chiark / gitweb /
site: Pass msg into generate_msg
[secnet.git] / udp.c
1 /* UDP send/receive module for secnet */
2
3 /*
4  * This file is part of secnet.
5  * See README for full list of copyright holders.
6  *
7  * secnet is free software; you can redistribute it and/or modify it
8  * under the terms of the GNU General Public License as published by
9  * the Free Software Foundation; either version 3 of the License, or
10  * (at your option) any later version.
11  * 
12  * secnet is distributed in the hope that it will be useful, but
13  * WITHOUT ANY WARRANTY; without even the implied warranty of
14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
15  * General Public License for more details.
16  * 
17  * You should have received a copy of the GNU General Public License
18  * version 3 along with secnet; if not, see
19  * https://www.gnu.org/licenses/gpl.html.
20  */
21
22 /* This module enables sites to communicate by sending UDP
23  * packets. When an instance of the module is created we can
24  * optionally bind to a particular local IP address (not implemented
25  * yet).
26  *
27  * Packets are offered to registered receivers in turn. Once one
28  * accepts it, it isn't offered to any more. */
29
30 #include "secnet.h"
31 #include <stdio.h>
32 #include <unistd.h>
33 #include <fcntl.h>
34 #include <string.h>
35 #include <errno.h>
36 #include <sys/socket.h>
37 #include <sys/wait.h>
38 #include <netinet/in.h>
39 #include <arpa/inet.h>
40 #include "util.h"
41 #include "magic.h"
42 #include "unaligned.h"
43 #include "ipaddr.h"
44 #include "magic.h"
45 #include "comm-common.h"
46
47 static comm_sendmsg_fn udp_sendmsg;
48
49 struct udp {
50     struct udpcommon uc;
51     struct udpsocks socks;
52     bool_t addr_configured;
53     unsigned counter;
54 };
55
56 /*
57  * Re comm_addr.ix: This field allows us to note in the comm_addr
58  * which socket an incoming packet was received on.  This is required
59  * for conveniently logging the actual source of a packet.  But the ix
60  * does not formally form part of the address: it is not used when
61  * sending, nor when comparing two comm_addrs.
62  *
63  * The special value -1 means that the comm_addr was constructed by
64  * another module in secnet (eg the resolver), rather than being a
65  * description of the source of an incoming packet.
66  */
67
68 static const char *udp_addr_to_string(void *commst, const struct comm_addr *ca)
69 {
70     struct udp *st=commst;
71     struct udpsocks *socks=&st->socks;
72     static char sbuf[100];
73     int ix=ca->ix>=0 ? ca->ix : 0;
74
75     assert(ix>=0 && ix<socks->n_socks);
76     snprintf(sbuf, sizeof(sbuf), "udp#%u@l%d:%s%s-%s",
77              st->counter, st->uc.cc.loc.line,
78              iaddr_to_string(&socks->socks[ix].addr),
79              ca->ix<0 && socks->n_socks>1 ? "&" : "",
80              iaddr_to_string(&ca->ia));
81     return sbuf;
82 }
83
84 static int udp_socks_beforepoll(void *state, struct pollfd *fds, int *nfds_io,
85                                 int *timeout_io)
86 {
87     struct udpsocks *socks=state;
88     int i;
89     BEFOREPOLL_WANT_FDS(socks->n_socks);
90     for (i=0; i<socks->n_socks; i++) {
91         fds[i].fd=socks->socks[i].fd;
92         fds[i].events=POLLIN;
93     }
94     return 0;
95 }
96
97 const char *af_name(int af)
98 {
99     switch (af) {
100     case AF_INET6: return "IPv6";
101     case AF_INET:  return "IPv4";
102     case 0:        return "(any)";
103     default: abort();
104     }
105 }
106
107 void udp_sock_experienced(struct log_if *lg, struct udpcommon *uc,
108                           struct udpsocks *socks, struct udpsock *us,
109                           const union iaddr *dest, int af,
