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authorths <ths@c046a42c-6fe2-441c-8c8c-71466251a162>2008-07-03 13:41:03 +0000
committerths <ths@c046a42c-6fe2-441c-8c8c-71466251a162>2008-07-03 13:41:03 +0000
commit75818250ba0f61d9e3008b11d8c63b7b46d80ba2 (patch)
tree10fdb06f655d82a6372bf918338f3de086895452
parentAllow to share a disk image via nbd, by Laurent Vivier. (diff)
downloadqemu-kvm-75818250ba0f61d9e3008b11d8c63b7b46d80ba2.tar.gz
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Allow QEMU to connect directly to an NBD server, by Laurent Vivier.
git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@4838 c046a42c-6fe2-441c-8c8c-71466251a162
-rw-r--r--Makefile8
-rw-r--r--block-nbd.c194
-rw-r--r--block.c1
-rw-r--r--block.h1
-rw-r--r--nbd.c211
-rw-r--r--nbd.h26
-rw-r--r--qemu-doc.texi35
-rw-r--r--qemu-nbd.c10
-rw-r--r--qemu-nbd.texi2
9 files changed, 412 insertions, 76 deletions
diff --git a/Makefile b/Makefile
index aabae78cd..adb36c69e 100644
--- a/Makefile
+++ b/Makefile
@@ -42,7 +42,7 @@ recurse-all: $(SUBDIR_RULES)
BLOCK_OBJS=cutils.o qemu-malloc.o
BLOCK_OBJS+=block-cow.o block-qcow.o aes.o block-vmdk.o block-cloop.o
BLOCK_OBJS+=block-dmg.o block-bochs.o block-vpc.o block-vvfat.o
-BLOCK_OBJS+=block-qcow2.o block-parallels.o
+BLOCK_OBJS+=block-qcow2.o block-parallels.o block-nbd.o
######################################################################
# libqemu_common.a: Target independent part of system emulation. The
@@ -50,7 +50,7 @@ BLOCK_OBJS+=block-qcow2.o block-parallels.o
# system emulation, i.e. a single QEMU executable should support all
# CPUs and machines.
-OBJS=$(BLOCK_OBJS)
+OBJS=nbd.o $(BLOCK_OBJS)
OBJS+=readline.o console.o
OBJS+=block.o
@@ -159,7 +159,7 @@ libqemu_user.a: $(USER_OBJS)
rm -f $@
$(AR) rcs $@ $(USER_OBJS)
-QEMU_IMG_BLOCK_OBJS = $(BLOCK_OBJS)
+QEMU_IMG_BLOCK_OBJS = nbd.o $(BLOCK_OBJS)
ifdef CONFIG_WIN32
QEMU_IMG_BLOCK_OBJS += qemu-img-block-raw-win32.o
else
@@ -180,7 +180,7 @@ qemu-img-%.o: %.c
qemu-nbd-%.o: %.c
$(CC) $(CFLAGS) $(CPPFLAGS) -DQEMU_NBD -c -o $@ $<
-qemu-nbd$(EXESUF): qemu-nbd.o nbd.o qemu-img-block.o \
+qemu-nbd$(EXESUF): qemu-nbd.o qemu-nbd-nbd.o qemu-img-block.o \
osdep.o qemu-nbd-block-raw-posix.o $(BLOCK_OBJS)
$(CC) $(LDFLAGS) -o $@ $^ -lz $(LIBS)
diff --git a/block-nbd.c b/block-nbd.c
new file mode 100644
index 000000000..f35005015
--- /dev/null
+++ b/block-nbd.c
@@ -0,0 +1,194 @@
+/*
+ * QEMU Block driver for NBD
+ *
+ * Copyright (C) 2008 Bull S.A.S.
