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qemu/include/block/nbd.h
Eric Blake a7c8ed36bf nbd/server: Prepare for alternate-size headers 
Upstream NBD now documents[1] an extension that supports 64-bit effect
lengths in requests.  As part of that extension, the size of the reply
headers will change in order to permit a 64-bit length in the reply
for symmetry[2].  Additionally, where the reply header is currently 16
bytes for simple reply, and 20 bytes for structured reply; with the
extension enabled, there will only be one extended reply header, of 32
bytes, with both structured and extended modes sending identical
payloads for chunked replies.

Since we are already wired up to use iovecs, it is easiest to allow
for this change in header size by splitting each structured reply
across multiple iovecs, one for the header (which will become wider in
a future patch according to client negotiation), and the other(s) for
the chunk payload, and removing the header from the payload struct
definitions.  Rename the affected functions with s/structured/chunk/
to make it obvious that the code will be reused in extended mode.

Interestingly, the client side code never utilized the packed types,
so only the server code needs to be updated.

[1] https://github.com/NetworkBlockDevice/nbd/blob/extension-ext-header/doc/proto.md
as of NBD commit e6f3b94a934

[2] Note that on the surface, this is because some future server might
permit a 4G+ NBD_CMD_READ and need to reply with that much data in one
transaction.  But even though the extended reply length is widened to
64 bits, for now the NBD spec is clear that servers will not reply
with more than a maximum payload bounded by the 32-bit
NBD_INFO_BLOCK_SIZE field; allowing a client and server to mutually
agree to transactions larger than 4G would require yet another
extension.

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-ID: <20230608135653.2918540-4-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
2023-07-19 15:25:27 -05:00

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/*
* Copyright Red Hat
* Copyright (C) 2005 Anthony Liguori <anthony@codemonkey.ws>
*
* Network Block Device
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; under version 2 of the License.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, see <http://www.gnu.org/licenses/>.
*/
#ifndef NBD_H
#define NBD_H
#include "block/export.h"
#include "io/channel-socket.h"
#include "crypto/tlscreds.h"
#include "qapi/error.h"
#include "qemu/bswap.h"
typedef struct NBDExport NBDExport;
typedef struct NBDClient NBDClient;
typedef struct NBDClientConnection NBDClientConnection;
extern const BlockExportDriver blk_exp_nbd;
/* Handshake phase structs - this struct is passed on the wire */
typedef struct NBDOption {
uint64_t magic; /* NBD_OPTS_MAGIC */
uint32_t option; /* NBD_OPT_* */
uint32_t length;
} QEMU_PACKED NBDOption;
typedef struct NBDOptionReply {
uint64_t magic; /* NBD_REP_MAGIC */
uint32_t option; /* NBD_OPT_* */
uint32_t type; /* NBD_REP_* */
uint32_t length;
} QEMU_PACKED NBDOptionReply;
typedef struct NBDOptionReplyMetaContext {
NBDOptionReply h; /* h.type = NBD_REP_META_CONTEXT, h.length > 4 */
uint32_t context_id;
/* metadata context name follows */
} QEMU_PACKED NBDOptionReplyMetaContext;
/* Transmission phase structs
*
* Note: these are _NOT_ the same as the network representation of an NBD
* request and reply!
