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 static const char *udp_addr_to_string(void *commst, const struct comm_addr *ca)
  36 {
  37     struct udp *st=commst;
  38     struct udpsocks *socks=&st->socks;
  39     static char sbuf[100];
  40     int ix=ca->ix>=0 ? ca->ix : 0;
  41
  42     assert(ix>=0 && ix<socks->n_socks);
  43     snprintf(sbuf, sizeof(sbuf), "udp:%d:%s-%s",
  44              ca->ix,
  45              iaddr_to_string(&socks->socks[ix].addr),
  46              iaddr_to_string(&ca->ia));
  47     return sbuf;
  48 }
  49
  50 static int udp_socks_beforepoll(void *state, struct pollfd *fds, int *nfds_io,
  51                                 int *timeout_io)
  52 {
  53     struct udpsocks *socks=state;
  54     int i;
  55     BEFOREPOLL_WANT_FDS(socks->n_socks);
  56     for (i=0; i<socks->n_socks; i++) {
  57         fds[i].fd=socks->socks[i].fd;
  58         fds[i].events=POLLIN;
  59     }
  60     return 0;
  61 }
  62
  63 const char *af_name(int af)
  64 {
  65     switch (af) {
  66     case AF_INET6: return "IPv6";
  67     case AF_INET:  return "IPv4";
  68     case 0:        return "(any)";
  69     default: abort();
  70     }
  71 }
  72
  73 void udp_sock_experienced(struct log_if *lg, struct udpcommon *uc,
  74                           const char *socksdesc, struct udpsock *us,
  75                           bool_t recvsend, int af,
  76                           int r, int errnoval)
  77 {
  78     bool_t success=r>=0;
  79     if (us->experienced[recvsend][af][success]++)
  80         return;
  81     lg_perror(lg, uc->cc.cl.description, &uc->cc.loc,
  82               success ? M_INFO : M_WARNING,
  83               success ? 0 : errnoval,
  84               "%s %s experiencing some %s %s%s%s",
  85               socksdesc,iaddr_to_string(&us->addr),
  86               success?"success":"trouble",
  87               recvsend?"transmitting":"receiving",
  88               af?" ":"", af?af_name(af):"");
  89 }
  90
  91 static void udp_socks_afterpoll(void *state, struct pollfd *fds, int nfds)
  92 {
  93     struct udpsocks *socks=state;
  94     struct udpcommon *uc=socks->uc;
  95     union iaddr from;
  96     socklen_t fromlen;
  97     bool_t done;
  98     int rv;
  99     int i;
 100
 101     struct commcommon *cc=&uc->cc;
 102
 103     for (i=0; i<socks->n_socks; i++) {
 104         struct udpsock *us=&socks->socks[i];
 105         if (i>=nfds) continue;
 106         if (!(fds[i].revents & POLLIN)) continue;
 107         assert(fds[i].fd == us->fd);
 108         int fd=us->fd;
 109         do {
 110             FILLZERO(from);
 111             fromlen=sizeof(from);
 112             BUF_ASSERT_FREE(cc->rbuf);
 113             BUF_ALLOC(cc->rbuf,"udp_afterpoll");
 114             buffer_init(cc->rbuf,calculate_max_start_pad());
 115             rv=recvfrom(fd, cc->rbuf->start,
 116                         buf_remaining_space(cc->rbuf),
 117                         0, (struct sockaddr *)&from, &fromlen);
 118             if (rv>0) {
 119                 cc->rbuf->size=rv;
 120                 if (uc->use_proxy) {
 121                     /* Check that the packet came from our poxy server;
 122                        we shouldn't be contacted directly by anybody else
 123                        (since they can trivially forge source addresses) */
 124                     if (!iaddr_equal(&from,&uc->proxy)) {
 125                         Message(M_INFO,"udp: received packet that's not "
 126                                 "from the proxy\n");