+ * Author: Laurent Vivier <Laurent.Vivier@bull;net>
+ *
+ * Some parts:
+ * Copyright (C) 2007 Anthony Liguori <anthony@codemonkey.ws>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "qemu-common.h"
+#include "nbd.h"
+
+#include <sys/types.h>
+#include <unistd.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+#include <pthread.h>
+
+typedef struct BDRVNBDState {
+ int sock;
+ off_t size;
+ size_t blocksize;
+} BDRVNBDState;
+
+static int nbd_open(BlockDriverState *bs, const char* filename, int flags)
+{
+ BDRVNBDState *s = bs->opaque;
+ const char *host;
+ const char *unixpath;
+ int sock;
+ off_t size;
+ size_t blocksize;
+ int ret;
+
+ if ((flags & BDRV_O_CREAT))
+ return -EINVAL;
+
+ if (!strstart(filename, "nbd:", &host))
+ return -EINVAL;
+
+ if (strstart(host, "unix:", &unixpath)) {
+
+ if (unixpath[0] != '/')
+ return -EINVAL;
+
+ sock = unix_socket_outgoing(unixpath);
+
+ } else {
+ uint16_t port;
+ char *p, *r;
+ char hostname[128];
+
+ pstrcpy(hostname, 128, host);
+
+ p = strchr(hostname, ':');
+ if (p == NULL)
+ return -EINVAL;
+
+ *p = '\0';
+ p++;
+
+ port = strtol(p, &r, 0);
+ if (r == p)
+ return -EINVAL;
+ sock = tcp_socket_outgoing(hostname, port);
+ }
+
+ if (sock == -1)
+ return -errno;
+
+ ret = nbd_receive_negotiate(sock, &size, &blocksize);
+ if (ret == -1)
+ return -errno;
+
+ s->sock = sock;
+ s->size = size;
+ s->blocksize = blocksize;
+
+ return 0;
+}
+
+static int nbd_read(BlockDriverState *bs, int64_t sector_num,
+ uint8_t *buf, int nb_sectors)
+{
+ BDRVNBDState *s = bs->opaque;
+ struct nbd_request request;
+ struct nbd_reply reply;
+
+ request.type = NBD_CMD_READ;
+ request.handle = (uint64_t)(intptr_t)bs;
+ request.from = sector_num * 512;;
+ request.len = nb_sectors * 512;
+
+ if (nbd_send_request(s->sock, &request) == -1)
+ return -errno;
+
+ if (nbd_receive_reply(s->sock, &reply) == -1)
+ return -errno;
+
+ if (reply.error !=0)
+ return -reply.error;
+
+ if (reply.handle != request.handle)
+ return -EIO;
+
+ if (nbd_wr_sync(s->sock, buf, request.len, 1) != request.len)
+ return -EIO;
+
+ return 0;
+}
+
+static int nbd_write(BlockDriverState *bs, int64_t sector_num,
+ const uint8_t *buf, int nb_sectors)
+{
+ BDRVNBDState *s = bs->opaque;
+ struct nbd_request request;
+ struct nbd_reply reply;
+
+ request.type = NBD_CMD_WRITE;
+ request.handle = (uint64_t)(intptr_t)bs;
+ request.from = sector_num * 512;;
+ request.len = nb_sectors * 512;
+
+ if (nbd_send_request(s->sock, &request) == -1)
+ return -errno;
+
+ if (nbd_wr_sync(s->sock, (uint8_t*)buf, request.len, 0) != request.len)
+ return -EIO;
+
+ if (nbd_receive_reply(s->sock, &reply) == -1)
+ return -errno;
+
+ if (reply.error !=0)
+ return -reply.error;
+
+ if (reply.handle != request.handle)
+ return -EIO;
+
+ return 0;
+}
+
+static void nbd_close(BlockDriverState *bs)
+{
+ BDRVNBDState *s = bs->opaque;
