drbd_protocol.h

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

#ifdef __KERNEL__
#include <linux/types.h>
#else
#include <stdint.h>
#define u64 uint64_t
#endif

#ifndef ARRAY_SIZE
#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]))
#endif

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,

	/* asender (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, /* Write ack for resync reply. */
	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 sock: Protocol < 122 version of P_OV_RESULT_ID */
	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: state change request */
	P_CONN_ST_CHG_REPLY   = 0x2b, /* meta sock: state change reply */
	P_RETRY_WRITE	      = 0x2c, /* Protocol C: retry conflicting write request */
	P_PROTOCOL_UPDATE     = 0x2d, /* data sock: is used in established connections */
	P_TWOPC_PREPARE       = 0x2e, /* data sock: prepare state change */
	P_TWOPC_ABORT         = 0x2f, /* data sock: abort state change */

	P_DAGTAG	      = 0x30, /* data sock: set the current dagtag */

	/* REQ_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, /* Protocol < 122 version of P_RS_DEALLOCATED_ID */

	/* REQ_WRITE_SAME.
	 * On a receiving side without REQ_WRITE_SAME,
	 * we may fall back to an opencoded loop instead. */
	P_WSAME               = 0x34,
	P_TWOPC_PREP_RSZ      = 0x35, /* PREPARE a 2PC resize operation*/
	P_ZEROES              = 0x36, /* data sock: zero-out, WRITE_ZEROES */

	/* place new packets for both 8.4 and 9 here,
	 * place new packets for 9-only in the next gap. */

	P_PEER_ACK            = 0x40, /* meta sock: tell which nodes have acked a request */
	P_PEERS_IN_SYNC       = 0x41, /* data sock: Mark area as in sync */

	P_UUIDS110	      = 0x42, /* data socket */
	P_PEER_DAGTAG         = 0x43, /* data socket, used to trigger reconciliation resync */
	P_CURRENT_UUID	      = 0x44, /* data socket */

	P_TWOPC_YES           = 0x45, /* meta sock: allow two-phase commit */
	P_TWOPC_NO            = 0x46, /* meta sock: reject two-phase commit */
	P_TWOPC_COMMIT        = 0x47, /* data sock: commit state change */
	P_TWOPC_RETRY         = 0x48, /* meta sock: retry two-phase commit */

	P_CONFIRM_STABLE      = 0x49, /* meta sock: similar to an unsolicited partial barrier ack */
	P_RS_CANCEL_AHEAD     = 0x4a, /* protocol version 115,
		 * meta: cancel RS_DATA_REQUEST packet if already Ahead again,
		 *       tell peer to stop sending resync requests... */
	P_DISCONNECT          = 0x4b, /* data sock: Disconnect and stop connection attempts */

	P_RS_DAGTAG_REQ       = 0x4c, /* data sock: Request a block for resync, with dagtag dependency */
	P_RS_CSUM_DAGTAG_REQ  = 0x4d, /* data sock: Request a block for resync if checksum differs, with dagtag dependency */
	P_RS_THIN_DAGTAG_REQ  = 0x4e, /* data sock: Request a block for resync or reply P_RS_DEALLOCATED, with dagtag dependency */
	P_OV_DAGTAG_REQ       = 0x4f, /* data sock: Request a checksum for online verify, with dagtag dependency */
	P_OV_DAGTAG_REPLY     = 0x50, /* data sock: Reply with a checksum for online verify, with dagtag dependency */

	P_WRITE_ACK_IN_SYNC   = 0x51, /* meta sock: Application write ack setting bits in sync. */
	P_RS_NEG_ACK          = 0x52, /* meta sock: Local disk is unusable writing resync reply. */
	P_OV_RESULT_ID        = 0x53, /* meta sock: Online verify result with block ID. */
	P_RS_DEALLOCATED_ID   = 0x54, /* data sock: Contains only zeros on sync source node. */

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

	/* 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 {
	uint32_t magic;
	uint16_t command;
	uint16_t length;	/* bytes of data after this header */
} __packed;

