src/util/client.c

   1 /*
   2      This file is part of GNUnet.
   3      Copyright (C) 2001-2016 GNUnet e.V.
   4
   5      GNUnet is free software; you can redistribute it and/or modify
   6      it under the terms of the GNU General Public License as published
   7      by the Free Software Foundation; either version 3, or (at your
   8      option) any later version.
   9
  10      GNUnet is distributed in the hope that it will be useful, but
  11      WITHOUT ANY WARRANTY; without even the implied warranty of
  12      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13      General Public License for more details.
  14
  15      You should have received a copy of the GNU General Public License
  16      along with GNUnet; see the file COPYING.  If not, write to the
  17      Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  18      Boston, MA 02110-1301, USA.
  19 */
  20
  21 /**
  22  * @file util/client.c
  23  * @brief code for access to services
  24  * @author Christian Grothoff
  25  *
  26  * Generic TCP code for reliable, record-oriented TCP
  27  * connections between clients and service providers.
  28  */
  29 #include "platform.h"
  30 #include "gnunet_protocols.h"
  31 #include "gnunet_util_lib.h"
  32 #include "gnunet_resolver_service.h"
  33 #include "gnunet_socks.h"
  34
  35
  36 #define LOG(kind,...) GNUNET_log_from (kind, "util-client",__VA_ARGS__)
  37
  38 /**
  39  * Timeout we use on TCP connect before trying another
  40  * result from the DNS resolver.  Actual value used
  41  * is this value divided by the number of address families.
  42  * Default is 5s.
  43  */
  44 #define CONNECT_RETRY_TIMEOUT GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_SECONDS, 5)
  45
  46
  47
  48 /**
  49  * Internal state for a client connected to a GNUnet service.
  50  */
  51 struct ClientState;
  52
  53
  54 /**
  55  * During connect, we try multiple possible IP addresses
  56  * to find out which one might work.
  57  */
  58 struct AddressProbe
  59 {
  60
  61   /**
  62    * This is a linked list.
  63    */
  64   struct AddressProbe *next;
  65
  66   /**
  67    * This is a doubly-linked list.
  68    */
  69   struct AddressProbe *prev;
  70
  71   /**
  72    * The address; do not free (allocated at the end of this struct).
  73    */
  74   const struct sockaddr *addr;
  75
  76   /**
  77    * Underlying OS's socket.
  78    */
  79   struct GNUNET_NETWORK_Handle *sock;
  80
  81   /**
  82    * Connection for which we are probing.
  83    */
  84   struct ClientState *cstate;
  85
  86   /**
  87    * Lenth of addr.
  88    */
  89   socklen_t addrlen;
  90
  91   /**
  92    * Task waiting for the connection to finish connecting.
  93    */
  94   struct GNUNET_SCHEDULER_Task *task;
  95 };
  96
  97
  98 /**
  99  * Internal state for a client connected to a GNUnet service.
 100  */
 101 struct ClientState
 102 {
 103
 104   /**
 105    * The connection handle, NULL if not live
 106    */
 107   struct GNUNET_NETWORK_Handle *sock;
 108
 109   /**
 110    * Handle to a pending DNS lookup request, NULL if DNS is finished.
 111    */
 112   struct GNUNET_RESOLVER_RequestHandle *dns_active;
 113
 114   /**
 115    * Our configuration.
 116    */
 117   const struct GNUNET_CONFIGURATION_Handle *cfg;
 118
 119   /**
 120    * Linked list of sockets we are currently trying out
 121    * (during connect).
 122    */
 123   struct AddressProbe *ap_head;
 124
 125   /**
 126    * Linked list of sockets we are currently trying out
 127    * (during connect).
 128    */
 129   struct AddressProbe *ap_tail;
 130
 131   /**
 132    * Name of the service we interact with.
 133    */
 134   char *service_name;
 135
 136   /**
 137    * Hostname, if any.
 138    */
 139   char *hostname;
 140
 141   /**
 142    * Next message to transmit to the service. NULL for none.