 127                         BUF_FREE(cc->rbuf);
 128                         continue;
 129                     }
 130                     /* proxy protocol supports ipv4 transport only */
 131                     FILLZERO(from);
 132                     from.sa.sa_family=AF_INET;
 133                     BUF_GET_BYTES(unprepend,cc->rbuf,&from.sin.sin_addr,4);
 134                     buf_unprepend(cc->rbuf,2);
 135                     BUF_GET_BYTES(unprepend,cc->rbuf,&from.sin.sin_port,2);
 136                 }
 137                 struct comm_addr ca;
 138                 FILLZERO(ca);
 139                 ca.comm=&cc->ops;
 140                 ca.ia=from;
 141                 ca.ix=i;
 142                 done=comm_notify(&cc->notify, cc->rbuf, &ca);
 143                 if (!done) {
 144                     uint32_t msgtype;
 145                     if (cc->rbuf->size>12 /* prevents traffic amplification */
 146                         && ((msgtype=get_uint32(cc->rbuf->start+8))
 147                             != LABEL_NAK)) {
 148                         uint32_t source,dest;
 149                         /* Manufacture and send NAK packet */
 150                         source=get_uint32(cc->rbuf->start); /* Us */
 151                         dest=get_uint32(cc->rbuf->start+4); /* Them */
 152                         send_nak(&ca,source,dest,msgtype,cc->rbuf,"unwanted");
 153                     }
 154                     BUF_FREE(cc->rbuf);
 155                 }
 156                 BUF_ASSERT_FREE(cc->rbuf);
 157             } else { /* rv<=0 */
 158                 if (errno!=EINTR && !iswouldblock(errno))
 159                     udp_sock_experienced(0,uc, "socket",us, 0,0, rv,errno);
 160                 BUF_FREE(cc->rbuf);
 161             }
 162         } while (rv>=0);
 163     }
 164 }
 165
 166 static bool_t udp_sendmsg(void *commst, struct buffer_if *buf,
 167                           const struct comm_addr *dest)
 168 {
 169     struct udp *st=commst;
 170     struct udpcommon *uc=&st->uc;
 171     struct udpsocks *socks=&st->socks;
 172     uint8_t *sa;
 173
 174     if (uc->use_proxy) {
 175         struct udpsock *us=&socks->socks[0];
 176         sa=buf_prepend(buf,8);
 177         if (dest->ia.sa.sa_family != AF_INET) {
 178             Message(M_INFO,
 179                "udp: proxy means dropping outgoing non-IPv4 packet to %s\n",
 180                     iaddr_to_string(&dest->ia));
 181             return False;
 182         }
 183         memcpy(sa,&dest->ia.sin.sin_addr,4);
 184         memset(sa+4,0,4);
 185         memcpy(sa+6,&dest->ia.sin.sin_port,2);
 186         int r=sendto(us->fd,sa,buf->size+8,0,
 187                      (struct sockaddr *)&uc->proxy,
 188                      sizeof(uc->proxy));
 189         udp_sock_experienced(0,uc, "proxy",us, 1,0, r,errno);
 190         buf_unprepend(buf,8);
 191     } else {
 192         int i,r;
 193         bool_t allunsupported=True;
 194         int af=dest->ia.sa.sa_family;
 195         for (i=0; i<socks->n_socks; i++) {
 196             struct udpsock *us=&socks->socks[i];
 197             if (us->addr.sa.sa_family != af)
 198                 /* no point even trying */
 199                 continue;
 200             r=sendto(us->fd, buf->start, buf->size, 0,
 201                      &dest->ia.sa, iaddr_socklen(&dest->ia));
 202             udp_sock_experienced(0,uc, "socket",us, 1,af, r,errno);
 203             if (!r) return True;
 204             if (!(errno==EAFNOSUPPORT || errno==ENETUNREACH))
