C++ Curl_closesocket函数代码示例

/* Used within the multi interface. Try next IP address, return TRUE if no
   more address exists or error */
static CURLcode trynextip(struct connectdata *conn,
                          int sockindex,
                          int tempindex,
                          bool *connected)
{
  curl_socket_t sockfd;
  Curl_addrinfo *ai;
  int family = tempindex ? AF_INET6 : AF_INET;

  /* First clean up after the failed socket.
     Don't close it yet to ensure that the next IP's socket gets a different
     file descriptor, which can prevent bugs when the curl_multi_socket_action
     interface is used with certain select() replacements such as kqueue. */
  curl_socket_t fd_to_close = conn->tempsock[tempindex];
  conn->tempsock[tempindex] = CURL_SOCKET_BAD;
  *connected = FALSE;

  if(sockindex != FIRSTSOCKET) {
    Curl_closesocket(conn, fd_to_close);
    return CURLE_COULDNT_CONNECT; /* no next */
  }

  /* try the next address with same family */
  ai = conn->tempaddr[tempindex]->ai_next;
  while(ai && ai->ai_family != family)
    ai = ai->ai_next;

  while(ai && ai->ai_family == family) {
    CURLcode res = singleipconnect(conn, ai, &sockfd, connected);
    if(res)
      return res;
    if(sockfd != CURL_SOCKET_BAD) {
      /* store the new socket descriptor */
      conn->tempsock[tempindex] = sockfd;
      conn->tempaddr[tempindex] = ai;
      Curl_closesocket(conn, fd_to_close);
      return CURLE_OK;
    }

    do {
      ai = ai->ai_next;
    } while(ai && ai->ai_family != family);
  }
  Curl_closesocket(conn, fd_to_close);
  return CURLE_COULDNT_CONNECT;
}

/* Used within the multi interface. Try next IP address, return TRUE if no
   more address exists or error */
static CURLcode trynextip(struct connectdata *conn,
                          int sockindex,
                          int tempindex)
{
  const int other = tempindex ^ 1;
  CURLcode result = CURLE_COULDNT_CONNECT;

  /* First clean up after the failed socket.
     Don't close it yet to ensure that the next IP's socket gets a different
     file descriptor, which can prevent bugs when the curl_multi_socket_action
     interface is used with certain select() replacements such as kqueue. */
  curl_socket_t fd_to_close = conn->tempsock[tempindex];
  conn->tempsock[tempindex] = CURL_SOCKET_BAD;

  if(sockindex == FIRSTSOCKET) {
    Curl_addrinfo *ai = NULL;
    int family = AF_UNSPEC;

    if(conn->tempaddr[tempindex]) {
      /* find next address in the same protocol family */
      family = conn->tempaddr[tempindex]->ai_family;
      ai = conn->tempaddr[tempindex]->ai_next;
    }
#ifdef ENABLE_IPV6
    else if(conn->tempaddr[0]) {
      /* happy eyeballs - try the other protocol family */
      int firstfamily = conn->tempaddr[0]->ai_family;
      family = (firstfamily == AF_INET) ? AF_INET6 : AF_INET;
      ai = conn->tempaddr[0]->ai_next;
    }
#endif

    while(ai) {
      if(conn->tempaddr[other]) {
        /* we can safely skip addresses of the other protocol family */
        while(ai && ai->ai_family != family)
          ai = ai->ai_next;
      }

      if(ai) {
        result = singleipconnect(conn, ai, &conn->tempsock[tempindex]);
        if(result == CURLE_COULDNT_CONNECT) {
          ai = ai->ai_next;
          continue;
        }

        conn->tempaddr[tempindex] = ai;
      }
      break;
    }
  }

  if(fd_to_close != CURL_SOCKET_BAD)
    Curl_closesocket(conn, fd_to_close);

  return result;
}

/*
 * Curl_ipv6works() returns TRUE if ipv6 seems to work.
 */
bool Curl_ipv6works(void)
{
  /* the nature of most system is that IPv6 status doesn't come and go
     during a program's lifetime so we only probe the first time and then we
     have the info kept for fast re-use */
  static int ipv6_works = -1;
  if(-1 == ipv6_works) {
    /* probe to see if we have a working IPv6 stack */
    curl_socket_t s = socket(PF_INET6, SOCK_DGRAM, 0);
    if(s == CURL_SOCKET_BAD)
      /* an ipv6 address was requested but we can't get/use one */
      ipv6_works = 0;
    else {
      ipv6_works = 1;
      Curl_closesocket(NULL, s);
    }
  }
  return (ipv6_works>0)?TRUE:FALSE;
}