 143    */
 144   const struct GNUNET_MessageHeader *msg;
 145
 146   /**
 147    * Task for trying to connect to the service.
 148    */
 149   struct GNUNET_SCHEDULER_Task *retry_task;
 150
 151   /**
 152    * Task for sending messages to the service.
 153    */
 154   struct GNUNET_SCHEDULER_Task *send_task;
 155
 156   /**
 157    * Task for sending messages to the service.
 158    */
 159   struct GNUNET_SCHEDULER_Task *recv_task;
 160
 161   /**
 162    * Tokenizer for inbound messages.
 163    */
 164   struct GNUNET_MessageStreamTokenizer *mst;
 165
 166   /**
 167    * Message queue under our control.
 168    */
 169   struct GNUNET_MQ_Handle *mq;
 170
 171   /**
 172    * Timeout for receiving a response (absolute time).
 173    */
 174   struct GNUNET_TIME_Absolute receive_timeout;
 175
 176   /**
 177    * Current value for our incremental back-off (for
 178    * connect re-tries).
 179    */
 180   struct GNUNET_TIME_Relative back_off;
 181
 182   /**
 183    * TCP port (0 for disabled).
 184    */
 185   unsigned long long port;
 186
 187   /**
 188    * Offset in the message where we are for transmission.
 189    */
 190   size_t msg_off;
 191
 192   /**
 193    * How often have we tried to connect?
 194    */
 195   unsigned int attempts;
 196
 197   /**
 198    * Are we supposed to die?  #GNUNET_SYSERR if destruction must be
 199    * deferred, #GNUNET_NO by default, #GNUNET_YES if destruction was
 200    * deferred.
 201    */
 202   int in_destroy;
 203
 204 };
 205
 206
 207 /**
 208  * Try to connect to the service.
 209  *
 210  * @param cls the `struct ClientState` to try to connect to the service
 211  */
 212 static void
 213 start_connect (void *cls);
 214
 215
 216 /**
 217  * We've failed for good to establish a connection (timeout or
 218  * no more addresses to try).
 219  *
 220  * @param cstate the connection we tried to establish
 221  */
 222 static void
 223 connect_fail_continuation (struct ClientState *cstate)
 224 {
 225   GNUNET_break (NULL == cstate->ap_head);
 226   GNUNET_break (NULL == cstate->ap_tail);
 227   GNUNET_break (NULL == cstate->dns_active);
 228   GNUNET_break (NULL == cstate->sock);
 229   GNUNET_assert (NULL == cstate->send_task);
 230   GNUNET_assert (NULL == cstate->recv_task);
 231   // GNUNET_assert (NULL == cstate->proxy_handshake);
 232
 233   cstate->back_off = GNUNET_TIME_STD_BACKOFF (cstate->back_off);
 234   LOG (GNUNET_ERROR_TYPE_DEBUG,
 235        "Failed to establish connection to `%s', no further addresses to try, will try again in %s.\n",
 236        cstate->service_name,
 237        GNUNET_STRINGS_relative_time_to_string (cstate->back_off,
 238                                                GNUNET_YES));
 239   cstate->retry_task
 240     = GNUNET_SCHEDULER_add_delayed (cstate->back_off,
 241                                     &start_connect,
 242                                     cstate);
 243 }
 244
 245
 246 /**
 247  * We are ready to send a message to the service.
