source: branches/samba-3.3.x/source/lib/recvfile.c@ 206

/*
 Unix SMB/Netbios implementation.
 Version 3.2.x
 recvfile implementations.
 Copyright (C) Jeremy Allison 2007.

 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 3 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, see <http://www.gnu.org/licenses/>.
*/

/*
 * This file handles the OS dependent recvfile implementations.
 * The API is such that it returns -1 on error, else returns the
 * number of bytes written.
 */

#include "includes.h"

/* Do this on our own in TRANSFER_BUF_SIZE chunks.
 * It's safe to make direct syscalls to lseek/write here
 * as we're below the Samba vfs layer.
 *
 * If tofd is -1 we just drain the incoming socket of count
 * bytes without writing to the outgoing fd.
 * If a write fails we do the same (to cope with disk full)
 * errors.
 *
 * Returns -1 on short reads from fromfd (read error)
 * and sets errno.
 *
 * Returns number of bytes written to 'tofd'
 * or thrown away if 'tofd == -1'.
 * return != count then sets errno.
 * Returns count if complete success.
 */

#ifndef TRANSFER_BUF_SIZE
#define TRANSFER_BUF_SIZE (128*1024)
#endif

static ssize_t default_sys_recvfile(int fromfd,
                        int tofd,
                        SMB_OFF_T offset,
                        size_t count)
{
        int saved_errno = 0;
        size_t total = 0;
        size_t bufsize = MIN(TRANSFER_BUF_SIZE,count);
        size_t total_written = 0;
        char *buffer = NULL;

        DEBUG(10,("default_sys_recvfile: from = %d, to = %d, "
                "offset=%.0f, count = %lu\n",
                fromfd, tofd, (double)offset,
                (unsigned long)count));

        if (count == 0) {
                return 0;
        }

        if (tofd != -1 && offset != (SMB_OFF_T)-1) {
                if (sys_lseek(tofd, offset, SEEK_SET) == -1) {
                        if (errno != ESPIPE) {
                                return -1;
                        }
                }
        }

        buffer = SMB_MALLOC_ARRAY(char, bufsize);
        if (buffer == NULL) {
                return -1;
        }

        while (total < count) {
                size_t num_written = 0;
                ssize_t read_ret;
                size_t toread = MIN(bufsize,count - total);

                /* Read from socket - ignore EINTR. */
                read_ret = sys_read(fromfd, buffer, toread);
                if (read_ret <= 0) {
                        /* EOF or socket error. */
                        free(buffer);
                        return -1;
                }

                num_written = 0;

                while (num_written < read_ret) {
                        ssize_t write_ret;

                        if (tofd == -1) {
                                write_ret = read_ret;
                        } else {
                                /* Write to file - ignore EINTR. */
                                write_ret = sys_write(tofd,
                                                buffer + num_written,
                                                read_ret - num_written);

                                if (write_ret <= 0) {
                                        /* write error - stop writing. */
                                        tofd = -1;
                                        saved_errno = errno;
                                        continue;
                                }
                        }

                        num_written += (size_t)write_ret;
                        total_written += (size_t)write_ret;
                }

                total += read_ret;
        }

        free(buffer);
        if (saved_errno) {
                /* Return the correct write error. */
                errno = saved_errno;
        }
        return (ssize_t)total_written;
}

#if defined(HAVE_LINUX_SPLICE)

/*
 * Try and use the Linux system call to do this.
 * Remember we only return -1 if the socket read
 * failed. Else we return the number of bytes
 * actually written. We always read count bytes
 * from the network in the case of return != -1.
 */


ssize_t sys_recvfile(int fromfd,
                        int tofd,
                        SMB_OFF_T offset,
                        size_t count)
{
        static bool try_splice_call = true;
        size_t total_written = 0;

        DEBUG(10,("sys_recvfile: from = %d, to = %d, "
                "offset=%.0f, count = %lu\n",
                fromfd, tofd, (double)offset,
                (unsigned long)count));

        if (count == 0) {
                return 0;
        }

        /*
         * Older Linux kernels have splice for sendfile,
         * but it fails for recvfile. Ensure we only try
         * this once and always fall back to the userspace
         * implementation if recvfile splice fails. JRA.
         */

        if (!try_splice_call) {
                return default_sys_recvfile(fromfd,
                                tofd,
                                offset,
                                count);
        }

        while (total_written < count) {
                ssize_t ret = splice(fromfd,
                                        NULL,
                                        tofd,
                                        &offset,
                                        count,
                                        0);
                if (ret == -1) {
                        if (errno != EINTR) {
                                if (total_written == 0 &&
                                                (errno == EBADF || errno == EINVAL)) {
                                        try_splice_call = false;
                                        return default_sys_recvfile(fromfd,
                                                                tofd,
                                                                offset,
                                                                count);
                                }
                                break;
                        }
                        continue;
                }
                total_written += ret;
                count -= ret;
        }

        if (total_written < count) {
                int saved_errno = errno;
                if (drain_socket(fromfd, count-total_written) !=
                                count-total_written) {
                        /* socket is dead. */
                        return -1;
                }
                errno = saved_errno;
        }

        return total_written;
}
#else

/*****************************************************************
 No recvfile system call - use the default 128 chunk implementation.
*****************************************************************/

ssize_t sys_recvfile(int fromfd,
                        int tofd,
                        SMB_OFF_T offset,
                        size_t count)
{
        return default_sys_recvfile(fromfd, tofd, offset, count);
}
#endif

/*****************************************************************
 Throw away "count" bytes from the client socket.
*****************************************************************/

ssize_t drain_socket(int sockfd, size_t count)
{
        return default_sys_recvfile(sockfd, -1, (SMB_OFF_T)-1, count);
}