remoteconnection.h

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/* Copyright (C) 2006,2007,2008,2010,2011,2014,2015,2019,2024 Olly Betts
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
 */

#ifndef XAPIAN_INCLUDED_REMOTECONNECTION_H
#define XAPIAN_INCLUDED_REMOTECONNECTION_H

#include <cerrno>
#include <string>

#include "remoteprotocol.h"
#include "safenetdb.h" // For EAI_* constants.
#include "safeunistd.h"

#ifdef __WIN32__
# include "safewinsock2.h"

# include <xapian/error.h>

struct WinsockInitializer {
    WinsockInitializer() {
        WSADATA wsadata;
        int wsaerror = WSAStartup(MAKEWORD(2, 2), &wsadata);
        // FIXME - should we check the returned information in wsadata to check
        // that we have a version of winsock which is recent enough for us?

        if (wsaerror != 0) {
            throw Xapian::NetworkError("Failed to initialize winsock", wsaerror);
        }
    }

    ~WinsockInitializer() {
        WSACleanup();
    }
};

inline int socket_errno() {
    int wsa_err = WSAGetLastError();
    switch (wsa_err) {
# ifdef EADDRINUSE
        case WSAEADDRINUSE: return EADDRINUSE;
# endif
# ifdef ETIMEDOUT
        case WSAETIMEDOUT: return ETIMEDOUT;
# endif
# ifdef EINPROGRESS
        case WSAEINPROGRESS: return EINPROGRESS;
# endif
        default: return wsa_err;
    }
}

/* Newer compilers define these, in which case we map to those already defined
 * values in socket_errno() above.
 */
# ifndef EADDRINUSE
#  define EADDRINUSE WSAEADDRINUSE
# endif
# ifndef ETIMEDOUT
#  define ETIMEDOUT WSAETIMEDOUT
# endif
# ifndef EINPROGRESS
#  define EINPROGRESS WSAEINPROGRESS
# endif

// We must call closesocket() (instead of just close()) under __WIN32__ or
// else the socket remains in the CLOSE_WAIT state.
# define CLOSESOCKET(S) closesocket(S)
#else
# include "safesyssocket.h"
inline int socket_errno() { return errno; }

# define CLOSESOCKET(S) close(S)
#endif

inline int eai_to_xapian(int e) {
    // Under WIN32, the EAI_* constants are defined to be WSA_* constants with
    // roughly equivalent meanings, so we can just let them be handled as any
    // other WSA_* error codes would be.
#ifndef __WIN32__
    // Ensure they all have the same sign - this switch will fail to compile if
    // we bitwise-or some 1 and some 2 bits to get 3.
#define C(X) ((X) < 0 ? 2 : 1)
    // Switch on a value there is a case for, to avoid clang warning:
    // "no case matching constant switch condition '0'"
    switch (3) {
        case
            C(EAI_AGAIN)|
            C(EAI_BADFLAGS)|
            C(EAI_FAIL)|
            C(EAI_FAMILY)|
            C(EAI_MEMORY)|
            C(EAI_NONAME)|
            C(EAI_SERVICE)|
            C(EAI_SOCKTYPE)|
            C(EAI_SYSTEM)|
#ifdef EAI_ADDRFAMILY
            // In RFC 2553 but not RFC 3493 or POSIX:
            C(EAI_ADDRFAMILY)|
#endif
#ifdef EAI_NODATA
            // In RFC 2553 but not RFC 3493 or POSIX:
            C(EAI_NODATA)|
#endif
#ifdef EAI_OVERFLOW
            // In RFC 3493 and POSIX but not RFC 2553:
            C(EAI_OVERFLOW)|
#endif
            0: break;
        case 3: break;
    }
#undef C

    // EAI_SYSTEM means "look at errno".
    if (e == EAI_SYSTEM)
        return errno;
    // POSIX only says that EAI_* constants are "non-zero".  On Linux they are
    // negative, but allow for them being positive too.
    if (EAI_FAIL > 0)
        return -e;
#endif
    return e;
}

class RemoteConnection {
    void operator=(const RemoteConnection &);

    RemoteConnection(const RemoteConnection &);

    int fdin;

    int fdout;

#ifndef __WIN32__
    // On Unix-like platforms we want to avoid generating SIGPIPE when writing
    // to a socket when the other end has been closed since signals break the
    // encapsulation of what we're doing inside the library - either user code
    // would need to handle the SIGPIPE, or we set a signal handler for SIGPIPE
    // but that would handle *any* SIGPIPE in the process, not just those we
    // might trigger, and that could break user code which expects to trigger
    // and handle SIGPIPE.
    //
    // We don't need SIGPIPE since we can check errno==EPIPE instead (which is
    // actually simpler to do).
    //
    // We support using SO_NOSIGPIPE (not standardised) or MSG_NOSIGNAL
    // (specified by POSIX but more awkward to use) which seems to cover all
    // modern Unix-like platforms.  For platforms without either we currently
    // just set the SIGPIPE signal handler to SIG_IGN.
# if defined(SO_NOSIGPIPE) && !defined(__NetBSD__)
    // Prefer using SO_NOSIGPIPE and write(), except on NetBSD where we seem to
    // still get SIGPIPE despite using it.
#  define USE_SO_NOSIGPIPE
# elif defined MSG_NOSIGNAL
    // Use send(..., MSG_NOSIGNAL).
    int send_flags = MSG_NOSIGNAL;
#  define USE_MSG_NOSIGNAL
# endif
#endif

    std::string buffer;

    off_t chunked_data_left;

    bool read_at_least(size_t min_len, double end_time);

#ifdef __WIN32__

    WSAOVERLAPPED overlapped;

    DWORD calc_read_wait_msecs(double end_time);
#else

    ssize_t send_or_write(const void* p, size_t n);
#endif

  protected:
    std::string context;

  public:
    RemoteConnection(int fdin_, int fdout_,
                     const std::string & context_ = std::string());

#ifdef __WIN32__
    ~RemoteConnection();
#endif

    bool ready_to_read() const;

    int sniff_next_message_type(double end_time);

    int get_message(std::string &result, double end_time);

    int get_message_chunked(double end_time);

    int get_message_chunk(std::string &result, size_t at_least,
                          double end_time);

    int receive_file(const std::string &file, double end_time);

    void send_message(char type, const std::string & s, double end_time);

    void send_file(char type, int fd, double end_time);

    void shutdown();

    void do_close();
};

class OwnedRemoteConnection : public RemoteConnection {
  public:
    OwnedRemoteConnection(int fdin_, int fdout_,
                          const std::string& context_ = std::string())
        : RemoteConnection(fdin_, fdout_, context_) { }

    ~OwnedRemoteConnection() {
        do_close();
    }
};

#endif // XAPIAN_INCLUDED_REMOTECONNECTION_H