/* Header for big packets, Used for data packets exceeding 64kB */
struct p_header95 {
	uint16_t magic;	/* use DRBD_MAGIC_BIG here */
	uint16_t command;
	uint32_t length;
} __packed;

struct p_header100 {
	uint32_t magic;
	uint16_t volume;
	uint16_t command;
	uint32_t length;
	uint32_t 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 /* equals REQ_UNPLUG (compat) */
#define DP_FUA               16 /* equals REQ_FUA     */
#define DP_FLUSH             32 /* equals REQ_PREFLUSH   */
#define DP_DISCARD           64 /* equals REQ_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 {
	uint64_t sector;    /* 64 bits sector number */
	uint64_t block_id;  /* to identify the request in protocol B&C */
	uint32_t seq_num;
	uint32_t dp_flags;
} __packed;

struct p_trim {
	struct p_data p_data;
	uint32_t size;	/* == bio->bi_size */
} __packed;

struct p_wsame {
	struct p_data p_data;
	uint32_t size;     /* == bio->bi_size */
} __packed;

/*
 * struct p_block_ack shared by commands:
 *   P_RECV_ACK (proto B)
 *   P_WRITE_ACK (proto C),
 *   P_WRITE_ACK_IN_SYNC,
 *   P_SUPERSEDED (proto C, two-primaries conflict detection)
 *   P_RS_WRITE_ACK
 *   P_NEG_ACK
 *   P_NEG_DREPLY
 *   P_NEG_RS_DREPLY
 *   P_RS_NEG_ACK
 *   P_OV_RESULT
 *   P_RS_IS_IN_SYNC
 *   P_RS_CANCEL
 *   P_RS_DEALLOCATED_ID
 *   P_RS_CANCEL_AHEAD
 */
struct p_block_ack {
	uint64_t sector;
	uint64_t block_id;
	uint32_t blksize;
	uint32_t seq_num;
} __packed;

/* For P_OV_RESULT_ID. */
struct p_ov_result {
	uint64_t sector;
	uint64_t block_id;
	uint32_t blksize;
	uint32_t seq_num;
	uint32_t result;
	uint32_t pad;
} __packed;

enum ov_result {
	OV_RESULT_SKIP = 0,
	OV_RESULT_IN_SYNC = 1,
	OV_RESULT_OUT_OF_SYNC = 2,
};

struct p_block_req_common {
	uint64_t sector;
	uint64_t block_id;
	uint32_t blksize;
} __packed;

/*
 * struct p_block_req shared by commands:
 *   P_DATA_REQUEST
 *   P_RS_DATA_REQUEST
 *   P_OV_REQUEST
 *   P_OV_REPLY
 *   P_CSUM_RS_REQUEST
 *   P_RS_THIN_REQ
 */
struct p_block_req {
	/* Allow fields to be addressed directly or via req_common. */
	union {
		struct {
			uint64_t sector;
			uint64_t block_id;
			uint32_t blksize;
		} __packed;
		struct p_block_req_common req_common;
	};
	uint32_t pad;	/* to multiple of 8 Byte */
} __packed;

/*
 * struct p_rs_req shared by commands:
 *   P_RS_DAGTAG_REQ
 *   P_RS_CSUM_DAGTAG_REQ
 *   P_RS_THIN_DAGTAG_REQ
 *   P_OV_DAGTAG_REQ
 *   P_OV_DAGTAG_REPLY
 */
struct p_rs_req {
	struct p_block_req_common req_common;
	uint32_t dagtag_node_id;
	uint64_t dagtag;
} __packed;

/* 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

/* Supports synchronization of application and resync IO using data generation
 * tags (dagtags). See Documentation/application-resync-synchronization.rst for
 * details.
 */
#define DRBD_FF_RESYNC_DAGTAG 16

/* V2 of p_twopc_request has a 32 bit flag field and the two fields for node
 * Ids are reduced to 8 bit instead of 32 bits.
 *
 * The flag TWOPC_HAS_RECHABLE indicates that in the commit phase
 * (P_TWOPC_COMMIT) the reachable_nodes mask is set.
 *
 * The old behavior sends the primary_nodes mask, mask, and val in
 * phase 2 (P_TWOPC_COMMIT), where mask and val are the same values as
 * in phase 1 (P_TWOPC_PREPARE).
 */
#define DRBD_FF_2PC_V2 32

/* Starting with drbd-9.1.15, a node with a backing disk sends the new
 * current-uuid also to diskless nodes when the initial resync is
 * skipped.
 *
 * The peer needs to know about this detail to apply the necessary
 * strictness regarding downgrading its view of the partner's disk
 * state.
 */
#define DRBD_FF_RS_SKIP_UUID 64

struct p_connection_features {
	uint32_t protocol_min;
	uint32_t feature_flags;
	uint32_t protocol_max;
	uint32_t sender_node_id;
	uint32_t receiver_node_id;

