drivers/block/drbd/drbd_protocol.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef __DRBD_PROTOCOL_H
   3 #define __DRBD_PROTOCOL_H
   4
   5 enum drbd_packet {
   6         /* receiver (data socket) */
   7         P_DATA                = 0x00,
   8         P_DATA_REPLY          = 0x01, /* Response to P_DATA_REQUEST */
   9         P_RS_DATA_REPLY       = 0x02, /* Response to P_RS_DATA_REQUEST */
  10         P_BARRIER             = 0x03,
  11         P_BITMAP              = 0x04,
  12         P_BECOME_SYNC_TARGET  = 0x05,
  13         P_BECOME_SYNC_SOURCE  = 0x06,
  14         P_UNPLUG_REMOTE       = 0x07, /* Used at various times to hint the peer */
  15         P_DATA_REQUEST        = 0x08, /* Used to ask for a data block */
  16         P_RS_DATA_REQUEST     = 0x09, /* Used to ask for a data block for resync */
  17         P_SYNC_PARAM          = 0x0a,
  18         P_PROTOCOL            = 0x0b,
  19         P_UUIDS               = 0x0c,
  20         P_SIZES               = 0x0d,
  21         P_STATE               = 0x0e,
  22         P_SYNC_UUID           = 0x0f,
  23         P_AUTH_CHALLENGE      = 0x10,
  24         P_AUTH_RESPONSE       = 0x11,
  25         P_STATE_CHG_REQ       = 0x12,
  26
  27         /* (meta socket) */
  28         P_PING                = 0x13,
  29         P_PING_ACK            = 0x14,
  30         P_RECV_ACK            = 0x15, /* Used in protocol B */
  31         P_WRITE_ACK           = 0x16, /* Used in protocol C */
  32         P_RS_WRITE_ACK        = 0x17, /* Is a P_WRITE_ACK, additionally call set_in_sync(). */
  33         P_SUPERSEDED          = 0x18, /* Used in proto C, two-primaries conflict detection */
  34         P_NEG_ACK             = 0x19, /* Sent if local disk is unusable */
  35         P_NEG_DREPLY          = 0x1a, /* Local disk is broken... */
  36         P_NEG_RS_DREPLY       = 0x1b, /* Local disk is broken... */
  37         P_BARRIER_ACK         = 0x1c,
  38         P_STATE_CHG_REPLY     = 0x1d,
  39
  40         /* "new" commands, no longer fitting into the ordering scheme above */
  41
  42         P_OV_REQUEST          = 0x1e, /* data socket */
  43         P_OV_REPLY            = 0x1f,
  44         P_OV_RESULT           = 0x20, /* meta socket */
  45         P_CSUM_RS_REQUEST     = 0x21, /* data socket */
  46         P_RS_IS_IN_SYNC       = 0x22, /* meta socket */
  47         P_SYNC_PARAM89        = 0x23, /* data socket, protocol version 89 replacement for P_SYNC_PARAM */
  48         P_COMPRESSED_BITMAP   = 0x24, /* compressed or otherwise encoded bitmap transfer */
  49         /* P_CKPT_FENCE_REQ      = 0x25, * currently reserved for protocol D */
  50         /* P_CKPT_DISABLE_REQ    = 0x26, * currently reserved for protocol D */
  51         P_DELAY_PROBE         = 0x27, /* is used on BOTH sockets */
  52         P_OUT_OF_SYNC         = 0x28, /* Mark as out of sync (Outrunning), data socket */
  53         P_RS_CANCEL           = 0x29, /* meta: Used to cancel RS_DATA_REQUEST packet by SyncSource */
  54         P_CONN_ST_CHG_REQ     = 0x2a, /* data sock: Connection wide state request */
  55         P_CONN_ST_CHG_REPLY   = 0x2b, /* meta sock: Connection side state req reply */
  56         P_RETRY_WRITE         = 0x2c, /* Protocol C: retry conflicting write request */
  57         P_PROTOCOL_UPDATE     = 0x2d, /* data sock: is used in established connections */
  58         /* 0x2e to 0x30 reserved, used in drbd 9 */
  59
  60         /* REQ_OP_DISCARD. We used "discard" in different contexts before,
  61          * which is why I chose TRIM here, to disambiguate. */
  62         P_TRIM                = 0x31,
  63
  64         /* Only use these two if both support FF_THIN_RESYNC */
  65         P_RS_THIN_REQ         = 0x32, /* Request a block for resync or reply P_RS_DEALLOCATED */
  66         P_RS_DEALLOCATED      = 0x33, /* Contains only zeros on sync source node */
  67
  68         /* REQ_WRITE_SAME.
