     {"linux", TUN_FLAVOUR_LINUX},
46     {"streams", TUN_FLAVOUR_STREAMS},
47     {"STREAMS", TUN_FLAVOUR_STREAMS},
48     {NULL, 0}
49 };
50
51 #define TUN_CONFIG_GUESS      0
52 #define TUN_CONFIG_IOCTL      1
53 #define TUN_CONFIG_BSD        2
54 #define TUN_CONFIG_LINUX      3
55 #define TUN_CONFIG_SOLARIS25  4
56
57 static struct flagstr config_types[]={
58     {"guess", TUN_CONFIG_GUESS},
59     {"ioctl", TUN_CONFIG_IOCTL},
60     {"bsd", TUN_CONFIG_BSD},
61     {"BSD", TUN_CONFIG_BSD},
62     {"linux", TUN_CONFIG_LINUX},
63     {"solaris-2.5", TUN_CONFIG_SOLARIS25},
64     {NULL, 0}
65 };
66
67 /* Connection to the kernel through the universal TUN/TAP driver */
68
69 struct tun {
70     struct netlink nl;
71     int fd;
72     cstring_t device_path;
73     cstring_t ip_path;
74     string_t interface_name;
75     cstring_t ifconfig_path;
76     uint32_t ifconfig_type;
77     cstring_t route_path;
78     uint32_t route_type;
79     uint32_t tun_flavour;
80     bool_t search_for_if; /* Applies to tun-BSD only */
81     struct buffer_if *buff; /* We receive packets into here
82                                and send them to the netlink code. */
83     netlink_deliver_fn *netlink_to_tunnel;
84 };
85
86 static cstring_t tun_flavour_str(uint32_t flavour)
87 {
88     switch (flavour) {
89     case TUN_FLAVOUR_GUESS: return "guess";
90     case TUN_FLAVOUR_BSD: return "BSD";
91     case TUN_FLAVOUR_LINUX: return "linux";
92     case TUN_FLAVOUR_STREAMS: return "STREAMS";
93     default: return "unknown";
94     }
95 }
96
97 static int tun_beforepoll(void *sst, struct pollfd *fds, int *nfds_io,
98                           int *timeout_io)
99 {
100     struct tun *st=sst;
101     BEFOREPOLL_WANT_FDS(1);
102     fds[0].fd=st->fd;
103     fds[0].events=POLLIN;
104     return 0;
105 }
106
107 static void tun_afterpoll(void *sst, struct pollfd *fds, int nfds)
108 {
109     struct tun *st=sst;
110     int l;
111
112     if (nfds==0) return;
113     if (fds[0].revents&POLLERR) {
114         printf("tun_afterpoll: hup!\n");
115     }
116     if (fds[0].revents&POLLIN) {
117         BUF_ALLOC(st->buff,"tun_afterpoll");
118         buffer_init(st->buff,calculate_max_start_pad());
119         l=read(st->fd, st->buff->start, buf_remaining_space(st->buff));
120         if (l<0) {
121             if (errno==EINTR || iswouldblock(errno)) return;
122             fatal_perror("tun_afterpoll: read()");
123         }
124         if (l==0) {
125             fatal("tun_afterpoll: read()=0; device gone away?");
126         }
127         if (l>0) {
128             st->buff->size=l;
129             st->netlink_to_tunnel(&st->nl,st->buff);
130             BUF_ASSERT_FREE(st->buff);
131         }
132     }
133 }
134
135 static void tun_deliver_to_kernel(void *sst, struct buffer_if *buf)
136 {
137     struct tun *st=sst;
138     ssize_t rc;
139
140     BUF_ASSERT_USED(buf);
141     
142     /* Log errors, so we can tell what's going on, but only once a
143        minute, so we don't flood the logs.  Short writes count as
144        errors. */
145     rc = write(st->fd,buf->start,buf->size);
146     if(rc != buf->size) {
147         static struct timeval last_report;
148         if(tv_now_global.tv_sec >= last_report.tv_sec + 60) {
149             if(rc < 0)
150                 Message(M_WARNING,
151                         "failed to deliver packet to tun device: %s\n",
152                         strerror(errno));
153             else
154                 Message(M_WARNING,
155                         "truncated packet delivered to tun device\n");
156             last_report = tv_now_global;
157         }
158     }
159     BUF_FREE(buf);
160 }
161
162 static bool_t tun_set_route(void *sst, struct netlink_client *routes)