 248  *
 249  * @param cls the `struct ClientState` with the `msg` to transmit
 250  */
 251 static void
 252 transmit_ready (void *cls)
 253 {
 254   struct ClientState *cstate = cls;
 255   ssize_t ret;
 256   size_t len;
 257   const char *pos;
 258   int notify_in_flight;
 259
 260   cstate->send_task = NULL;
 261   pos = (const char *) cstate->msg;
 262   len = ntohs (cstate->msg->size);
 263   GNUNET_assert (cstate->msg_off < len);
 264  RETRY:
 265   ret = GNUNET_NETWORK_socket_send (cstate->sock,
 266                                     &pos[cstate->msg_off],
 267                                     len - cstate->msg_off);
 268   if (-1 == ret)
 269   {
 270     GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
 271                 "client: error during sending message of type %u\n", ntohs(cstate->msg->type));
 272     if (EINTR == errno){
 273       GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
 274                   "client: retrying message of type %u\n", ntohs(cstate->msg->type));
 275       goto RETRY;
 276     }
 277     GNUNET_MQ_inject_error (cstate->mq,
 278                             GNUNET_MQ_ERROR_WRITE);
 279     return;
 280   }
 281   notify_in_flight = (0 == cstate->msg_off);
 282   cstate->msg_off += ret;
 283   if (cstate->msg_off < len)
 284   {
 285     GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
 286                 "client: rescheduling message of type %u\n", ntohs(cstate->msg->type));
 287     cstate->send_task
 288       = GNUNET_SCHEDULER_add_write_net (GNUNET_TIME_UNIT_FOREVER_REL,
 289                                         cstate->sock,
 290                                         &transmit_ready,
 291                                         cstate);
 292     if (notify_in_flight)
 293       GNUNET_MQ_impl_send_in_flight (cstate->mq);
 294     return;
 295   }
 296   GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
 297               "client: sending message of type %u successful\n", ntohs(cstate->msg->type));
 298   cstate->msg = NULL;
 299   GNUNET_MQ_impl_send_continue (cstate->mq);
 300 }
 301
 302
 303 /**
 304  * We have received a full message, pass to the MQ dispatcher.
 305  * Called by the tokenizer via #receive_ready().
 306  *
 307  * @param cls the `struct ClientState`
 308  * @param msg message we received.
 309  * @return #GNUNET_OK on success, #GNUNET_SYSERR to stop further processing
 310  */
 311 static int
 312 recv_message (void *cls,
 313               const struct GNUNET_MessageHeader *msg)
 314 {
 315   struct ClientState *cstate = cls;
 316
 317   if (GNUNET_YES == cstate->in_destroy)
 318     return GNUNET_SYSERR;
 319   LOG (GNUNET_ERROR_TYPE_DEBUG,
 320        "Received message of type %u and size %u from %s\n",
 321        ntohs (msg->type),
 322        ntohs (msg->size),
 323        cstate->service_name);
 324   GNUNET_MQ_inject_message (cstate->mq,
 325                             msg);
 326   if (GNUNET_YES == cstate->in_destroy)
 327     return GNUNET_SYSERR;
 328   return GNUNET_OK;
 329 }
 330
 331
 332 /**
 333  * Cancel all remaining connect attempts
 334  *
 335  * @param cstate handle of the client state to process
 336  */
 337 static void
 338 cancel_aps (struct ClientState *cstate)
 339 {
 340   struct AddressProbe *pos;
 341
 342   while (NULL != (pos = cstate->ap_head))
 343   {
 344     GNUNET_break (GNUNET_OK ==
 345                   GNUNET_NETWORK_socket_close (pos->sock));
 346     GNUNET_SCHEDULER_cancel (pos->task);
 347     GNUNET_CONTAINER_DLL_remove (cstate->ap_head,
 348                                  cstate->ap_tail,
 349                                  pos);
 350     GNUNET_free (pos);
 351   }
 352 }
 353
 354
 355 /**
 356  * Implement the destruction of a message queue.  Implementations must
 357  * not free @a mq, but should take care of @a impl_state.
