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     if (EINTR == errno)
 271       goto RETRY;
 272     GNUNET_MQ_inject_error (cstate->mq,
 273                             GNUNET_MQ_ERROR_WRITE);
 274     return;
 275   }
 276   notify_in_flight = (0 == cstate->msg_off);
 277   cstate->msg_off += ret;
 278   if (cstate->msg_off < len)
 279   {
 280     cstate->send_task
 281       = GNUNET_SCHEDULER_add_write_net (GNUNET_TIME_UNIT_FOREVER_REL,
 282                                         cstate->sock,
 283                                         &transmit_ready,
 284                                         cstate);
 285     if (notify_in_flight)
 286       GNUNET_MQ_impl_send_in_flight (cstate->mq);
 287     return;
 288   }
 289   cstate->msg = NULL;
 290   GNUNET_MQ_impl_send_continue (cstate->mq);
 291 }
 292
 293
 294 /**
 295  * We have received a full message, pass to the MQ dispatcher.
 296  * Called by the tokenizer via #receive_ready().
 297  *
 298  * @param cls the `struct ClientState`
 299  * @param msg message we received.
 300  * @return #GNUNET_OK on success, #GNUNET_SYSERR to stop further processing
 301  */
 302 static int
 303 recv_message (void *cls,
 304               const struct GNUNET_MessageHeader *msg)
 305 {
 306   struct ClientState *cstate = cls;
 307
 308   if (GNUNET_YES == cstate->in_destroy)
 309     return GNUNET_SYSERR;
 310   LOG (GNUNET_ERROR_TYPE_DEBUG,
 311        "Received message of type %u and size %u from %s\n",
 312        ntohs (msg->type),
 313        ntohs (msg->size),
 314        cstate->service_name);
 315   GNUNET_MQ_inject_message (cstate->mq,
 316                             msg);
 317   if (GNUNET_YES == cstate->in_destroy)
 318     return GNUNET_SYSERR;
 319   return GNUNET_OK;
 320 }
 321
 322
 323 /**
 324  * Cancel all remaining connect attempts
 325  *
 326  * @param cstate handle of the client state to process
 327  */
 328 static void
 329 cancel_aps (struct ClientState *cstate)
 330 {
 331   struct AddressProbe *pos;
 332
 333   while (NULL != (pos = cstate->ap_head))
 334   {
 335     GNUNET_break (GNUNET_OK ==
 336                   GNUNET_NETWORK_socket_close (pos->sock));
 337     GNUNET_SCHEDULER_cancel (pos->task);
 338     GNUNET_CONTAINER_DLL_remove (cstate->ap_head,
 339                                  cstate->ap_tail,
 340                                  pos);
 341     GNUNET_free (pos);
 342   }
 343 }
 344
 345
 346 /**
 347  * Implement the destruction of a message queue.  Implementations must
 348  * not free @a mq, but should take care of @a impl_state.
 349  *
 350  * @param mq the message queue to destroy
 351  * @param impl_state our `struct ClientState`
 352  */
 353 static void
 354 connection_client_destroy_impl (struct GNUNET_MQ_Handle *mq,
 355                                 void *impl_state)
 356 {
 357   struct ClientState *cstate = impl_state;
 358
 359   if (GNUNET_SYSERR == cstate->in_destroy)
 360   {
 361     /* defer destruction */
 362     cstate->in_destroy = GNUNET_YES;
 363     cstate->mq = NULL;
 364     return;
 365   }
 366   if (NULL != cstate->dns_active)
 367     GNUNET_RESOLVER_request_cancel (cstate->dns_active);
 368   if (NULL != cstate->send_task)
 369     GNUNET_SCHEDULER_cancel (cstate->send_task);
 370   if (NULL != cstate->recv_task)
 371     GNUNET_SCHEDULER_cancel (cstate->recv_task);
 372   if (NULL != cstate->retry_task)
 373     GNUNET_SCHEDULER_cancel (cstate->retry_task);
 374   if (NULL != cstate->sock)
 375     GNUNET_NETWORK_socket_close (cstate->sock);
 376   cancel_aps (cstate);
 377   GNUNET_free (cstate->service_name);
 378   GNUNET_free_non_null (cstate->hostname);
 379   GNUNET_MST_destroy (cstate->mst);
 380   GNUNET_free (cstate);
 381 }
 382
 383
 384 /**
 385  * This function is called once we have data ready to read.
