connect.c

       over alternative addresses/socket families etc. */
    return CURLE_OK;

  /* store remote address and port used in this connection attempt */
  if(!getaddressinfo((struct sockaddr*)&addr.sa_addr,
                     ipaddress, &port)) {
    /* malformed address or bug in inet_ntop, try next address */
    error = ERRNO;
    failf(data, "sa_addr inet_ntop() failed with errno %d: %s",
          error, Curl_strerror(conn, error));
    Curl_closesocket(conn, sockfd);
    return CURLE_OK;
  }
  infof(data, "  Trying %s...\n", ipaddress);

  if(data->set.tcp_nodelay)
    tcpnodelay(conn, sockfd);

  nosigpipe(conn, sockfd);

  Curl_sndbufset(sockfd);

  if(data->set.tcp_keepalive)
    tcpkeepalive(data, sockfd);

  if(data->set.fsockopt) {
    /* activate callback for setting socket options */
    error = data->set.fsockopt(data->set.sockopt_client,
                               sockfd,
                               CURLSOCKTYPE_IPCXN);

    if(error == CURL_SOCKOPT_ALREADY_CONNECTED)
      isconnected = TRUE;
    else if(error) {
      Curl_closesocket(conn, sockfd); /* close the socket and bail out */
      return CURLE_ABORTED_BY_CALLBACK;
    }
  }

  /* possibly bind the local end to an IP, interface or port */
  res = bindlocal(conn, sockfd, addr.family);
  if(res) {
    Curl_closesocket(conn, sockfd); /* close socket and bail out */
    if(res == CURLE_UNSUPPORTED_PROTOCOL) {
      /* The address family is not supported on this interface.
         We can continue trying addresses */
      return CURLE_OK;
    }
    return res;
  }

  /* set socket non-blocking */
  curlx_nonblock(sockfd, TRUE);

  conn->connecttime = Curl_tvnow();
  if(conn->num_addr > 1)
    Curl_expire(data, conn->timeoutms_per_addr);

  /* Connect TCP sockets, bind UDP */
  if(!isconnected && (conn->socktype == SOCK_STREAM)) {
    rc = connect(sockfd, &addr.sa_addr, addr.addrlen);
    if(-1 == rc)
      error = SOCKERRNO;
  }
  else {
    *sockp = sockfd;
    return CURLE_OK;
  }

#ifdef ENABLE_IPV6
  conn->bits.ipv6 = (addr.family == AF_INET6)?TRUE:FALSE;
#endif

  if(-1 == rc) {
    switch(error) {
    case EINPROGRESS:
    case EWOULDBLOCK:
#if defined(EAGAIN)
#if (EAGAIN) != (EWOULDBLOCK)
      /* On some platforms EAGAIN and EWOULDBLOCK are the
       * same value, and on others they are different, hence
       * the odd #if
       */
    case EAGAIN:
#endif
#endif
      res = CURLE_OK;
      break;

    default:
      /* unknown error, fallthrough and try another address! */
      infof(data, "Immediate connect fail for %s: %s\n",
            ipaddress, Curl_strerror(conn,error));
      data->state.os_errno = error;

      /* connect failed */
      Curl_closesocket(conn, sockfd);
      res = CURLE_COULDNT_CONNECT;
    }
  }

  if(!res)
    *sockp = sockfd;

  return res;
}

/*
 * TCP connect to the given host with timeout, proxy or remote doesn't matter.
 * There might be more than one IP address to try out. Fill in the passed
 * pointer with the connected socket.
 */

CURLcode Curl_connecthost(struct connectdata *conn,  /* context */
                          const struct Curl_dns_entry *remotehost)
{
  struct SessionHandle *data = conn->data;
  struct timeval before = Curl_tvnow();
  CURLcode res = CURLE_COULDNT_CONNECT;

  long timeout_ms = Curl_timeleft(data, &before, TRUE);

  if(timeout_ms < 0) {
    /* a precaution, no need to continue if time already is up */
    failf(data, "Connection time-out");
    return CURLE_OPERATION_TIMEDOUT;
  }

  conn->num_addr = Curl_num_addresses(remotehost->addr);
  conn->tempaddr[0] = remotehost->addr;
  conn->tempaddr[1] = NULL;
  conn->tempsock[0] = CURL_SOCKET_BAD;
  conn->tempsock[1] = CURL_SOCKET_BAD;
  Curl_expire(conn->data, HAPPY_EYEBALLS_TIMEOUT);

  /* Max time for the next connection attempt */
  conn->timeoutms_per_addr =
    conn->tempaddr[0]->ai_next == NULL ? timeout_ms : timeout_ms / 2;

  /* start connecting to first IP */
  while(conn->tempaddr[0]) {
    res = singleipconnect(conn, conn->tempaddr[0], &(conn->tempsock[0]));
    if(res == CURLE_OK)
        break;
    conn->tempaddr[0] = conn->tempaddr[0]->ai_next;
  }

  if(conn->tempsock[0] == CURL_SOCKET_BAD)
    return res;

  data->info.numconnects++; /* to track the number of connections made */

  return CURLE_OK;
}

struct connfind {
  struct connectdata *tofind;
  bool found;
};

static int conn_is_conn(struct connectdata *conn, void *param)
{
  struct connfind *f = (struct connfind *)param;
  if(conn == f->tofind) {
    f->found = TRUE;
    return 1;
  }
  return 0;
}