 358  *
 359  * @param mq the message queue to destroy
 360  * @param impl_state our `struct ClientState`
 361  */
 362 static void
 363 connection_client_destroy_impl (struct GNUNET_MQ_Handle *mq,
 364                                 void *impl_state)
 365 {
 366   struct ClientState *cstate = impl_state;
 367
 368   if (GNUNET_SYSERR == cstate->in_destroy)
 369   {
 370     /* defer destruction */
 371     cstate->in_destroy = GNUNET_YES;
 372     cstate->mq = NULL;
 373     return;
 374   }
 375   if (NULL != cstate->dns_active)
 376     GNUNET_RESOLVER_request_cancel (cstate->dns_active);
 377   if (NULL != cstate->send_task)
 378     GNUNET_SCHEDULER_cancel (cstate->send_task);
 379   if (NULL != cstate->recv_task)
 380     GNUNET_SCHEDULER_cancel (cstate->recv_task);
 381   if (NULL != cstate->retry_task)
 382     GNUNET_SCHEDULER_cancel (cstate->retry_task);
 383   if (NULL != cstate->sock)
 384     GNUNET_NETWORK_socket_close (cstate->sock);
 385   cancel_aps (cstate);
 386   GNUNET_free (cstate->service_name);
 387   GNUNET_free_non_null (cstate->hostname);
 388   GNUNET_MST_destroy (cstate->mst);
 389   GNUNET_free (cstate);
 390 }
 391
 392
 393 /**
 394  * This function is called once we have data ready to read.
 395  *
 396  * @param cls `struct ClientState` with connection to read from
 397  */
 398 static void
 399 receive_ready (void *cls)
 400 {
 401   struct ClientState *cstate = cls;
 402   int ret;
 403
 404   cstate->recv_task = NULL;
 405   cstate->in_destroy = GNUNET_SYSERR;
 406   ret = GNUNET_MST_read (cstate->mst,
 407                          cstate->sock,
 408                          GNUNET_NO,
 409                          GNUNET_NO);
 410   if (GNUNET_SYSERR == ret)
 411   {
 412     if (NULL != cstate->mq)
 413       GNUNET_MQ_inject_error (cstate->mq,
 414                               GNUNET_MQ_ERROR_READ);
 415     if (GNUNET_YES == cstate->in_destroy)
 416       connection_client_destroy_impl (cstate->mq,
 417                                       cstate);
 418     return;
 419   }
 420   if (GNUNET_YES == cstate->in_destroy)
 421   {
 422     connection_client_destroy_impl (cstate->mq,
 423                                     cstate);
 424     return;
 425   }
 426   cstate->in_destroy = GNUNET_NO;
 427   cstate->recv_task
 428     = GNUNET_SCHEDULER_add_read_net (GNUNET_TIME_UNIT_FOREVER_REL,
 429                                      cstate->sock,
 430                                      &receive_ready,
 431                                      cstate);
 432 }
 433
 434
 435 /**
 436  * We've succeeded in establishing a connection.
 437  *
 438  * @param cstate the connection we tried to establish
 439  */
 440 static void
 441 connect_success_continuation (struct ClientState *cstate)
 442 {
 443   GNUNET_assert (NULL == cstate->recv_task);
 444   cstate->recv_task
 445     = GNUNET_SCHEDULER_add_read_net (GNUNET_TIME_UNIT_FOREVER_REL,
 446                                      cstate->sock,
 447                                      &receive_ready,
 448                                      cstate);
 449   if (NULL != cstate->msg)
 450   {
 451     GNUNET_assert (NULL == cstate->send_task);
 452     cstate->send_task
 453       = GNUNET_SCHEDULER_add_write_net (GNUNET_TIME_UNIT_FOREVER_REL,
 454                                         cstate->sock,
 455                                         &transmit_ready,
 456                                         cstate);
 457   }
 458 }
 459
 460
 461 /**
 462  * Try connecting to the server using UNIX domain sockets.
