server/protocol-handshake.c

   1 /* nbdkit
   2  * Copyright (C) 2013-2019 Red Hat Inc.
   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 (struct connection *conn)
  48 {
  49   int r;
  50
  51   lock_request (conn);
  52   if (!newstyle)
  53     r = protocol_handshake_oldstyle (conn);
  54   else
  55     r = protocol_handshake_newstyle (conn);
  56   unlock_request (conn);
  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 (struct connection *conn,
  76                       uint64_t *exportsize, uint16_t *flags)
  77 {
  78   int64_t size;
  79   uint16_t eflags = NBD_FLAG_HAS_FLAGS;
  80   int fl;
  81
  82   if (backend_open (backend, conn, read_only) == -1)
  83     return -1;
  84
  85   /* Prepare (for filters), called just after open. */
  86   if (backend_prepare (backend, conn) == -1)
  87     return -1;
  88
  89   size = backend_get_size (backend, conn);
  90   if (size == -1)
  91     return -1;
  92   if (size < 0) {
  93     nbdkit_error (".get_size function returned invalid value "
  94                   "(%" PRIi64 ")", size);
  95     return -1;
  96   }
  97
  98   /* Check all flags even if they won't be advertised, to prime the
  99    * cache and make later request validation easier.
 100    */
 101   fl = backend_can_write (backend, conn);
 102   if (fl == -1)
 103     return -1;
 104   if (!fl)
 105     eflags |= NBD_FLAG_READ_ONLY;
 106
 107   fl = backend_can_zero (backend, conn);
 108   if (fl == -1)
 109     return -1;
 110   if (fl)
 111     eflags |= NBD_FLAG_SEND_WRITE_ZEROES;
 112
 113   fl = backend_can_fast_zero (backend, conn);
 114   if (fl == -1)
 115     return -1;
 116   if (fl)
 117     eflags |= NBD_FLAG_SEND_FAST_ZERO;
 118
 119   fl = backend_can_trim (backend, conn);
 120   if (fl == -1)
 121     return -1;
 122   if (fl)
 123     eflags |= NBD_FLAG_SEND_TRIM;
 124
 125   fl = backend_can_fua (backend, conn);
 126   if (fl == -1)
 127     return -1;
 128   if (fl)
 129     eflags |= NBD_FLAG_SEND_FUA;
 130
 131   fl = backend_can_flush (backend, conn);
 132   if (fl == -1)
 133     return -1;
 134   if (fl)
 135     eflags |= NBD_FLAG_SEND_FLUSH;
 136
 137   fl = backend_is_rotational (backend, conn);
 138   if (fl == -1)
 139     return -1;
 140   if (fl)
 141     eflags |= NBD_FLAG_ROTATIONAL;
 142
 143   /* multi-conn is useless if parallel connections are not allowed. */
 144   fl = backend_can_multi_conn (backend, conn);
 145   if (fl == -1)
 146     return -1;
 147   if (fl && (backend->thread_model (backend) >
 148              NBDKIT_THREAD_MODEL_SERIALIZE_CONNECTIONS))
 149     eflags |= NBD_FLAG_CAN_MULTI_CONN;
 150
 151   fl = backend_can_cache (backend, conn);
 152   if (fl == -1)
 153     return -1;
 154   if (fl)
 155     eflags |= NBD_FLAG_SEND_CACHE;
 156
 157   /* The result of this is not directly advertised as part of the
 158    * handshake, but priming the cache here makes BLOCK_STATUS handling
 159    * not have to worry about errors, and makes test-layers easier to
 160    * write.
 161    */
 162   fl = backend_can_extents (backend, conn);
 163   if (fl == -1)
 164     return -1;
 165
 166   if (conn->structured_replies)
 167     eflags |= NBD_FLAG_SEND_DF;
 168
 169   *exportsize = size;
 170   *flags = eflags;
 171   return 0;
 172 }