/* Used within the multi interface. Try next IP address, return TRUE if no
   more address exists or error */
static CURLcode trynextip(struct connectdata *conn,
                          int sockindex,
                          int tempindex)
{
  CURLcode rc = CURLE_COULDNT_CONNECT;

  /* First clean up after the failed socket.
     Don't close it yet to ensure that the next IP's socket gets a different
     file descriptor, which can prevent bugs when the curl_multi_socket_action
     interface is used with certain select() replacements such as kqueue. */
  curl_socket_t fd_to_close = conn->tempsock[tempindex];
  conn->tempsock[tempindex] = CURL_SOCKET_BAD;

  if(sockindex == FIRSTSOCKET) {
    Curl_addrinfo *ai;
    int family;

    if(conn->tempaddr[tempindex]) {
      /* find next address in the same protocol family */
      family = conn->tempaddr[tempindex]->ai_family;
      ai = conn->tempaddr[tempindex]->ai_next;
    }
    else {
      /* happy eyeballs - try the other protocol family */
      int firstfamily = conn->tempaddr[0]->ai_family;
      family = (firstfamily == AF_INET) ? AF_INET6 : AF_INET;
      ai = conn->tempaddr[0]->ai_next;
    }

    while(ai && ai->ai_family != family)
      ai = ai->ai_next;
    if(ai) {
      rc = singleipconnect(conn, ai, &conn->tempsock[tempindex]);
      conn->tempaddr[tempindex] = ai;
    }
  }

  if(fd_to_close != CURL_SOCKET_BAD)
    Curl_closesocket(conn, fd_to_close);

  return rc;
}

/*
 * singleipconnect()
 *
 * Note that even on connect fail it returns CURLE_OK, but with 'sock' set to
 * CURL_SOCKET_BAD. Other errors will however return proper errors.
 *
 * singleipconnect() connects to the given IP only, and it may return without
 * having connected.
 */
static CURLcode singleipconnect(struct connectdata *conn,
                                const Curl_addrinfo *ai,
                                curl_socket_t *sockp)
{
  struct Curl_sockaddr_ex addr;
  int rc;
  int error = 0;
  bool isconnected = FALSE;
  struct SessionHandle *data = conn->data;
  curl_socket_t sockfd;
  CURLcode result;
  char ipaddress[MAX_IPADR_LEN];
  long port;
  bool is_tcp;

  *sockp = CURL_SOCKET_BAD;

  result = Curl_socket(conn, ai, &addr, &sockfd);
  if(result)
    /* Failed to create the socket, but still return OK since we signal the
       lack of socket as well. This allows the parent function to keep looping
       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);

  is_tcp = (addr.family == AF_INET || addr.family == AF_INET6) &&
           addr.socktype == SOCK_STREAM;
  if(is_tcp && data->set.tcp_nodelay)
    tcpnodelay(conn, sockfd);

  nosigpipe(conn, sockfd);

  Curl_sndbufset(sockfd);

  if(is_tcp && 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 */
  if(addr.family == AF_INET || addr.family == AF_INET6) {
    result = bindlocal(conn, sockfd, addr.family,
                       Curl_ipv6_scope((struct sockaddr*)&addr.sa_addr));
    if(result) {
      Curl_closesocket(conn, sockfd); /* close socket and bail out */
      if(result == CURLE_UNSUPPORTED_PROTOCOL) {
        /* The address family is not supported on this interface.
           We can continue trying addresses */
        return CURLE_COULDNT_CONNECT;
      }
      return result;
    }
  }

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

  conn->connecttime = Curl_tvnow();
  if(conn->num_addr > 1)
    Curl_expire_latest(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 {
//.........这里部分代码省略.........

