net/remoteconnection.cc

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/* Copyright (C) 2006,2007,2008,2009,2010,2011 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
 */

#include <config.h>

#include "remoteconnection.h"

#include <xapian/error.h>

#include "safeerrno.h"
#include "safefcntl.h"
#include "safesysselect.h"
#include "safesysstat.h"
#include "safeunistd.h"

#include <algorithm>
#include <string>

#include "debuglog.h"
#include "omassert.h"
#include "realtime.h"
#include "serialise.h"
#include "socket_utils.h"
#include "utils.h"

#ifdef __WIN32__
# include "msvc_posix_wrapper.h"
#endif

using namespace std;

#define CHUNKSIZE 4096

#ifdef __WIN32__
inline void
update_overlapped_offset(WSAOVERLAPPED & overlapped, DWORD n)
{
    STATIC_ASSERT_UNSIGNED_TYPE(DWORD); // signed overflow is undefined.
    overlapped.Offset += n;
    if (overlapped.Offset < n) ++overlapped.OffsetHigh;
}
#endif

RemoteConnection::RemoteConnection(int fdin_, int fdout_,
                                   const string & context_)
    : fdin(fdin_), fdout(fdout_), context(context_)
{
#ifdef __WIN32__
    memset(&overlapped, 0, sizeof(overlapped));
    overlapped.hEvent = CreateEvent(NULL, FALSE, FALSE, NULL);
    if (!overlapped.hEvent)
        throw Xapian::NetworkError("Failed to setup OVERLAPPED",
                                   context, -(int)GetLastError());

#endif
}

RemoteConnection::~RemoteConnection()
{
#ifdef __WIN32__
    if (overlapped.hEvent)
        CloseHandle(overlapped.hEvent);
#endif
}

void
RemoteConnection::read_at_least(size_t min_len, double end_time)
{
    LOGCALL_VOID(REMOTE, "RemoteConnection::read_at_least", min_len | end_time);

    if (buffer.length() >= min_len) return;

#ifdef __WIN32__
    HANDLE hin = fd_to_handle(fdin);
    do {
        char buf[CHUNKSIZE];
        DWORD received;
        BOOL ok = ReadFile(hin, buf, sizeof(buf), &received, &overlapped);
        if (!ok) {
            int errcode = GetLastError();
            if (errcode != ERROR_IO_PENDING)
                throw Xapian::NetworkError("read failed", context, -errcode);
            // Is asynch - just wait for the data to be received or a timeout.
            DWORD waitrc;
            waitrc = WaitForSingleObject(overlapped.hEvent, calc_read_wait_msecs(end_time));
            if (waitrc != WAIT_OBJECT_0) {
                LOGLINE(REMOTE, "read: timeout has expired");
                throw Xapian::NetworkTimeoutError("Timeout expired while trying to read", context);
            }
            // Get the final result of the read.
            if (!GetOverlappedResult(hin, &overlapped, &received, FALSE))
                throw Xapian::NetworkError("Failed to get overlapped result",
                                           context, -(int)GetLastError());
        }

        if (received == 0)
            throw Xapian::NetworkError("Received EOF", context);

        buffer.append(buf, received);

        // We must update the offset in the OVERLAPPED structure manually.
        update_overlapped_offset(overlapped, received);
    } while (buffer.length() < min_len);
#else
    // If there's no end_time, just use blocking I/O.
    if (fcntl(fdin, F_SETFL, (end_time != 0.0) ? O_NONBLOCK : 0) < 0) {
        throw Xapian::NetworkError("Failed to set fdin non-blocking-ness",
                                   context, errno);
    }

    while (true) {
        char buf[CHUNKSIZE];
        ssize_t received = read(fdin, buf, sizeof(buf));

        if (received > 0) {
            buffer.append(buf, received);
            if (buffer.length() >= min_len) return;
            continue;
        }

        if (received == 0)
            throw Xapian::NetworkError("Received EOF", context);

        LOGLINE(REMOTE, "read gave errno = " << strerror(errno));
        if (errno == EINTR) continue;

        if (errno != EAGAIN)
            throw Xapian::NetworkError("read failed", context, errno);

        Assert(end_time != 0.0);
        while (true) {
            // Calculate how far in the future end_time is.
            double time_diff = end_time - RealTime::now();
            // Check if the timeout has expired.
            if (time_diff < 0) {
                LOGLINE(REMOTE, "read: timeout has expired");
                throw Xapian::NetworkTimeoutError("Timeout expired while trying to read", context);
            }

