/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __DRBD_PROTOCOL_H
#define __DRBD_PROTOCOL_H

enum drbd_packet {
        /* receiver (data socket) */
        P_DATA                = 0x00,
        P_DATA_REPLY          = 0x01, /* Response to P_DATA_REQUEST */
        P_RS_DATA_REPLY       = 0x02, /* Response to P_RS_DATA_REQUEST */
        P_BARRIER             = 0x03,
        P_BITMAP              = 0x04,
        P_BECOME_SYNC_TARGET  = 0x05,
        P_BECOME_SYNC_SOURCE  = 0x06,
        P_UNPLUG_REMOTE       = 0x07, /* Used at various times to hint the peer */
        P_DATA_REQUEST        = 0x08, /* Used to ask for a data block */
        P_RS_DATA_REQUEST     = 0x09, /* Used to ask for a data block for resync */
        P_SYNC_PARAM          = 0x0a,
        P_PROTOCOL            = 0x0b,
        P_UUIDS               = 0x0c,
        P_SIZES               = 0x0d,
        P_STATE               = 0x0e,
        P_SYNC_UUID           = 0x0f,
        P_AUTH_CHALLENGE      = 0x10,
        P_AUTH_RESPONSE       = 0x11,
        P_STATE_CHG_REQ       = 0x12,

        /* (meta socket) */
        P_PING                = 0x13,
        P_PING_ACK            = 0x14,
        P_RECV_ACK            = 0x15, /* Used in protocol B */
        P_WRITE_ACK           = 0x16, /* Used in protocol C */
        P_RS_WRITE_ACK        = 0x17, /* Is a P_WRITE_ACK, additionally call set_in_sync(). */
        P_SUPERSEDED          = 0x18, /* Used in proto C, two-primaries conflict detection */
        P_NEG_ACK             = 0x19, /* Sent if local disk is unusable */
        P_NEG_DREPLY          = 0x1a, /* Local disk is broken... */
        P_NEG_RS_DREPLY       = 0x1b, /* Local disk is broken... */
        P_BARRIER_ACK         = 0x1c,
        P_STATE_CHG_REPLY     = 0x1d,

        /* "new" commands, no longer fitting into the ordering scheme above */

        P_OV_REQUEST          = 0x1e, /* data socket */
        P_OV_REPLY            = 0x1f,
        P_OV_RESULT           = 0x20, /* meta socket */
        P_CSUM_RS_REQUEST     = 0x21, /* data socket */
        P_RS_IS_IN_SYNC       = 0x22, /* meta socket */
        P_SYNC_PARAM89        = 0x23, /* data socket, protocol version 89 replacement for P_SYNC_PARAM */
        P_COMPRESSED_BITMAP   = 0x24, /* compressed or otherwise encoded bitmap transfer */
        /* P_CKPT_FENCE_REQ      = 0x25, * currently reserved for protocol D */
        /* P_CKPT_DISABLE_REQ    = 0x26, * currently reserved for protocol D */
        P_DELAY_PROBE         = 0x27, /* is used on BOTH sockets */
        P_OUT_OF_SYNC         = 0x28, /* Mark as out of sync (Outrunning), data socket */
        P_RS_CANCEL           = 0x29, /* meta: Used to cancel RS_DATA_REQUEST packet by SyncSource */
        P_CONN_ST_CHG_REQ     = 0x2a, /* data sock: Connection wide state request */
        P_CONN_ST_CHG_REPLY   = 0x2b, /* meta sock: Connection side state req reply */
        P_RETRY_WRITE         = 0x2c, /* Protocol C: retry conflicting write request */
        P_PROTOCOL_UPDATE     = 0x2d, /* data sock: is used in established connections */
        /* 0x2e to 0x30 reserved, used in drbd 9 */

        /* REQ_OP_DISCARD. We used "discard" in different contexts before,
         * which is why I chose TRIM here, to disambiguate. */
        P_TRIM                = 0x31,