 386  *
 387  * @param cls `struct ClientState` with connection to read from
 388  */
 389 static void
 390 receive_ready (void *cls)
 391 {
 392   struct ClientState *cstate = cls;
 393   int ret;
 394
 395   cstate->recv_task = NULL;
 396   cstate->in_destroy = GNUNET_SYSERR;
 397   ret = GNUNET_MST_read (cstate->mst,
 398                          cstate->sock,
 399                          GNUNET_NO,
 400                          GNUNET_NO);
 401   if (GNUNET_SYSERR == ret)
 402   {
 403     if (NULL != cstate->mq)
 404       GNUNET_MQ_inject_error (cstate->mq,
 405                               GNUNET_MQ_ERROR_READ);
 406     if (GNUNET_YES == cstate->in_destroy)
 407       connection_client_destroy_impl (cstate->mq,
 408                                       cstate);
 409     return;
 410   }
 411   if (GNUNET_YES == cstate->in_destroy)
 412   {
 413     connection_client_destroy_impl (cstate->mq,
 414                                     cstate);
 415     return;
 416   }
 417   cstate->in_destroy = GNUNET_NO;
 418   cstate->recv_task
 419     = GNUNET_SCHEDULER_add_read_net (GNUNET_TIME_UNIT_FOREVER_REL,
 420                                      cstate->sock,
 421                                      &receive_ready,
 422                                      cstate);
 423 }
 424
 425
 426 /**
 427  * We've succeeded in establishing a connection.
 428  *
 429  * @param cstate the connection we tried to establish
 430  */
 431 static void
 432 connect_success_continuation (struct ClientState *cstate)
 433 {
 434   GNUNET_assert (NULL == cstate->recv_task);
 435   cstate->recv_task
 436     = GNUNET_SCHEDULER_add_read_net (GNUNET_TIME_UNIT_FOREVER_REL,
 437                                      cstate->sock,
 438                                      &receive_ready,
 439                                      cstate);
 440   if (NULL != cstate->msg)
 441   {
 442     GNUNET_assert (NULL == cstate->send_task);
 443     cstate->send_task
 444       = GNUNET_SCHEDULER_add_write_net (GNUNET_TIME_UNIT_FOREVER_REL,
 445                                         cstate->sock,
 446                                         &transmit_ready,
 447                                         cstate);
 448   }
 449 }
 450
 451
 452 /**
 453  * Try connecting to the server using UNIX domain sockets.