163 {
164     struct tun *st=sst;
165     string_t network, mask, secnetaddr;
166     struct subnet_list *nets;
167     int32_t i;
168     int fd=-1;
169     bool_t up;
170
171     if (routes->options & OPT_SOFTROUTE)
172         up = routes->up;
173     else
174         up = routes->link_quality > LINK_QUALITY_UNUSED;
175
176     if (up == routes->kup) return False;
177     if (st->route_type==TUN_CONFIG_IOCTL) {
178         if (st->tun_flavour==TUN_FLAVOUR_STREAMS) {
179             fd=open(st->ip_path,O_RDWR);
180             if (fd<0) {
181                 fatal_perror("tun_set_route: can't open %s",st->ip_path);
182             }
183         } else {
184             fd=socket(PF_INET, SOCK_DGRAM, IPPROTO_IP);
185             if (fd<0) {
186                 fatal_perror("tun_set_route: socket()");
187             }
188         }
189     }
190     nets=routes->subnets;
191     secnetaddr=ipaddr_to_string(st->nl.secnet_address);
192     for (i=0; i<nets->entries; i++) {
193         network=ipaddr_to_string(nets->list[i].prefix);
194         mask=ipaddr_to_string(nets->list[i].mask);
195         Message(M_INFO,"%s: %s route %s/%d %s kernel routing table\n",
196                 st->nl.name,up?"adding":"deleting",network,
197                 nets->list[i].len,up?"to":"from");
198         switch (st->route_type) {
199         case TUN_CONFIG_LINUX:
200             sys_cmd(st->route_path,"route",up?"add":"del",
201                     "-net",network,"netmask",mask,
202                     "gw",secnetaddr,(char *)0);
203             break;
204         case TUN_CONFIG_BSD:
205             sys_cmd(st->route_path,"route",up?"add":"del",
206                     "-net",network,secnetaddr,mask,(char *)0);
207             break;
208         case TUN_CONFIG_SOLARIS25:
209             sys_cmd(st->route_path,"route",up?"add":"del",
210                     network,secnetaddr,(char *)0);
211             break;
212         case TUN_CONFIG_IOCTL:
213         {
214           /* darwin rtentry has a different format, use /sbin/route instead */
215 #if HAVE_NET_ROUTE_H && ! __APPLE__
216             struct rtentry rt;
217             struct sockaddr_in *sa;
218             int action;
219             
220             FILLZERO(rt);
221             sa=(struct sockaddr_in *)&rt.rt_dst;
222             sa->sin_family=AF_INET;
223             sa->sin_addr.s_addr=htonl(nets->list[i].prefix);
224             sa=(struct sockaddr_in *)&rt.rt_genmask;
225             sa->sin_family=AF_INET;
226             sa->sin_addr.s_addr=htonl(nets->list[i].mask);
227             sa=(struct sockaddr_in *)&rt.rt_gateway;
228             sa->sin_family=AF_INET;
229             sa->sin_addr.s_addr=htonl(st->nl.secnet_address);
230             rt.rt_flags=RTF_UP|RTF_GATEWAY;
231             action=up?SIOCADDRT:SIOCDELRT;
232             if (ioctl(fd,action,&rt)<0) {
233                 fatal_perror("tun_set_route: ioctl()");
234             }
235 #else
236             fatal("tun_set_route: ioctl method not supported");
237 #endif
238         }
239         break;
240         default:
241             fatal("tun_set_route: unsupported route command type");
242             break;
243         }
244     }
245     if (fd >= 0) {
246         close(fd);
247     }
248     routes->kup=up;
249     return True;
250 }
251
252 static void tun_phase_hook(void *sst, uint32_t newphase)
253 {
254     struct tun *st=sst;
255     string_t hostaddr,secnetaddr;
256     char mtu[6];
257     struct netlink_client *r;
258
259     if (st->tun_flavour==TUN_FLAVOUR_BSD) {
260         if (st->search_for_if) {
261             string_t dname;
262             int i;
263
264             dname=safe_malloc(strlen(st->device_path)+4,"tun_old_apply");
