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[secnet.git] / udp.c
1 /* UDP send/receive module for secnet */
2
3 /* This module enables sites to communicate by sending UDP
4  * packets. When an instance of the module is created we can
5  * optionally bind to a particular local IP address (not implemented
6  * yet).
7  *
8  * Packets are offered to registered receivers in turn. Once one
9  * accepts it, it isn't offered to any more. */
10
11 #include "secnet.h"
12 #include <stdio.h>
13 #include <unistd.h>
14 #include <fcntl.h>
15 #include <string.h>
16 #include <errno.h>
17 #include <sys/socket.h>
18 #include <sys/wait.h>
19 #include <netinet/in.h>
20 #include <arpa/inet.h>
21 #include "util.h"
22 #include "magic.h"
23 #include "unaligned.h"
24 #include "ipaddr.h"
25 #include "magic.h"
26 #include "comm-common.h"
27
28 static comm_sendmsg_fn udp_sendmsg;
29
30 struct udp {
31     struct udpcommon uc;
32     struct udpsocks socks;
33 };
34
35 /*
36  * Re comm_addr.ix: This field allows us to note in the comm_addr
37  * which socket an incoming packet was received on.  This is required
38  * for conveniently logging the actual source of a packet.  But the ix
39  * does not formally form part of the address: it is not used when
40  * sending, nor when comparing two comm_addrs.
41  *
42  * The special value -1 means that the comm_addr was constructed by
43  * another module in secnet (eg the resolver), rather than being a
44  * description of the source of an incoming packet.
45  */
46
47 static const char *udp_addr_to_string(void *commst, const struct comm_addr *ca)
48 {
49     struct udp *st=commst;
50     struct udpsocks *socks=&st->socks;
51     static char sbuf[100];
52     int ix=ca->ix>=0 ? ca->ix : 0;
53
54     assert(ix>=0 && ix<socks->n_socks);
55     snprintf(sbuf, sizeof(sbuf), "udp:%s%s-%s",
56              iaddr_to_string(&socks->socks[ix].addr),
57              ca->ix<0 ? "&" : "",
58              iaddr_to_string(&ca->ia));
59     return sbuf;
60 }
61
62 static int udp_socks_beforepoll(void *state, struct pollfd *fds, int *nfds_io,
63                                 int *timeout_io)
64 {
65     struct udpsocks *socks=state;
66     int i;
67     BEFOREPOLL_WANT_FDS(socks->n_socks);
68     for (i=0; i<socks->n_socks; i++) {
69         fds[i].fd=socks->socks[i].fd;
70         fds[i].events=POLLIN;
71     }
72     return 0;
73 }
74
75 static void udp_socks_afterpoll(void *state, struct pollfd *fds, int nfds)
76 {
77     struct udpsocks *socks=state;
78     struct udpcommon *uc=socks->uc;
79     union iaddr from;
80     socklen_t fromlen;
81     bool_t done;
82     int rv;
83     int i;
84
85     struct commcommon *cc=&uc->cc;
86
87     for (i=0; i<socks->n_socks; i++) {
88         if (i>=nfds) continue;
89         if (!(fds[i].revents & POLLIN)) continue;
90         assert(fds[i].fd == socks->socks[i].fd);
91         int fd=socks->socks[i].fd;
92         do {
93             fromlen=sizeof(from);
94             BUF_ASSERT_FREE(cc->rbuf);
95             BUF_ALLOC(cc->rbuf,"udp_afterpoll");
96             buffer_init(cc->rbuf,calculate_max_start_pad());
97             rv=recvfrom(fd, cc->rbuf->start,
98                         buf_remaining_space(cc->rbuf),
99                         0, &from.sa, &fromlen);
100             if (rv>0) {
101                 cc->rbuf->size=rv;
102                 if (uc->use_proxy) {
103                     /* Check that the packet came from our poxy server;
104                        we shouldn't be contacted directly by anybody else
105                        (since they can trivially forge source addresses) */
106                     if (!iaddr_equal(&from,&uc->proxy)) {
107                         Message(M_INFO,"udp: received packet that's not "
108                                 "from the proxy\n");
109                         BUF_FREE(cc->rbuf);
110                         continue;
111                     }
112                     /* proxy protocol supports ipv4 transport only */
113                     from.sa.sa_family=AF_INET;
114                     BUF_GET_BYTES(unprepend,cc->rbuf,&from.sin.sin_addr,4);
115                     buf_unprepend(cc->rbuf,2);
116                     BUF_GET_BYTES(unprepend,cc->rbuf,&from.sin.sin_port,2);
117                 }
118                 struct comm_addr ca;
119                 ca.comm=&cc->ops;
120                 ca.ia=from;
121                 ca.ix=i;
122                 done=comm_notify(&cc->notify, cc->rbuf, &ca);