110                           int r, int errnoval)
111 {
112     bool_t success=r>=0;
113     if (us->experienced[!!dest][af][success]++)
114         return;
115     lg_perror(lg, uc->cc.cl.description, &uc->cc.loc,
116               success ? M_INFO : M_WARNING,
117               success ? 0 : errnoval,
118               "%s %s experiencing some %s %s%s%s%s%s%s",
119               socks->desc,iaddr_to_string(&us->addr),
120               success?"success":"trouble",
121               dest?"transmitting":"receiving",
122               af?" ":"", af?af_name(af):"",
123               dest?" (to ":"",
124               dest?iaddr_to_string(dest):"",
125               dest?")":"");
126 }
127
128 static void udp_socks_afterpoll(void *state, struct pollfd *fds, int nfds)
129 {
130     struct udpsocks *socks=state;
131     struct udpcommon *uc=socks->uc;
132     union iaddr from;
133     socklen_t fromlen;
134     bool_t done;
135     int rv;
136     int i;
137
138     struct commcommon *cc=&uc->cc;
139
140     for (i=0; i<socks->n_socks; i++) {
141         struct udpsock *us=&socks->socks[i];
142         if (i>=nfds) continue;
143         if (!(fds[i].revents & POLLIN)) continue;
144         assert(fds[i].fd == us->fd);
145         int fd=us->fd;
146         do {
147             fromlen=sizeof(from);
148             BUF_ASSERT_FREE(cc->rbuf);
149             BUF_ALLOC(cc->rbuf,"udp_afterpoll");
150             buffer_init(cc->rbuf,calculate_max_start_pad());
151             rv=recvfrom(fd, cc->rbuf->start,
152                         buf_remaining_space(cc->rbuf),
153                         0, &from.sa, &fromlen);
154             if (rv>0) {
155                 cc->rbuf->size=rv;
156                 if (uc->use_proxy) {
157                     /* Check that the packet came from our poxy server;
158                        we shouldn't be contacted directly by anybody else
159                        (since they can trivially forge source addresses) */
160                     if (!iaddr_equal(&from,&uc->proxy,False)) {
161                         Message(M_INFO,"udp: received packet that's not "
162                                 "from the proxy\n");
163                         BUF_FREE(cc->rbuf);
164                         continue;
165                     }
166                     /* proxy protocol supports ipv4 transport only */
167                     from.sa.sa_family=AF_INET;
168                     BUF_GET_BYTES(unprepend,cc->rbuf,&from.sin.sin_addr,4);
169                     buf_unprepend(cc->rbuf,2);
170                     BUF_GET_BYTES(unprepend,cc->rbuf,&from.sin.sin_port,2);
171                 }
172                 struct comm_addr ca;
173                 ca.comm=&cc->ops;
174                 ca.ia=from;
175                 ca.ix=i;
176                 done=comm_notify(&cc->notify, cc->rbuf, &ca);
177                 if (done) {
178                     udp_sock_experienced(0,uc,socks,us,0,
179                                          from.sa.sa_family,0,0);
180                 } else {
181                     uint32_t msgtype;
182                     if (cc->rbuf->size>12 /* prevents traffic amplification */
183                         && ((msgtype=get_uint32(cc->rbuf->start+8))
184                             != LABEL_NAK)) {
185                         uint32_t source,dest;
186                         /* Manufacture and send NAK packet */
187                         source=get_uint32(cc->rbuf->start); /* Us */
188                         dest=get_uint32(cc->rbuf->start+4); /* Them */
189                         send_nak(&ca,source,dest,msgtype,cc->rbuf,"unwanted");
190                     }