 454  *
 455  * @param service_name name of service to connect to
 456  * @param cfg configuration to use
 457  * @return NULL on error, socket connected to UNIX otherwise
 458  */
 459 static struct GNUNET_NETWORK_Handle *
 460 try_unixpath (const char *service_name,
 461               const struct GNUNET_CONFIGURATION_Handle *cfg)
 462 {
 463 #if AF_UNIX
 464   struct GNUNET_NETWORK_Handle *sock;
 465   char *unixpath;
 466   struct sockaddr_un s_un;
 467
 468   unixpath = NULL;
 469   if ((GNUNET_OK ==
 470        GNUNET_CONFIGURATION_get_value_filename (cfg,
 471                                                 service_name,
 472                                                 "UNIXPATH",
 473                                                 &unixpath)) &&
 474       (0 < strlen (unixpath)))
 475   {
 476     /* We have a non-NULL unixpath, need to validate it */
 477     if (strlen (unixpath) >= sizeof (s_un.sun_path))
 478     {
 479       LOG (GNUNET_ERROR_TYPE_WARNING,
 480            _("UNIXPATH `%s' too long, maximum length is %llu\n"),
 481            unixpath,
 482            (unsigned long long) sizeof (s_un.sun_path));
 483       unixpath = GNUNET_NETWORK_shorten_unixpath (unixpath);
 484       LOG (GNUNET_ERROR_TYPE_INFO,
 485            _("Using `%s' instead\n"),
 486            unixpath);
 487       if (NULL == unixpath)
 488         return NULL;
 489     }
 490     memset (&s_un,
 491             0,
 492             sizeof (s_un));
 493     s_un.sun_family = AF_UNIX;
 494     strncpy (s_un.sun_path,
 495              unixpath,
 496              sizeof (s_un.sun_path) - 1);
 497 #ifdef LINUX
 498     {
 499       int abstract;
 500
 501       abstract = GNUNET_CONFIGURATION_get_value_yesno (cfg,
 502                                                        "TESTING",
 503                                                        "USE_ABSTRACT_SOCKETS");
 504       if (GNUNET_YES == abstract)
 505         s_un.sun_path[0] = '\0';
 506     }
 507 #endif
 508 #if HAVE_SOCKADDR_UN_SUN_LEN
 509     s_un.sun_len = (u_char) sizeof (struct sockaddr_un);
 510 #endif
 511     sock = GNUNET_NETWORK_socket_create (AF_UNIX,
 512                                          SOCK_STREAM,
 513                                          0);
 514     if ( (NULL != sock) &&
 515          ( (GNUNET_OK ==
 516             GNUNET_NETWORK_socket_connect (sock,
 517                                            (struct sockaddr *) &s_un,
 518                                            sizeof (s_un))) ||
 519            (EINPROGRESS == errno) ) )
 520     {
 521       LOG (GNUNET_ERROR_TYPE_DEBUG,
 522            "Successfully connected to unixpath `%s'!\n",
 523            unixpath);
 524       GNUNET_free (unixpath);
 525       return sock;
 526     }
 527     if (NULL != sock)
 528       GNUNET_NETWORK_socket_close (sock);
 529   }
 530   GNUNET_free_non_null (unixpath);
 531 #endif
 532   return NULL;
 533 }
 534
 535
 536 /**
 537  * Scheduler let us know that we're either ready to write on the
 538  * socket OR connect timed out.  Do the right thing.
 539  *
 540  * @param cls the `struct AddressProbe *` with the address that we are probing
 541  */
 542 static void
 543 connect_probe_continuation (void *cls)
 544 {
 545   struct AddressProbe *ap = cls;
 546   struct ClientState *cstate = ap->cstate;
 547   const struct GNUNET_SCHEDULER_TaskContext *tc;
 548   int error;
 549   socklen_t len;
 550
 551   ap->task = NULL;
 552   GNUNET_assert (NULL != ap->sock);
 553   GNUNET_CONTAINER_DLL_remove (cstate->ap_head,
 554                                cstate->ap_tail,
 555                                ap);
 556   len = sizeof (error);
 557   error = 0;
 558   tc = GNUNET_SCHEDULER_get_task_context ();
 559   if ( (0 == (tc->reason & GNUNET_SCHEDULER_REASON_WRITE_READY)) ||
 560        (GNUNET_OK !=
 561         GNUNET_NETWORK_socket_getsockopt (ap->sock,
 562                                           SOL_SOCKET,
 563                                           SO_ERROR,
 564                                           &error,
 565                                           &len)) ||
 566        (0 != error) )
 567   {
 568     GNUNET_break (GNUNET_OK ==
 569                   GNUNET_NETWORK_socket_close (ap->sock));
 570     GNUNET_free (ap);
 571     if ( (NULL == cstate->ap_head) &&
 572          //      (NULL == cstate->proxy_handshake) &&
 573          (NULL == cstate->dns_active) )
 574       connect_fail_continuation (cstate);
 575     return;
 576   }
 577   LOG (GNUNET_ERROR_TYPE_DEBUG,
 578        "Connection to `%s' succeeded!\n",
 579        cstate->service_name);
 580   /* trigger jobs that waited for the connection */
 581   GNUNET_assert (NULL == cstate->sock);
 582   cstate->sock = ap->sock;
 583   GNUNET_free (ap);
 584   cancel_aps (cstate);
 585   connect_success_continuation (cstate);
 586 }
 587
 588
 589 /**
 590  * Try to establish a connection given the specified address.