/*
 * Used to extract socket and connectdata struct for the most recent
 * transfer on the given SessionHandle.
 *
 * The returned socket will be CURL_SOCKET_BAD in case of failure!
 */
curl_socket_t Curl_getconnectinfo(struct SessionHandle *data,
                                  struct connectdata **connp)
{
  curl_socket_t sockfd;

  DEBUGASSERT(data);

  /* this only works for an easy handle that has been used for
     curl_easy_perform()! */
  if(data->state.lastconnect && data->multi_easy) {
    struct connectdata *c = data->state.lastconnect;
    struct connfind find;
    find.tofind = data->state.lastconnect;
    find.found = FALSE;

    Curl_conncache_foreach(data->multi_easy->conn_cache, &find, conn_is_conn);

    if(!find.found) {
      data->state.lastconnect = NULL;
      return CURL_SOCKET_BAD;
    }

    if(connp)
      /* only store this if the caller cares for it */
      *connp = c;
    sockfd = c->sock[FIRSTSOCKET];
    /* we have a socket connected, let's determine if the server shut down */
    /* determine if ssl */
    if(c->ssl[FIRSTSOCKET].use) {
      /* use the SSL context */
      if(!Curl_ssl_check_cxn(c))
        return CURL_SOCKET_BAD;   /* FIN received */
    }
/* Minix 3.1 doesn't support any flags on recv; just assume socket is OK */
#ifdef MSG_PEEK
    else {
      /* use the socket */
      char buf;
      if(recv((RECV_TYPE_ARG1)c->sock[FIRSTSOCKET], (RECV_TYPE_ARG2)&buf,
              (RECV_TYPE_ARG3)1, (RECV_TYPE_ARG4)MSG_PEEK) == 0) {
        return CURL_SOCKET_BAD;   /* FIN received */
      }
    }
#endif
  }
  else
    return CURL_SOCKET_BAD;

  return sockfd;
}

/*
 * Close a socket.
 *
 * 'conn' can be NULL, beware!
 */
int Curl_closesocket(struct connectdata *conn,
                      curl_socket_t sock)
{
  if(conn && conn->fclosesocket) {
    if((sock == conn->sock[SECONDARYSOCKET]) &&
       conn->sock_accepted[SECONDARYSOCKET])
      /* if this socket matches the second socket, and that was created with
         accept, then we MUST NOT call the callback but clear the accepted
         status */
      conn->sock_accepted[SECONDARYSOCKET] = FALSE;
    else
      return conn->fclosesocket(conn->closesocket_client, sock);
  }
  sclose(sock);

  if(conn)
    /* tell the multi-socket code about this */
    Curl_multi_closed(conn, sock);

  return 0;
}

/*
 * Create a socket based on info from 'conn' and 'ai'.
 *
 * 'addr' should be a pointer to the correct struct to get data back, or NULL.
 * 'sockfd' must be a pointer to a socket descriptor.
 *
 * If the open socket callback is set, used that!
 *
 */
CURLcode Curl_socket(struct connectdata *conn,
                     const Curl_addrinfo *ai,
                     struct Curl_sockaddr_ex *addr,
                     curl_socket_t *sockfd)
{
  struct SessionHandle *data = conn->data;
  struct Curl_sockaddr_ex dummy;

  if(!addr)
    /* if the caller doesn't want info back, use a local temp copy */
    addr = &dummy;

  /*
   * The Curl_sockaddr_ex structure is basically libcurl's external API
   * curl_sockaddr structure with enough space available to directly hold
   * any protocol-specific address structures. The variable declared here
   * will be used to pass / receive data to/from the fopensocket callback
   * if this has been set, before that, it is initialized from parameters.
   */

  addr->family = ai->ai_family;
  addr->socktype = conn->socktype;
  addr->protocol = conn->socktype==SOCK_DGRAM?IPPROTO_UDP:ai->ai_protocol;
  addr->addrlen = ai->ai_addrlen;

  if(addr->addrlen > sizeof(struct Curl_sockaddr_storage))
     addr->addrlen = sizeof(struct Curl_sockaddr_storage);
  memcpy(&addr->sa_addr, ai->ai_addr, addr->addrlen);

  if(data->set.fopensocket)
   /*
    * If the opensocket callback is set, all the destination address
    * information is passed to the callback. Depending on this information the
    * callback may opt to abort the connection, this is indicated returning
    * CURL_SOCKET_BAD; otherwise it will return a not-connected socket. When
    * the callback returns a valid socket the destination address information
    * might have been changed and this 'new' address will actually be used
    * here to connect.
    */
    *sockfd = data->set.fopensocket(data->set.opensocket_client,
                                    CURLSOCKTYPE_IPCXN,
                                    (struct curl_sockaddr *)addr);
  else
    /* opensocket callback not set, so simply create the socket now */
    *sockfd = socket(addr->family, addr->socktype, addr->protocol);

  if(*sockfd == CURL_SOCKET_BAD)
    /* no socket, no connection */
    return CURLE_COULDNT_CONNECT;

#if defined(ENABLE_IPV6) && defined(HAVE_SOCKADDR_IN6_SIN6_SCOPE_ID)
  if(conn->scope && (addr->family == AF_INET6)) {
    struct sockaddr_in6 * const sa6 = (void *)&addr->sa_addr;
    sa6->sin6_scope_id = conn->scope;
  }
#endif

  return CURLE_OK;

}