265             st->interface_name=safe_malloc(8,"tun_phase_hook");
266         
267             for (i=0; i<255; i++) {
268                 sprintf(dname,"%s%d",st->device_path,i);
269                 if ((st->fd=open(dname,O_RDWR))>0) {
270                     sprintf(st->interface_name,"tun%d",i);
271                     Message(M_INFO,"%s: allocated network interface %s "
272                             "through %s\n",st->nl.name,st->interface_name,
273                             dname);
274                     break;
275                 }
276             }
277             if (st->fd==-1) {
278                 fatal("%s: unable to open any TUN device (%s...)",
279                       st->nl.name,st->device_path);
280             }
281         } else {
282             st->fd=open(st->device_path,O_RDWR);
283             if (st->fd==-1) {
284                 fatal_perror("%s: unable to open TUN device file %s",
285                              st->nl.name,st->device_path);
286             }
287         }
288     } else if (st->tun_flavour==TUN_FLAVOUR_LINUX) {
289 #ifdef LINUX_TUN_SUPPORTED
290         struct ifreq ifr;
291
292         /* New TUN interface: open the device, then do ioctl TUNSETIFF
293            to set or find out the network interface name. */
294         st->fd=open(st->device_path,O_RDWR);
295         if (st->fd==-1) {
296             fatal_perror("%s: can't open device file %s",st->nl.name,
297                          st->device_path);
298         }
299         FILLZERO(ifr);
300         ifr.ifr_flags = IFF_TUN | IFF_NO_PI; /* Just send/receive IP packets,
301                                                 no extra headers */
302         if (st->interface_name)
303             strncpy(ifr.ifr_name,st->interface_name,IFNAMSIZ);
304         if (ioctl(st->fd,TUNSETIFF,&ifr)<0) {
305             fatal_perror("%s: ioctl(TUNSETIFF)",st->nl.name);
306         }
307         if (!st->interface_name) {
308             st->interface_name=safe_malloc(strlen(ifr.ifr_name)+1,"tun_apply");
309             strcpy(st->interface_name,ifr.ifr_name);
310             Message(M_INFO,"%s: allocated network interface %s\n",st->nl.name,
311                     st->interface_name);
312         }
313 #else
314         fatal("tun_phase_hook: TUN_FLAVOUR_LINUX unexpected");
315 #endif /* LINUX_TUN_SUPPORTED */
316     } else if (st->tun_flavour==TUN_FLAVOUR_STREAMS) {
317 #ifdef HAVE_TUN_STREAMS
318         int tun_fd, if_fd, ppa=-1, ip_fd;
319
320         if ((ip_fd=open(st->ip_path, O_RDWR)) < 0) {
321             fatal_perror("%s: can't open %s",st->nl.name,st->ip_path);
322         }
323         if ((tun_fd=open(st->device_path,O_RDWR)) < 0) {
324             fatal_perror("%s: can't open %s",st->nl.name,st->device_path);
325         }
326         if ((ppa=ioctl(tun_fd,TUNNEWPPA,ppa)) < 0) {
327             fatal_perror("%s: can't assign new interface");
328         }
329         if ((if_fd=open(st->device_path,O_RDWR)) < 0) {
330             fatal_perror("%s: can't open %s (2)",st->nl.name,st->device_path);
331         }
332         if (ioctl(if_fd,I_PUSH,"ip") < 0) {
333             fatal_perror("%s: can't push IP module",st->nl.name);
334         }
335         if (ioctl(if_fd,IF_UNITSEL,(char *)&ppa) < 0) {
336             fatal_perror("%s: can't set ppa %d",st->nl.name,ppa);
337         }
338         if (ioctl(ip_fd, I_LINK, if_fd) < 0) {
339             fatal_perror("%s: can't link TUN device to IP",st->nl.name);
340         }
341         st->interface_name=safe_malloc(10,"tun_apply");
342         sprintf(st->interface_name,"tun%d",ppa);
343         st->fd=tun_fd;
344         setcloexec(if_ifd);
345         setcloexec(ip_ifd);
346 #else
347         fatal("tun_phase_hook: TUN_FLAVOUR_STREAMS unexpected");