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

	uint32_t _pad;
	uint64_t reserved[6];
} __packed;

struct p_barrier {
	uint32_t barrier;	/* barrier number _handle_ only */
	uint32_t pad;	/* to multiple of 8 Byte */
} __packed;

struct p_barrier_ack {
	uint32_t barrier;
	uint32_t set_size;
} __packed;

struct p_confirm_stable {
	uint64_t oldest_block_id;
	uint64_t youngest_block_id;
	uint32_t set_size;
	uint32_t pad; /* to multiple of 8 Byte */
} __packed;

struct p_rs_param {
	uint32_t resync_rate;

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

struct p_rs_param_89 {
	uint32_t resync_rate;
        /* protocol version 89: */
	char verify_alg[SHARED_SECRET_MAX];
	char csums_alg[SHARED_SECRET_MAX];
} __packed;

struct p_rs_param_95 {
	uint32_t resync_rate;
	char verify_alg[SHARED_SECRET_MAX];
	char csums_alg[SHARED_SECRET_MAX];
	uint32_t c_plan_ahead;
	uint32_t c_delay_target;
	uint32_t c_fill_target;
	uint32_t c_max_rate;
} __packed;

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

struct p_protocol {
	uint32_t protocol;
	uint32_t after_sb_0p;
	uint32_t after_sb_1p;
	uint32_t after_sb_2p;
	uint32_t conn_flags;
	uint32_t two_primaries;

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

} __packed;

#define UUID_FLAG_DISCARD_MY_DATA     ((u64)1 << 0)
#define UUID_FLAG_CRASHED_PRIMARY     ((u64)1 << 1)
#define UUID_FLAG_INCONSISTENT        ((u64)1 << 2)
#define UUID_FLAG_SKIP_INITIAL_SYNC   ((u64)1 << 3)

#define UUID_FLAG_MASK_COMPAT_84 \
	(UUID_FLAG_DISCARD_MY_DATA|\
	 UUID_FLAG_CRASHED_PRIMARY|\
	 UUID_FLAG_INCONSISTENT|\
	 UUID_FLAG_SKIP_INITIAL_SYNC)

#define UUID_FLAG_NEW_DATAGEN         ((u64)1 << 4)
#define UUID_FLAG_STABLE              ((u64)1 << 5)
#define UUID_FLAG_GOT_STABLE          ((u64)1 << 6) /* send UUIDs */
#define UUID_FLAG_RESYNC              ((u64)1 << 7) /* compare UUIDs and eventually start resync */
#define UUID_FLAG_RECONNECT           ((u64)1 << 8)
#define UUID_FLAG_DISKLESS_PRIMARY    ((u64)1 << 9) /* Use with UUID_FLAG_RESYNC if a diskless primary is the reason */
#define UUID_FLAG_PRIMARY_LOST_QUORUM ((u64)1 << 10)
#define UUID_FLAG_SYNC_TARGET         ((u64)1 << 11) /* currently L_SYNC_TARGET to some peer */
#define UUID_FLAG_HAS_UNALLOC         ((u64)1 << 12) /* highest byte contains index of not allocated bitmap uuid */

#define UUID_FLAG_UNALLOC_SHIFT       56
#define UUID_FLAG_UNALLOC_MASK        ((u64)0xff << UUID_FLAG_UNALLOC_SHIFT)

struct p_uuids {
	uint64_t current_uuid;
	uint64_t bitmap_uuid;
	uint64_t history_uuids[HISTORY_UUIDS_V08];
	uint64_t dirty_bits;
	uint64_t uuid_flags;
} __packed;

struct p_uuids110 {
	uint64_t current_uuid;
	uint64_t dirty_bits;
	uint64_t uuid_flags;
	uint64_t node_mask; /* weak_nodes when UUID_FLAG_NEW_DATAGEN is set ;
			       authoritative nodes when UUID_FLAG_STABLE not set */

	uint64_t bitmap_uuids_mask; /* non zero bitmap UUIDS for these nodes */
	uint64_t other_uuids[]; /* the first hweight(bitmap_uuids_mask) slots carry bitmap uuids.
				    The node with the lowest node_id first.
				    The remaining slots carry history uuids */
} __packed;

struct p_current_uuid {
	uint64_t uuid;
	uint64_t weak_nodes;
} __packed;

struct p_uuid {
	uint64_t 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 */
	uint32_t physical_block_size;