123                 if (!done) {
124                     uint32_t msgtype;
125                     if (cc->rbuf->size>12 /* prevents traffic amplification */
126                         && ((msgtype=get_uint32(cc->rbuf->start+8))
127                             != LABEL_NAK)) {
128                         uint32_t source,dest;
129                         /* Manufacture and send NAK packet */
130                         source=get_uint32(cc->rbuf->start); /* Us */
131                         dest=get_uint32(cc->rbuf->start+4); /* Them */
132                         send_nak(&ca,source,dest,msgtype,cc->rbuf,"unwanted");
133                     }
134                     BUF_FREE(cc->rbuf);
135                 }
136                 BUF_ASSERT_FREE(cc->rbuf);
137             } else {
138                 BUF_FREE(cc->rbuf);
139             }
140         } while (rv>=0);
141     }
142 }
143
144 static bool_t udp_sendmsg(void *commst, struct buffer_if *buf,
145                           const struct comm_addr *dest)
146 {
147     struct udp *st=commst;
148     struct udpcommon *uc=&st->uc;
149     struct udpsocks *socks=&st->socks;
150     uint8_t *sa;
151
152     if (uc->use_proxy) {
153         sa=buf_prepend(buf,8);
154         if (dest->ia.sa.sa_family != AF_INET) {
155             Message(M_INFO,
156                "udp: proxy means dropping outgoing non-IPv4 packet to %s\n",
157                     iaddr_to_string(&dest->ia));
158             return False;
159         }
160         memcpy(sa,&dest->ia.sin.sin_addr,4);
161         memset(sa+4,0,4);
162         memcpy(sa+6,&dest->ia.sin.sin_port,2);
163         sendto(socks->socks[0].fd,sa,buf->size+8,0,&uc->proxy.sa,
164                iaddr_socklen(&uc->proxy));
165         buf_unprepend(buf,8);
166     } else {
167         int i,r;
168         bool_t allunsupported=True;
169         for (i=0; i<socks->n_socks; i++) {
170             if (dest->ia.sa.sa_family != socks->socks[i].addr.sa.sa_family)
171                 /* no point even trying */
172                 continue;
173             r=sendto(socks->socks[i].fd, buf->start, buf->size, 0,
174                      &dest->ia.sa, iaddr_socklen(&dest->ia));
175             if (r>=0) return True;
176             if (!(errno==EAFNOSUPPORT || errno==ENETUNREACH))
177                 /* who knows what that error means? */
178                 allunsupported=False;
179         }
180         return !allunsupported; /* see doc for comm_sendmsg_fn in secnet.h */
181     }
182
183     return True;
184 }
185
186 bool_t udp_make_socket(struct udpcommon *uc, struct udpsock *us,
187                        int failmsgclass)
188 {
189     const union iaddr *addr=&us->addr;
190     struct commcommon *cc=&uc->cc;
191     us->fd=-1;
192
193 #define FAIL_LG 0, cc->cl.description, &cc->loc, failmsgclass
194 #define FAIL(...) do{                                           \
195         lg_perror(FAIL_LG,errno,__VA_ARGS__);   \
196         goto failed;                                            \
197     }while(0)
198
199     us->fd=socket(addr->sa.sa_family, SOCK_DGRAM, IPPROTO_UDP);
200     if (us->fd<0) FAIL("socket");
201     if (fcntl(us->fd, F_SETFL, fcntl(us->fd, F_GETFL)|O_NONBLOCK)==-1)
202         FAIL("fcntl(set O_NONBLOCK)");
203     setcloexec(us->fd);
204 #ifdef CONFIG_IPV6
205     if (addr->sa.sa_family==AF_INET6) {
206         int r;
207         int optval=1;
208         socklen_t optlen=sizeof(optval);
209         r=setsockopt(us->fd,IPPROTO_IPV6,IPV6_V6ONLY,&optval,optlen);
210         if (r) FAIL("setsockopt(,IPV6_V6ONLY,&1,)");
211     }
212 #endif
213
214     if (uc->authbind) {
215         pid_t c;
216         int status;
217
218         /* XXX this fork() and waitpid() business needs to be hidden
219            in some system-specific library functions. */
220         c=fork();
221         if (c==-1)
222             FAIL("fork() for authbind");
223         if (c==0) {
224             char *argv[5], addrstr[33], portstr[5];
225             const char *addrfam;
226             int port;
227             switch (addr->sa.sa_family) {
228             case AF_INET:
229                 sprintf(addrstr,"%08lX",(long)addr->sin.sin_addr.s_addr);
230                 port=addr->sin.sin_port;
231                 addrfam=NULL;
232                 break;
233 #ifdef CONFIG_IPV6
234             case AF_INET6: {
235                 int i;
236                 for (i=0; i<16; i++)
237                     sprintf(addrstr+i*2,"%02X",addr->sin6.sin6_addr.s6_addr[i]);