348 #endif /* HAVE_TUN_STREAMS */
349     } else {
350         fatal("tun_phase_hook: unknown flavour of TUN");
351     }
352     /* All the networks we'll be using have been registered. Invoke ifconfig
353        to set the TUN device's address, and route to add routes to all
354        our networks. */
355
356     setcloexec(st->fd);
357     setnonblock(st->fd);
358
359     hostaddr=ipaddr_to_string(st->nl.local_address);
360     secnetaddr=ipaddr_to_string(st->nl.secnet_address);
361     snprintf(mtu,sizeof(mtu),"%d",st->nl.mtu);
362     mtu[5]=0;
363
364     switch (st->ifconfig_type) {
365     case TUN_CONFIG_LINUX:
366         sys_cmd(st->ifconfig_path,"ifconfig",st->interface_name,
367                 hostaddr,"netmask","255.255.255.255","-broadcast",
368                 "-multicast",
369                 "pointopoint",secnetaddr,"mtu",mtu,"up",(char *)0);
370         break;
371     case TUN_CONFIG_BSD:
372         sys_cmd(st->ifconfig_path,"ifconfig",st->interface_name,
373                 hostaddr,"netmask","255.255.255.255",
374                 secnetaddr,"mtu",mtu,"up",(char *)0);
375         break;
376     case TUN_CONFIG_SOLARIS25:
377         sys_cmd(st->ifconfig_path,"ifconfig",st->interface_name,
378                 hostaddr,secnetaddr,"mtu",mtu,"up",(char *)0);
379         break;
380     case TUN_CONFIG_IOCTL:
381 #if HAVE_NET_IF_H && ! __APPLE__
382     {
383         int fd;
384         struct ifreq ifr;
385         struct sockaddr_in *sa;
386         fd=socket(PF_INET, SOCK_DGRAM, IPPROTO_IP);
387
388         /* Interface address */
389         strncpy(ifr.ifr_name,st->interface_name,IFNAMSIZ);
390         sa=(struct sockaddr_in *)&ifr.ifr_addr;
391         FILLZERO(*sa);
392         sa->sin_family=AF_INET;
393         sa->sin_addr.s_addr=htonl(st->nl.local_address);
394         if (ioctl(fd,SIOCSIFADDR, &ifr)!=0) {
395             fatal_perror("tun_apply: SIOCSIFADDR");
396         }
397 #ifdef SIOCSIFNETMASK
398         /* Netmask */
399         strncpy(ifr.ifr_name,st->interface_name,IFNAMSIZ);
400         sa=(struct sockaddr_in *)&ifr.ifr_netmask;
401         FILLZERO(*sa);
402         sa->sin_family=AF_INET;
403         sa->sin_addr.s_addr=htonl(0xffffffff);
404         if (ioctl(fd,SIOCSIFNETMASK, &ifr)!=0) {
405             fatal_perror("tun_apply: SIOCSIFNETMASK");
406         }
407 #endif
408         /* Destination address (point-to-point) */
409         strncpy(ifr.ifr_name,st->interface_name,IFNAMSIZ);
410         sa=(struct sockaddr_in *)&ifr.ifr_dstaddr;
411         FILLZERO(*sa);
412         sa->sin_family=AF_INET;
413         sa->sin_addr.s_addr=htonl(st->nl.secnet_address);
414         if (ioctl(fd,SIOCSIFDSTADDR, &ifr)!=0) {
415             fatal_perror("tun_apply: SIOCSIFDSTADDR");
416         }
417         /* MTU */
418         strncpy(ifr.ifr_name,st->interface_name,IFNAMSIZ);
419         ifr.ifr_mtu=st->nl.mtu;
420         if (ioctl(fd,SIOCSIFMTU, &ifr)!=0) {
421             fatal_perror("tun_apply: SIOCSIFMTU");
422         }
423         /* Flags */
424         strncpy(ifr.ifr_name,st->interface_name,IFNAMSIZ);
425         ifr.ifr_flags=IFF_UP|IFF_POINTOPOINT|IFF_RUNNING|IFF_NOARP;
426         if (ioctl(fd,SIOCSIFFLAGS, &ifr)!=0) {
427             fatal_perror("tun_apply: SIOCSIFFLAGS");
428         }
429
430         close(fd);
431     }
432 #else
433     fatal("tun_apply: ifconfig by ioctl() not supported");
434 #endif /* HAVE_NET_IF_H */
435     break;
436     default:
437         fatal("tun_apply: unsupported ifconfig method");
438         break;
439     }
440         
441     for (r=st->nl.clients; r; r=r->next) {
442         tun_set_route(st,r);
443     }
444
445     /* Register for poll() */
446     register_for_poll(st, tun_beforepoll, tun_afterpoll, st->nl.name);
