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