 591  * This function is called by the resolver once we have a DNS reply.
 592  *
 593  * @param cls our `struct ClientState *`
 594  * @param addr address to try, NULL for "last call"
 595  * @param addrlen length of @a addr
 596  */
 597 static void
 598 try_connect_using_address (void *cls,
 599                            const struct sockaddr *addr,
 600                            socklen_t addrlen)
 601 {
 602   struct ClientState *cstate = cls;
 603   struct AddressProbe *ap;
 604
 605   if (NULL == addr)
 606   {
 607     cstate->dns_active = NULL;
 608     if ( (NULL == cstate->ap_head) &&
 609          //  (NULL == cstate->proxy_handshake) &&
 610          (NULL == cstate->sock) )
 611       connect_fail_continuation (cstate);
 612     return;
 613   }
 614   if (NULL != cstate->sock)
 615     return;                     /* already connected */
 616   /* try to connect */
 617   LOG (GNUNET_ERROR_TYPE_DEBUG,
 618        "Trying to connect using address `%s:%u'\n",
 619        GNUNET_a2s (addr,
 620                    addrlen),
 621        cstate->port);
 622   ap = GNUNET_malloc (sizeof (struct AddressProbe) + addrlen);
 623   ap->addr = (const struct sockaddr *) &ap[1];
 624   GNUNET_memcpy (&ap[1],
 625                  addr,
 626                  addrlen);
 627   ap->addrlen = addrlen;
 628   ap->cstate = cstate;
 629
 630   switch (ap->addr->sa_family)
 631   {
 632   case AF_INET:
 633     ((struct sockaddr_in *) ap->addr)->sin_port = htons (cstate->port);
 634     break;
 635   case AF_INET6:
 636     ((struct sockaddr_in6 *) ap->addr)->sin6_port = htons (cstate->port);
 637     break;
 638   default:
 639     GNUNET_break (0);
 640     GNUNET_free (ap);
 641     return;                     /* not supported by us */
 642   }
 643   ap->sock = GNUNET_NETWORK_socket_create (ap->addr->sa_family,
 644                                            SOCK_STREAM,
 645                                            0);
 646   if (NULL == ap->sock)
 647   {
 648     GNUNET_free (ap);
 649     return;                     /* not supported by OS */
 650   }
 651   if ( (GNUNET_OK !=
 652         GNUNET_NETWORK_socket_connect (ap->sock,
 653                                        ap->addr,
 654                                        ap->addrlen)) &&
 655        (EINPROGRESS != errno) )
 656   {
 657     /* maybe refused / unsupported address, try next */
 658     GNUNET_log_strerror (GNUNET_ERROR_TYPE_INFO,
 659                          "connect");
 660     GNUNET_break (GNUNET_OK ==
 661                   GNUNET_NETWORK_socket_close (ap->sock));
 662     GNUNET_free (ap);
 663     return;
 664   }
 665   GNUNET_CONTAINER_DLL_insert (cstate->ap_head,
 666                                cstate->ap_tail,
 667                                ap);
 668   ap->task = GNUNET_SCHEDULER_add_write_net (CONNECT_RETRY_TIMEOUT,
 669                                              ap->sock,
 670                                              &connect_probe_continuation,
 671                                              ap);
 672 }
 673
 674
 675 /**
 676  * Test whether the configuration has proper values for connection
 677  * (UNIXPATH || (PORT && HOSTNAME)).