447 }
448
449 static list_t *tun_create(closure_t *self, struct cloc loc, dict_t *context,
450                           list_t *args,uint32_t default_flavour)
451 {
452     struct tun *st;
453     item_t *item;
454     dict_t *dict;
455     string_t flavour,type;
456
457     st=safe_malloc(sizeof(*st),"tun_apply");
458
459     /* First parameter must be a dict */
460     item=list_elem(args,0);
461     if (!item || item->type!=t_dict)
462         cfgfatal(loc,"tun","parameter must be a dictionary\n");
463     
464     dict=item->data.dict;
465
466     st->netlink_to_tunnel=
467         netlink_init(&st->nl,st,loc,dict,
468                      "netlink-tun",tun_set_route,tun_deliver_to_kernel);
469
470     flavour=dict_read_string(dict,"flavour",False,"tun-netlink",loc);
471     if (flavour)
472         st->tun_flavour=string_to_word(flavour,loc,flavours,"tun-flavour");
473     else
474         st->tun_flavour=default_flavour;
475
476     st->device_path=dict_read_string(dict,"device",False,"tun-netlink",loc);
477     st->ip_path=dict_read_string(dict,"ip-path",False,"tun-netlink",loc);
478     st->interface_name=dict_read_string(dict,"interface",False,
479                                         "tun-netlink",loc);
480     st->search_for_if=dict_read_bool(dict,"interface-search",False,
481                                      "tun-netlink",loc,st->device_path==NULL);
482
483     type=dict_read_string(dict,"ifconfig-type",False,"tun-netlink",loc);
484     if (type) st->ifconfig_type=string_to_word(type,loc,config_types,
485                                                "ifconfig-type");
486     else st->ifconfig_type=TUN_CONFIG_GUESS;
487     st->ifconfig_path=dict_read_string(dict,"ifconfig-path",False,
488                                        "tun-netlink",loc);
489
490     type=dict_read_string(dict,"route-type",False,"tun-netlink",loc);
491     if (type) st->route_type=string_to_word(type,loc,config_types,
492                                             "route-type");
493     else st->route_type=TUN_CONFIG_GUESS;
494     st->route_path=dict_read_string(dict,"route-path",False,"tun-netlink",loc);
495
496     st->buff=find_cl_if(dict,"buffer",CL_BUFFER,True,"tun-netlink",loc);
497
498     if (st->tun_flavour==TUN_FLAVOUR_GUESS) {
499         /* If we haven't been told what type of TUN we're using, take
500            a guess based on the system details. */
501         struct utsname u;
502         if (uname(&u)<0) {
503             fatal_perror("tun_create: uname");
504         }
505         if (strcmp(u.sysname,"Linux")==0) {
506             st->tun_flavour=TUN_FLAVOUR_LINUX;
507         } else if (strcmp(u.sysname,"SunOS")==0) {
508             st->tun_flavour=TUN_FLAVOUR_STREAMS;
509         } else if (strcmp(u.sysname,"FreeBSD")==0
510                    || strcmp(u.sysname,"Darwin")==0) {
511             st->tun_flavour=TUN_FLAVOUR_BSD;
512         }
513     }
514     if (st->tun_flavour==TUN_FLAVOUR_GUESS) {
515         cfgfatal(loc,"tun","cannot guess which type of TUN is in use; "
516                  "specify the flavour explicitly\n");
517     }
518
519     if (st->ifconfig_type==TUN_CONFIG_GUESS) {
520         switch (st->tun_flavour) {
521         case TUN_FLAVOUR_LINUX:
522             st->ifconfig_type=TUN_CONFIG_IOCTL;
523             break;
524         case TUN_FLAVOUR_BSD:
525 #if __linux__
526             /* XXX on Linux we still want TUN_CONFIG_IOCTL.  Perhaps we can
527                use this on BSD too. */
528             st->ifconfig_type=TUN_CONFIG_IOCTL;
529 #else     
530             st->ifconfig_type=TUN_CONFIG_BSD;
531 #endif
532             break;
533         case TUN_FLAVOUR_STREAMS:
534             st->ifconfig_type=TUN_CONFIG_BSD;
