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nbd: support feature negotiation 

nbd supports writing flags in bytes 24...27 of the header,
and uses that for the read-only flag.  Add support for it
in qemu-nbd.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Paolo Bonzini 2011-09-08 17:24:54 +02:00 committed by Kevin Wolf
parent 530889ff95
commit b90fb4b8f5
4 changed files with 39 additions and 19 deletions
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4
block/nbd.c
View File

@ -48,6 +48,7 @@
typedef struct BDRVNBDState {
int sock;
uint32_t nbdflags;
off_t size;
size_t blocksize;
char *export_name; /* An NBD server may export several devices */
@ -111,7 +112,6 @@ static int nbd_establish_connection(BlockDriverState *bs)
int ret;
off_t size;
size_t blocksize;
uint32_t nbdflags;
if (s->host_spec[0] == '/') {
sock = unix_socket_outgoing(s->host_spec);
@ -126,7 +126,7 @@ static int nbd_establish_connection(BlockDriverState *bs)
}
/* NBD handshake */
ret = nbd_receive_negotiate(sock, s->export_name, &nbdflags, &size,
ret = nbd_receive_negotiate(sock, s->export_name, &s->nbdflags, &size,
&blocksize);
if (ret == -1) {
logout("Failed to negotiate with the NBD server\n");

32
nbd.c
View File

@ -30,6 +30,10 @@
#include <ctype.h>
#include <inttypes.h>
#ifdef __linux__
#include <linux/fs.h>
#endif
#include "qemu_socket.h"
//#define DEBUG_NBD
@ -172,7 +176,7 @@ int unix_socket_outgoing(const char *path)
Request (type == 2)
*/
int nbd_negotiate(int csock, off_t size)
int nbd_negotiate(int csock, off_t size, uint32_t flags)
{
char buf[8 + 8 + 8 + 128];
@ -180,14 +184,16 @@ int nbd_negotiate(int csock, off_t size)
[ 0 .. 7] passwd ("NBDMAGIC")
[ 8 .. 15] magic (0x00420281861253)
[16 .. 23] size
[24 .. 151] reserved (0)
[24 .. 27] flags
[28 .. 151] reserved (0)
*/
TRACE("Beginning negotiation.");
memcpy(buf, "NBDMAGIC", 8);
cpu_to_be64w((uint64_t*)(buf + 8), 0x00420281861253LL);
cpu_to_be64w((uint64_t*)(buf + 16), size);
memset(buf + 24, 0, 128);
cpu_to_be32w((uint32_t*)(buf + 24), flags | NBD_FLAG_HAS_FLAGS);
memset(buf + 28, 0, 124);
if (write_sync(csock, buf, sizeof(buf)) != sizeof(buf)) {
LOG("write failed");
@ -337,8 +343,8 @@ int nbd_receive_negotiate(int csock, const char *name, uint32_t *flags,
return 0;
}
#ifndef _WIN32
int nbd_init(int fd, int csock, off_t size, size_t blocksize)
#ifdef __linux__
int nbd_init(int fd, int csock, uint32_t flags, off_t size, size_t blocksize)
{
TRACE("Setting block size to %lu", (unsigned long)blocksize);
@ -358,6 +364,18 @@ int nbd_init(int fd, int csock, off_t size, size_t blocksize)
return -1;
}
if (flags & NBD_FLAG_READ_ONLY) {
int read_only = 1;
TRACE("Setting readonly attribute");
if (ioctl(fd, BLKROSET, (unsigned long) &read_only) < 0) {
int serrno = errno;
LOG("Failed setting read-only attribute");
errno = serrno;
return -1;
}
}
TRACE("Clearing NBD socket");
if (ioctl(fd, NBD_CLEAR_SOCK) == -1) {
@ -548,7 +566,7 @@ static int nbd_send_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)
off_t *offset, uint32_t nbdflags, uint8_t *data, int data_size)
{
struct nbd_request request;
struct nbd_reply reply;
@ -632,7 +650,7 @@ int nbd_trip(BlockDriverState *bs, int csock, off_t size, uint64_t dev_offset,
return -1;
}
if (readonly) {
if (nbdflags & NBD_FLAG_READ_ONLY) {
TRACE("Server is read-only, return error");
reply.error = 1;
} else {

9
nbd.h
View File

@ -37,6 +37,9 @@ struct nbd_reply {
uint64_t handle;
} QEMU_PACKED;
#define NBD_FLAG_HAS_FLAGS (1 << 0) /* Flags are there */
#define NBD_FLAG_READ_ONLY (1 << 1) /* Device is read-only */
enum {
NBD_CMD_READ = 0,
NBD_CMD_WRITE = 1,
@ -53,14 +56,14 @@ int tcp_socket_incoming_spec(const char *address_and_port);
int unix_socket_outgoing(const char *path);
int unix_socket_incoming(const char *path);
int nbd_negotiate(int csock, off_t size);
int nbd_negotiate(int csock, off_t size, uint32_t flags);
int nbd_receive_negotiate(int csock, const char *name, uint32_t *flags,
off_t *size, size_t *blocksize);
int nbd_init(int fd, int csock, off_t size, size_t blocksize);
int nbd_init(int fd, int csock, uint32_t flags, 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);
off_t *offset, uint32_t nbdflags, uint8_t *data, int data_size);
int nbd_client(int fd);
int nbd_disconnect(int fd);

11
qemu-nbd.c
View File

@ -185,7 +185,7 @@ int main(int argc, char **argv)
BlockDriverState *bs;
off_t dev_offset = 0;
off_t offset = 0;
bool readonly = false;
uint32_t nbdflags = 0;
bool disconnect = false;
const char *bindto = "0.0.0.0";
int port = NBD_DEFAULT_PORT;
@ -230,7 +230,6 @@ int main(int argc, char **argv)
int nb_fds = 0;
int max_fd;
int persistent = 0;
uint32_t nbdflags;
while ((ch = getopt_long(argc, argv, sopt, lopt, &opt_ind)) != -1) {
switch (ch) {
@ -263,7 +262,7 @@ int main(int argc, char **argv)
}
break;
case 'r':
readonly = true;
nbdflags |= NBD_FLAG_READ_ONLY;
flags &= ~BDRV_O_RDWR;
break;
case 'P':
@ -404,7 +403,7 @@ int main(int argc, char **argv)
goto out;
}
ret = nbd_init(fd, sock, size, blocksize);
ret = nbd_init(fd, sock, nbdflags, size, blocksize);
if (ret == -1) {
ret = 1;
goto out;
@ -463,7 +462,7 @@ int main(int argc, char **argv)
for (i = 1; i < nb_fds && ret; i++) {
if (FD_ISSET(sharing_fds[i], &fds)) {
if (nbd_trip(bs, sharing_fds[i], fd_size, dev_offset,
&offset, readonly, data, NBD_BUFFER_SIZE) != 0) {
&offset, nbdflags, data, NBD_BUFFER_SIZE) != 0) {
close(sharing_fds[i]);
nb_fds--;
sharing_fds[i] = sharing_fds[nb_fds];
@ -479,7 +478,7 @@ int main(int argc, char **argv)
(struct sockaddr *)&addr,
&addr_len);
if (sharing_fds[nb_fds] != -1 &&
nbd_negotiate(sharing_fds[nb_fds], fd_size) != -1) {
nbd_negotiate(sharing_fds[nb_fds], fd_size, nbdflags) != -1) {
if (sharing_fds[nb_fds] > max_fd)
max_fd = sharing_fds[nb_fds];
nb_fds++;