            // Use select to wait until there is data or the timeout is reached.
            fd_set fdset;
            FD_ZERO(&fdset);
            FD_SET(fdin, &fdset);

            struct timeval tv;
            tv.tv_sec = long(time_diff);
            tv.tv_usec = long(fmod(time_diff, 1.0) * 1000000);

            int select_result = select(fdin + 1, &fdset, 0, &fdset, &tv);
            if (select_result > 0) break;

            if (select_result == 0)
                throw Xapian::NetworkTimeoutError("Timeout expired while trying to read", context);

            // EINTR means select was interrupted by a signal.
            if (errno != EINTR)
                throw Xapian::NetworkError("select failed during read", context, errno);
        }
    }
#endif
}

bool
RemoteConnection::ready_to_read() const
{
    LOGCALL(REMOTE, bool, "RemoteConnection::ready_to_read", NO_ARGS);
    if (fdin == -1) {
        throw Xapian::DatabaseError("Database has been closed");
    }

    if (!buffer.empty()) RETURN(true);

    // Use select to see if there's data available to be read.
    fd_set fdset;
    FD_ZERO(&fdset);
    FD_SET(fdin, &fdset);

    // Set a 0.1 second timeout to avoid a busy loop.
    // FIXME: this would be much better done by exposing the fd so that the
    // matcher can call select on all the fds involved...
    struct timeval tv;
    tv.tv_sec = 0;
    tv.tv_usec = 100000;
    RETURN(select(fdin + 1, &fdset, 0, &fdset, &tv) > 0);
}

void
RemoteConnection::send_message(char type, const string &message,
                               double end_time)
{
    LOGCALL_VOID(REMOTE, "RemoteConnection::send_message", type | message | end_time);
    if (fdout == -1) {
        throw Xapian::DatabaseError("Database has been closed");
    }

    string header;
    header += type;
    header += encode_length(message.size());

#ifdef __WIN32__
    HANDLE hout = fd_to_handle(fdout);
    const string * str = &header;

    size_t count = 0;
    while (true) {
        DWORD n;
        BOOL ok = WriteFile(hout, str->data() + count, str->size() - count, &n, &overlapped);
        if (!ok) {
            int errcode = GetLastError();
            if (errcode != ERROR_IO_PENDING)
                throw Xapian::NetworkError("write failed", context, -errcode);
            // Just wait for the data to be received, or a timeout.
            DWORD waitrc;
            waitrc = WaitForSingleObject(overlapped.hEvent, calc_read_wait_msecs(end_time));
            if (waitrc != WAIT_OBJECT_0) {
                LOGLINE(REMOTE, "write: timeout has expired");
                throw Xapian::NetworkTimeoutError("Timeout expired while trying to write", context);
            }
            // Get the final result.
            if (!GetOverlappedResult(hout, &overlapped, &n, FALSE))
                throw Xapian::NetworkError("Failed to get overlapped result",
                                           context, -(int)GetLastError());
        }

        count += n;

        // We must update the offset in the OVERLAPPED structure manually.
        update_overlapped_offset(overlapped, n);

        if (count == str->size()) {
            if (str == &message || message.empty()) return;
            str = &message;
            count = 0;
        }
    }
#else
    // If there's no end_time, just use blocking I/O.
    if (fcntl(fdout, F_SETFL, (end_time != 0.0) ? O_NONBLOCK : 0) < 0) {
        throw Xapian::NetworkError("Failed to set fdout non-blocking-ness",
                                   context, errno);
    }

    const string * str = &header;

    fd_set fdset;
    size_t count = 0;
    while (true) {
        // We've set write to non-blocking, so just try writing as there
        // will usually be space.
        ssize_t n = write(fdout, str->data() + count, str->size() - count);

        if (n >= 0) {
            count += n;
            if (count == str->size()) {
                if (str == &message || message.empty()) return;
                str = &message;
                count = 0;
            }
            continue;
        }

        LOGLINE(REMOTE, "write gave errno = " << strerror(errno));
        if (errno == EINTR) continue;

        if (errno != EAGAIN)
            throw Xapian::NetworkError("write failed", context, errno);