*/
typedef struct NBDRequest {
uint64_t handle;
uint64_t from;
uint32_t len;
uint16_t flags; /* NBD_CMD_FLAG_* */
uint16_t type; /* NBD_CMD_* */
} NBDRequest;
typedef struct NBDSimpleReply {
uint32_t magic; /* NBD_SIMPLE_REPLY_MAGIC */
uint32_t error;
uint64_t handle;
} QEMU_PACKED NBDSimpleReply;
/* Header of all structured replies */
typedef struct NBDStructuredReplyChunk {
uint32_t magic; /* NBD_STRUCTURED_REPLY_MAGIC */
uint16_t flags; /* combination of NBD_REPLY_FLAG_* */
uint16_t type; /* NBD_REPLY_TYPE_* */
uint64_t handle; /* request handle */
uint32_t length; /* length of payload */
} QEMU_PACKED NBDStructuredReplyChunk;
typedef union NBDReply {
NBDSimpleReply simple;
NBDStructuredReplyChunk structured;
struct {
/* @magic and @handle fields have the same offset and size both in
* simple reply and structured reply chunk, so let them be accessible
* without ".simple." or ".structured." specification
*/
uint32_t magic;
uint32_t _skip;
uint64_t handle;
} QEMU_PACKED;
} NBDReply;
/* Header of chunk for NBD_REPLY_TYPE_OFFSET_DATA */
typedef struct NBDStructuredReadData {
/* header's .length >= 9 */
uint64_t offset;
/* At least one byte of data payload follows, calculated from h.length */
} QEMU_PACKED NBDStructuredReadData;
/* Complete chunk for NBD_REPLY_TYPE_OFFSET_HOLE */
typedef struct NBDStructuredReadHole {
/* header's length == 12 */
uint64_t offset;
uint32_t length;
} QEMU_PACKED NBDStructuredReadHole;
/* Header of all NBD_REPLY_TYPE_ERROR* errors */
typedef struct NBDStructuredError {
/* header's length >= 6 */
uint32_t error;
uint16_t message_length;
} QEMU_PACKED NBDStructuredError;
/* Header of NBD_REPLY_TYPE_BLOCK_STATUS */
typedef struct NBDStructuredMeta {
/* header's length >= 12 (at least one extent) */
uint32_t context_id;
/* extents follows */
} QEMU_PACKED NBDStructuredMeta;
/* Extent chunk for NBD_REPLY_TYPE_BLOCK_STATUS */
typedef struct NBDExtent {
uint32_t length;
uint32_t flags; /* NBD_STATE_* */
} QEMU_PACKED NBDExtent;
/* Transmission (export) flags: sent from server to client during handshake,
but describe what will happen during transmission */
enum {
NBD_FLAG_HAS_FLAGS_BIT = 0, /* Flags are there */
NBD_FLAG_READ_ONLY_BIT = 1, /* Device is read-only */
NBD_FLAG_SEND_FLUSH_BIT = 2, /* Send FLUSH */
NBD_FLAG_SEND_FUA_BIT = 3, /* Send FUA (Force Unit Access) */
NBD_FLAG_ROTATIONAL_BIT = 4, /* Use elevator algorithm -
rotational media */
NBD_FLAG_SEND_TRIM_BIT = 5, /* Send TRIM (discard) */
NBD_FLAG_SEND_WRITE_ZEROES_BIT = 6, /* Send WRITE_ZEROES */
NBD_FLAG_SEND_DF_BIT = 7, /* Send DF (Do not Fragment) */
NBD_FLAG_CAN_MULTI_CONN_BIT = 8, /* Multi-client cache consistent */
NBD_FLAG_SEND_RESIZE_BIT = 9, /* Send resize */
NBD_FLAG_SEND_CACHE_BIT = 10, /* Send CACHE (prefetch) */
NBD_FLAG_SEND_FAST_ZERO_BIT = 11, /* FAST_ZERO flag for WRITE_ZEROES */
};
#define NBD_FLAG_HAS_FLAGS (1 << NBD_FLAG_HAS_FLAGS_BIT)
#define NBD_FLAG_READ_ONLY (1 << NBD_FLAG_READ_ONLY_BIT)
#define NBD_FLAG_SEND_FLUSH (1 << NBD_FLAG_SEND_FLUSH_BIT)
#define NBD_FLAG_SEND_FUA (1 << NBD_FLAG_SEND_FUA_BIT)
#define NBD_FLAG_ROTATIONAL (1 << NBD_FLAG_ROTATIONAL_BIT)
#define NBD_FLAG_SEND_TRIM (1 << NBD_FLAG_SEND_TRIM_BIT)