+ struct nbd_request request;
+
+ request.type = NBD_CMD_DISC;
+ request.handle = (uint64_t)(intptr_t)bs;
+ request.from = 0;
+ request.len = 0;
+ nbd_send_request(s->sock, &request);
+
+ close(s->sock);
+}
+
+static int64_t nbd_getlength(BlockDriverState *bs)
+{
+ BDRVNBDState *s = bs->opaque;
+
+ return s->size;
+}
+
+BlockDriver bdrv_nbd = {
+ "nbd",
+ sizeof(BDRVNBDState),
+ NULL, /* no probe for protocols */
+ nbd_open,
+ nbd_read,
+ nbd_write,
+ nbd_close,
+ .bdrv_getlength = nbd_getlength,
+ .protocol_name = "nbd",
+};
diff --git a/block.c b/block.c
index 2aaefe832..544176f1d 100644
--- a/block.c
+++ b/block.c
@@ -1332,6 +1332,7 @@ void bdrv_init(void)
bdrv_register(&bdrv_vvfat);
bdrv_register(&bdrv_qcow2);
bdrv_register(&bdrv_parallels);
+ bdrv_register(&bdrv_nbd);
}
void *qemu_aio_get(BlockDriverState *bs, BlockDriverCompletionFunc *cb,
diff --git a/block.h b/block.h
index e18f4532a..fa741b55a 100644
--- a/block.h
+++ b/block.h
@@ -16,6 +16,7 @@ extern BlockDriver bdrv_vpc;
extern BlockDriver bdrv_vvfat;
extern BlockDriver bdrv_qcow2;
extern BlockDriver bdrv_parallels;
+extern BlockDriver bdrv_nbd;
typedef struct BlockDriverInfo {
/* in bytes, 0 if irrelevant */
diff --git a/nbd.c b/nbd.c
index 49ee7dfad..306d1fa28 100644
--- a/nbd.c
+++ b/nbd.c
@@ -1,4 +1,4 @@
-/*\
+/*
* Copyright (C) 2005 Anthony Liguori <anthony@codemonkey.ws>
*
* Network Block Device
@@ -15,7 +15,7 @@
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
-\*/
+ */
#include "nbd.h"
@@ -31,17 +31,21 @@
#include <arpa/inet.h>
#include <netdb.h>
+#if defined(QEMU_NBD)
extern int verbose;
+#else
+static int verbose = 0;
+#endif
+
+#define TRACE(msg, ...) do { \
+ if (verbose) LOG(msg, ## __VA_ARGS__); \
+} while(0)
#define LOG(msg, ...) do { \
fprintf(stderr, "%s:%s():L%d: " msg "\n", \
__FILE__, __FUNCTION__, __LINE__, ## __VA_ARGS__); \
} while(0)
-#define TRACE(msg, ...) do { \
- if (verbose) LOG(msg, ## __VA_ARGS__); \
-} while(0)
-
/* This is all part of the "official" NBD API */
#define NBD_REQUEST_MAGIC 0x25609513
@@ -59,10 +63,10 @@ extern int verbose;
/* That's all folks */
-#define read_sync(fd, buffer, size) wr_sync(fd, buffer, size, true)
-#define write_sync(fd, buffer, size) wr_sync(fd, buffer, size, false)
+#define read_sync(fd, buffer, size) nbd_wr_sync(fd, buffer, size, true)
+#define write_sync(fd, buffer, size) nbd_wr_sync(fd, buffer, size, false)
-static size_t wr_sync(int fd, void *buffer, size_t size, bool do_read)
+size_t nbd_wr_sync(int fd, void *buffer, size_t size, bool do_read)
{
size_t offset = 0;
@@ -76,7 +80,7 @@ static size_t wr_sync(int fd, void *buffer, size_t size, bool do_read)
}
/* recoverable error */
- if (len == -1 && errno == EAGAIN) {
+ if (len == -1 && (errno == EAGAIN || errno == EINTR)) {
continue;
}
@@ -96,7 +100,7 @@ static size_t wr_sync(int fd, void *buffer, size_t size, bool do_read)