CURLcode Curl_is_connected(struct connectdata *conn,
                           int sockindex,
                           bool *connected)
{
  struct SessionHandle *data = conn->data;
  CURLcode result = CURLE_OK;
  long allow;
  int error = 0;
  struct timeval now;
  int rc;
  int i;

  DEBUGASSERT(sockindex >= FIRSTSOCKET && sockindex <= SECONDARYSOCKET);

  *connected = FALSE; /* a very negative world view is best */

  if(conn->bits.tcpconnect[sockindex]) {
    /* we are connected already! */
    *connected = TRUE;
    return CURLE_OK;
  }

  now = Curl_tvnow();

  /* figure out how long time we have left to connect */
  allow = Curl_timeleft(data, &now, TRUE);

  if(allow < 0) {
    /* time-out, bail out, go home */
    failf(data, "Connection time-out");
    return CURLE_OPERATION_TIMEDOUT;
  }

  for(i=0; i<2; i++) {
    if(conn->tempsock[i] == CURL_SOCKET_BAD)
      continue;

#ifdef mpeix
    /* Call this function once now, and ignore the results. We do this to
       "clear" the error state on the socket so that we can later read it
       reliably. This is reported necessary on the MPE/iX operating system. */
    (void)verifyconnect(conn->tempsock[i], NULL);
#endif

    /* check socket for connect */
    rc = Curl_socket_ready(CURL_SOCKET_BAD, conn->tempsock[i], 0);

    if(rc == 0) { /* no connection yet */
      if(curlx_tvdiff(now, conn->connecttime) >= conn->timeoutms_per_addr) {
        infof(data, "After %ldms connect time, move on!\n",
              conn->timeoutms_per_addr);
        error = ETIMEDOUT;
      }

      /* should we try another protocol family? */
      if(i == 0 && conn->tempaddr[1] == NULL &&
         curlx_tvdiff(now, conn->connecttime) >= HAPPY_EYEBALLS_TIMEOUT) {
        trynextip(conn, sockindex, 1);
      }
    }
    else if(rc == CURL_CSELECT_OUT) {
      if(verifyconnect(conn->tempsock[i], &error)) {
        /* we are connected with TCP, awesome! */
        int other = i ^ 1;

        /* use this socket from now on */
        conn->sock[sockindex] = conn->tempsock[i];
        conn->ip_addr = conn->tempaddr[i];
        conn->tempsock[i] = CURL_SOCKET_BAD;

        /* close the other socket, if open */
        if(conn->tempsock[other] != CURL_SOCKET_BAD) {
          Curl_closesocket(conn, conn->tempsock[other]);
          conn->tempsock[other] = CURL_SOCKET_BAD;
        }

        /* see if we need to do any proxy magic first once we connected */
        result = Curl_connected_proxy(conn, sockindex);
        if(result)
          return result;

        conn->bits.tcpconnect[sockindex] = TRUE;

        *connected = TRUE;
        if(sockindex == FIRSTSOCKET)
          Curl_pgrsTime(data, TIMER_CONNECT); /* connect done */
        Curl_updateconninfo(conn, conn->sock[sockindex]);
        Curl_verboseconnect(conn);

        return CURLE_OK;
      }
      else
        infof(data, "Connection failed\n");
    }
    else if(rc & CURL_CSELECT_ERR)
      (void)verifyconnect(conn->tempsock[i], &error);

    /*
     * The connection failed here, we should attempt to connect to the "next
     * address" for the given host. But first remember the latest error.
//.........这里部分代码省略.........

//.........这里部分代码省略.........
                    chunked_encoding = TRUE;
                    /* init our chunky engine */
                    Curl_httpchunk_init(conn);
                  }
                  else if(Curl_compareheader(line_start,
                                             "Proxy-Connection:", "close"))
                    closeConnection = TRUE;
                  else if(2 == sscanf(line_start, "HTTP/1.%d %d",
                                      &subversion,
                                      &k->httpcode)) {
                    /* store the HTTP code from the proxy */
                    data->info.httpproxycode = k->httpcode;
                  }
                  /* put back the letter we blanked out before */
                  line_start[perline]= letter;

                  perline=0; /* line starts over here */
                  line_start = ptr+1; /* this skips the zero byte we wrote */
                }
              }
          }
          break;
        } /* switch */
        if(Curl_pgrsUpdate(conn))
          return CURLE_ABORTED_BY_CALLBACK;
      } /* while there's buffer left and loop is requested */