 463  *
 464  * @param service_name name of service to connect to
 465  * @param cfg configuration to use
 466  * @return NULL on error, socket connected to UNIX otherwise
 467  */
 468 static struct GNUNET_NETWORK_Handle *
 469 try_unixpath (const char *service_name,
 470               const struct GNUNET_CONFIGURATION_Handle *cfg)
 471 {
 472 #if AF_UNIX
 473   struct GNUNET_NETWORK_Handle *sock;
 474   char *unixpath;
 475   struct sockaddr_un s_un;
 476
 477   unixpath = NULL;
 478   if ((GNUNET_OK ==
 479        GNUNET_CONFIGURATION_get_value_filename (cfg,
 480                                                 service_name,
 481                                                 "UNIXPATH",
 482                                                 &unixpath)) &&
 483       (0 < strlen (unixpath)))
 484   {
 485     /* We have a non-NULL unixpath, need to validate it */
 486     if (strlen (unixpath) >= sizeof (s_un.sun_path))
 487     {
 488       LOG (GNUNET_ERROR_TYPE_WARNING,
 489            _("UNIXPATH `%s' too long, maximum length is %llu\n"),
 490            unixpath,
 491            (unsigned long long) sizeof (s_un.sun_path));
 492       unixpath = GNUNET_NETWORK_shorten_unixpath (unixpath);
 493       LOG (GNUNET_ERROR_TYPE_INFO,
 494            _("Using `%s' instead\n"),
 495            unixpath);
 496       if (NULL == unixpath)
 497         return NULL;
 498     }
 499     memset (&s_un,
 500             0,
 501             sizeof (s_un));
 502     s_un.sun_family = AF_UNIX;
 503     strncpy (s_un.sun_path,
 504              unixpath,
 505              sizeof (s_un.sun_path) - 1);
 506 #ifdef LINUX
 507     {
 508       int abstract;
 509
 510       abstract = GNUNET_CONFIGURATION_get_value_yesno (cfg,
 511                                                        "TESTING",
 512                                                        "USE_ABSTRACT_SOCKETS");
 513       if (GNUNET_YES == abstract)
 514         s_un.sun_path[0] = '\0';
 515     }
 516 #endif
 517 #if HAVE_SOCKADDR_UN_SUN_LEN
 518     s_un.sun_len = (u_char) sizeof (struct sockaddr_un);
 519 #endif
 520     sock = GNUNET_NETWORK_socket_create (AF_UNIX,
 521                                          SOCK_STREAM,
 522                                          0);
 523     if ( (NULL != sock) &&
 524          ( (GNUNET_OK ==
 525             GNUNET_NETWORK_socket_connect (sock,
 526                                            (struct sockaddr *) &s_un,
 527                                            sizeof (s_un))) ||
 528            (EINPROGRESS == errno) ) )
 529     {
 530       LOG (GNUNET_ERROR_TYPE_DEBUG,
 531            "Successfully connected to unixpath `%s'!\n",
 532            unixpath);
 533       GNUNET_free (unixpath);
 534       return sock;
 535     }
 536     if (NULL != sock)
 537       GNUNET_NETWORK_socket_close (sock);
 538   }
 539   GNUNET_free_non_null (unixpath);
 540 #endif
 541   return NULL;
 542 }
 543
 544
 545 /**
 546  * Scheduler let us know that we're either ready to write on the
 547  * socket OR connect timed out.  Do the right thing.
 548  *
 549  * @param cls the `struct AddressProbe *` with the address that we are probing
 550  */
 551 static void
 552 connect_probe_continuation (void *cls)
 553 {
 554   struct AddressProbe *ap = cls;
 555   struct ClientState *cstate = ap->cstate;
 556   const struct GNUNET_SCHEDULER_TaskContext *tc;
 557   int error;
 558   socklen_t len;
 559
 560   ap->task = NULL;
 561   GNUNET_assert (NULL != ap->sock);
 562   GNUNET_CONTAINER_DLL_remove (cstate->ap_head,
 563                                cstate->ap_tail,
 564                                ap);
 565   len = sizeof (error);
 566   error = 0;
 567   tc = GNUNET_SCHEDULER_get_task_context ();
 568   if ( (0 == (tc->reason & GNUNET_SCHEDULER_REASON_WRITE_READY)) ||
 569        (GNUNET_OK !=
 570         GNUNET_NETWORK_socket_getsockopt (ap->sock,
 571                                           SOL_SOCKET,
 572                                           SO_ERROR,
 573                                           &error,
 574                                           &len)) ||
 575        (0 != error) )
 576   {
 577     GNUNET_break (GNUNET_OK ==
 578                   GNUNET_NETWORK_socket_close (ap->sock));
 579     GNUNET_free (ap);
 580     if ( (NULL == cstate->ap_head) &&
 581          //      (NULL == cstate->proxy_handshake) &&
 582          (NULL == cstate->dns_active) )
 583       connect_fail_continuation (cstate);
 584     return;
 585   }
 586   LOG (GNUNET_ERROR_TYPE_DEBUG,
 587        "Connection to `%s' succeeded!\n",
 588        cstate->service_name);
 589   /* trigger jobs that waited for the connection */
 590   GNUNET_assert (NULL == cstate->sock);
 591   cstate->sock = ap->sock;
 592   GNUNET_free (ap);
 593   cancel_aps (cstate);
 594   connect_success_continuation (cstate);
 595 }
 596
 597
 598 /**
 599  * Try to establish a connection given the specified address.