return offset;
}
-static int tcp_socket_outgoing(const char *address, uint16_t port)
+int tcp_socket_outgoing(const char *address, uint16_t port)
{
int s;
struct in_addr in;
@@ -404,16 +408,31 @@ int nbd_client(int fd, int csock)
return ret;
}
-int nbd_trip(BlockDriverState *bs, int csock, off_t size, uint64_t dev_offset,
- off_t *offset, bool readonly, uint8_t *data, int data_size)
+int nbd_send_request(int csock, struct nbd_request *request)
{
uint8_t buf[4 + 4 + 8 + 8 + 4];
- uint32_t magic;
- uint32_t type;
- uint64_t from;
- uint32_t len;
- TRACE("Reading request.");
+ cpu_to_be32w((uint32_t*)buf, NBD_REQUEST_MAGIC);
+ cpu_to_be32w((uint32_t*)(buf + 4), request->type);
+ cpu_to_be64w((uint64_t*)(buf + 8), request->handle);
+ cpu_to_be64w((uint64_t*)(buf + 16), request->from);
+ cpu_to_be32w((uint32_t*)(buf + 24), request->len);
+
+ TRACE("Sending request to client");
+
+ if (write_sync(csock, buf, sizeof(buf)) != sizeof(buf)) {
+ LOG("writing to socket failed");
+ errno = EINVAL;
+ return -1;
+ }
+ return 0;
+}
+
+
+static int nbd_receive_request(int csock, struct nbd_request *request)
+{
+ uint8_t buf[4 + 4 + 8 + 8 + 4];
+ uint32_t magic;
if (read_sync(csock, buf, sizeof(buf)) != sizeof(buf)) {
LOG("read failed");
@@ -422,97 +441,158 @@ int nbd_trip(BlockDriverState *bs, int csock, off_t size, uint64_t dev_offset,
}
/* Request
- [ 0 .. 3] magic (NBD_REQUEST_MAGIC)
- [ 4 .. 7] type (0 == READ, 1 == WRITE)
- [ 8 .. 15] handle
- [16 .. 23] from
- [24 .. 27] len
+ [ 0 .. 3] magic (NBD_REQUEST_MAGIC)
+ [ 4 .. 7] type (0 == READ, 1 == WRITE)
+ [ 8 .. 15] handle
+ [16 .. 23] from
+ [24 .. 27] len
*/
magic = be32_to_cpup((uint32_t*)buf);
- type = be32_to_cpup((uint32_t*)(buf + 4));
- from = be64_to_cpup((uint64_t*)(buf + 16));
- len = be32_to_cpup((uint32_t*)(buf + 24));
+ request->type = be32_to_cpup((uint32_t*)(buf + 4));
+ request->handle = be64_to_cpup((uint64_t*)(buf + 8));
+ request->from = be64_to_cpup((uint64_t*)(buf + 16));
+ request->len = be32_to_cpup((uint32_t*)(buf + 24));
TRACE("Got request: "
"{ magic = 0x%x, .type = %d, from = %" PRIu64" , len = %u }",
- magic, type, from, len);
-
+ magic, request->type, request->from, request->len);
if (magic != NBD_REQUEST_MAGIC) {
LOG("invalid magic (got 0x%x)", magic);
errno = EINVAL;
return -1;
}
+}
+
+int nbd_receive_reply(int csock, struct nbd_reply *reply)
+{
+ uint8_t buf[4 + 4 + 8];
+ uint32_t magic;
+
+ memset(buf, 0xAA, sizeof(buf));
+
+ if (read_sync(csock, buf, sizeof(buf)) != sizeof(buf)) {
+ LOG("read failed");
+ errno = EINVAL;
+ return -1;
+ }
+
+ /* Reply
+ [ 0 .. 3] magic (NBD_REPLY_MAGIC)
+ [ 4 .. 7] error (0 == no error)
+ [ 7 .. 15] handle
+ */
+
+ magic = be32_to_cpup((uint32_t*)buf);
+ reply->error = be32_to_cpup((uint32_t*)(buf + 4));
+ reply->handle = be64_to_cpup((uint64_t*)(buf + 8));
+
+ TRACE("Got reply: "