  69          * On a receiving side without REQ_WRITE_SAME,
  70          * we may fall back to an opencoded loop instead. */
  71         P_WSAME               = 0x34,
  72
  73         /* 0x35 already claimed in DRBD 9 */
  74         P_ZEROES              = 0x36, /* data sock: zero-out, WRITE_ZEROES */
  75
  76         /* 0x40 .. 0x48 already claimed in DRBD 9 */
  77
  78         P_MAY_IGNORE          = 0x100, /* Flag to test if (cmd > P_MAY_IGNORE) ... */
  79         P_MAX_OPT_CMD         = 0x101,
  80
  81         /* special command ids for handshake */
  82
  83         P_INITIAL_META        = 0xfff1, /* First Packet on the MetaSock */
  84         P_INITIAL_DATA        = 0xfff2, /* First Packet on the Socket */
  85
  86         P_CONNECTION_FEATURES = 0xfffe  /* FIXED for the next century! */
  87 };
  88
  89 #ifndef __packed
  90 #define __packed __attribute__((packed))
  91 #endif
  92
  93 /* This is the layout for a packet on the wire.
  94  * The byteorder is the network byte order.
  95  *     (except block_id and barrier fields.
  96  *      these are pointers to local structs
  97  *      and have no relevance for the partner,
  98  *      which just echoes them as received.)
  99  *
 100  * NOTE that the payload starts at a long aligned offset,
 101  * regardless of 32 or 64 bit arch!
 102  */
 103 struct p_header80 {
 104         u32       magic;
 105         u16       command;
 106         u16       length;       /* bytes of data after this header */
 107 } __packed;
 108
 109 /* Header for big packets, Used for data packets exceeding 64kB */
 110 struct p_header95 {
 111         u16       magic;        /* use DRBD_MAGIC_BIG here */
 112         u16       command;
 113         u32       length;
 114 } __packed;
 115
 116 struct p_header100 {
 117         u32       magic;
 118         u16       volume;
 119         u16       command;
 120         u32       length;
 121         u32       pad;
 122 } __packed;
 123
 124 /* These defines must not be changed without changing the protocol version.
 125  * New defines may only be introduced together with protocol version bump or
 126  * new protocol feature flags.
 127  */
 128 #define DP_HARDBARRIER        1 /* no longer used */
 129 #define DP_RW_SYNC            2 /* equals REQ_SYNC    */
 130 #define DP_MAY_SET_IN_SYNC    4
 131 #define DP_UNPLUG             8 /* not used anymore   */
 132 #define DP_FUA               16 /* equals REQ_FUA     */
 133 #define DP_FLUSH             32 /* equals REQ_PREFLUSH   */
 134 #define DP_DISCARD           64 /* equals REQ_OP_DISCARD */
 135 #define DP_SEND_RECEIVE_ACK 128 /* This is a proto B write request */
 136 #define DP_SEND_WRITE_ACK   256 /* This is a proto C write request */
 137 #define DP_WSAME            512 /* equiv. REQ_WRITE_SAME */
 138 #define DP_ZEROES          1024 /* equiv. REQ_OP_WRITE_ZEROES */
 139
 140 /* possible combinations:
 141  * REQ_OP_WRITE_ZEROES:  DP_DISCARD | DP_ZEROES
 142  * REQ_OP_WRITE_ZEROES + REQ_NOUNMAP: DP_ZEROES
 143  */
 144
 145 struct p_data {
 146         u64         sector;    /* 64 bits sector number */
 147         u64         block_id;  /* to identify the request in protocol B&C */
 148         u32         seq_num;
 149         u32         dp_flags;
 150 } __packed;
 151
 152 struct p_trim {
 153         struct p_data p_data;
 154         u32         size;       /* == bio->bi_size */
 155 } __packed;
 156
 157 struct p_wsame {
 158         struct p_data p_data;
 159         u32           size;     /* == bio->bi_size */
 160 } __packed;
 161
 162 /*
 163  * commands which share a struct:
 164  *  p_block_ack:
 165  *   P_RECV_ACK (proto B), P_WRITE_ACK (proto C),
 166  *   P_SUPERSEDED (proto C, two-primaries conflict detection)
 167  *  p_block_req:
 168  *   P_DATA_REQUEST, P_RS_DATA_REQUEST
 169  */
 170 struct p_block_ack {
 171         u64         sector;
 172         u64         block_id;
 173         u32         blksize;
 174         u32         seq_num;
 175 } __packed;
 176
 177 struct p_block_req {
 178         u64 sector;
 179         u64 block_id;
 180         u32 blksize;
 181         u32 pad;        /* to multiple of 8 Byte */
 182 } __packed;
 183
 184 /*
 185  * commands with their own struct for additional fields:
 186  *   P_CONNECTION_FEATURES
 187  *   P_BARRIER
 188  *   P_BARRIER_ACK
 189  *   P_SYNC_PARAM
 190  *   ReportParams
 191  */
 192
 193 /* supports TRIM/DISCARD on the "wire" protocol */
 194 #define DRBD_FF_TRIM 1
 195
 196 /* Detect all-zeros during resync, and rather TRIM/UNMAP/DISCARD those blocks
 197  * instead of fully allocate a supposedly thin volume on initial resync */
 198 #define DRBD_FF_THIN_RESYNC 2
 199
 200 /* supports REQ_WRITE_SAME on the "wire" protocol.
