1f4d6d18ed
Upstream NBD protocol recently added the ability to efficiently write zeroes without having to send the zeroes over the wire, along with a flag to control whether the client wants to allow a hole. Note that when it comes to requiring full allocation, vs. permitting optimizations, the NBD spec intentionally picked a different sense for the flag; the rules in qemu are: MAY_UNMAP == 0: must write zeroes MAY_UNMAP == 1: may use holes if reads will see zeroes while in NBD, the rules are: FLAG_NO_HOLE == 1: must write zeroes FLAG_NO_HOLE == 0: may use holes if reads will see zeroes In all cases, the 'may use holes' scenario is optional (the server need not use a hole, and must not use a hole if subsequent reads would not see zeroes). Signed-off-by: Eric Blake <eblake@redhat.com> Message-Id: <1476469998-28592-16-git-send-email-eblake@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
168 lines
6.2 KiB
C
168 lines
6.2 KiB
C
/*
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* Copyright (C) 2016 Red Hat, Inc.
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* Copyright (C) 2005 Anthony Liguori <anthony@codemonkey.ws>
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*
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* Network Block Device
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; under version 2 of the License.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef NBD_H
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#define NBD_H
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#include "qemu-common.h"
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#include "qemu/option.h"
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#include "io/channel-socket.h"
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#include "crypto/tlscreds.h"
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/* Handshake phase structs - this struct is passed on the wire */
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struct nbd_option {
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uint64_t magic; /* NBD_OPTS_MAGIC */
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uint32_t option; /* NBD_OPT_* */
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uint32_t length;
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} QEMU_PACKED;
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typedef struct nbd_option nbd_option;
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struct nbd_opt_reply {
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uint64_t magic; /* NBD_REP_MAGIC */
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uint32_t option; /* NBD_OPT_* */
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uint32_t type; /* NBD_REP_* */
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uint32_t length;
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} QEMU_PACKED;
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typedef struct nbd_opt_reply nbd_opt_reply;
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/* Transmission phase structs
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*
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* Note: these are _NOT_ the same as the network representation of an NBD
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* request and reply!
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*/
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struct NBDRequest {
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uint64_t handle;
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uint64_t from;
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uint32_t len;
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uint16_t flags; /* NBD_CMD_FLAG_* */
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uint16_t type; /* NBD_CMD_* */
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};
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typedef struct NBDRequest NBDRequest;
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struct NBDReply {
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uint64_t handle;
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uint32_t error;
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};
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typedef struct NBDReply NBDReply;
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/* Transmission (export) flags: sent from server to client during handshake,
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but describe what will happen during transmission */
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#define NBD_FLAG_HAS_FLAGS (1 << 0) /* Flags are there */
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#define NBD_FLAG_READ_ONLY (1 << 1) /* Device is read-only */
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#define NBD_FLAG_SEND_FLUSH (1 << 2) /* Send FLUSH */
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#define NBD_FLAG_SEND_FUA (1 << 3) /* Send FUA (Force Unit Access) */
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#define NBD_FLAG_ROTATIONAL (1 << 4) /* Use elevator algorithm - rotational media */
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#define NBD_FLAG_SEND_TRIM (1 << 5) /* Send TRIM (discard) */
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#define NBD_FLAG_SEND_WRITE_ZEROES (1 << 6) /* Send WRITE_ZEROES */
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/* New-style handshake (global) flags, sent from server to client, and
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control what will happen during handshake phase. */
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#define NBD_FLAG_FIXED_NEWSTYLE (1 << 0) /* Fixed newstyle protocol. */
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#define NBD_FLAG_NO_ZEROES (1 << 1) /* End handshake without zeroes. */
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/* New-style client flags, sent from client to server to control what happens
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during handshake phase. */
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#define NBD_FLAG_C_FIXED_NEWSTYLE (1 << 0) /* Fixed newstyle protocol. */
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#define NBD_FLAG_C_NO_ZEROES (1 << 1) /* End handshake without zeroes. */
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/* Reply types. */
