source3/lib/recvfile.c

   1 /*
   2  Unix SMB/Netbios implementation.
   3  Version 3.2.x
   4  recvfile implementations.
   5  Copyright (C) Jeremy Allison 2007.
   6
   7  This program is free software; you can redistribute it and/or modify
   8  it under the terms of the GNU General Public License as published by
   9  the Free Software Foundation; either version 3 of the License, or
  10  (at your option) any later version.
  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, see <http://www.gnu.org/licenses/>.
  18 */
  19
  20 /*
  21  * This file handles the OS dependent recvfile implementations.
  22  * The API is such that it returns -1 on error, else returns the
  23  * number of bytes written.
  24  */
  25
  26 #include "includes.h"
  27 #include "system/filesys.h"
  28
  29 /* Do this on our own in TRANSFER_BUF_SIZE chunks.
  30  * It's safe to make direct syscalls to lseek/write here
  31  * as we're below the Samba vfs layer.
  32  *
  33  * Returns -1 on short reads from fromfd (read error)
  34  * and sets errno.
  35  *
  36  * Returns number of bytes written to 'tofd'
  37  * return != count then sets errno.
  38  * Returns count if complete success.
  39  */
  40
  41 #ifndef TRANSFER_BUF_SIZE
  42 #define TRANSFER_BUF_SIZE (128*1024)
  43 #endif
  44
  45 static ssize_t default_sys_recvfile(int fromfd,
  46                         int tofd,
  47                         off_t offset,
  48                         size_t count)
  49 {
  50         int saved_errno = 0;
  51         size_t total = 0;
  52         size_t bufsize = MIN(TRANSFER_BUF_SIZE,count);
  53         size_t total_written = 0;
  54         char buffer[bufsize];
  55
  56         DEBUG(10,("default_sys_recvfile: from = %d, to = %d, "
  57                 "offset=%.0f, count = %lu\n",
  58                 fromfd, tofd, (double)offset,
  59                 (unsigned long)count));
  60
  61         if (count == 0) {
  62                 return 0;
  63         }
  64
  65         if (tofd != -1 && offset != (off_t)-1) {
  66                 if (lseek(tofd, offset, SEEK_SET) == -1) {
  67                         if (errno != ESPIPE) {
  68                                 return -1;
  69                         }
  70                 }
  71         }
  72
  73         while (total < count) {
  74                 size_t num_written = 0;
  75                 ssize_t read_ret;
  76                 size_t toread = MIN(bufsize,count - total);
  77
  78                 /*
  79                  * Read from socket - ignore EINTR.
  80                  * Can't use sys_read() as that also
  81                  * ignores EAGAIN and EWOULDBLOCK.
  82                  */
  83                 do {
  84                         read_ret = read(fromfd, buffer, toread);
  85                 } while (read_ret == -1 && errno == EINTR);
  86
  87 #if defined(EWOULDBLOCK)
  88                 if (read_ret == -1 && (errno == EAGAIN || errno == EWOULDBLOCK)) {
  89 #else
  90                 if (read_ret == -1 && (errno == EAGAIN)) {
  91 #endif
  92                         /*
  93                          * fromfd socket is in non-blocking mode.
  94                          * If we already read some and wrote
  95                          * it successfully, return that.
  96                          * Only return -1 if this is the first read
  97                          * attempt. Caller will handle both cases.
  98                          */
  99                         if (total_written != 0) {
 100                                 return total_written;
 101                         }
 102                         return -1;
 103                 }
 104
 105                 if (read_ret <= 0) {
 106                         /* EOF or socket error. */
 107                         return -1;
 108                 }
 109
 110                 num_written = 0;
 111
 112                 /* Don't write any more after a write error. */
 113                 while (tofd != -1 && (num_written < read_ret)) {
 114                         ssize_t write_ret;
 115
 116                         /* Write to file - ignore EINTR. */
 117                         write_ret = sys_write(tofd,
 118                                         buffer + num_written,
 119                                         read_ret - num_written);
 120
 121                         if (write_ret <= 0) {
 122                                 /* write error - stop writing. */
 123                                 tofd = -1;
 124                                 if (total_written == 0) {
 125                                         /* Ensure we return
 126                                            -1 if the first
 127                                            write failed. */
 128                                         total_written = -1;
 129                                 }
 130                                 saved_errno = errno;
 131                                 break;
 132                         }
 133
 134                         num_written += (size_t)write_ret;
 135                         total_written += (size_t)write_ret;
 136                 }
 137
 138                 total += read_ret;
 139         }
 140
 141         if (saved_errno) {
 142                 /* Return the correct write error. */
 143                 errno = saved_errno;
 144         }
 145         return (ssize_t)total_written;
 146 }
 147
 148 #if defined(HAVE_LINUX_SPLICE)
 149
 150 /*
 151  * Try and use the Linux system call to do this.
 152  * Remember we only return -1 if the socket read
 153  * failed. Else we return the number of bytes
 154  * actually written. We always read count bytes
 155  * from the network in the case of return != -1.