191                     BUF_FREE(cc->rbuf);
192                 }
193                 BUF_ASSERT_FREE(cc->rbuf);
194             } else { /* rv<=0 */
195                 if (errno!=EINTR && !iswouldblock(errno))
196                     udp_sock_experienced(0,uc,socks,us, 0,0, rv,errno);
197                 BUF_FREE(cc->rbuf);
198             }
199         } while (rv>=0);
200     }
201 }
202
203 static bool_t udp_sendmsg(void *commst, struct buffer_if *buf,
204                           const struct comm_addr *dest,
205                           struct comm_clientinfo *clientinfo)
206 {
207     struct udp *st=commst;
208     struct udpcommon *uc=&st->uc;
209     struct udpsocks *socks=&st->socks;
210     uint8_t *sa;
211
212     if (uc->use_proxy) {
213         struct udpsock *us=&socks->socks[0];
214         sa=buf_prepend(buf,8);
215         if (dest->ia.sa.sa_family != AF_INET) {
216             Message(M_INFO,
217                "udp: proxy means dropping outgoing non-IPv4 packet to %s\n",
218                     iaddr_to_string(&dest->ia));
219             return False;
220         }
221         memcpy(sa,&dest->ia.sin.sin_addr,4);
222         memset(sa+4,0,4);
223         memcpy(sa+6,&dest->ia.sin.sin_port,2);
224         int r=sendto(us->fd,sa,buf->size+8,0,&uc->proxy.sa,
225                iaddr_socklen(&uc->proxy));
226         udp_sock_experienced(0,uc,socks,us, &dest->ia,0, r,errno);
227         buf_unprepend(buf,8);
228     } else {
229         int i,r;
230         bool_t allunsupported=True;
231         int af=dest->ia.sa.sa_family;
232         for (i=0; i<socks->n_socks; i++) {
233             struct udpsock *us=&socks->socks[i];
234             if (us->addr.sa.sa_family != af)
235                 /* no point even trying */
236                 continue;
237             r=sendto(us->fd, buf->start, buf->size, 0,
238                      &dest->ia.sa, iaddr_socklen(&dest->ia));
239             udp_sock_experienced(0,uc,socks,us, &dest->ia,af, r,errno);
240             if (r>=0) return True;
241             if (!(errno==EAFNOSUPPORT || errno==ENETUNREACH))
242                 /* who knows what that error means? */
243                 allunsupported=False;
244         }
245         return !allunsupported; /* see doc for comm_sendmsg_fn in secnet.h */
246     }
247
248     return True;
249 }
250
251 void udp_destroy_socket(struct udpcommon *uc, struct udpsock *us)
252 {
253     if (us->fd>=0) {
254         close(us->fd);
255         us->fd=-1;
256     }
257 }
258
259 #define FAIL_LG 0, cc->cl.description, &cc->loc, failmsgclass
260 #define FAIL(...) do{                                           \
261         lg_perror(FAIL_LG,errno,__VA_ARGS__);   \
262         goto failed;                                            \
263     }while(0)
264
265 static bool_t record_socket_gotaddr(struct udpcommon *uc, struct udpsock *us,
266                                     int failmsgclass)
267 {
268     struct commcommon *cc=&uc->cc;
269     socklen_t salen=sizeof(us->addr);
270     int r=getsockname(us->fd,&us->addr.sa,&salen);
271     if (r) FAIL("getsockname()");
272     if ((size_t)salen>sizeof(us->addr)) /* cast squashes clang warning */
273       { errno=0; FAIL("getsockname() length"); }
274     return True;
275
276  failed:
277     return False;
278 }
279
280 bool_t udp_import_socket(struct udpcommon *uc, struct udpsock *us,
281                          int failmsgclass, int fd)
282 {
283     FILLZERO(us->experienced);
284     us->fd=fd;
285     return record_socket_gotaddr(uc,us,failmsgclass);
286 }
287
288 bool_t udp_make_socket(struct udpcommon *uc, struct udpsock *us,
289                        int failmsgclass)
290 {
291     const union iaddr *addr=&us->addr;