+ "{ magic = 0x%x, .error = %d, handle = %" PRIu64" }",
+ magic, reply->error, reply->handle);
+
+ if (magic != NBD_REPLY_MAGIC) {
+ LOG("invalid magic (got 0x%x)", magic);
+ errno = EINVAL;
+ return -1;
+ }
+ return 0;
+}
+
+static int nbd_send_reply(int csock, struct nbd_reply *reply)
+{
+ uint8_t buf[4 + 4 + 8];
+
+ /* Reply
+ [ 0 .. 3] magic (NBD_REPLY_MAGIC)
+ [ 4 .. 7] error (0 == no error)
+ [ 7 .. 15] handle
+ */
+ cpu_to_be32w((uint32_t*)buf, NBD_REPLY_MAGIC);
+ cpu_to_be32w((uint32_t*)(buf + 4), reply->error);
+ cpu_to_be64w((uint64_t*)(buf + 8), reply->handle);
+
+ TRACE("Sending response to client");
+
+ if (write_sync(csock, buf, sizeof(buf)) != sizeof(buf)) {
+ LOG("writing to socket failed");
+ errno = EINVAL;
+ return -1;
+ }
+ return 0;
+}
- if (len > data_size) {
+int nbd_trip(BlockDriverState *bs, int csock, off_t size, uint64_t dev_offset,
+ off_t *offset, bool readonly, uint8_t *data, int data_size)
+{
+ struct nbd_request request;
+ struct nbd_reply reply;
+
+ TRACE("Reading request.");
+
+ if (nbd_receive_request(csock, &request) == -1)
+ return -1;
+
+ if (request.len > data_size) {
LOG("len (%u) is larger than max len (%u)",
- len, data_size);
+ request.len, data_size);
errno = EINVAL;
return -1;
}
- if ((from + len) < from) {
+ if ((request.from + request.len) < request.from) {
LOG("integer overflow detected! "
"you're probably being attacked");
errno = EINVAL;
return -1;
}
- if ((from + len) > size) {
+ if ((request.from + request.len) > size) {
LOG("From: %" PRIu64 ", Len: %u, Size: %" PRIu64
", Offset: %" PRIu64 "\n",
- from, len, size, dev_offset);
+ request.from, request.len, size, dev_offset);
LOG("requested operation past EOF--bad client?");
errno = EINVAL;
return -1;
}
- /* Reply
- [ 0 .. 3] magic (NBD_REPLY_MAGIC)
- [ 4 .. 7] error (0 == no error)
- [ 7 .. 15] handle
- */
- cpu_to_be32w((uint32_t*)buf, NBD_REPLY_MAGIC);
- cpu_to_be32w((uint32_t*)(buf + 4), 0);
-
TRACE("Decoding type");
- switch (type) {
- case 0:
+ reply.handle = request.handle;
+ reply.error = 0;
+
+ switch (request.type) {
+ case NBD_CMD_READ:
TRACE("Request type is READ");
- if (bdrv_read(bs, (from + dev_offset) / 512, data, len / 512) == -1) {
+ if (bdrv_read(bs, (request.from + dev_offset) / 512, data,
+ request.len / 512) == -1) {
LOG("reading from file failed");
errno = EINVAL;
return -1;
}
- *offset += len;
-
- TRACE("Read %u byte(s)", len);
+ *offset += request.len;
- TRACE("Sending OK response");
+ TRACE("Read %u byte(s)", request.len);
- if (write_sync(csock, buf, 16) != 16) {
- LOG("writing to socket failed");
- errno = EINVAL;
+ if (nbd_send_reply(csock, &reply) == -1)
return -1;
- }
TRACE("Sending data to client");
- if (write_sync(csock, data, len) != len) {
+ if (write_sync(csock, data, request.len) != request.len) {
LOG("writing to socket failed");
errno = EINVAL;
return -1;
}
break;
- case 1:
+ case NBD_CMD_WRITE:
TRACE("Request type is WRITE");
- TRACE("Reading %u byte(s)", len);
+ TRACE("Reading %u byte(s)", request.len);
- if (read_sync(csock, data, len) != len) {
+ if (read_sync(csock, data, request.len) != request.len) {
LOG("reading from socket failed");
errno = EINVAL;
return -1;
@@ -520,34 +600,29 @@ int nbd_trip(BlockDriverState *bs, int csock, off_t size, uint64_t dev_offset,
if (readonly) {
TRACE("Server is read-only, return error");
-
- cpu_to_be32w((uint32_t*)(buf + 4), 1);
+ reply.error = 1;
} else {
TRACE("Writing to device");
- if (bdrv_write(bs, (from + dev_offset) / 512, data, len / 512) == -1) {
+ if (bdrv_write(bs, (request.from + dev_offset) / 512,
+ data, request.len / 512) == -1) {
LOG("writing to file failed");
errno = EINVAL;
return -1;
}
- *offset += len;
+ *offset += request.len;
}
- TRACE("Sending response to client");
-
- if (write_sync(csock, buf, 16) != 16) {
- LOG("writing to socket failed");
- errno = EINVAL;
+ if (nbd_send_reply(csock, &reply) == -1)
return -1;
- }
break;
- case 2:
+ case NBD_CMD_DISC:
TRACE("Request type is DISCONNECT");
errno = 0;
return 1;
default:
- LOG("invalid request type (%u) received", type);
+ LOG("invalid request type (%u) received", request.type);
errno = EINVAL;
return -1;
}
diff --git a/nbd.h b/nbd.h
index 01e4a6af1..55ba1ba01 100644
--- a/nbd.h
+++ b/nbd.h
@@ -1,4 +1,4 @@
-/*\
+/*
* Copyright (C) 2005 Anthony Liguori <anthony@codemonkey.ws>
*
* Network Block Device
@@ -15,7 +15,7 @@
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
-\*/
+ */
#ifndef NBD_H
#define NBD_H
@@ -26,6 +26,26 @@
#include <qemu-common.h>
#include "block_int.h"
+struct nbd_request {
+ uint32_t type;
+ uint64_t handle;
+ uint64_t from;
+ uint32_t len;
+};
+
+struct nbd_reply {
+ uint32_t error;
+ uint64_t handle;
+};
+
+enum {
+ NBD_CMD_READ = 0,
+ NBD_CMD_WRITE = 1,
+ NBD_CMD_DISC = 2
+};
+
+size_t nbd_wr_sync(int fd, void *buffer, size_t size, bool do_read);
+int tcp_socket_outgoing(const char *address, uint16_t port);
int tcp_socket_incoming(const char *address, uint16_t port);
int unix_socket_outgoing(const char *path);
int unix_socket_incoming(const char *path);
@@ -33,6 +53,8 @@ int unix_socket_incoming(const char *path);
int nbd_negotiate(BlockDriverState *bs, int csock, off_t size);
int nbd_receive_negotiate(int csock, off_t *size, size_t *blocksize);
int nbd_init(int fd, int csock, off_t size, size_t blocksize);
+int nbd_send_request(int csock, struct nbd_request *request);
+int nbd_receive_reply(int csock, struct nbd_reply *reply);
int nbd_trip(BlockDriverState *bs, int csock, off_t size, uint64_t dev_offset,
off_t *offset, bool readonly, uint8_t *data, int data_size);
int nbd_client(int fd, int csock);
diff --git a/qemu-doc.texi b/qemu-doc.texi
index 3e53d887c..ec02685fc 100644
--- a/qemu-doc.texi
+++ b/qemu-doc.texi
@@ -1321,6 +1321,7 @@ snapshots.