238                 port=addr->sin6.sin6_port;
239                 addrfam="6";
240                 break;
241             }
242 #endif /*CONFIG_IPV6*/
243             default:
244                 fatal("udp (%s:%d): unsupported address family for authbind",
245                       cc->loc.file,cc->loc.line);
246             }
247             sprintf(portstr,"%04X",port);
248             argv[0]=uc->authbind;
249             argv[1]=addrstr;
250             argv[2]=portstr;
251             argv[3]=(char*)addrfam;
252             argv[4]=NULL;
253             dup2(us->fd,0);
254             execvp(uc->authbind,argv);
255             _exit(255);
256         }
257         while (waitpid(c,&status,0)==-1) {
258             if (errno==EINTR) continue;
259             FAIL("waitpid for authbind");
260         }
261         if (status) {
262             lg_exitstatus(FAIL_LG,status,"authbind");
263             goto failed;
264         }
265     } else {
266         if (bind(us->fd, &addr->sa, iaddr_socklen(addr))!=0)
267             FAIL("bind (%s)",iaddr_to_string(addr));
268     }
269     return True;
270
271 failed:
272     if (us->fd>=0) {
273         close(us->fd);
274         us->fd=-1;
275     }
276     return False;
277
278 #undef FAIL
279 }
280
281 void udp_socks_register(struct udpcommon *uc, struct udpsocks *socks)
282 {
283     socks->uc=uc;
284     socks->interest=
285         register_for_poll(socks,udp_socks_beforepoll,udp_socks_afterpoll,"udp");
286 }
287
288 void udp_socks_deregister(struct udpcommon *uc, struct udpsocks *socks)
289 {
290     socks->uc=uc;
291     deregister_for_poll(socks->interest);
292 }
293
294 static void udp_phase_hook(void *sst, uint32_t new_phase)
295 {
296     struct udp *st=sst;
297     struct udpsocks *socks=&st->socks;
298     struct udpcommon *uc=&st->uc;
299     int i;
300     for (i=0; i<socks->n_socks; i++)
301         udp_make_socket(uc,&socks->socks[i],M_FATAL);
302
303     udp_socks_register(uc,socks);
304 }
305
306 static list_t *udp_apply(closure_t *self, struct cloc loc, dict_t *context,
307                          list_t *args)
308 {
309     struct udp *st;
310     list_t *caddrl;
311     list_t *l;
312     uint32_t a;
313     int i;
314
315     COMM_APPLY(st,&st->uc.cc,udp_,"udp",loc);
316     COMM_APPLY_STANDARD(st,&st->uc.cc,"udp",args);
317     UDP_APPLY_STANDARD(st,&st->uc,"udp");
318
319     struct udpcommon *uc=&st->uc;
320     struct udpsocks *socks=&st->socks;
321     struct commcommon *cc=&uc->cc;
322
323     union iaddr defaultaddrs[] = {
324 #ifdef CONFIG_IPV6
325         { .sin6 = { .sin6_family=AF_INET6,
326                     .sin6_port=htons(uc->port),
327                     .sin6_addr=IN6ADDR_ANY_INIT } },
328 #endif
329         { .sin = { .sin_family=AF_INET,
330                    .sin_port=htons(uc->port),
331                    .sin_addr= { .s_addr=INADDR_ANY } } }
332     };
333
334     caddrl=dict_lookup(d,"address");
335     socks->n_socks=caddrl ? list_length(caddrl) : (int)ARRAY_SIZE(defaultaddrs);
336     if (socks->n_socks<=0 || socks->n_socks>UDP_MAX_SOCKETS)
337         cfgfatal(cc->loc,"udp","`address' must be 1..%d addresses",
338                  UDP_MAX_SOCKETS);
339
340     for (i=0; i<socks->n_socks; i++) {
341         struct udpsock *us=&socks->socks[i];
342         if (!list_length(caddrl)) {
343             us->addr=defaultaddrs[i];
344         } else {
345             string_item_to_iaddr(list_elem(caddrl,i),uc->port,&us->addr,"udp");
346         }
347         us->fd=-1;
348     }
349
350     l=dict_lookup(d,"proxy");
351     if (l) {
352         uc->use_proxy=True;
353         uc->proxy.sa.sa_family=AF_INET;
354         item=list_elem(l,0);
355         if (!item || item->type!=t_string) {
356             cfgfatal(cc->loc,"udp","proxy must supply ""addr"",port\n");
357         }
358         a=string_item_to_ipaddr(item,"proxy");
359         uc->proxy.sin.sin_addr.s_addr=htonl(a);
360         item=list_elem(l,1);
361         if (!item || item->type!=t_number) {
362             cfgfatal(cc->loc,"udp","proxy must supply ""addr"",port\n");
363         }
364         uc->proxy.sin.sin_port=htons(item->data.number);
365     }
366
367     update_max_start_pad(&comm_max_start_pad, uc->use_proxy ? 8 : 0);
368
369     add_hook(PHASE_GETRESOURCES,udp_phase_hook,st);
370
371     return new_closure(&cc->cl);
372 }
373
374 void udp_module(dict_t *dict)
375 {
376     add_closure(dict,"udp",udp_apply);
377 }