 600  * This function is called by the resolver once we have a DNS reply.
 601  *
 602  * @param cls our `struct ClientState *`
 603  * @param addr address to try, NULL for "last call"
 604  * @param addrlen length of @a addr
 605  */
 606 static void
 607 try_connect_using_address (void *cls,
 608                            const struct sockaddr *addr,
 609                            socklen_t addrlen)
 610 {
 611   struct ClientState *cstate = cls;
 612   struct AddressProbe *ap;
 613
 614   if (NULL == addr)
 615   {
 616     cstate->dns_active = NULL;
 617     if ( (NULL == cstate->ap_head) &&
 618          //  (NULL == cstate->proxy_handshake) &&
 619          (NULL == cstate->sock) )
 620       connect_fail_continuation (cstate);
 621     return;
 622   }
 623   if (NULL != cstate->sock)
 624     return;                     /* already connected */
 625   /* try to connect */
 626   LOG (GNUNET_ERROR_TYPE_DEBUG,
 627        "Trying to connect using address `%s:%u'\n",
 628        GNUNET_a2s (addr,
 629                    addrlen),
 630        cstate->port);
 631   ap = GNUNET_malloc (sizeof (struct AddressProbe) + addrlen);
 632   ap->addr = (const struct sockaddr *) &ap[1];
 633   GNUNET_memcpy (&ap[1],
 634                  addr,
 635                  addrlen);
 636   ap->addrlen = addrlen;
 637   ap->cstate = cstate;
 638
 639   switch (ap->addr->sa_family)
 640   {
 641   case AF_INET:
 642     ((struct sockaddr_in *) ap->addr)->sin_port = htons (cstate->port);
 643     break;
 644   case AF_INET6:
 645     ((struct sockaddr_in6 *) ap->addr)->sin6_port = htons (cstate->port);
 646     break;
 647   default:
 648     GNUNET_break (0);
 649     GNUNET_free (ap);
 650     return;                     /* not supported by us */
 651   }
 652   ap->sock = GNUNET_NETWORK_socket_create (ap->addr->sa_family,
 653                                            SOCK_STREAM,
 654                                            0);
 655   if (NULL == ap->sock)
 656   {
 657     GNUNET_free (ap);
 658     return;                     /* not supported by OS */
 659   }
 660   if ( (GNUNET_OK !=
 661         GNUNET_NETWORK_socket_connect (ap->sock,
 662                                        ap->addr,
 663                                        ap->addrlen)) &&
 664        (EINPROGRESS != errno) )
 665   {
 666     /* maybe refused / unsupported address, try next */
 667     GNUNET_log_strerror (GNUNET_ERROR_TYPE_INFO,
 668                          "connect");
 669     GNUNET_break (GNUNET_OK ==
 670                   GNUNET_NETWORK_socket_close (ap->sock));
 671     GNUNET_free (ap);
 672     return;
 673   }
 674   GNUNET_CONTAINER_DLL_insert (cstate->ap_head,
 675                                cstate->ap_tail,
 676                                ap);
 677   ap->task = GNUNET_SCHEDULER_add_write_net (CONNECT_RETRY_TIMEOUT,
 678                                              ap->sock,
 679                                              &connect_probe_continuation,
 680                                              ap);
 681 }
 682
 683
 684 /**
 685  * Test whether the configuration has proper values for connection
 686  * (UNIXPATH || (PORT && HOSTNAME)).