#define NBD_FLAG_SEND_WRITE_ZEROES (1 << NBD_FLAG_SEND_WRITE_ZEROES_BIT)
#define NBD_FLAG_SEND_DF (1 << NBD_FLAG_SEND_DF_BIT)
#define NBD_FLAG_CAN_MULTI_CONN (1 << NBD_FLAG_CAN_MULTI_CONN_BIT)
#define NBD_FLAG_SEND_RESIZE (1 << NBD_FLAG_SEND_RESIZE_BIT)
#define NBD_FLAG_SEND_CACHE (1 << NBD_FLAG_SEND_CACHE_BIT)
#define NBD_FLAG_SEND_FAST_ZERO (1 << NBD_FLAG_SEND_FAST_ZERO_BIT)
/* New-style handshake (global) flags, sent from server to client, and
control what will happen during handshake phase. */
#define NBD_FLAG_FIXED_NEWSTYLE (1 << 0) /* Fixed newstyle protocol. */
#define NBD_FLAG_NO_ZEROES (1 << 1) /* End handshake without zeroes. */
/* New-style client flags, sent from client to server to control what happens
during handshake phase. */
#define NBD_FLAG_C_FIXED_NEWSTYLE (1 << 0) /* Fixed newstyle protocol. */
#define NBD_FLAG_C_NO_ZEROES (1 << 1) /* End handshake without zeroes. */
/* Option requests. */
#define NBD_OPT_EXPORT_NAME (1)
#define NBD_OPT_ABORT (2)
#define NBD_OPT_LIST (3)
/* #define NBD_OPT_PEEK_EXPORT (4) not in use */
#define NBD_OPT_STARTTLS (5)
#define NBD_OPT_INFO (6)
#define NBD_OPT_GO (7)
#define NBD_OPT_STRUCTURED_REPLY (8)
#define NBD_OPT_LIST_META_CONTEXT (9)
#define NBD_OPT_SET_META_CONTEXT (10)
/* Option reply types. */
#define NBD_REP_ERR(value) ((UINT32_C(1) << 31) | (value))
#define NBD_REP_ACK (1) /* Data sending finished. */
#define NBD_REP_SERVER (2) /* Export description. */
#define NBD_REP_INFO (3) /* NBD_OPT_INFO/GO. */
#define NBD_REP_META_CONTEXT (4) /* NBD_OPT_{LIST,SET}_META_CONTEXT */
#define NBD_REP_ERR_UNSUP NBD_REP_ERR(1) /* Unknown option */
#define NBD_REP_ERR_POLICY NBD_REP_ERR(2) /* Server denied */
#define NBD_REP_ERR_INVALID NBD_REP_ERR(3) /* Invalid length */
#define NBD_REP_ERR_PLATFORM NBD_REP_ERR(4) /* Not compiled in */
#define NBD_REP_ERR_TLS_REQD NBD_REP_ERR(5) /* TLS required */
#define NBD_REP_ERR_UNKNOWN NBD_REP_ERR(6) /* Export unknown */
#define NBD_REP_ERR_SHUTDOWN NBD_REP_ERR(7) /* Server shutting down */
#define NBD_REP_ERR_BLOCK_SIZE_REQD NBD_REP_ERR(8) /* Need INFO_BLOCK_SIZE */
/* Info types, used during NBD_REP_INFO */
#define NBD_INFO_EXPORT 0
#define NBD_INFO_NAME 1
#define NBD_INFO_DESCRIPTION 2
#define NBD_INFO_BLOCK_SIZE 3
/* Request flags, sent from client to server during transmission phase */
#define NBD_CMD_FLAG_FUA (1 << 0) /* 'force unit access' during write */
#define NBD_CMD_FLAG_NO_HOLE (1 << 1) /* don't punch hole on zero run */
#define NBD_CMD_FLAG_DF (1 << 2) /* don't fragment structured read */
#define NBD_CMD_FLAG_REQ_ONE (1 << 3) /* only one extent in BLOCK_STATUS
* reply chunk */
#define NBD_CMD_FLAG_FAST_ZERO (1 << 4) /* fail if WRITE_ZEROES is not fast */
/* Supported request types */
enum {
NBD_CMD_READ = 0,
NBD_CMD_WRITE = 1,
NBD_CMD_DISC = 2,
NBD_CMD_FLUSH = 3,
NBD_CMD_TRIM = 4,
NBD_CMD_CACHE = 5,
NBD_CMD_WRITE_ZEROES = 6,
NBD_CMD_BLOCK_STATUS = 7,
};
#define NBD_DEFAULT_PORT 10809
/* Maximum size of a single READ/WRITE data buffer */
#define NBD_MAX_BUFFER_SIZE (32 * 1024 * 1024)
/*
* Maximum size of a protocol string (export name, metadata context name,
* etc.). Use malloc rather than stack allocation for storage of a
* string.