 201  * Note: this flag is overloaded,
 202  * its presence also
 203  *   - indicates support for 128 MiB "batch bios",
 204  *     max discard size of 128 MiB
 205  *     instead of 4M before that.
 206  *   - indicates that we exchange additional settings in p_sizes
 207  *     drbd_send_sizes()/receive_sizes()
 208  */
 209 #define DRBD_FF_WSAME 4
 210
 211 /* supports REQ_OP_WRITE_ZEROES on the "wire" protocol.
 212  *
 213  * We used to map that to "discard" on the sending side, and if we cannot
 214  * guarantee that discard zeroes data, the receiving side would map discard
 215  * back to zero-out.
 216  *
 217  * With the introduction of REQ_OP_WRITE_ZEROES,
 218  * we started to use that for both WRITE_ZEROES and DISCARDS,
 219  * hoping that WRITE_ZEROES would "do what we want",
 220  * UNMAP if possible, zero-out the rest.
 221  *
 222  * The example scenario is some LVM "thin" backend.
 223  *
 224  * While an un-allocated block on dm-thin reads as zeroes, on a dm-thin
 225  * with "skip_block_zeroing=true", after a partial block write allocated
 226  * that block, that same block may well map "undefined old garbage" from
 227  * the backends on LBAs that have not yet been written to.
 228  *
 229  * If we cannot distinguish between zero-out and discard on the receiving
 230  * side, to avoid "undefined old garbage" to pop up randomly at later times
 231  * on supposedly zero-initialized blocks, we'd need to map all discards to
 232  * zero-out on the receiving side.  But that would potentially do a full
 233  * alloc on thinly provisioned backends, even when the expectation was to
 234  * unmap/trim/discard/de-allocate.
 235  *
 236  * We need to distinguish on the protocol level, whether we need to guarantee
 237  * zeroes (and thus use zero-out, potentially doing the mentioned full-alloc),
 238  * or if we want to put the emphasis on discard, and only do a "best effort
 239  * zeroing" (by "discarding" blocks aligned to discard-granularity, and zeroing
 240  * only potential unaligned head and tail clippings), to at least *try* to
 241  * avoid "false positives" in an online-verify later, hoping that someone
 242  * set skip_block_zeroing=false.
 243  */
 244 #define DRBD_FF_WZEROES 8
 245
 246
 247 struct p_connection_features {
 248         u32 protocol_min;
 249         u32 feature_flags;
 250         u32 protocol_max;
 251
 252         /* should be more than enough for future enhancements
 253          * for now, feature_flags and the reserved array shall be zero.
 254          */
 255
 256         u32 _pad;
 257         u64 reserved[7];
 258 } __packed;
 259
 260 struct p_barrier {
 261         u32 barrier;    /* barrier number _handle_ only */
 262         u32 pad;        /* to multiple of 8 Byte */
 263 } __packed;
 264
 265 struct p_barrier_ack {
 266         u32 barrier;
 267         u32 set_size;
 268 } __packed;
 269
 270 struct p_rs_param {
 271         u32 resync_rate;
 272
 273               /* Since protocol version 88 and higher. */
 274         char verify_alg[];
 275 } __packed;
 276
 277 struct p_rs_param_89 {
 278         u32 resync_rate;
 279         /* protocol version 89: */
 280         char verify_alg[SHARED_SECRET_MAX];
 281         char csums_alg[SHARED_SECRET_MAX];
 282 } __packed;
 283
 284 struct p_rs_param_95 {
 285         u32 resync_rate;
 286         char verify_alg[SHARED_SECRET_MAX];
 287         char csums_alg[SHARED_SECRET_MAX];
 288         u32 c_plan_ahead;
 289         u32 c_delay_target;
 290         u32 c_fill_target;
 291         u32 c_max_rate;
 292 } __packed;
 293
 294 enum drbd_conn_flags {
 295         CF_DISCARD_MY_DATA = 1,
 296         CF_DRY_RUN = 2,
 297 };
 298
 299 struct p_protocol {
 300         u32 protocol;
 301         u32 after_sb_0p;
 302         u32 after_sb_1p;
 303         u32 after_sb_2p;
 304         u32 conn_flags;
 305         u32 two_primaries;
 306
 307         /* Since protocol version 87 and higher. */
 308         char integrity_alg[];
 309
 310 } __packed;
 311
 312 struct p_uuids {
 313         u64 uuid[UI_EXTENDED_SIZE];
 314 } __packed;
 315
 316 struct p_rs_uuid {
 317         u64         uuid;
 318 } __packed;
 319
 320 /* optional queue_limits if (agreed_features & DRBD_FF_WSAME)
 321  * see also struct queue_limits, as of late 2015 */
 322 struct o_qlim {
 323         /* we don't need it yet, but we may as well communicate it now */
 324         u32 physical_block_size;
 325
 326         /* so the original in struct queue_limits is unsigned short,
 327          * but I'd have to put in padding anyways. */
 328         u32 logical_block_size;
 329
 330         /* One incoming bio becomes one DRBD request,
 331          * which may be translated to several bio on the receiving side.