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#define NBD_REP_ERR(value) ((UINT32_C(1) << 31) | (value))
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#define NBD_REP_ACK (1) /* Data sending finished. */
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#define NBD_REP_SERVER (2) /* Export description. */
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#define NBD_REP_ERR_UNSUP NBD_REP_ERR(1) /* Unknown option */
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#define NBD_REP_ERR_POLICY NBD_REP_ERR(2) /* Server denied */
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#define NBD_REP_ERR_INVALID NBD_REP_ERR(3) /* Invalid length */
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#define NBD_REP_ERR_PLATFORM NBD_REP_ERR(4) /* Not compiled in */
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#define NBD_REP_ERR_TLS_REQD NBD_REP_ERR(5) /* TLS required */
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#define NBD_REP_ERR_SHUTDOWN NBD_REP_ERR(7) /* Server shutting down */
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/* Request flags, sent from client to server during transmission phase */
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#define NBD_CMD_FLAG_FUA (1 << 0) /* 'force unit access' during write */
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#define NBD_CMD_FLAG_NO_HOLE (1 << 1) /* don't punch hole on zero run */
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/* Supported request types */
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enum {
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NBD_CMD_READ = 0,
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NBD_CMD_WRITE = 1,
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NBD_CMD_DISC = 2,
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NBD_CMD_FLUSH = 3,
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NBD_CMD_TRIM = 4,
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/* 5 reserved for failed experiment NBD_CMD_CACHE */
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NBD_CMD_WRITE_ZEROES = 6,
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};
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#define NBD_DEFAULT_PORT 10809
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/* Maximum size of a single READ/WRITE data buffer */
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#define NBD_MAX_BUFFER_SIZE (32 * 1024 * 1024)
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/* Maximum size of an export name. The NBD spec requires 256 and
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* suggests that servers support up to 4096, but we stick to only the
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* required size so that we can stack-allocate the names, and because
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* going larger would require an audit of more code to make sure we
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* aren't overflowing some other buffer. */
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#define NBD_MAX_NAME_SIZE 256
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ssize_t nbd_wr_syncv(QIOChannel *ioc,
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struct iovec *iov,
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size_t niov,
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size_t length,
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bool do_read);
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int nbd_receive_negotiate(QIOChannel *ioc, const char *name, uint16_t *flags,
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QCryptoTLSCreds *tlscreds, const char *hostname,
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QIOChannel **outioc,
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off_t *size, Error **errp);
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int nbd_init(int fd, QIOChannelSocket *sioc, uint16_t flags, off_t size);
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ssize_t nbd_send_request(QIOChannel *ioc, NBDRequest *request);
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ssize_t nbd_receive_reply(QIOChannel *ioc, NBDReply *reply);
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int nbd_client(int fd);
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int nbd_disconnect(int fd);
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typedef struct NBDExport NBDExport;
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typedef struct NBDClient NBDClient;
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NBDExport *nbd_export_new(BlockDriverState *bs, off_t dev_offset, off_t size,
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uint16_t nbdflags, void (*close)(NBDExport *),
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bool writethrough, BlockBackend *on_eject_blk,
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Error **errp);
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void nbd_export_close(NBDExport *exp);
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void nbd_export_get(NBDExport *exp);
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void nbd_export_put(NBDExport *exp);
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BlockBackend *nbd_export_get_blockdev(NBDExport *exp);
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NBDExport *nbd_export_find(const char *name);
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void nbd_export_set_name(NBDExport *exp, const char *name);
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void nbd_export_set_description(NBDExport *exp, const char *description);
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void nbd_export_close_all(void);
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void nbd_client_new(NBDExport *exp,
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QIOChannelSocket *sioc,
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QCryptoTLSCreds *tlscreds,
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const char *tlsaclname,
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void (*close)(NBDClient *));
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void nbd_client_get(NBDClient *client);
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void nbd_client_put(NBDClient *client);
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#endif
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