* qemu_nbd_invocation:: qemu-nbd Invocation
* host_drives:: Using host drives
* disk_images_fat_images:: Virtual FAT disk images
+* disk_images_nbd:: NBD access
@end menu
@node disk_images_quickstart
@@ -1503,6 +1504,40 @@ What you should @emph{never} do:
@item write to the FAT directory on the host system while accessing it with the guest system.
@end itemize
+@node disk_images_nbd
+@subsection NBD access
+
+QEMU can access directly to block device exported using the Network Block Device
+protocol.
+
+@example
+qemu linux.img -hdb nbd:my_nbd_server.mydomain.org:1024
+@end example
+
+If the NBD server is located on the same host, you can use an unix socket instead
+of an inet socket:
+
+@example
+qemu linux.img -hdb nbd:unix:/tmp/my_socket
+@end example
+
+In this case, the block device must be exported using qemu-nbd:
+
+@example
+qemu-nbd --socket=/tmp/my_socket my_disk.qcow2
+@end example
+
+The use of qemu-nbd allows to share a disk between several guests:
+@example
+qemu-nbd --socket=/tmp/my_socket --share=2 my_disk.qcow2
+@end example
+
+and then you can use it with two guests:
+@example
+qemu linux1.img -hdb nbd:unix:/tmp/my_socket
+qemu linux2.img -hdb nbd:unix:/tmp/my_socket
+@end example
+
@node pcsys_network
@section Network emulation
diff --git a/qemu-nbd.c b/qemu-nbd.c
index 605d4e324..45464a0c8 100644
--- a/qemu-nbd.c
+++ b/qemu-nbd.c
@@ -56,6 +56,7 @@ static void usage(const char *name)
" -c, --connect=DEV connect FILE to the local NBD device DEV\n"
" -d, --disconnect disconnect the specified device\n"
" -e, --shared=NUM device can be shared by NUM clients (default '1')\n"
+" -t, --persistent don't exit on the last connection\n"
" -v, --verbose display extra debugging information\n"
" -h, --help display this help and exit\n"
" -V, --version output version information and exit\n"
@@ -189,7 +190,7 @@ int main(int argc, char **argv)
char *device = NULL;
char *socket = NULL;
char sockpath[128];
- const char *sopt = "hVbo:p:rsnP:c:dvk:e:";
+ const char *sopt = "hVbo:p:rsnP:c:dvk:e:t";
struct option lopt[] = {
{ "help", 0, 0, 'h' },
{ "version", 0, 0, 'V' },
@@ -204,6 +205,7 @@ int main(int argc, char **argv)
{ "snapshot", 0, 0, 's' },
{ "nocache", 0, 0, 'n' },
{ "shared", 1, 0, 'e' },
+ { "persistent", 0, 0, 't' },
{ "verbose", 0, 0, 'v' },
{ NULL, 0, 0, 0 }
};
@@ -222,6 +224,7 @@ int main(int argc, char **argv)
int i;
int nb_fds = 0;
int max_fd;
+ int persistent = 0;
while ((ch = getopt_long(argc, argv, sopt, lopt, &opt_ind)) != -1) {
switch (ch) {
@@ -283,6 +286,9 @@ int main(int argc, char **argv)
errx(EINVAL, "Shared device number must be greater than 0\n");
}
break;
+ case 't':
+ persistent = 1;
+ break;
case 'v':
verbose = 1;
break;
@@ -459,7 +465,7 @@ int main(int argc, char **argv)
}
}
}
- } while (nb_fds > 1);
+ } while (persistent || nb_fds > 1);
qemu_free(data);
close(sharing_fds[0]);
diff --git a/qemu-nbd.texi b/qemu-nbd.texi
index b196a3471..ff2f20792 100644
--- a/qemu-nbd.texi
+++ b/qemu-nbd.texi
@@ -36,6 +36,8 @@ Export Qemu disk image using NBD protocol.
disconnect the specified device
@item -e, --shared=NUM
device can be shared by NUM clients (default '1')
+@item -t, --persistent
+ don't exit on the last connection
@item -v, --verbose
display extra debugging information
@item -h, --help