server/protocol-handshake.c

   1 /* nbdkit
   2  * Copyright Red Hat
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions are
   6  * met:
   7  *
   8  * * Redistributions of source code must retain the above copyright
   9  * notice, this list of conditions and the following disclaimer.
  10  *
  11  * * Redistributions in binary form must reproduce the above copyright
  12  * notice, this list of conditions and the following disclaimer in the
  13  * documentation and/or other materials provided with the distribution.
  14  *
  15  * * Neither the name of Red Hat nor the names of its contributors may be
  16  * used to endorse or promote products derived from this software without
  17  * specific prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND
  20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
  21  * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
  22  * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR
  23  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  24  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  25  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
  26  * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  27  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  28  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  29  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30  * SUCH DAMAGE.
  31  */
  32
  33 #include <config.h>
  34
  35 #include <stdio.h>
  36 #include <stdlib.h>
  37 #include <stdint.h>
  38 #include <inttypes.h>
  39 #include <string.h>
  40 #include <unistd.h>
  41
  42 #include "internal.h"
  43 #include "byte-swapping.h"
  44 #include "nbd-protocol.h"
  45
  46 int
  47 protocol_handshake ()
  48 {
  49   int r;
  50
  51   lock_request ();
  52   if (!newstyle)
  53     r = protocol_handshake_oldstyle ();
  54   else
  55     r = protocol_handshake_newstyle ();
  56   unlock_request ();
  57
  58   return r;
  59 }
  60
  61 /* Common code used by oldstyle and newstyle protocols to:
  62  *
  63  * - call the backend .open method
  64  *
  65  * - get the export size
  66  *
  67  * - compute the eflags (same between oldstyle and newstyle
  68  *   protocols)
  69  *
  70  * The protocols must defer this as late as possible so that
  71  * unauthorized clients can't cause unnecessary work in .open by
  72  * simply opening a TCP connection.
  73  */
  74 int
  75 protocol_common_open (uint64_t *exportsize, uint16_t *flags,
  76                       const char *exportname)
  77 {
  78   GET_CONN;
  79   int64_t size;
  80   uint16_t eflags = NBD_FLAG_HAS_FLAGS;
  81   int fl;
  82
  83   conn->top_context = backend_open (top, read_only, exportname, false);
  84   if (conn->top_context == NULL)
  85     return -1;
  86
  87   /* Prepare (for filters), called just after open. */
  88   if (backend_prepare (conn->top_context) == -1)
  89     return -1;
  90
  91   size = backend_get_size (conn->top_context);
  92   if (size == -1)
  93     return -1;
  94   if (size < 0) {
  95     nbdkit_error (".get_size function returned invalid value "
  96                   "(%" PRIi64 ")", size);
  97     return -1;
  98   }
  99
 100   /* Check all flags even if they won't be advertised, to prime the
 101    * cache and make later request validation easier.
 102    */
 103   fl = backend_can_write (conn->top_context);
 104   if (fl == -1)
 105     return -1;
 106   if (!fl)
 107     eflags |= NBD_FLAG_READ_ONLY;
 108
 109   fl = backend_can_zero (conn->top_context);
 110   if (fl == -1)
 111     return -1;
 112   if (fl)
 113     eflags |= NBD_FLAG_SEND_WRITE_ZEROES;
 114
 115   fl = backend_can_fast_zero (conn->top_context);
 116   if (fl == -1)
 117     return -1;
 118   if (fl)
 119     eflags |= NBD_FLAG_SEND_FAST_ZERO;
 120
 121   fl = backend_can_trim (conn->top_context);
 122   if (fl == -1)
 123     return -1;
 124   if (fl)
 125     eflags |= NBD_FLAG_SEND_TRIM;
 126
 127   fl = backend_can_fua (conn->top_context);
 128   if (fl == -1)
 129     return -1;
 130   if (fl)
 131     eflags |= NBD_FLAG_SEND_FUA;
 132
 133   fl = backend_can_flush (conn->top_context);
 134   if (fl == -1)
 135     return -1;
 136   if (fl)
 137     eflags |= NBD_FLAG_SEND_FLUSH;
 138
 139   fl = backend_is_rotational (conn->top_context);
 140   if (fl == -1)
 141     return -1;
 142   if (fl)
 143     eflags |= NBD_FLAG_ROTATIONAL;
 144
 145   /* multi-conn is useless if parallel connections are not allowed. */
 146   fl = backend_can_multi_conn (conn->top_context);
 147   if (fl == -1)
 148     return -1;
 149   if (fl && (thread_model > NBDKIT_THREAD_MODEL_SERIALIZE_CONNECTIONS))
 150     eflags |= NBD_FLAG_CAN_MULTI_CONN;
 151
 152   fl = backend_can_cache (conn->top_context);
 153   if (fl == -1)
 154     return -1;
 155   if (fl)
 156     eflags |= NBD_FLAG_SEND_CACHE;
 157
 158   /* The result of this is not directly advertised as part of the
 159    * handshake, but priming the cache here makes BLOCK_STATUS handling
 160    * not have to worry about errors, and makes test-layers easier to
 161    * write.
 162    */
 163   fl = backend_can_extents (conn->top_context);
 164   if (fl == -1)
 165     return -1;
 166
 167   if (conn->structured_replies)
 168     eflags |= NBD_FLAG_SEND_DF;
 169
 170   *exportsize = size;
 171   *flags = eflags;
 172   return 0;
 173 }