      if(error)
        return CURLE_RECV_ERROR;

      if(data->info.httpproxycode != 200) {
        /* Deal with the possibly already received authenticate
           headers. 'newurl' is set to a new URL if we must loop. */
        result = Curl_http_auth_act(conn);
        if(result)
          return result;

        if(conn->bits.close)
          /* the connection has been marked for closure, most likely in the
             Curl_http_auth_act() function and thus we can kill it at once
             below
          */
          closeConnection = TRUE;
      }

      if(closeConnection && data->req.newurl) {
        /* Connection closed by server. Don't use it anymore */
        Curl_closesocket(conn, conn->sock[sockindex]);
        conn->sock[sockindex] = CURL_SOCKET_BAD;
        break;
      }
    } /* END NEGOTIATION PHASE */

    /* If we are supposed to continue and request a new URL, which basically
     * means the HTTP authentication is still going on so if the tunnel
     * is complete we start over in INIT state */
    if(data->req.newurl &&
       (TUNNEL_COMPLETE == conn->tunnel_state[sockindex])) {
      conn->tunnel_state[sockindex] = TUNNEL_INIT;
      infof(data, "TUNNEL_STATE switched to: %d\n",
            conn->tunnel_state[sockindex]);
    }

  } while(data->req.newurl);

  if(200 != data->req.httpcode) {
    failf(data, "Received HTTP code %d from proxy after CONNECT",
          data->req.httpcode);

    if(closeConnection && data->req.newurl)
      conn->bits.proxy_connect_closed = TRUE;

    if(data->req.newurl) {
      /* this won't be used anymore for the CONNECT so free it now */
      free(data->req.newurl);
      data->req.newurl = NULL;
    }

    /* to back to init state */
    conn->tunnel_state[sockindex] = TUNNEL_INIT;

    return CURLE_RECV_ERROR;
  }

  conn->tunnel_state[sockindex] = TUNNEL_COMPLETE;

  /* If a proxy-authorization header was used for the proxy, then we should
     make sure that it isn't accidentally used for the document request
     after we've connected. So let's free and clear it here. */
  Curl_safefree(conn->allocptr.proxyuserpwd);
  conn->allocptr.proxyuserpwd = NULL;

  data->state.authproxy.done = TRUE;

  infof (data, "Proxy replied OK to CONNECT request\n");
  data->req.ignorebody = FALSE; /* put it (back) to non-ignore state */
  conn->bits.rewindaftersend = FALSE; /* make sure this isn't set for the
                                         document request  */
  return CURLE_OK;
}

/*
 * singleipconnect()
 *
 * Note that even on connect fail it returns CURLE_OK, but with 'sock' set to
 * CURL_SOCKET_BAD. Other errors will however return proper errors.
 *
 * singleipconnect() connects to the given IP only, and it may return without
 * having connected if used from the multi interface.
 */
static CURLcode
singleipconnect(struct connectdata *conn,
                const Curl_addrinfo *ai,
                long timeout_ms,
                curl_socket_t *sockp,
                bool *connected)
{
  struct Curl_sockaddr_ex addr;
  int rc;
  int error = 0;
  bool isconnected = FALSE;
  struct SessionHandle *data = conn->data;
  curl_socket_t sockfd;
  CURLcode res = CURLE_OK;

  *sockp = CURL_SOCKET_BAD;
  *connected = FALSE; /* default is not connected */

  res = Curl_socket(conn, ai, &addr, &sockfd);
  if(res)
    /* Failed to create the socket, but still return OK since we signal the
       lack of socket as well. This allows the parent function to keep looping
       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,
                     conn->primary_ip, &conn->primary_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;
  }
  memcpy(conn->ip_addr_str, conn->primary_ip, MAX_IPADR_LEN);
  infof(data, "  Trying %s...\n", conn->ip_addr_str);

  Curl_persistconninfo(conn);

  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 */
    return res;
  }

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

  /* Connect TCP sockets, bind UDP */
  if(!isconnected && (conn->socktype == SOCK_STREAM)) {
    rc = connect(sockfd, &addr.sa_addr, addr.addrlen);
    if(-1 == rc)
      error = SOCKERRNO;
    conn->connecttime = Curl_tvnow();
    if(conn->num_addr > 1)
      Curl_expire(data, conn->timeoutms_per_addr);
  }
  else
    rc = 0;

  if(-1 == rc) {
    switch (error) {
    case EINPROGRESS:
    case EWOULDBLOCK:
#if defined(EAGAIN)
//.........这里部分代码省略.........

