xapian-core/net/tcpclient.cc

   1 /** @file
   2  *  @brief Open a TCP connection to a server.
   3  */
   4 /* Copyright 2007-2024 Olly Betts
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License as
   8  * published by the Free Software Foundation; either version 2 of the
   9  * License, or (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, write to the Free Software
  18  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  19  */
  20
  21 #include <config.h>
  22
  23 #include "tcpclient.h"
  24
  25 #include <xapian/error.h>
  26
  27 #include "realtime.h"
  28 #include "resolver.h"
  29 #include "socket_utils.h"
  30
  31 #include "safefcntl.h"
  32 #include "safesyssocket.h"
  33
  34 #ifdef HAVE_POLL_H
  35 # include <poll.h>
  36 #else
  37 # include "safesysselect.h"
  38 #endif
  39
  40 #include <cerrno>
  41 #ifndef __WIN32__
  42 # include <netinet/in.h>
  43 # include <netinet/tcp.h>
  44 #endif
  45
  46 #include <string_view>
  47
  48 using namespace std;
  49
  50 int
  51 TcpClient::open_socket(std::string_view hostname, int port,
  52                        double timeout_connect, bool tcp_nodelay,
  53                        const string& context)
  54 {
  55     int socketfd = -1;
  56     int connect_errno = 0;
  57     for (auto&& r : Resolver(hostname, port)) {
  58         int socktype = r.ai_socktype | SOCK_CLOEXEC;
  59 #ifdef SOCK_NONBLOCK
  60         // Set the socket as non-blocking so we can implement a timeout on
  61         // the connection attempt by using select() or poll().  If
  62         // SOCK_NONBLOCK is available we can get socket() to do this, but
  63         // if not we call fcntl()/ioctlsocket() below to set it.
  64         socktype |= SOCK_NONBLOCK;
  65 #endif
  66         int fd = socket(r.ai_family, socktype, r.ai_protocol);
  67         if (fd < 0)
  68             continue;
  69
  70 #if !defined __WIN32__ && defined F_SETFD && defined FD_CLOEXEC
  71         // We can't use a preprocessor check on the *value* of SOCK_CLOEXEC as
  72         // on Linux SOCK_CLOEXEC is an enum, with '#define SOCK_CLOEXEC
  73         // SOCK_CLOEXEC' to allow '#ifdef SOCK_CLOEXEC' to work.
  74         if (SOCK_CLOEXEC == 0)
  75             (void)fcntl(fd, F_SETFD, FD_CLOEXEC);
  76 #endif
  77
  78 #ifndef SOCK_NONBLOCK
  79 #ifdef __WIN32__
  80         int rc = [&]() {
  81             ULONG on = 1;
  82             return ioctlsocket(fd, FIONBIO, &on);
  83         }();
  84 #define FLAG_NAME "FIONBIO"
  85 #elif defined O_NONBLOCK
  86         int rc = fcntl(fd, F_SETFL, O_NONBLOCK);
  87 #define FLAG_NAME "O_NONBLOCK"
  88 #else
  89         int rc = fcntl(fd, F_SETFL, O_NDELAY);
  90 #define FLAG_NAME "O_NDELAY"
  91 #endif
  92         if (rc < 0) {
  93             int saved_errno = socket_errno();
  94             CLOSESOCKET(fd);
  95             throw Xapian::NetworkError("Couldn't set " FLAG_NAME,
  96                                        context,
  97                                        saved_errno);
  98 #undef FLAG_NAME
  99         }
 100 #endif
 101
 102         if (tcp_nodelay) {
 103             int on = 1;
 104             // 4th argument might need to be void* or char* - cast it to char*
 105             // since C++ allows implicit conversion to void* but not from
 106             // void*.
 107             if (setsockopt(fd, IPPROTO_TCP, TCP_NODELAY,
 108                            reinterpret_cast<char*>(&on),
 109                            sizeof(on)) < 0) {
 110                 int setsockopt_errno = socket_errno();
 111                 CLOSESOCKET(fd);
 112                 throw Xapian::NetworkError("Couldn't set TCP_NODELAY",
 113                                            context,
 114                                            setsockopt_errno);
 115             }
 116         }
 117
 118         int retval = connect(fd, r.ai_addr, r.ai_addrlen);
 119         if (retval == 0) {
 120             socketfd = fd;
 121             break;
 122         }
 123
 124         int err = socket_errno();
 125         if (
 126 #ifndef __WIN32__
 127             err == EINPROGRESS
 128 #else
 129             err == WSAEWOULDBLOCK
 130 #endif
 131            ) {
 132             // Wait for the socket to be writable or give an error, with a
 133             // timeout.  FIXME: Reduce the timeout if we retry.
 134 #ifdef HAVE_POLL
 135             struct pollfd fds;
 136             fds.fd = fd;
 137             fds.events = POLLOUT;
 138             do {
 139                 retval = poll(&fds, 1, int(timeout_connect * 1000));
 140             } while (retval < 0 && (errno == EINTR || errno == EAGAIN));
 141 # define FUNC_NAME "poll()"
 142 #else
 143             fd_set fdset;
 144             FD_ZERO(&fdset);
 145             do {
 146                 FD_SET(fd, &fdset);
 147                 struct timeval tv;
 148                 RealTime::to_timeval(timeout_connect, &tv);
 149                 retval = select(fd + 1, 0, &fdset, 0, &tv);
 150             } while (retval < 0 && (errno == EINTR || errno == EAGAIN));
 151 # define FUNC_NAME "select()"
 152 #endif
 153
 154             if (retval <= 0) {
 155                 int saved_errno = errno;
 156                 CLOSESOCKET(fd);
 157                 if (retval < 0) {
 158                     throw Xapian::NetworkError("Couldn't connect ("
 159                                                FUNC_NAME " on socket failed)",
 160                                                context,
 161                                                saved_errno);
 162 #undef FUNC_NAME
 163                 }
 164                 throw Xapian::NetworkTimeoutError("Timed out waiting to "
 165                                                   "connect",
 166                                                   context,
 167                                                   ETIMEDOUT);
 168             }
 169
 170             err = 0;
 171             SOCKLEN_T len = sizeof(err);
 172
 173             // 4th argument might need to be void* or char* - cast it to char*
 174             // since C++ allows implicit conversion to void* but not from void*.
 175             retval = getsockopt(fd, SOL_SOCKET, SO_ERROR,
 176                                 reinterpret_cast<char*>(&err), &len);
 177
 178             if (retval < 0) {
 179                 int getsockopt_errno = socket_errno();
 180                 CLOSESOCKET(fd);
 181                 throw Xapian::NetworkError("getsockopt failed",
 182                                            context,
 183                                            getsockopt_errno);
 184             }
 185             if (err == 0) {
 186                 // Connected successfully.
 187                 socketfd = fd;
 188                 break;
 189             }
 190         }
 191
 192         // Note down the error code for the first address we try, which seems
 193         // likely to be more helpful than the last in the case where they
 194         // differ.
 195         if (connect_errno == 0)
 196             connect_errno = err;
 197
 198         // Failed to connect.
 199         CLOSESOCKET(fd);
 200     }
 201
 202     if (socketfd < 0) {
 203         throw Xapian::NetworkError("connect failed",
 204                                    context,
 205                                    connect_errno);
 206     }
 207
 208     // Set the socket to be blocking.
 209 #ifndef __WIN32__
 210     fcntl(socketfd, F_SETFL, 0);
 211 #else
 212     ULONG off = 0;
 213     ioctlsocket(socketfd, FIONBIO, &off);
 214 #endif
 215
 216     return socketfd;
 217 }