 205                 /* who knows what that error means? */
 206                 allunsupported=False;
 207         }
 208         return !allunsupported; /* see doc for comm_sendmsg_fn in secnet.h */
 209     }
 210
 211     return True;
 212 }
 213
 214 void udp_destroy_socket(struct udpcommon *uc, struct udpsock *us)
 215 {
 216     if (us->fd>=0) {
 217         close(us->fd);
 218         us->fd=-1;
 219     }
 220 }
 221
 222 bool_t udp_make_socket(struct udpcommon *uc, struct udpsock *us,
 223                        int failmsgclass)
 224 {
 225     const union iaddr *addr=&us->addr;
 226     struct commcommon *cc=&uc->cc;
 227     us->fd=-1;
 228
 229 #define FAIL_LG 0, cc->cl.description, &cc->loc, failmsgclass
 230 #define FAIL(...) do{                                           \
 231         lg_perror(FAIL_LG,errno,__VA_ARGS__);   \
 232         goto failed;                                            \
 233     }while(0)
 234
 235     FILLZERO(us->experienced);
 236     us->fd=socket(addr->sa.sa_family, SOCK_DGRAM, IPPROTO_UDP);
 237     if (us->fd<0) FAIL("socket");
 238     setnonblock(us->fd);
 239     setcloexec(us->fd);
 240 #ifdef CONFIG_IPV6
 241     if (addr->sa.sa_family==AF_INET6) {
 242         int r;
 243         int optval=1;
 244         socklen_t optlen=sizeof(optval);
 245         r=setsockopt(us->fd,IPPROTO_IPV6,IPV6_V6ONLY,&optval,optlen);
 246         if (r) FAIL("setsockopt(,IPV6_V6ONLY,&1,)");
 247     }
 248 #endif
 249
 250     if (uc->authbind) {
 251         pid_t c;
 252         int status;
 253
 254         /* XXX this fork() and waitpid() business needs to be hidden
 255            in some system-specific library functions. */
 256         c=fork();
 257         if (c==-1)
 258             FAIL("fork() for authbind");
 259         if (c==0) {
 260             char *argv[5], addrstr[33], portstr[5];
 261             const char *addrfam;
 262             int port;
 263             afterfork();
 264             switch (addr->sa.sa_family) {
 265             case AF_INET:
 266                 sprintf(addrstr,"%08lX",(long)addr->sin.sin_addr.s_addr);
 267                 port=addr->sin.sin_port;
 268                 addrfam=NULL;
 269                 break;
 270 #ifdef CONFIG_IPV6
 271             case AF_INET6: {
 272                 int i;
 273                 for (i=0; i<16; i++)
 274                     sprintf(addrstr+i*2,"%02X",addr->sin6.sin6_addr.s6_addr[i]);
 275                 port=addr->sin6.sin6_port;
 276                 addrfam="6";
 277                 break;
 278             }
 279 #endif /*CONFIG_IPV6*/
 280             default:
 281                 fatal("udp (%s:%d): unsupported address family for authbind",
 282                       cc->loc.file,cc->loc.line);
 283             }
 284             sprintf(portstr,"%04X",port);
 285             argv[0]=uc->authbind;
 286             argv[1]=addrstr;
 287             argv[2]=portstr;
 288             argv[3]=(char*)addrfam;
 289             argv[4]=NULL;
 290             dup2(us->fd,0);
 291             execvp(uc->authbind,argv);
 292             _exit(255);
 293         }
 294         while (waitpid(c,&status,0)==-1) {
 295             if (errno==EINTR) continue;
 296             FAIL("waitpid for authbind");
 297         }
 298         if (status) {
 299             lg_exitstatus(FAIL_LG,status,"authbind");
 300             goto failed;
 301         }
 302     } else {
 303         if (bind(us->fd, &addr->sa, iaddr_socklen(addr))!=0)
 304             FAIL("bind (%s)",iaddr_to_string(addr));
 305     }
 306     return True;