 678  *
 679  * @param service_name name of service to connect to
 680  * @param cfg configuration to use
 681  * @return #GNUNET_OK if the configuration is valid, #GNUNET_SYSERR if not
 682  */
 683 static int
 684 test_service_configuration (const char *service_name,
 685                             const struct GNUNET_CONFIGURATION_Handle *cfg)
 686 {
 687   int ret = GNUNET_SYSERR;
 688   char *hostname = NULL;
 689   unsigned long long port;
 690 #if AF_UNIX
 691   char *unixpath = NULL;
 692
 693   if ((GNUNET_OK ==
 694        GNUNET_CONFIGURATION_get_value_filename (cfg,
 695                                                 service_name,
 696                                                 "UNIXPATH",
 697                                                 &unixpath)) &&
 698       (0 < strlen (unixpath)))
 699     ret = GNUNET_OK;
 700   GNUNET_free_non_null (unixpath);
 701 #endif
 702
 703   if ( (GNUNET_YES ==
 704         GNUNET_CONFIGURATION_have_value (cfg,
 705                                          service_name,
 706                                          "PORT")) &&
 707        (GNUNET_OK ==
 708         GNUNET_CONFIGURATION_get_value_number (cfg,
 709                                                service_name,
 710                                                "PORT",
 711                                                &port)) &&
 712        (port <= 65535) &&
 713        (0 != port) &&
 714        (GNUNET_OK ==
 715         GNUNET_CONFIGURATION_get_value_string (cfg,
 716                                                service_name,
 717                                                "HOSTNAME",
 718                                                &hostname)) &&
 719        (0 != strlen (hostname)) )
 720     ret = GNUNET_OK;
 721   GNUNET_free_non_null (hostname);
 722   return ret;
 723 }
 724
 725
 726 /**
 727  * Try to connect to the service.
 728  *
 729  * @param cls the `struct ClientState` to try to connect to the service
 730  */
 731 static void
 732 start_connect (void *cls)
 733 {
 734   struct ClientState *cstate = cls;
 735
 736   cstate->retry_task = NULL;
 737 #if 0
 738   /* Never use a local source if a proxy is configured */
 739   if (GNUNET_YES ==
 740       GNUNET_SOCKS_check_service (cstate->service_name,
 741                                   cstate->cfg))
 742   {
 743     socks_connect (cstate);
 744     return;
 745   }
 746 #endif
 747
 748   if ( (0 == (cstate->attempts++ % 2)) ||
 749        (0 == cstate->port) ||
 750        (NULL == cstate->hostname) )
 751   {
 752     /* on even rounds, try UNIX first, or always
 753        if we do not have a DNS name and TCP port. */
 754     cstate->sock = try_unixpath (cstate->service_name,
 755                                  cstate->cfg);
 756     if (NULL != cstate->sock)
 757     {
 758       connect_success_continuation (cstate);
 759       return;
 760     }
 761   }
 762   if ( (NULL == cstate->hostname) ||
 763        (0 == cstate->port) )
 764   {
 765     /* All options failed. Boo! */
 766     connect_fail_continuation (cstate);
 767     return;
 768   }
 769   cstate->dns_active
 770     = GNUNET_RESOLVER_ip_get (cstate->hostname,
 771                               AF_UNSPEC,
 772                               CONNECT_RETRY_TIMEOUT,
 773                               &try_connect_using_address,
 774                               cstate);
 775 }
 776
 777
 778 /**
 779  * Implements the transmission functionality of a message queue.
 780  *
 781  * @param mq the message queue
 782  * @param msg the message to send
 783  * @param impl_state our `struct ClientState`
 784  */
 785 static void
 786 connection_client_send_impl (struct GNUNET_MQ_Handle *mq,
 787                              const struct GNUNET_MessageHeader *msg,
 788                              void *impl_state)
 789 {
 790   struct ClientState *cstate = impl_state;
 791
 792   /* only one message at a time allowed */
 793   GNUNET_assert (NULL == cstate->msg);
 794   GNUNET_assert (NULL == cstate->send_task);
 795   cstate->msg = msg;
 796   cstate->msg_off = 0;
 797   if (NULL == cstate->sock)
 798     return; /* still waiting for connection */
 799   cstate->send_task
 800     = GNUNET_SCHEDULER_add_write_net (GNUNET_TIME_UNIT_FOREVER_REL,
 801                                       cstate->sock,
 802                                       &transmit_ready,
 803                                       cstate);
 804 }
 805
 806
 807 /**
 808  * Cancel the currently sent message.