 687  *
 688  * @param service_name name of service to connect to
 689  * @param cfg configuration to use
 690  * @return #GNUNET_OK if the configuration is valid, #GNUNET_SYSERR if not
 691  */
 692 static int
 693 test_service_configuration (const char *service_name,
 694                             const struct GNUNET_CONFIGURATION_Handle *cfg)
 695 {
 696   int ret = GNUNET_SYSERR;
 697   char *hostname = NULL;
 698   unsigned long long port;
 699 #if AF_UNIX
 700   char *unixpath = NULL;
 701
 702   if ((GNUNET_OK ==
 703        GNUNET_CONFIGURATION_get_value_filename (cfg,
 704                                                 service_name,
 705                                                 "UNIXPATH",
 706                                                 &unixpath)) &&
 707       (0 < strlen (unixpath)))
 708     ret = GNUNET_OK;
 709   GNUNET_free_non_null (unixpath);
 710 #endif
 711
 712   if ( (GNUNET_YES ==
 713         GNUNET_CONFIGURATION_have_value (cfg,
 714                                          service_name,
 715                                          "PORT")) &&
 716        (GNUNET_OK ==
 717         GNUNET_CONFIGURATION_get_value_number (cfg,
 718                                                service_name,
 719                                                "PORT",
 720                                                &port)) &&
 721        (port <= 65535) &&
 722        (0 != port) &&
 723        (GNUNET_OK ==
 724         GNUNET_CONFIGURATION_get_value_string (cfg,
 725                                                service_name,
 726                                                "HOSTNAME",
 727                                                &hostname)) &&
 728        (0 != strlen (hostname)) )
 729     ret = GNUNET_OK;
 730   GNUNET_free_non_null (hostname);
 731   return ret;
 732 }
 733
 734
 735 /**
 736  * Try to connect to the service.
 737  *
 738  * @param cls the `struct ClientState` to try to connect to the service
 739  */
 740 static void
 741 start_connect (void *cls)
 742 {
 743   struct ClientState *cstate = cls;
 744
 745   cstate->retry_task = NULL;
 746 #if 0
 747   /* Never use a local source if a proxy is configured */
 748   if (GNUNET_YES ==
 749       GNUNET_SOCKS_check_service (cstate->service_name,
 750                                   cstate->cfg))
 751   {
 752     socks_connect (cstate);
 753     return;
 754   }
 755 #endif
 756
 757   if ( (0 == (cstate->attempts++ % 2)) ||
 758        (0 == cstate->port) ||
 759        (NULL == cstate->hostname) )
 760   {
 761     /* on even rounds, try UNIX first, or always
 762        if we do not have a DNS name and TCP port. */
 763     cstate->sock = try_unixpath (cstate->service_name,
 764                                  cstate->cfg);
 765     if (NULL != cstate->sock)
 766     {
 767       connect_success_continuation (cstate);
 768       return;
 769     }
 770   }
 771   if ( (NULL == cstate->hostname) ||
 772        (0 == cstate->port) )
 773   {
 774     /* All options failed. Boo! */
 775     connect_fail_continuation (cstate);
 776     return;
 777   }
 778   cstate->dns_active
 779     = GNUNET_RESOLVER_ip_get (cstate->hostname,
 780                               AF_UNSPEC,
 781                               CONNECT_RETRY_TIMEOUT,
 782                               &try_connect_using_address,
 783                               cstate);
 784 }
 785
 786
 787 /**
 788  * Implements the transmission functionality of a message queue.
