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