 156  */
 157
 158
 159 ssize_t sys_recvfile(int fromfd,
 160                         int tofd,
 161                         off_t offset,
 162                         size_t count)
 163 {
 164         static int pipefd[2] = { -1, -1 };
 165         static bool try_splice_call = false;
 166         size_t total_written = 0;
 167         loff_t splice_offset = offset;
 168
 169         DEBUG(10,("sys_recvfile: from = %d, to = %d, "
 170                 "offset=%.0f, count = %lu\n",
 171                 fromfd, tofd, (double)offset,
 172                 (unsigned long)count));
 173
 174         if (count == 0) {
 175                 return 0;
 176         }
 177
 178         /*
 179          * Older Linux kernels have splice for sendfile,
 180          * but it fails for recvfile. Ensure we only try
 181          * this once and always fall back to the userspace
 182          * implementation if recvfile splice fails. JRA.
 183          */
 184
 185         if (!try_splice_call) {
 186                 return default_sys_recvfile(fromfd,
 187                                 tofd,
 188                                 offset,
 189                                 count);
 190         }
 191
 192         if ((pipefd[0] == -1) && (pipe(pipefd) == -1)) {
 193                 try_splice_call = false;
 194                 return default_sys_recvfile(fromfd, tofd, offset, count);
 195         }
 196
 197         while (count > 0) {
 198                 int nread, to_write;
 199
 200                 nread = splice(fromfd, NULL, pipefd[1], NULL,
 201                                MIN(count, 16384), SPLICE_F_MOVE);
 202                 if (nread == -1) {
 203                         if (errno == EINTR) {
 204                                 continue;
 205                         }
 206                         if (total_written == 0 &&
 207                             (errno == EBADF || errno == EINVAL)) {
 208                                 try_splice_call = false;
 209                                 return default_sys_recvfile(fromfd, tofd,
 210                                                             offset, count);
 211                         }
 212 #if defined(EWOULDBLOCK)
 213                         if (errno == EAGAIN || errno == EWOULDBLOCK) {
 214 #else
 215                         if (errno == EAGAIN) {
 216 #endif
 217                                 /*
 218                                  * fromfd socket is in non-blocking mode.
 219                                  * If we already read some and wrote
 220                                  * it successfully, return that.
 221                                  * Only return -1 if this is the first read
 222                                  * attempt. Caller will handle both cases.
 223                                  */
 224                                 if (total_written != 0) {
 225                                         return total_written;
 226                                 }
 227                                 return -1;
 228                         }
 229                         break;
 230                 }
 231
 232                 to_write = nread;
 233                 while (to_write > 0) {
 234                         int thistime;
 235                         thistime = splice(pipefd[0], NULL, tofd,
 236                                           &splice_offset, to_write,
 237                                           SPLICE_F_MOVE);
 238                         if (thistime == -1) {
 239                                 goto done;
 240                         }
 241                         to_write -= thistime;
 242                 }
 243
 244                 total_written += nread;
 245                 count -= nread;
 246         }
 247
 248  done:
 249         if (count) {
 250                 int saved_errno = errno;
 251                 if (drain_socket(fromfd, count) != count) {
 252                         /* socket is dead. */
 253                         return -1;
 254                 }
 255                 errno = saved_errno;
 256         }
 257
 258         return total_written;
 259 }
 260 #else
 261
 262 /*****************************************************************
 263  No recvfile system call - use the default 128 chunk implementation.
 264 *****************************************************************/
 265
 266 ssize_t sys_recvfile(int fromfd,
 267                         int tofd,
 268                         off_t offset,
 269                         size_t count)
 270 {
 271         return default_sys_recvfile(fromfd, tofd, offset, count);
 272 }
 273 #endif
 274
 275 /*****************************************************************
 276  Throw away "count" bytes from the client socket.
 277  Returns count or -1 on error.
 278  Must only operate on a blocking socket.
 279 *****************************************************************/
 280
 281 ssize_t drain_socket(int sockfd, size_t count)
 282 {
 283         size_t total = 0;
 284         size_t bufsize = MIN(TRANSFER_BUF_SIZE,count);
 285         char buffer[bufsize];
 286         int old_flags = 0;
 287
 288         if (count == 0) {
 289                 return 0;
 290         }
 291
 292         old_flags = fcntl(sockfd, F_GETFL, 0);
 293         if (set_blocking(sockfd, true) == -1) {
 294                 return -1;
 295         }
 296
 297         while (total < count) {
 298                 ssize_t read_ret;
 299                 size_t toread = MIN(bufsize,count - total);
 300
 301                 /* Read from socket - ignore EINTR. */
 302                 read_ret = sys_read(sockfd, buffer, toread);
 303                 if (read_ret <= 0) {
 304                         /* EOF or socket error. */
 305                         count = (size_t)-1;
 306                         goto out;
 307                 }
 308                 total += read_ret;
 309         }
 310
 311   out:
 312
 313         if (fcntl(sockfd, F_SETFL, old_flags) == -1) {
 314                 return -1;
 315         }
 316         return count;
 317 }