 789  *
 790  * @param mq the message queue
 791  * @param msg the message to send
 792  * @param impl_state our `struct ClientState`
 793  */
 794 static void
 795 connection_client_send_impl (struct GNUNET_MQ_Handle *mq,
 796                              const struct GNUNET_MessageHeader *msg,
 797                              void *impl_state)
 798 {
 799   struct ClientState *cstate = impl_state;
 800
 801   /* only one message at a time allowed */
 802   GNUNET_assert (NULL == cstate->msg);
 803   GNUNET_assert (NULL == cstate->send_task);
 804   cstate->msg = msg;
 805   cstate->msg_off = 0;
 806   if (NULL == cstate->sock){
 807     GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
 808                 "client: waiting for socket\n");
 809     return; /* still waiting for connection */
 810    }
 811   cstate->send_task
 812     = GNUNET_SCHEDULER_add_write_net (GNUNET_TIME_UNIT_FOREVER_REL,
 813                                       cstate->sock,
 814                                       &transmit_ready,
 815                                       cstate);
 816 }
 817
 818
 819 /**
 820  * Cancel the currently sent message.
 821  *
 822  * @param mq message queue
 823  * @param impl_state our `struct ClientState`
 824  */
 825 static void
 826 connection_client_cancel_impl (struct GNUNET_MQ_Handle *mq,
 827                                void *impl_state)
 828 {
 829   struct ClientState *cstate = impl_state;
 830
 831   GNUNET_assert (NULL != cstate->msg);
 832   GNUNET_assert (0 == cstate->msg_off);
 833   cstate->msg = NULL;
 834   if (NULL != cstate->send_task)
 835   {
 836     GNUNET_SCHEDULER_cancel (cstate->send_task);
 837     cstate->send_task = NULL;
 838   }
 839 }
 840
 841
 842 /**
 843  * Create a message queue to connect to a GNUnet service.
 844  * If handlers are specfied, receive messages from the connection.
 845  *
 846  * @param cfg our configuration
 847  * @param service_name name of the service to connect to
 848  * @param handlers handlers for receiving messages, can be NULL
 849  * @param error_handler error handler
 850  * @param error_handler_cls closure for the @a error_handler
 851  * @return the message queue, NULL on error
 852  */
 853 struct GNUNET_MQ_Handle *
 854 GNUNET_CLIENT_connect (const struct GNUNET_CONFIGURATION_Handle *cfg,
 855                        const char *service_name,
 856                        const struct GNUNET_MQ_MessageHandler *handlers,
 857                        GNUNET_MQ_ErrorHandler error_handler,
 858                        void *error_handler_cls)
 859 {
 860   struct ClientState *cstate;
 861
 862   if (GNUNET_OK !=
 863       test_service_configuration (service_name,
 864                                   cfg))
 865     return NULL;
 866   cstate = GNUNET_new (struct ClientState);
 867   cstate->service_name = GNUNET_strdup (service_name);
 868   cstate->cfg = cfg;
 869   cstate->retry_task = GNUNET_SCHEDULER_add_now (&start_connect,
 870                                                  cstate);
 871   cstate->mst = GNUNET_MST_create (&recv_message,
 872                                    cstate);
 873   if (GNUNET_YES ==
 874       GNUNET_CONFIGURATION_have_value (cfg,
 875                                        service_name,
 876                                        "PORT"))
 877   {
 878     if (! ( (GNUNET_OK !=
 879              GNUNET_CONFIGURATION_get_value_number (cfg,
 880                                                     service_name,
 881                                                     "PORT",
 882                                                     &cstate->port)) ||
 883             (cstate->port > 65535) ||
 884             (GNUNET_OK !=
 885              GNUNET_CONFIGURATION_get_value_string (cfg,
 886                                                     service_name,
 887                                                     "HOSTNAME",
 888                                                     &cstate->hostname)) ) &&
 889         (0 == strlen (cstate->hostname)) )
 890     {
 891       GNUNET_free (cstate->hostname);
 892       cstate->hostname = NULL;
 893       LOG (GNUNET_ERROR_TYPE_WARNING,
 894            _("Need a non-empty hostname for service `%s'.\n"),
 895            service_name);
 896     }
 897   }
 898   cstate->mq = GNUNET_MQ_queue_for_callbacks (&connection_client_send_impl,
 899                                               &connection_client_destroy_impl,
 900                                               &connection_client_cancel_impl,
 901                                               cstate,
 902                                               handlers,
 903                                               error_handler,
 904                                               error_handler_cls);
 905   return cstate->mq;
 906 }
 907
 908 /* end of client.c */