292     struct commcommon *cc=&uc->cc;
293     us->fd=-1;
294
295     FILLZERO(us->experienced);
296     us->fd=socket(addr->sa.sa_family, SOCK_DGRAM, IPPROTO_UDP);
297     if (us->fd<0) FAIL("socket");
298     setnonblock(us->fd);
299     setcloexec(us->fd);
300 #ifdef CONFIG_IPV6
301     if (addr->sa.sa_family==AF_INET6) {
302         int r;
303         int optval=1;
304         socklen_t optlen=sizeof(optval);
305         r=setsockopt(us->fd,IPPROTO_IPV6,IPV6_V6ONLY,&optval,optlen);
306         if (r) FAIL("setsockopt(,IPV6_V6ONLY,&1,)");
307     }
308 #endif
309
310     if (uc->authbind) {
311         pid_t c;
312         int status;
313         char desc[200];
314         snprintf(desc,sizeof(desc),"authbind for %s: %s",
315                  iaddr_to_string(addr), uc->authbind);
316
317         /* XXX this fork() and waitpid() business needs to be hidden
318            in some system-specific library functions. */
319         c=fork();
320         if (c==-1)
321             FAIL("fork() for authbind");
322         if (c==0) {
323             char *argv[5], addrstr[33], portstr[5];
324             const char *addrfam;
325             int port;
326             afterfork();
327             switch (addr->sa.sa_family) {
328             case AF_INET:
329                 sprintf(addrstr,"%08lX",(long)addr->sin.sin_addr.s_addr);
330                 port=addr->sin.sin_port;
331                 addrfam=NULL;
332                 break;
333 #ifdef CONFIG_IPV6
334             case AF_INET6: {
335                 int i;
336                 for (i=0; i<16; i++)
337                     sprintf(addrstr+i*2,"%02X",addr->sin6.sin6_addr.s6_addr[i]);
338                 port=addr->sin6.sin6_port;
339                 addrfam="6";
340                 break;
341             }
342 #endif /*CONFIG_IPV6*/
343             default:
344                 fatal("udp (%s:%d): unsupported address family for authbind",
345                       cc->loc.file,cc->loc.line);
346             }
347             sprintf(portstr,"%04X",port);
348             argv[0]=uc->authbind;
349             argv[1]=addrstr;
350             argv[2]=portstr;
351             argv[3]=(char*)addrfam;
352             argv[4]=NULL;
353             dup2(us->fd,0);
354             execvp(uc->authbind,argv);
355             _exit(255);
356         }
357         while (waitpid(c,&status,0)==-1) {
358             if (errno==EINTR) continue;
359             FAIL("waitpid for authbind");
360         }
361         if (status) {
362             if (WIFEXITED(status) && WEXITSTATUS(status)<127) {
363                 int es=WEXITSTATUS(status);
364                 lg_perror(FAIL_LG,es,
365                           "%s exited with error exit status %d;"
366                           " indicates error",desc,es);
367             } else {
368                 lg_exitstatus(FAIL_LG,status,desc);
369             }
370             goto failed;
371         }
372     } else {
373         if (bind(us->fd, &addr->sa, iaddr_socklen(addr))!=0)
374             FAIL("bind (%s)",iaddr_to_string(addr));
375     }
376
377     bool_t ok=record_socket_gotaddr(uc,us,failmsgclass);
378     if (!ok) goto failed;
379
380     return True;
381
382 failed:
383     udp_destroy_socket(uc,us);
384     return False;
385 }
386
387 #undef FAIL
388
389 void udp_socks_register(struct udpcommon *uc, struct udpsocks *socks,
390                         const char *desc)
391 {
392     socks->uc=uc;
393     socks->desc=desc;
394     socks->interest=
395         register_for_poll(socks,udp_socks_beforepoll,udp_socks_afterpoll,"udp");
396 }
397
398 void udp_socks_deregister(struct udpcommon *uc, struct udpsocks *socks)
399 {