        // Use select to wait until there is space or the timeout is reached.
        FD_ZERO(&fdset);
        FD_SET(fdout, &fdset);

        double time_diff = end_time - RealTime::now();
        if (time_diff < 0) {
            LOGLINE(REMOTE, "write: timeout has expired");
            throw Xapian::NetworkTimeoutError("Timeout expired while trying to write", context);
        }

        struct timeval tv;
        tv.tv_sec = long(time_diff);
        tv.tv_usec = long(fmod(time_diff, 1.0) * 1000000);

        int select_result = select(fdout + 1, 0, &fdset, &fdset, &tv);

        if (select_result < 0) {
            if (errno == EINTR) {
                // EINTR means select was interrupted by a signal.
                // We could just retry the select, but it's easier to just
                // retry the write.
                continue;
            }
            throw Xapian::NetworkError("select failed during write", context, errno);
        }

        if (select_result == 0)
            throw Xapian::NetworkTimeoutError("Timeout expired while trying to write", context);
    }
#endif
}

void
RemoteConnection::send_file(char type, int fd, double end_time)
{
    LOGCALL_VOID(REMOTE, "RemoteConnection::send_file", type | fd | end_time);
    if (fdout == -1) {
        throw Xapian::DatabaseError("Database has been closed");
    }

    off_t size;
    {
        struct stat sb;
        if (fstat(fd, &sb) == -1)
            throw Xapian::NetworkError("Couldn't stat file to send", errno);
        size = sb.st_size;
    }
    // FIXME: Use sendfile() or similar if available?

    char buf[CHUNKSIZE];
    buf[0] = type;
    size_t c = 1;
    {
        string enc_size = encode_length(size);
        c += enc_size.size();
        // An encoded length should be just a few bytes.
        AssertRel(c, <=, sizeof(buf));
        memcpy(buf + 1, enc_size.data(), enc_size.size());
    }

#ifdef __WIN32__
    HANDLE hout = fd_to_handle(fdout);
    size_t count = 0;
    while (true) {
        DWORD n;
        BOOL ok = WriteFile(hout, buf + count, c - count, &n, &overlapped);
        if (!ok) {
            int errcode = GetLastError();
            if (errcode != ERROR_IO_PENDING)
                throw Xapian::NetworkError("write failed", context, -errcode);
            // Just wait for the data to be received, or a timeout.
            DWORD waitrc;
            waitrc = WaitForSingleObject(overlapped.hEvent, calc_read_wait_msecs(end_time));
            if (waitrc != WAIT_OBJECT_0) {
                LOGLINE(REMOTE, "write: timeout has expired");
                throw Xapian::NetworkTimeoutError("Timeout expired while trying to write", context);
            }
            // Get the final result.
            if (!GetOverlappedResult(hout, &overlapped, &n, FALSE))
                throw Xapian::NetworkError("Failed to get overlapped result",
                                           context, -(int)GetLastError());
        }

        count += n;

        // We must update the offset in the OVERLAPPED structure manually.
        update_overlapped_offset(overlapped, n);

        if (count == c) {
            if (size == 0) return;

            ssize_t res;
            do {
                res = read(fd, buf, sizeof(buf));
            } while (res < 0 && errno == EINTR);
            if (res < 0) throw Xapian::NetworkError("read failed", errno);
            c = size_t(res);

            size -= c;
            count = 0;
        }
    }
#else
    // If there's no end_time, just use blocking I/O.
    if (fcntl(fdout, F_SETFL, (end_time != 0.0) ? O_NONBLOCK : 0) < 0) {
        throw Xapian::NetworkError("Failed to set fdout non-blocking-ness",
                                   context, errno);
    }

    fd_set fdset;
    size_t count = 0;
    while (true) {
        // We've set write to non-blocking, so just try writing as there
        // will usually be space.
        ssize_t n = write(fdout, buf + count, c - count);

        if (n >= 0) {
            count += n;
            if (count == c) {
                if (size == 0) return;

                ssize_t res;
                do {
                    res = read(fd, buf, sizeof(buf));
                } while (res < 0 && errno == EINTR);
                if (res < 0) throw Xapian::NetworkError("read failed", errno);
                c = size_t(res);

                size -= c;
                count = 0;
            }
            continue;
        }

        LOGLINE(REMOTE, "write gave errno = " << strerror(errno));
        if (errno == EINTR) continue;

        if (errno != EAGAIN)
            throw Xapian::NetworkError("write failed", context, errno);