*/
#define NBD_MAX_STRING_SIZE 4096
/* Two types of reply structures */
#define NBD_SIMPLE_REPLY_MAGIC 0x67446698
#define NBD_STRUCTURED_REPLY_MAGIC 0x668e33ef
/* Structured reply flags */
#define NBD_REPLY_FLAG_DONE (1 << 0) /* This reply-chunk is last */
/* Structured reply types */
#define NBD_REPLY_ERR(value) ((1 << 15) | (value))
#define NBD_REPLY_TYPE_NONE 0
#define NBD_REPLY_TYPE_OFFSET_DATA 1
#define NBD_REPLY_TYPE_OFFSET_HOLE 2
#define NBD_REPLY_TYPE_BLOCK_STATUS 5
#define NBD_REPLY_TYPE_ERROR NBD_REPLY_ERR(1)
#define NBD_REPLY_TYPE_ERROR_OFFSET NBD_REPLY_ERR(2)
/* Extent flags for base:allocation in NBD_REPLY_TYPE_BLOCK_STATUS */
#define NBD_STATE_HOLE (1 << 0)
#define NBD_STATE_ZERO (1 << 1)
/* Extent flags for qemu:dirty-bitmap in NBD_REPLY_TYPE_BLOCK_STATUS */
#define NBD_STATE_DIRTY (1 << 0)
/* No flags needed for qemu:allocation-depth in NBD_REPLY_TYPE_BLOCK_STATUS */
static inline bool nbd_reply_type_is_error(int type)
{
return type & (1 << 15);
}
/* NBD errors are based on errno numbers, so there is a 1:1 mapping,
* but only a limited set of errno values is specified in the protocol.
* Everything else is squashed to EINVAL.
*/
#define NBD_SUCCESS 0
#define NBD_EPERM 1
#define NBD_EIO 5
#define NBD_ENOMEM 12
#define NBD_EINVAL 22
#define NBD_ENOSPC 28
#define NBD_EOVERFLOW 75
#define NBD_ENOTSUP 95
#define NBD_ESHUTDOWN 108
/* Details collected by NBD_OPT_EXPORT_NAME and NBD_OPT_GO */
typedef struct NBDExportInfo {
/* Set by client before nbd_receive_negotiate() */
bool request_sizes;
char *x_dirty_bitmap;
/* Set by client before nbd_receive_negotiate(), or by server results
* during nbd_receive_export_list() */
char *name; /* must be non-NULL */
/* In-out fields, set by client before nbd_receive_negotiate() and
* updated by server results during nbd_receive_negotiate() */
bool structured_reply;
bool base_allocation; /* base:allocation context for NBD_CMD_BLOCK_STATUS */
/* Set by server results during nbd_receive_negotiate() and
* nbd_receive_export_list() */
uint64_t size;
uint16_t flags;
uint32_t min_block;
uint32_t opt_block;
uint32_t max_block;
uint32_t context_id;
/* Set by server results during nbd_receive_export_list() */
char *description;
int n_contexts;
char **contexts;
} NBDExportInfo;
int nbd_receive_negotiate(AioContext *aio_context, QIOChannel *ioc,
QCryptoTLSCreds *tlscreds,
const char *hostname, QIOChannel **outioc,
NBDExportInfo *info, Error **errp);
void nbd_free_export_list(NBDExportInfo *info, int count);
int nbd_receive_export_list(QIOChannel *ioc, QCryptoTLSCreds *tlscreds,
const char *hostname, NBDExportInfo **info,
Error **errp);
int nbd_init(int fd, QIOChannelSocket *sioc, NBDExportInfo *info,
Error **errp);
int nbd_send_request(QIOChannel *ioc, NBDRequest *request);