400     socks->uc=uc;
401     deregister_for_poll(socks->interest);
402 }
403
404 void udp_socks_childpersist(struct udpcommon *uc, struct udpsocks *socks)
405 {
406     int i;
407     for (i=0; i<socks->n_socks; i++)
408         udp_destroy_socket(uc,&socks->socks[i]);
409 }
410
411 static void udp_childpersist_hook(void *sst, uint32_t new_phase)
412 {
413     struct udp *st=sst;
414     udp_socks_childpersist(&st->uc,&st->socks);
415 }
416
417 static void udp_phase_hook(void *sst, uint32_t new_phase)
418 {
419     struct udp *st=sst;
420     struct udpsocks *socks=&st->socks;
421     struct udpcommon *uc=&st->uc;
422     int i;
423     bool_t anydone=0;
424
425     for (i=0; i<socks->n_socks; i++) {
426         bool_t required=st->addr_configured
427             || (!anydone && i==socks->n_socks-1);
428         anydone += udp_make_socket(uc,&socks->socks[i],
429                                    required ? M_FATAL : M_WARNING);
430     }
431
432     udp_socks_register(uc,socks, uc->use_proxy ? "proxy" : "socket");
433
434     add_hook(PHASE_CHILDPERSIST,udp_childpersist_hook,st);
435 }
436
437 static list_t *udp_apply(closure_t *self, struct cloc loc, dict_t *context,
438                          list_t *args)
439 {
440     static unsigned counter;
441
442     struct udp *st;
443     list_t *caddrl;
444     list_t *l;
445     uint32_t a;
446     int i;
447
448     COMM_APPLY(st,&st->uc.cc,udp_,"udp",loc);
449     COMM_APPLY_STANDARD(st,&st->uc.cc,"udp",args);
450     UDP_APPLY_STANDARD(st,&st->uc,"udp");
451
452     struct udpcommon *uc=&st->uc;
453     struct udpsocks *socks=&st->socks;
454     struct commcommon *cc=&uc->cc;
455
456     st->counter=counter++;
457
458     union iaddr defaultaddrs[] = {
459 #ifdef CONFIG_IPV6
460         { .sin6 = { .sin6_family=AF_INET6,
461                     .sin6_port=htons(uc->port),
462                     .sin6_addr=IN6ADDR_ANY_INIT } },
463 #endif
464         { .sin = { .sin_family=AF_INET,
465                    .sin_port=htons(uc->port),
466                    .sin_addr= { .s_addr=INADDR_ANY } } }
467     };
468
469     caddrl=dict_lookup(d,"address");
470     st->addr_configured=!!caddrl;
471     socks->n_socks=st->addr_configured ? list_length(caddrl)
472         : (int)ARRAY_SIZE(defaultaddrs);
473     if (socks->n_socks<=0 || socks->n_socks>UDP_MAX_SOCKETS)
474         cfgfatal(cc->loc,"udp","`address' must be 1..%d addresses",
475                  UDP_MAX_SOCKETS);
476
477     for (i=0; i<socks->n_socks; i++) {
478         struct udpsock *us=&socks->socks[i];
479         if (!st->addr_configured) {
480             us->addr=defaultaddrs[i];
481         } else {
482             string_item_to_iaddr(list_elem(caddrl,i),uc->port,&us->addr,"udp");
483         }
484         us->fd=-1;
485     }
486
487     l=dict_lookup(d,"proxy");
488     if (l) {
489         uc->use_proxy=True;
490         uc->proxy.sa.sa_family=AF_INET;
491         item=list_elem(l,0);
492         if (!item || item->type!=t_string) {
493             cfgfatal(cc->loc,"udp","proxy must supply ""addr"",port\n");
494         }
495         a=string_item_to_ipaddr(item,"proxy");
496         uc->proxy.sin.sin_addr.s_addr=htonl(a);
497         item=list_elem(l,1);
498         if (!item || item->type!=t_number) {
499             cfgfatal(cc->loc,"udp","proxy must supply ""addr"",port\n");
500         }
501         uc->proxy.sin.sin_port=htons(item->data.number);
502     }
503
504     update_max_start_pad(&comm_max_start_pad, uc->use_proxy ? 8 : 0);
505
506     add_hook(PHASE_GETRESOURCES,udp_phase_hook,st);
507
508     return new_closure(&cc->cl);
509 }
510
511 void udp_module(dict_t *dict)
512 {
513     add_closure(dict,"udp",udp_apply);
514 }