        // Use select to wait until there is space or the timeout is reached.
        FD_ZERO(&fdset);
        FD_SET(fdout, &fdset);

        double time_diff = end_time - RealTime::now();
        if (time_diff < 0) {
            LOGLINE(REMOTE, "write: timeout has expired");
            throw Xapian::NetworkTimeoutError("Timeout expired while trying to write", context);
        }

        struct timeval tv;
        tv.tv_sec = long(time_diff);
        tv.tv_usec = long(fmod(time_diff, 1.0) * 1000000);

        int select_result = select(fdout + 1, 0, &fdset, &fdset, &tv);

        if (select_result < 0) {
            if (errno == EINTR) {
                // EINTR means select was interrupted by a signal.
                // We could just retry the select, but it's easier to just
                // retry the write.
                continue;
            }
            throw Xapian::NetworkError("select failed during write", context, errno);
        }

        if (select_result == 0)
            throw Xapian::NetworkTimeoutError("Timeout expired while trying to write", context);
    }
#endif
}

char
RemoteConnection::sniff_next_message_type(double end_time)
{
    LOGCALL(REMOTE, char, "RemoteConnection::sniff_next_message_type", end_time);
    if (fdin == -1) {
        throw Xapian::DatabaseError("Database has been closed");
    }

    read_at_least(1, end_time);
    char type = buffer[0];
    RETURN(type);
}

char
RemoteConnection::get_message(string &result, double end_time)
{
    LOGCALL(REMOTE, char, "RemoteConnection::get_message", result | end_time);
    if (fdin == -1) {
        throw Xapian::DatabaseError("Database has been closed");
    }

    read_at_least(2, end_time);
    size_t len = static_cast<unsigned char>(buffer[1]);
    read_at_least(len + 2, end_time);
    if (len != 0xff) {
        result.assign(buffer.data() + 2, len);
        char type = buffer[0];
        buffer.erase(0, len + 2);
        RETURN(type);
    }
    len = 0;
    string::const_iterator i = buffer.begin() + 2;
    unsigned char ch;
    int shift = 0;
    do {
        if (i == buffer.end() || shift > 28) {
            // Something is very wrong...
            throw Xapian::NetworkError("Insane message length specified!");
        }
        ch = *i++;
        len |= size_t(ch & 0x7f) << shift;
        shift += 7;
    } while ((ch & 0x80) == 0);
    len += 255;
    size_t header_len = (i - buffer.begin());
    read_at_least(header_len + len, end_time);
    result.assign(buffer.data() + header_len, len);
    char type = buffer[0];
    buffer.erase(0, header_len + len);
    RETURN(type);
}

char
RemoteConnection::get_message_chunked(double end_time)
{
    LOGCALL(REMOTE, char, "RemoteConnection::get_message_chunked", end_time);
    if (fdin == -1) {
        throw Xapian::DatabaseError("Database has been closed");
    }

    read_at_least(2, end_time);
    off_t len = static_cast<unsigned char>(buffer[1]);
    if (len != 0xff) {
        chunked_data_left = len;
        char type = buffer[0];
        buffer.erase(0, 2);
        RETURN(type);
    }
    read_at_least(len + 2, end_time);
    len = 0;
    string::const_iterator i = buffer.begin() + 2;
    unsigned char ch;
    int shift = 0;
    do {
        // Allow a full 64 bits for message lengths - anything longer than that
        // is almost certainly a corrupt value.
        if (i == buffer.end() || shift > 63) {
            // Something is very wrong...
            throw Xapian::NetworkError("Insane message length specified!");
        }
        ch = *i++;
        len |= off_t(ch & 0x7f) << shift;
        shift += 7;
    } while ((ch & 0x80) == 0);
    len += 255;
    chunked_data_left = len;
    char type = buffer[0];
    size_t header_len = (i - buffer.begin());
    buffer.erase(0, header_len);
    RETURN(type);
}

bool
RemoteConnection::get_message_chunk(string &result, size_t at_least,
                                    double end_time)
{
    LOGCALL(REMOTE, bool, "RemoteConnection::get_message_chunk", result | at_least | end_time);
    if (fdin == -1) {
        throw Xapian::DatabaseError("Database has been closed");
    }

    if (at_least <= result.size()) RETURN(true);
    at_least -= result.size();

    bool read_enough = (off_t(at_least) <= chunked_data_left);
    if (!read_enough) at_least = size_t(chunked_data_left);

    read_at_least(at_least, end_time);

    size_t retlen(min(off_t(buffer.size()), chunked_data_left));
    result.append(buffer, 0, retlen);
    buffer.erase(0, retlen);
    chunked_data_left -= retlen;