 307
 308 failed:
 309     udp_destroy_socket(uc,us);
 310     return False;
 311
 312 #undef FAIL
 313 }
 314
 315 void udp_socks_register(struct udpcommon *uc, struct udpsocks *socks)
 316 {
 317     socks->uc=uc;
 318     socks->interest=
 319         register_for_poll(socks,udp_socks_beforepoll,udp_socks_afterpoll,"udp");
 320 }
 321
 322 void udp_socks_deregister(struct udpcommon *uc, struct udpsocks *socks)
 323 {
 324     socks->uc=uc;
 325     deregister_for_poll(socks->interest);
 326 }
 327
 328 static void udp_phase_hook(void *sst, uint32_t new_phase)
 329 {
 330     struct udp *st=sst;
 331     struct udpsocks *socks=&st->socks;
 332     struct udpcommon *uc=&st->uc;
 333     int i;
 334     for (i=0; i<socks->n_socks; i++)
 335         udp_make_socket(uc,&socks->socks[i],M_FATAL);
 336
 337     udp_socks_register(uc,socks);
 338 }
 339
 340 static list_t *udp_apply(closure_t *self, struct cloc loc, dict_t *context,
 341                          list_t *args)
 342 {
 343     struct udp *st;
 344     list_t *caddrl;
 345     list_t *l;
 346     uint32_t a;
 347     int i;
 348
 349     COMM_APPLY(st,&st->uc.cc,udp_,"udp",loc);
 350     COMM_APPLY_STANDARD(st,&st->uc.cc,"udp",args);
 351     UDP_APPLY_STANDARD(st,&st->uc,"udp");
 352
 353     struct udpcommon *uc=&st->uc;
 354     struct udpsocks *socks=&st->socks;
 355     struct commcommon *cc=&uc->cc;
 356
 357     union iaddr defaultaddrs[] = {
 358 #ifdef CONFIG_IPV6
 359         { .sin6 = { .sin6_family=AF_INET6,
 360                     .sin6_port=htons(uc->port),
 361                     .sin6_addr=IN6ADDR_ANY_INIT } },
 362 #endif
 363         { .sin = { .sin_family=AF_INET,
 364                    .sin_port=htons(uc->port),
 365                    .sin_addr= { .s_addr=INADDR_ANY } } }
 366     };
 367
 368     caddrl=dict_lookup(d,"address");
 369     socks->n_socks=caddrl ? list_length(caddrl) : (int)ARRAY_SIZE(defaultaddrs);
 370     if (socks->n_socks<=0 || socks->n_socks>UDP_MAX_SOCKETS)
 371         cfgfatal(cc->loc,"udp","`address' must be 1..%d addresses",
 372                  UDP_MAX_SOCKETS);
 373
 374     for (i=0; i<socks->n_socks; i++) {
 375         struct udpsock *us=&socks->socks[i];
 376         FILLZERO(us->addr);
 377         if (!list_length(caddrl)) {
 378             us->addr=defaultaddrs[i];
 379         } else {
 380             text2iaddr(list_elem(caddrl,i),uc->port,
 381                        &us->addr,"udp");
 382         }
 383         us->fd=-1;
 384     }
 385
 386     uc->authbind=dict_read_string(d,"authbind",False,"udp",cc->loc);
 387     l=dict_lookup(d,"proxy");
 388     if (l) {
 389         uc->use_proxy=True;
 390         FILLZERO(uc->proxy);
 391         uc->proxy.sa.sa_family=AF_INET;
 392         item=list_elem(l,0);
 393         if (!item || item->type!=t_string) {
 394             cfgfatal(cc->loc,"udp","proxy must supply ""addr"",port\n");
 395         }
 396         a=string_item_to_ipaddr(item,"proxy");
 397         uc->proxy.sin.sin_addr.s_addr=htonl(a);
 398         item=list_elem(l,1);
 399         if (!item || item->type!=t_number) {
 400             cfgfatal(cc->loc,"udp","proxy must supply ""addr"",port\n");
 401         }
 402         uc->proxy.sin.sin_port=htons(item->data.number);
 403     }
 404
 405     update_max_start_pad(&comm_max_start_pad, uc->use_proxy ? 8 : 0);
 406
 407     add_hook(PHASE_GETRESOURCES,udp_phase_hook,st);
 408
 409     return new_closure(&cc->cl);
 410 }
 411
 412 void udp_module(dict_t *dict)
 413 {
 414     add_closure(dict,"udp",udp_apply);
 415 }