        /* Only use these two if both support FF_THIN_RESYNC */
        P_RS_THIN_REQ         = 0x32, /* Request a block for resync or reply P_RS_DEALLOCATED */
        P_RS_DEALLOCATED      = 0x33, /* Contains only zeros on sync source node */

        /* REQ_WRITE_SAME.
         * On a receiving side without REQ_WRITE_SAME,
         * we may fall back to an opencoded loop instead. */
        P_WSAME               = 0x34,

        /* 0x35 already claimed in DRBD 9 */
        P_ZEROES              = 0x36, /* data sock: zero-out, WRITE_ZEROES */

        /* 0x40 .. 0x48 already claimed in DRBD 9 */

        P_MAY_IGNORE          = 0x100, /* Flag to test if (cmd > P_MAY_IGNORE) ... */
        P_MAX_OPT_CMD         = 0x101,

        /* special command ids for handshake */

        P_INITIAL_META        = 0xfff1, /* First Packet on the MetaSock */
        P_INITIAL_DATA        = 0xfff2, /* First Packet on the Socket */

        P_CONNECTION_FEATURES = 0xfffe  /* FIXED for the next century! */
};

#ifndef __packed
#define __packed __attribute__((packed))
#endif

/* This is the layout for a packet on the wire.
 * The byteorder is the network byte order.
 *     (except block_id and barrier fields.
 *      these are pointers to local structs
 *      and have no relevance for the partner,
 *      which just echoes them as received.)
 *
 * NOTE that the payload starts at a long aligned offset,
 * regardless of 32 or 64 bit arch!
 */
struct p_header80 {
        u32       magic;
        u16       command;
        u16       length;       /* bytes of data after this header */
} __packed;

/* Header for big packets, Used for data packets exceeding 64kB */
struct p_header95 {
        u16       magic;        /* use DRBD_MAGIC_BIG here */
        u16       command;
        u32       length;
} __packed;

struct p_header100 {
        u32       magic;
        u16       volume;
        u16       command;
        u32       length;
        u32       pad;
} __packed;

/* These defines must not be changed without changing the protocol version.
 * New defines may only be introduced together with protocol version bump or
 * new protocol feature flags.
 */
#define DP_HARDBARRIER        1 /* no longer used */
#define DP_RW_SYNC            2 /* equals REQ_SYNC    */
#define DP_MAY_SET_IN_SYNC    4
#define DP_UNPLUG             8 /* not used anymore   */
#define DP_FUA               16 /* equals REQ_FUA     */
#define DP_FLUSH             32 /* equals REQ_PREFLUSH   */
#define DP_DISCARD           64 /* equals REQ_OP_DISCARD */
#define DP_SEND_RECEIVE_ACK 128 /* This is a proto B write request */
#define DP_SEND_WRITE_ACK   256 /* This is a proto C write request */
#define DP_WSAME            512 /* equiv. REQ_WRITE_SAME */
#define DP_ZEROES          1024 /* equiv. REQ_OP_WRITE_ZEROES */

/* possible combinations:
 * REQ_OP_WRITE_ZEROES:  DP_DISCARD | DP_ZEROES
 * REQ_OP_WRITE_ZEROES + REQ_NOUNMAP: DP_ZEROES
 */

struct p_data {
        u64         sector;    /* 64 bits sector number */
        u64         block_id;  /* to identify the request in protocol B&C */
        u32         seq_num;
        u32         dp_flags;
} __packed;

struct p_trim {
        struct p_data p_data;
        u32         size;       /* == bio->bi_size */
} __packed;

struct p_wsame {
        struct p_data p_data;
        u32           size;     /* == bio->bi_size */
} __packed;

/*
 * commands which share a struct:
 *  p_block_ack:
 *   P_RECV_ACK (proto B), P_WRITE_ACK (proto C),
 *   P_SUPERSEDED (proto C, two-primaries conflict detection)
 *  p_block_req:
 *   P_DATA_REQUEST, P_RS_DATA_REQUEST
 */
struct p_block_ack {
        u64         sector;
        u64         block_id;
        u32         blksize;
        u32         seq_num;
} __packed;

struct p_block_req {
        u64 sector;
        u64 block_id;
        u32 blksize;
        u32 pad;        /* to multiple of 8 Byte */
} __packed;