535             break;
536         }
537     }
538     if (st->route_type==TUN_CONFIG_GUESS)
539         st->route_type=st->ifconfig_type;
540
541     if (st->ifconfig_type==TUN_CONFIG_GUESS) {
542         cfgfatal(loc,"tun","cannot guess which ifconfig method to use\n");
543     }
544     if (st->route_type==TUN_CONFIG_GUESS) {
545         cfgfatal(loc,"tun","cannot guess which route method to use\n");
546     }
547
548     if (st->ifconfig_type==TUN_CONFIG_IOCTL && st->ifconfig_path) {
549         cfgfatal(loc,"tun","ifconfig-type \"ioctl\" is incompatible with "
550                  "ifconfig-path\n");
551     }
552     if (st->route_type==TUN_CONFIG_IOCTL && st->route_path) {
553         cfgfatal(loc,"tun","route-type \"ioctl\" is incompatible with "
554                  "route-path\n");
555     }
556
557     Message(M_DEBUG_CONFIG,"%s: tun flavour %s\n",st->nl.name,
558             tun_flavour_str(st->tun_flavour));
559     switch (st->tun_flavour) {
560     case TUN_FLAVOUR_BSD:
561         if (!st->device_path) st->device_path="/dev/tun";
562         break;
563     case TUN_FLAVOUR_LINUX:
564         if (!st->device_path) st->device_path="/dev/net/tun";
565         break;
566     case TUN_FLAVOUR_STREAMS:
567         if (!st->device_path) st->device_path="/dev/tun";
568         if (st->interface_name) cfgfatal(loc,"tun","interface name cannot "
569                                          "be specified with STREAMS TUN\n");
570         break;
571     }
572     
573     if (!st->ip_path) st->ip_path="/dev/ip";
574     if (!st->ifconfig_path) st->ifconfig_path="ifconfig";
575     if (!st->route_path) st->route_path="route";
576
577 #ifndef HAVE_TUN_STREAMS
578     if (st->tun_flavour==TUN_FLAVOUR_STREAMS) {
579         cfgfatal(loc,"tun","TUN flavour STREAMS unsupported in this build "
580                  "of secnet\n");
581     }
582 #endif
583 #ifndef LINUX_TUN_SUPPORTED
584     if (st->tun_flavour==TUN_FLAVOUR_LINUX) {
585         cfgfatal(loc,"tun","TUN flavour LINUX unsupported in this build "
586                  "of secnet\n");
587     }
588 #endif
589
590     /* Old TUN interface: the network interface name depends on which
591        /dev/tunX file we open. If 'interface-search' is set to true, treat
592        'device' as the prefix and try numbers from 0--255. If it's set
593        to false, treat 'device' as the whole name, and require than an
594        appropriate interface name be specified. */
595     if (st->tun_flavour==TUN_FLAVOUR_BSD) {
596         if (st->search_for_if && st->interface_name) {
597             cfgfatal(loc,"tun","you may not specify an interface name "
598                      "in interface-search mode\n");
599         }
600         if (!st->search_for_if && !st->interface_name) {
601             cfgfatal(loc,"tun","you must specify an interface name "
602                      "when you explicitly specify a TUN device file\n");
603         }
604     }
605
606     add_hook(PHASE_GETRESOURCES,tun_phase_hook,st);
607
608     return new_closure(&st->nl.cl);
609 }
610
611 static list_t *tun_apply(closure_t *self, struct cloc loc, dict_t *context,
612                          list_t *args)
613 {
614     return tun_create(self,loc,context,args,TUN_FLAVOUR_GUESS);
615 }
616
617 static list_t *tun_bsd_apply(closure_t *self, struct cloc loc, dict_t *context,
618                              list_t *args)
619 {
620     Message(M_WARNING,"(%s,%d): obsolete use of tun-old; replace with tun "
621             "and specify flavour \"bsd\".\n",loc.file,loc.line);
622     return tun_create(self,loc,context,args,TUN_FLAVOUR_BSD);
623 }
624
625 void tun_module(dict_t *dict)
626 {
627     add_closure(dict,"tun",tun_apply);
628     add_closure(dict,"tun-old",tun_bsd_apply);
629 }