    RETURN(read_enough);
}

static void
write_all(int fd, const char * p, size_t n)
{
    while (n) {
        ssize_t c = write(fd, p, n);
        if (c < 0) {
            if (errno == EINTR) continue;
            throw Xapian::NetworkError("Error writing to file", errno);
        }
        p += c;
        n -= c;
    }
}

char
RemoteConnection::receive_file(const string &file, double end_time)
{
    LOGCALL(REMOTE, char, "RemoteConnection::receive_file", file | end_time);
    if (fdin == -1) {
        throw Xapian::DatabaseError("Database has been closed");
    }

#ifdef __WIN32__
    // Do we want to be able to delete the file during writing?
    int fd = msvc_posix_open(file.c_str(), O_WRONLY|O_CREAT|O_TRUNC);
#else
    int fd = open(file.c_str(), O_WRONLY|O_CREAT|O_TRUNC, 0666);
#endif
    if (fd == -1) throw Xapian::NetworkError("Couldn't open file for writing: " + file, errno);
    fdcloser closefd(fd);

    read_at_least(2, end_time);
    size_t len = static_cast<unsigned char>(buffer[1]);
    read_at_least(len + 2, end_time);
    if (len != 0xff) {
        write_all(fd, buffer.data() + 2, len);
        char type = buffer[0];
        buffer.erase(0, len + 2);
        RETURN(type);
    }
    len = 0;
    string::const_iterator i = buffer.begin() + 2;
    unsigned char ch;
    int shift = 0;
    do {
        if (i == buffer.end() || shift > 28) {
            // Something is very wrong...
            throw Xapian::NetworkError("Insane message length specified!");
        }
        ch = *i++;
        len |= size_t(ch & 0x7f) << shift;
        shift += 7;
    } while ((ch & 0x80) == 0);
    len += 255;
    size_t header_len = (i - buffer.begin());
    size_t remainlen(min(buffer.size() - header_len, len));
    write_all(fd, buffer.data() + header_len, remainlen);
    len -= remainlen;
    char type = buffer[0];
    buffer.erase(0, header_len + remainlen);
    while (len > 0) {
        read_at_least(min(len, size_t(CHUNKSIZE)), end_time);
        remainlen = min(buffer.size(), len);
        write_all(fd, buffer.data(), remainlen);
        len -= remainlen;
        buffer.erase(0, remainlen);
    }
    RETURN(type);
}

void
RemoteConnection::do_close(bool wait)
{
    LOGCALL_VOID(REMOTE, "RemoteConnection::do_close", wait);

    if (fdin >= 0) {
        if (wait) {
            // We can be called from a destructor, so we can't throw an
            // exception.
            try {
                send_message(MSG_SHUTDOWN, string(), 0.0);
            } catch (...) {
            }
#ifdef __WIN32__
            HANDLE hin = fd_to_handle(fdin);
            char dummy;
            DWORD received;
            BOOL ok = ReadFile(hin, &dummy, 1, &received, &overlapped);
            if (!ok && GetLastError() == ERROR_IO_PENDING) {
                // Wait for asynchronous read to complete.
                (void)WaitForSingleObject(overlapped.hEvent, INFINITE);
            }
#else
            // Wait for the connection to be closed - when this happens
            // select() will report that a read won't block.
            fd_set fdset;
            FD_ZERO(&fdset);
            FD_SET(fdin, &fdset);
            int res;
            do {
                res = select(fdin + 1, &fdset, 0, &fdset, NULL);
            } while (res < 0 && errno == EINTR);
#endif
        }
        close_fd_or_socket(fdin);

        // If the same fd is used in both directions, don't close it twice.
        if (fdin == fdout) fdout = -1;

        fdin = -1;
    }

    if (fdout >= 0) {
        close_fd_or_socket(fdout);
        fdout = -1;
    }
}

#ifdef __WIN32__
DWORD
RemoteConnection::calc_read_wait_msecs(double end_time)
{
    if (end_time == 0.0)
        return INFINITE;

    // Calculate how far in the future end_time is.
    double time_diff = end_time - RealTime::now();

    // DWORD is unsigned, so we mustn't try and return a negative value.
    if (time_diff < 0.0) {
        throw Xapian::NetworkTimeoutError("Timeout expired before starting read", context);
    }
    return static_cast<DWORD>(time_diff * 1000.0);
}
#endif

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