/*
 * commands with their own struct for additional fields:
 *   P_CONNECTION_FEATURES
 *   P_BARRIER
 *   P_BARRIER_ACK
 *   P_SYNC_PARAM
 *   ReportParams
 */

/* supports TRIM/DISCARD on the "wire" protocol */
#define DRBD_FF_TRIM 1

/* Detect all-zeros during resync, and rather TRIM/UNMAP/DISCARD those blocks
 * instead of fully allocate a supposedly thin volume on initial resync */
#define DRBD_FF_THIN_RESYNC 2

/* supports REQ_WRITE_SAME on the "wire" protocol.
 * Note: this flag is overloaded,
 * its presence also
 *   - indicates support for 128 MiB "batch bios",
 *     max discard size of 128 MiB
 *     instead of 4M before that.
 *   - indicates that we exchange additional settings in p_sizes
 *     drbd_send_sizes()/receive_sizes()
 */
#define DRBD_FF_WSAME 4

/* supports REQ_OP_WRITE_ZEROES on the "wire" protocol.
 *
 * We used to map that to "discard" on the sending side, and if we cannot
 * guarantee that discard zeroes data, the receiving side would map discard
 * back to zero-out.
 *
 * With the introduction of REQ_OP_WRITE_ZEROES,
 * we started to use that for both WRITE_ZEROES and DISCARDS,
 * hoping that WRITE_ZEROES would "do what we want",
 * UNMAP if possible, zero-out the rest.
 *
 * The example scenario is some LVM "thin" backend.
 *
 * While an un-allocated block on dm-thin reads as zeroes, on a dm-thin
 * with "skip_block_zeroing=true", after a partial block write allocated
 * that block, that same block may well map "undefined old garbage" from
 * the backends on LBAs that have not yet been written to.
 *
 * If we cannot distinguish between zero-out and discard on the receiving
 * side, to avoid "undefined old garbage" to pop up randomly at later times
 * on supposedly zero-initialized blocks, we'd need to map all discards to
 * zero-out on the receiving side.  But that would potentially do a full
 * alloc on thinly provisioned backends, even when the expectation was to
 * unmap/trim/discard/de-allocate.
 *
 * We need to distinguish on the protocol level, whether we need to guarantee
 * zeroes (and thus use zero-out, potentially doing the mentioned full-alloc),
 * or if we want to put the emphasis on discard, and only do a "best effort
 * zeroing" (by "discarding" blocks aligned to discard-granularity, and zeroing
 * only potential unaligned head and tail clippings), to at least *try* to
 * avoid "false positives" in an online-verify later, hoping that someone
 * set skip_block_zeroing=false.
 */
#define DRBD_FF_WZEROES 8


struct p_connection_features {
        u32 protocol_min;
        u32 feature_flags;
        u32 protocol_max;

        /* should be more than enough for future enhancements
         * for now, feature_flags and the reserved array shall be zero.
         */

        u32 _pad;
        u64 reserved[7];
} __packed;

struct p_barrier {
        u32 barrier;    /* barrier number _handle_ only */
        u32 pad;        /* to multiple of 8 Byte */
} __packed;

struct p_barrier_ack {
        u32 barrier;
        u32 set_size;
} __packed;

struct p_rs_param {
        u32 resync_rate;

              /* Since protocol version 88 and higher. */
        char verify_alg[0];
} __packed;

struct p_rs_param_89 {
        u32 resync_rate;
        /* protocol version 89: */
        char verify_alg[SHARED_SECRET_MAX];
        char csums_alg[SHARED_SECRET_MAX];
} __packed;

struct p_rs_param_95 {
        u32 resync_rate;
        char verify_alg[SHARED_SECRET_MAX];
        char csums_alg[SHARED_SECRET_MAX];
        u32 c_plan_ahead;
        u32 c_delay_target;
        u32 c_fill_target;
        u32 c_max_rate;
} __packed;

enum drbd_conn_flags {
        CF_DISCARD_MY_DATA = 1,
        CF_DRY_RUN = 2,
};

struct p_protocol {
        u32 protocol;
        u32 after_sb_0p;
        u32 after_sb_1p;
        u32 after_sb_2p;
        u32 conn_flags;
        u32 two_primaries;

