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* QEMU Block driver for NBD
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* Copyright (C) 2008 Bull S.A.S.
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* Author: Laurent Vivier <Laurent.Vivier@bull.net>
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* Copyright (C) 2007 Anthony Liguori <anthony@codemonkey.ws>
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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#include "qemu-common.h"
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#include "qemu_socket.h"
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#include <sys/types.h>
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#define EN_OPTSTR ":exportname="
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/* #define DEBUG_NBD */
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#if defined(DEBUG_NBD)
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#define logout(fmt, ...) \
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fprintf(stderr, "nbd\t%-24s" fmt, __func__, ##__VA_ARGS__)
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#define logout(fmt, ...) ((void)0)
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typedef struct BDRVNBDState {
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char *export_name; /* An NBD server may export several devices */
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/* If it begins with '/', this is a UNIX domain socket. Otherwise,
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* it's a string of the form <hostname|ip4|\[ip6\]>:port
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static int nbd_config(BDRVNBDState *s, const char *filename, int flags)
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const char *host_spec;
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file = qemu_strdup(filename);
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export_name = strstr(file, EN_OPTSTR);
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if (export_name[strlen(EN_OPTSTR)] == 0) {
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export_name[0] = 0; /* truncate 'file' */
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export_name += strlen(EN_OPTSTR);
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s->export_name = qemu_strdup(export_name);
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/* extract the host_spec - fail if it's not nbd:... */
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if (!strstart(file, "nbd:", &host_spec)) {
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/* are we a UNIX or TCP socket? */
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if (strstart(host_spec, "unix:", &unixpath)) {
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if (unixpath[0] != '/') { /* We demand an absolute path*/
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s->host_spec = qemu_strdup(unixpath);
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s->host_spec = qemu_strdup(host_spec);
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qemu_free(s->export_name);
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qemu_free(s->host_spec);
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static int nbd_establish_connection(BlockDriverState *bs)
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BDRVNBDState *s = bs->opaque;
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if (s->host_spec[0] == '/') {
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sock = unix_socket_outgoing(s->host_spec);
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sock = tcp_socket_outgoing_spec(s->host_spec);
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/* Failed to establish connection */
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logout("Failed to establish connection to NBD server\n");
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ret = nbd_receive_negotiate(sock, s->export_name, &nbdflags, &size,
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logout("Failed to negotiate with the NBD server\n");
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/* Now that we're connected, set the socket to be non-blocking */
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socket_set_nonblock(sock);
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s->blocksize = blocksize;
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logout("Established connection with NBD server\n");
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static void nbd_teardown_connection(BlockDriverState *bs)
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BDRVNBDState *s = bs->opaque;
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struct nbd_request request;
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request.type = NBD_CMD_DISC;
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request.handle = (uint64_t)(intptr_t)bs;
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nbd_send_request(s->sock, &request);
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closesocket(s->sock);
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static int nbd_open(BlockDriverState *bs, const char* filename, int flags)
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BDRVNBDState *s = bs->opaque;
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/* Pop the config into our state object. Exit if invalid. */
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result = nbd_config(s, filename, flags);
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/* establish TCP connection, return error if it fails
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* TODO: Configurable retry-until-timeout behaviour.
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result = nbd_establish_connection(bs);
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static int nbd_read(BlockDriverState *bs, int64_t sector_num,
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uint8_t *buf, int nb_sectors)
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BDRVNBDState *s = bs->opaque;
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struct nbd_request request;
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struct nbd_reply reply;
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request.type = NBD_CMD_READ;
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request.handle = (uint64_t)(intptr_t)bs;
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request.from = sector_num * 512;;
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request.len = nb_sectors * 512;
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if (nbd_send_request(s->sock, &request) == -1)
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if (nbd_receive_reply(s->sock, &reply) == -1)
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if (reply.handle != request.handle)
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if (nbd_wr_sync(s->sock, buf, request.len, 1) != request.len)
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static int nbd_write(BlockDriverState *bs, int64_t sector_num,
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const uint8_t *buf, int nb_sectors)
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BDRVNBDState *s = bs->opaque;
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struct nbd_request request;
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struct nbd_reply reply;
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request.type = NBD_CMD_WRITE;
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request.handle = (uint64_t)(intptr_t)bs;
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request.from = sector_num * 512;;
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request.len = nb_sectors * 512;
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if (nbd_send_request(s->sock, &request) == -1)
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if (nbd_wr_sync(s->sock, (uint8_t*)buf, request.len, 0) != request.len)
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if (nbd_receive_reply(s->sock, &reply) == -1)
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if (reply.handle != request.handle)
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static void nbd_close(BlockDriverState *bs)
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BDRVNBDState *s = bs->opaque;
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qemu_free(s->export_name);
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qemu_free(s->host_spec);
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nbd_teardown_connection(bs);
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static int64_t nbd_getlength(BlockDriverState *bs)
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BDRVNBDState *s = bs->opaque;
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static BlockDriver bdrv_nbd = {
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.format_name = "nbd",
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.instance_size = sizeof(BDRVNBDState),
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.bdrv_file_open = nbd_open,
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.bdrv_read = nbd_read,
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.bdrv_write = nbd_write,
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.bdrv_close = nbd_close,
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.bdrv_getlength = nbd_getlength,
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.protocol_name = "nbd",
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static void bdrv_nbd_init(void)
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bdrv_register(&bdrv_nbd);
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block_init(bdrv_nbd_init);