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nbd: support feature negotiation

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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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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 {