int coroutine_fn nbd_receive_reply(BlockDriverState *bs, QIOChannel *ioc,
NBDReply *reply, Error **errp);
int nbd_client(int fd);
int nbd_disconnect(int fd);
int nbd_errno_to_system_errno(int err);
void nbd_export_set_on_eject_blk(BlockExport *exp, BlockBackend *blk);
AioContext *nbd_export_aio_context(NBDExport *exp);
NBDExport *nbd_export_find(const char *name);
void nbd_client_new(QIOChannelSocket *sioc,
QCryptoTLSCreds *tlscreds,
const char *tlsauthz,
void (*close_fn)(NBDClient *, bool));
void nbd_client_get(NBDClient *client);
void nbd_client_put(NBDClient *client);
void nbd_server_is_qemu_nbd(int max_connections);
bool nbd_server_is_running(void);
int nbd_server_max_connections(void);
void nbd_server_start(SocketAddress *addr, const char *tls_creds,
const char *tls_authz, uint32_t max_connections,
Error **errp);
void nbd_server_start_options(NbdServerOptions *arg, Error **errp);
/* nbd_read
* Reads @size bytes from @ioc. Returns 0 on success.
*/
static inline int nbd_read(QIOChannel *ioc, void *buffer, size_t size,
const char *desc, Error **errp)
{
ERRP_GUARD();
int ret = qio_channel_read_all(ioc, buffer, size, errp) < 0 ? -EIO : 0;
if (ret < 0) {
if (desc) {
error_prepend(errp, "Failed to read %s: ", desc);
}
return ret;
}
return 0;
}
#define DEF_NBD_READ_N(bits) \
static inline int nbd_read##bits(QIOChannel *ioc, \
uint##bits##_t *val, \
const char *desc, Error **errp) \
{ \
int ret = nbd_read(ioc, val, sizeof(*val), desc, errp); \
if (ret < 0) { \
return ret; \
} \
*val = be##bits##_to_cpu(*val); \
return 0; \
}
DEF_NBD_READ_N(16) /* Defines nbd_read16(). */
DEF_NBD_READ_N(32) /* Defines nbd_read32(). */
DEF_NBD_READ_N(64) /* Defines nbd_read64(). */
#undef DEF_NBD_READ_N
static inline bool nbd_reply_is_simple(NBDReply *reply)
{
return reply->magic == NBD_SIMPLE_REPLY_MAGIC;
}
static inline bool nbd_reply_is_structured(NBDReply *reply)
{
return reply->magic == NBD_STRUCTURED_REPLY_MAGIC;
}
const char *nbd_reply_type_lookup(uint16_t type);
const char *nbd_opt_lookup(uint32_t opt);
const char *nbd_rep_lookup(uint32_t rep);
const char *nbd_info_lookup(uint16_t info);
const char *nbd_cmd_lookup(uint16_t info);
const char *nbd_err_lookup(int err);
/* nbd/client-connection.c */
void nbd_client_connection_enable_retry(NBDClientConnection *conn);
NBDClientConnection *nbd_client_connection_new(const SocketAddress *saddr,
bool do_negotiation,
const char *export_name,
const char *x_dirty_bitmap,
QCryptoTLSCreds *tlscreds,
const char *tlshostname);
void nbd_client_connection_release(NBDClientConnection *conn);
QIOChannel *coroutine_fn
nbd_co_establish_connection(NBDClientConnection *conn, NBDExportInfo *info,
bool blocking, Error **errp);
void nbd_co_establish_connection_cancel(NBDClientConnection *conn);
#endif
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