//.........这里部分代码省略.........
            s->chunked_encoding = TRUE;
            /* init our chunky engine */
            Curl_httpchunk_init(conn);
          }
        }
        else if(Curl_compareheader(s->line_start,
                                   "Proxy-Connection:", "close"))
          s->close_connection = TRUE;
        else if(2 == sscanf(s->line_start, "HTTP/1.%d %d",
                            &subversion,
                            &k->httpcode)) {
          /* store the HTTP code from the proxy */
          data->info.httpproxycode = k->httpcode;
        }

        s->perline = 0; /* line starts over here */
        s->ptr = s->connect_buffer;
        s->line_start = s->ptr;
      } /* while there's buffer left and loop is requested */

      if(Curl_pgrsUpdate(conn))
        return CURLE_ABORTED_BY_CALLBACK;

      if(error)
        return CURLE_RECV_ERROR;

      if(data->info.httpproxycode/100 != 2) {
        /* Deal with the possibly already received authenticate
           headers. 'newurl' is set to a new URL if we must loop. */
        result = Curl_http_auth_act(conn);
        if(result)
          return result;

        if(conn->bits.close)
          /* the connection has been marked for closure, most likely in the
             Curl_http_auth_act() function and thus we can kill it at once
             below */
          s->close_connection = TRUE;
      }

      if(s->close_connection && data->req.newurl) {
        /* Connection closed by server. Don't use it anymore */
        Curl_closesocket(conn, conn->sock[sockindex]);
        conn->sock[sockindex] = CURL_SOCKET_BAD;
        break;
      }
    } /* END READING RESPONSE PHASE */

    /* If we are supposed to continue and request a new URL, which basically
     * means the HTTP authentication is still going on so if the tunnel
     * is complete we start over in INIT state */
    if(data->req.newurl && (TUNNEL_COMPLETE == s->tunnel_state)) {
      connect_init(conn, TRUE); /* reinit */
    }

  } while(data->req.newurl);

  if(data->info.httpproxycode/100 != 2) {
    if(s->close_connection && data->req.newurl) {
      conn->bits.proxy_connect_closed = TRUE;
      infof(data, "Connect me again please\n");
      connect_done(conn);
    }
    else {
      free(data->req.newurl);
      data->req.newurl = NULL;
      /* failure, close this connection to avoid re-use */
      streamclose(conn, "proxy CONNECT failure");
      Curl_closesocket(conn, conn->sock[sockindex]);
      conn->sock[sockindex] = CURL_SOCKET_BAD;
    }

    /* to back to init state */
    s->tunnel_state = TUNNEL_INIT;

    if(conn->bits.proxy_connect_closed)
      /* this is not an error, just part of the connection negotiation */
      return CURLE_OK;
    failf(data, "Received HTTP code %d from proxy after CONNECT",
          data->req.httpcode);
    return CURLE_RECV_ERROR;
  }

  s->tunnel_state = TUNNEL_COMPLETE;

  /* If a proxy-authorization header was used for the proxy, then we should
     make sure that it isn't accidentally used for the document request
     after we've connected. So let's free and clear it here. */
  Curl_safefree(conn->allocptr.proxyuserpwd);
  conn->allocptr.proxyuserpwd = NULL;

  data->state.authproxy.done = TRUE;

  infof(data, "Proxy replied %d to CONNECT request\n",
        data->info.httpproxycode);
  data->req.ignorebody = FALSE; /* put it (back) to non-ignore state */
  conn->bits.rewindaftersend = FALSE; /* make sure this isn't set for the
                                         document request  */
  return CURLE_OK;
}