        /* Since protocol version 87 and higher. */
        char integrity_alg[0];

} __packed;

struct p_uuids {
        u64 uuid[UI_EXTENDED_SIZE];
} __packed;

struct p_rs_uuid {
        u64         uuid;
} __packed;

/* optional queue_limits if (agreed_features & DRBD_FF_WSAME)
 * see also struct queue_limits, as of late 2015 */
struct o_qlim {
        /* we don't need it yet, but we may as well communicate it now */
        u32 physical_block_size;

        /* so the original in struct queue_limits is unsigned short,
         * but I'd have to put in padding anyways. */
        u32 logical_block_size;

        /* One incoming bio becomes one DRBD request,
         * which may be translated to several bio on the receiving side.
         * We don't need to communicate chunk/boundary/segment ... limits.
         */

        /* various IO hints may be useful with "diskless client" setups */
        u32 alignment_offset;
        u32 io_min;
        u32 io_opt;

        /* We may need to communicate integrity stuff at some point,
         * but let's not get ahead of ourselves. */

        /* Backend discard capabilities.
         * Receiving side uses "blkdev_issue_discard()", no need to communicate
         * more specifics.  If the backend cannot do discards, the DRBD peer
         * may fall back to blkdev_issue_zeroout().
         */
        u8 discard_enabled;
        u8 discard_zeroes_data;
        u8 write_same_capable;
        u8 _pad;
} __packed;

struct p_sizes {
        u64         d_size;  /* size of disk */
        u64         u_size;  /* user requested size */
        u64         c_size;  /* current exported size */
        u32         max_bio_size;  /* Maximal size of a BIO */
        u16         queue_order_type;  /* not yet implemented in DRBD*/
        u16         dds_flags; /* use enum dds_flags here. */

        /* optional queue_limits if (agreed_features & DRBD_FF_WSAME) */
        struct o_qlim qlim[0];
} __packed;

struct p_state {
        u32         state;
} __packed;

struct p_req_state {
        u32         mask;
        u32         val;
} __packed;

struct p_req_state_reply {
        u32         retcode;
} __packed;

struct p_drbd06_param {
        u64       size;
        u32       state;
        u32       blksize;
        u32       protocol;
        u32       version;
        u32       gen_cnt[5];
        u32       bit_map_gen[5];
} __packed;

struct p_block_desc {
        u64 sector;
        u32 blksize;
        u32 pad;        /* to multiple of 8 Byte */
} __packed;

/* Valid values for the encoding field.
 * Bump proto version when changing this. */
enum drbd_bitmap_code {
        /* RLE_VLI_Bytes = 0,
         * and other bit variants had been defined during
         * algorithm evaluation. */
        RLE_VLI_Bits = 2,
};

struct p_compressed_bm {
        /* (encoding & 0x0f): actual encoding, see enum drbd_bitmap_code
         * (encoding & 0x80): polarity (set/unset) of first runlength
         * ((encoding >> 4) & 0x07): pad_bits, number of trailing zero bits
         * used to pad up to head.length bytes
         */
        u8 encoding;

        u8 code[0];
} __packed;

struct p_delay_probe93 {
        u32     seq_num; /* sequence number to match the two probe packets */
        u32     offset;  /* usecs the probe got sent after the reference time point */
} __packed;

/*
 * Bitmap packets need to fit within a single page on the sender and receiver,
 * so we are limited to 4 KiB (and not to PAGE_SIZE, which can be bigger).
 */
#define DRBD_SOCKET_BUFFER_SIZE 4096

#endif  /* __DRBD_PROTOCOL_H */