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