/*
 * singleipconnect()
 *
 * Note that even on connect fail it returns CURLE_OK, but with 'sock' set to
 * CURL_SOCKET_BAD. Other errors will however return proper errors.
 *
 * singleipconnect() connects to the given IP only, and it may return without
 * having connected if used from the multi interface.
 */
static CURLcode
singleipconnect(struct connectdata *conn,
                const Curl_addrinfo *ai,
                long timeout_ms,
                curl_socket_t *sockp,
                bool *connected)
{
  struct Curl_sockaddr_ex addr;
  int rc;
  int error;
  bool isconnected = FALSE;
  struct SessionHandle *data = conn->data;
  curl_socket_t sockfd;
  CURLcode res = CURLE_OK;
#if defined(ENABLE_IPV6) && defined(HAVE_SOCKADDR_IN6_SIN6_SCOPE_ID)
  struct sockaddr_in6 * const sa6 = (void *)&addr.sa_addr;
#endif

  *sockp = CURL_SOCKET_BAD;

  /*
   * 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);

  *connected = FALSE; /* default is not connected */

  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_OK;

#if defined(ENABLE_IPV6) && defined(HAVE_SOCKADDR_IN6_SIN6_SCOPE_ID)
  if(conn->scope && (addr.family == AF_INET6))
    sa6->sin6_scope_id = conn->scope;
#endif

  /* store remote address and port used in this connection attempt */
  if(!getaddressinfo((struct sockaddr*)&addr.sa_addr,
                     conn->primary_ip, &conn->primary_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;
  }
  memcpy(conn->ip_addr_str, conn->primary_ip, MAX_IPADR_LEN);
  infof(data, "  Trying %s... ", conn->ip_addr_str);

  Curl_persistconninfo(conn);

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

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

  nosigpipe(conn, sockfd);

  Curl_sndbufset(sockfd);
//.........这里部分代码省略.........

/*
 * singleipconnect()
 *
 * Note that even on connect fail it returns CURLE_OK, but with 'sock' set to
 * CURL_SOCKET_BAD. Other errors will however return proper errors.
 *
 * singleipconnect() connects to the given IP only, and it may return without
 * having connected.
 */
static CURLcode singleipconnect(struct connectdata *conn,
                                const Curl_addrinfo *ai,
                                curl_socket_t *sockp)
{
  struct Curl_sockaddr_ex addr;
  int rc = -1;
  int error = 0;
  bool isconnected = FALSE;
  struct Curl_easy *data = conn->data;
  curl_socket_t sockfd;
  CURLcode result;
  char ipaddress[MAX_IPADR_LEN];
  long port;
  bool is_tcp;

  *sockp = CURL_SOCKET_BAD;

  result = Curl_socket(conn, ai, &addr, &sockfd);
  if(result)
    /* Failed to create the socket, but still return OK since we signal the
       lack of socket as well. This allows the parent function to keep looping
       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 */
    failf(data, "sa_addr inet_ntop() failed with errno %d: %s",
          errno, Curl_strerror(conn, errno));
    Curl_closesocket(conn, sockfd);
    return CURLE_OK;
  }
  infof(data, "  Trying %s...\n", ipaddress);

#ifdef ENABLE_IPV6
  is_tcp = (addr.family == AF_INET || addr.family == AF_INET6) &&
    addr.socktype == SOCK_STREAM;
#else
  is_tcp = (addr.family == AF_INET) && addr.socktype == SOCK_STREAM;
#endif
  if(is_tcp && data->set.tcp_nodelay)
    Curl_tcpnodelay(conn, sockfd);

  nosigpipe(conn, sockfd);

  Curl_sndbufset(sockfd);

  if(is_tcp && 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 */
  if(addr.family == AF_INET
#ifdef ENABLE_IPV6
     || addr.family == AF_INET6
#endif
    ) {
    result = bindlocal(conn, sockfd, addr.family,
                       Curl_ipv6_scope((struct sockaddr*)&addr.sa_addr));
    if(result) {
      Curl_closesocket(conn, sockfd); /* close socket and bail out */
      if(result == CURLE_UNSUPPORTED_PROTOCOL) {
        /* The address family is not supported on this interface.
           We can continue trying addresses */
        return CURLE_COULDNT_CONNECT;
      }
      return result;
    }
  }

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

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

//.........这里部分代码省略.........