	/* so the original in struct queue_limits is unsigned short,
	 * but I'd have to put in padding anyways. */
	uint32_t 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 */
	uint32_t alignment_offset;
	uint32_t io_min;
	uint32_t 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().
	 */
	uint8_t discard_enabled;
	uint8_t discard_zeroes_data;
	uint8_t write_same_capable;
	uint8_t _pad;
} __packed;

struct p_sizes {
	uint64_t d_size;  /* size of disk */
	uint64_t u_size;  /* user requested size */
	uint64_t c_size;  /* current exported size */
	uint32_t max_bio_size;  /* Maximal size of a BIO */
	uint16_t queue_order_type;  /* not yet implemented in DRBD*/
	uint16_t dds_flags; /* use enum dds_flags here. */

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

struct p_state {
	uint32_t state;
} __packed;

struct p_req_state {
	uint32_t mask;
	uint32_t val;
} __packed;

struct p_req_state_reply {
	uint32_t retcode;
} __packed;

struct p_twopc_request {
	uint32_t tid;  /* transaction identifier */
	union {
		struct { /* when DRBD_FF_2PC_V2 is set */
			uint32_t flags;
			uint16_t _pad;
			int8_t  s8_initiator_node_id;  /* initiator of the transaction */
			int8_t  s8_target_node_id;  /* target of the transaction (or -1) */
		};
		struct { /* original packet version */
			uint32_t u32_initiator_node_id;  /* initiator of the transaction */
			uint32_t u32_target_node_id;  /* target of the transaction (or -1) */
		};
	};
	uint64_t nodes_to_reach;
	union {
		union { /* TWOPC_STATE_CHANGE */
			struct {    /* P_TWOPC_PREPARE */
				uint64_t _compat_pad;
				uint32_t mask;
				uint32_t val;
			};
			struct { /* P_TWOPC_COMMIT */
				uint64_t primary_nodes;
				uint64_t reachable_nodes; /* when TWOPC_HAS_RECHABLE flag is set */
			};
		};
		union {	 /* TWOPC_RESIZE */
			struct {    /* P_TWOPC_PREP_RSZ */
				uint64_t user_size;
				uint16_t dds_flags;
			};
			struct {    /* P_TWOPC_COMMIT	*/
				uint64_t diskful_primary_nodes;
				uint64_t exposed_size;
			};
		};
	};
} __packed;

#define TWOPC_HAS_FLAGS     0x80000000 /* For packet dissectors */
#define TWOPC_HAS_REACHABLE 0x40000000 /* The reachable_nodes field is valid */
#define TWOPC_PRI_INCAPABLE 0x20000000 /* The primary has no access to data */

struct p_twopc_reply {
	uint32_t tid;  /* transaction identifier */
	uint32_t initiator_node_id;  /* initiator of the transaction */
	uint64_t reachable_nodes;

	union {
		struct { /* TWOPC_STATE_CHANGE */
			uint64_t primary_nodes;
			uint64_t weak_nodes;
		};
		struct { /* TWOPC_RESIZE */
			uint64_t diskful_primary_nodes;
			uint64_t max_possible_size;
		};
	};
} __packed;

struct p_drbd06_param {
	uint64_t size;
	uint32_t state;
	uint32_t blksize;
	uint32_t protocol;
	uint32_t version;
	uint32_t gen_cnt[5];
	uint32_t bit_map_gen[5];
} __packed;

struct p_block_desc {
	uint64_t sector;
	uint32_t blksize;
	uint32_t 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
	 */
	uint8_t encoding;

	uint8_t code[];
} __packed;

struct p_delay_probe93 {
	uint32_t seq_num; /* sequence number to match the two probe packets */
	uint32_t offset;  /* usecs the probe got sent after the reference time point */
} __packed;

struct p_dagtag {
	uint64_t dagtag;
} __packed;

struct p_peer_ack {
	uint64_t mask;
	uint64_t dagtag;
} __packed;

struct p_peer_block_desc {
	uint64_t sector;
	uint64_t mask;
	uint32_t size;
	uint32_t pad;	/* to multiple of 8 Byte */
} __packed;

struct p_peer_dagtag {
	uint64_t dagtag;
	uint32_t node_id;
} __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 */