xref: /linux/drivers/block/drbd/drbd_protocol.h (revision 7ae9fb1b7ecbb5d85d07857943f677fd1a559b18)
1  /* SPDX-License-Identifier: GPL-2.0-only */
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  	struct_group(algs,
287  		char verify_alg[SHARED_SECRET_MAX];
288  		char csums_alg[SHARED_SECRET_MAX];
289  	);
290  	u32 c_plan_ahead;
291  	u32 c_delay_target;
292  	u32 c_fill_target;
293  	u32 c_max_rate;
294  } __packed;
295  
296  enum drbd_conn_flags {
297  	CF_DISCARD_MY_DATA = 1,
298  	CF_DRY_RUN = 2,
299  };
300  
301  struct p_protocol {
302  	u32 protocol;
303  	u32 after_sb_0p;
304  	u32 after_sb_1p;
305  	u32 after_sb_2p;
306  	u32 conn_flags;
307  	u32 two_primaries;
308  
309  	/* Since protocol version 87 and higher. */
310  	char integrity_alg[];
311  
312  } __packed;
313  
314  struct p_uuids {
315  	u64 uuid[UI_EXTENDED_SIZE];
316  } __packed;
317  
318  struct p_rs_uuid {
319  	u64	    uuid;
320  } __packed;
321  
322  /* optional queue_limits if (agreed_features & DRBD_FF_WSAME)
323   * see also struct queue_limits, as of late 2015 */
324  struct o_qlim {
325  	/* we don't need it yet, but we may as well communicate it now */
326  	u32 physical_block_size;
327  
328  	/* so the original in struct queue_limits is unsigned short,
329  	 * but I'd have to put in padding anyways. */
330  	u32 logical_block_size;
331  
332  	/* One incoming bio becomes one DRBD request,
333  	 * which may be translated to several bio on the receiving side.
334  	 * We don't need to communicate chunk/boundary/segment ... limits.
335  	 */
336  
337  	/* various IO hints may be useful with "diskless client" setups */
338  	u32 alignment_offset;
339  	u32 io_min;
340  	u32 io_opt;
341  
342  	/* We may need to communicate integrity stuff at some point,
343  	 * but let's not get ahead of ourselves. */
344  
345  	/* Backend discard capabilities.
346  	 * Receiving side uses "blkdev_issue_discard()", no need to communicate
347  	 * more specifics.  If the backend cannot do discards, the DRBD peer
348  	 * may fall back to blkdev_issue_zeroout().
349  	 */
350  	u8 discard_enabled;
351  	u8 discard_zeroes_data;
352  	u8 write_same_capable;
353  	u8 _pad;
354  } __packed;
355  
356  struct p_sizes {
357  	u64	    d_size;  /* size of disk */
358  	u64	    u_size;  /* user requested size */
359  	u64	    c_size;  /* current exported size */
360  	u32	    max_bio_size;  /* Maximal size of a BIO */
361  	u16	    queue_order_type;  /* not yet implemented in DRBD*/
362  	u16	    dds_flags; /* use enum dds_flags here. */
363  
364  	/* optional queue_limits if (agreed_features & DRBD_FF_WSAME) */
365  	struct o_qlim qlim[];
366  } __packed;
367  
368  struct p_state {
369  	u32	    state;
370  } __packed;
371  
372  struct p_req_state {
373  	u32	    mask;
374  	u32	    val;
375  } __packed;
376  
377  struct p_req_state_reply {
378  	u32	    retcode;
379  } __packed;
380  
381  struct p_drbd06_param {
382  	u64	  size;
383  	u32	  state;
384  	u32	  blksize;
385  	u32	  protocol;
386  	u32	  version;
387  	u32	  gen_cnt[5];
388  	u32	  bit_map_gen[5];
389  } __packed;
390  
391  struct p_block_desc {
392  	u64 sector;
393  	u32 blksize;
394  	u32 pad;	/* to multiple of 8 Byte */
395  } __packed;
396  
397  /* Valid values for the encoding field.
398   * Bump proto version when changing this. */
399  enum drbd_bitmap_code {
400  	/* RLE_VLI_Bytes = 0,
401  	 * and other bit variants had been defined during
402  	 * algorithm evaluation. */
403  	RLE_VLI_Bits = 2,
404  };
405  
406  struct p_compressed_bm {
407  	/* (encoding & 0x0f): actual encoding, see enum drbd_bitmap_code
408  	 * (encoding & 0x80): polarity (set/unset) of first runlength
409  	 * ((encoding >> 4) & 0x07): pad_bits, number of trailing zero bits
410  	 * used to pad up to head.length bytes
411  	 */
412  	u8 encoding;
413  
414  	u8 code[];
415  } __packed;
416  
417  struct p_delay_probe93 {
418  	u32     seq_num; /* sequence number to match the two probe packets */
419  	u32     offset;  /* usecs the probe got sent after the reference time point */
420  } __packed;
421  
422  /*
423   * Bitmap packets need to fit within a single page on the sender and receiver,
424   * so we are limited to 4 KiB (and not to PAGE_SIZE, which can be bigger).
425   */
426  #define DRBD_SOCKET_BUFFER_SIZE 4096
427  
428  #endif  /* __DRBD_PROTOCOL_H */
429