 809  *
 810  * @param mq message queue
 811  * @param impl_state our `struct ClientState`
 812  */
 813 static void
 814 connection_client_cancel_impl (struct GNUNET_MQ_Handle *mq,
 815                                void *impl_state)
 816 {
 817   struct ClientState *cstate = impl_state;
 818
 819   GNUNET_assert (NULL != cstate->msg);
 820   GNUNET_assert (0 == cstate->msg_off);
 821   cstate->msg = NULL;
 822   if (NULL != cstate->send_task)
 823   {
 824     GNUNET_SCHEDULER_cancel (cstate->send_task);
 825     cstate->send_task = NULL;
 826   }
 827 }
 828
 829
 830 /**
 831  * Create a message queue to connect to a GNUnet service.
 832  * If handlers are specfied, receive messages from the connection.
 833  *
 834  * @param cfg our configuration
 835  * @param service_name name of the service to connect to
 836  * @param handlers handlers for receiving messages, can be NULL
 837  * @param error_handler error handler
 838  * @param error_handler_cls closure for the @a error_handler
 839  * @return the message queue, NULL on error
 840  */
 841 struct GNUNET_MQ_Handle *
 842 GNUNET_CLIENT_connect (const struct GNUNET_CONFIGURATION_Handle *cfg,
 843                        const char *service_name,
 844                        const struct GNUNET_MQ_MessageHandler *handlers,
 845                        GNUNET_MQ_ErrorHandler error_handler,
 846                        void *error_handler_cls)
 847 {
 848   struct ClientState *cstate;
 849
 850   if (GNUNET_OK !=
 851       test_service_configuration (service_name,
 852                                   cfg))
 853     return NULL;
 854   cstate = GNUNET_new (struct ClientState);
 855   cstate->service_name = GNUNET_strdup (service_name);
 856   cstate->cfg = cfg;
 857   cstate->retry_task = GNUNET_SCHEDULER_add_now (&start_connect,
 858                                                  cstate);
 859   cstate->mst = GNUNET_MST_create (&recv_message,
 860                                    cstate);
 861   if (GNUNET_YES ==
 862       GNUNET_CONFIGURATION_have_value (cfg,
 863                                        service_name,
 864                                        "PORT"))
 865   {
 866     if (! ( (GNUNET_OK !=
 867              GNUNET_CONFIGURATION_get_value_number (cfg,
 868                                                     service_name,
 869                                                     "PORT",
 870                                                     &cstate->port)) ||
 871             (cstate->port > 65535) ||
 872             (GNUNET_OK !=
 873              GNUNET_CONFIGURATION_get_value_string (cfg,
 874                                                     service_name,
 875                                                     "HOSTNAME",
 876                                                     &cstate->hostname)) ) &&
 877         (0 == strlen (cstate->hostname)) )
 878     {
 879       GNUNET_free (cstate->hostname);
 880       cstate->hostname = NULL;
 881       LOG (GNUNET_ERROR_TYPE_WARNING,
 882            _("Need a non-empty hostname for service `%s'.\n"),
 883            service_name);
 884     }
 885   }
 886   cstate->mq = GNUNET_MQ_queue_for_callbacks (&connection_client_send_impl,
 887                                               &connection_client_destroy_impl,
 888                                               &connection_client_cancel_impl,
 889                                               cstate,
 890                                               handlers,
 891                                               error_handler,
 892                                               error_handler_cls);
 893   return cstate->mq;
 894 }
 895
 896 /* end of client.c */