 332          * We don't need to communicate chunk/boundary/segment ... limits.
 333          */
 334
 335         /* various IO hints may be useful with "diskless client" setups */
 336         u32 alignment_offset;
 337         u32 io_min;
 338         u32 io_opt;
 339
 340         /* We may need to communicate integrity stuff at some point,
 341          * but let's not get ahead of ourselves. */
 342
 343         /* Backend discard capabilities.
 344          * Receiving side uses "blkdev_issue_discard()", no need to communicate
 345          * more specifics.  If the backend cannot do discards, the DRBD peer
 346          * may fall back to blkdev_issue_zeroout().
 347          */
 348         u8 discard_enabled;
 349         u8 discard_zeroes_data;
 350         u8 write_same_capable;
 351         u8 _pad;
 352 } __packed;
 353
 354 struct p_sizes {
 355         u64         d_size;  /* size of disk */
 356         u64         u_size;  /* user requested size */
 357         u64         c_size;  /* current exported size */
 358         u32         max_bio_size;  /* Maximal size of a BIO */
 359         u16         queue_order_type;  /* not yet implemented in DRBD*/
 360         u16         dds_flags; /* use enum dds_flags here. */
 361
 362         /* optional queue_limits if (agreed_features & DRBD_FF_WSAME) */
 363         struct o_qlim qlim[];
 364 } __packed;
 365
 366 struct p_state {
 367         u32         state;
 368 } __packed;
 369
 370 struct p_req_state {
 371         u32         mask;
 372         u32         val;
 373 } __packed;
 374
 375 struct p_req_state_reply {
 376         u32         retcode;
 377 } __packed;
 378
 379 struct p_drbd06_param {
 380         u64       size;
 381         u32       state;
 382         u32       blksize;
 383         u32       protocol;
 384         u32       version;
 385         u32       gen_cnt[5];
 386         u32       bit_map_gen[5];
 387 } __packed;
 388
 389 struct p_block_desc {
 390         u64 sector;
 391         u32 blksize;
 392         u32 pad;        /* to multiple of 8 Byte */
 393 } __packed;
 394
 395 /* Valid values for the encoding field.
 396  * Bump proto version when changing this. */
 397 enum drbd_bitmap_code {
 398         /* RLE_VLI_Bytes = 0,
 399          * and other bit variants had been defined during
 400          * algorithm evaluation. */
 401         RLE_VLI_Bits = 2,
 402 };
 403
 404 struct p_compressed_bm {
 405         /* (encoding & 0x0f): actual encoding, see enum drbd_bitmap_code
 406          * (encoding & 0x80): polarity (set/unset) of first runlength
 407          * ((encoding >> 4) & 0x07): pad_bits, number of trailing zero bits
 408          * used to pad up to head.length bytes
 409          */
 410         u8 encoding;
 411
 412         u8 code[];
 413 } __packed;
 414
 415 struct p_delay_probe93 {
 416         u32     seq_num; /* sequence number to match the two probe packets */
 417         u32     offset;  /* usecs the probe got sent after the reference time point */
 418 } __packed;
 419
 420 /*
 421  * Bitmap packets need to fit within a single page on the sender and receiver,
 422  * so we are limited to 4 KiB (and not to PAGE_SIZE, which can be bigger).
 423  */
 424 #define DRBD_SOCKET_BUFFER_SIZE 4096
 425
 426 #endif  /* __DRBD_PROTOCOL_H */