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xemu/nbd.c
Paolo Bonzini ca44148041 qemu-nbd: only send a limited number of errno codes on the wire 
Right now, NBD includes potentially platform-specific error values in
the wire protocol.

Luckily, most common error values are more or less universal: in
particular, of all errno values <= 34 (up to ERANGE), they are all the
same on supported platforms except for 11 (which is EAGAIN on Windows and
Linux, but EDEADLK on Darwin and the *BSDs).  So, in order to guarantee
some portability, only keep a handful of possible error codes and squash
everything else to EINVAL.

This patch defines a limited set of errno values that are valid for the
NBD protocol, and specifies recommendations for what error to return
in specific corner cases.  The set of errno values is roughly based on
the errors listed in the read(2) and write(2) man pages, with some
exceptions:

- ENOMEM is added for servers that implement copy-on-write or other
  formats that require dynamic allocation.

- EDQUOT is not part of the universal set of errors; it can be changed
  to ENOSPC on the wire format.

- EFBIG is part of the universal set of errors, but it is also changed
  to ENOSPC because it is pretty similar to ENOSPC or EDQUOT.

Incoming values will in general match system errno values, but not
on the Hurd which has different errno values (they have a "subsystem
code" equal to 0x10 in bits 24-31).  The Hurd is probably not something
to which QEMU has been ported, but still do the right thing and
reverse-map the NBD errno values to the system errno values.

The corresponding patch to the NBD protocol description can be found at
http://article.gmane.org/gmane.linux.drivers.nbd.general/3154.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2015-05-08 14:45:11 +02:00

1490 lines
37 KiB
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/*
* Copyright (C) 2005 Anthony Liguori <anthony@codemonkey.ws>
*
* Network Block Device
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; under version 2 of the License.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, see <http://www.gnu.org/licenses/>.
*/
#include "block/nbd.h"
#include "sysemu/block-backend.h"
#include "block/coroutine.h"
#include <errno.h>
#include <string.h>
#ifndef _WIN32
#include <sys/ioctl.h>
#endif
#if defined(__sun__) || defined(__HAIKU__)
#include <sys/ioccom.h>
#endif
#include <ctype.h>
#include <inttypes.h>
#ifdef __linux__
#include <linux/fs.h>
#endif
#include "qemu/sockets.h"
#include "qemu/queue.h"
#include "qemu/main-loop.h"
//#define DEBUG_NBD
#ifdef DEBUG_NBD
#define TRACE(msg, ...) do { \
LOG(msg, ## __VA_ARGS__); \
} while(0)
#else
#define TRACE(msg, ...) \
do { } while (0)
#endif
#define LOG(msg, ...) do { \
fprintf(stderr, "%s:%s():L%d: " msg "\n", \
__FILE__, __FUNCTION__, __LINE__, ## __VA_ARGS__); \
} while(0)
/* This is all part of the "official" NBD API.
*
* The most up-to-date documentation is available at:
* https://github.com/yoe/nbd/blob/master/doc/proto.txt
*/
#define NBD_REQUEST_SIZE (4 + 4 + 8 + 8 + 4)
#define NBD_REPLY_SIZE (4 + 4 + 8)
#define NBD_REQUEST_MAGIC 0x25609513
#define NBD_REPLY_MAGIC 0x67446698
#define NBD_OPTS_MAGIC 0x49484156454F5054LL
#define NBD_CLIENT_MAGIC 0x0000420281861253LL
#define NBD_REP_MAGIC 0x3e889045565a9LL
#define NBD_SET_SOCK _IO(0xab, 0)
#define NBD_SET_BLKSIZE _IO(0xab, 1)
#define NBD_SET_SIZE _IO(0xab, 2)
#define NBD_DO_IT _IO(0xab, 3)
#define NBD_CLEAR_SOCK _IO(0xab, 4)
#define NBD_CLEAR_QUE _IO(0xab, 5)
#define NBD_PRINT_DEBUG _IO(0xab, 6)
#define NBD_SET_SIZE_BLOCKS _IO(0xab, 7)
#define NBD_DISCONNECT _IO(0xab, 8)
#define NBD_SET_TIMEOUT _IO(0xab, 9)
#define NBD_SET_FLAGS _IO(0xab, 10)
#define NBD_OPT_EXPORT_NAME (1)
#define NBD_OPT_ABORT (2)
#define NBD_OPT_LIST (3)
/* NBD errors are based on errno numbers, so there is a 1:1 mapping,
* but only a limited set of errno values is specified in the protocol.
* Everything else is squashed to EINVAL.
*/
#define NBD_SUCCESS 0
#define NBD_EPERM 1
#define NBD_EIO 5
#define NBD_ENOMEM 12
#define NBD_EINVAL 22
#define NBD_ENOSPC 28
static int system_errno_to_nbd_errno(int err)
{
switch (err) {
case 0:
return NBD_SUCCESS;
case EPERM:
return NBD_EPERM;
case EIO:
return NBD_EIO;
case ENOMEM:
return NBD_ENOMEM;
#ifdef EDQUOT
case EDQUOT:
#endif
case EFBIG:
case ENOSPC:
return NBD_ENOSPC;
case EINVAL:
default:
return NBD_EINVAL;
}
}
static int nbd_errno_to_system_errno(int err)
{
switch (err) {
case NBD_SUCCESS:
return 0;
case NBD_EPERM:
return EPERM;
case NBD_EIO:
return EIO;
case NBD_ENOMEM:
return ENOMEM;
case NBD_ENOSPC:
return ENOSPC;
case NBD_EINVAL:
default:
return EINVAL;
}
}
/* Definitions for opaque data types */
typedef struct NBDRequest NBDRequest;
struct NBDRequest {
QSIMPLEQ_ENTRY(NBDRequest) entry;
NBDClient *client;
uint8_t *data;
};
struct NBDExport {
int refcount;
void (*close)(NBDExport *exp);
BlockBackend *blk;
char *name;
off_t dev_offset;
off_t size;
uint32_t nbdflags;
QTAILQ_HEAD(, NBDClient) clients;
QTAILQ_ENTRY(NBDExport) next;
AioContext *ctx;
};
static QTAILQ_HEAD(, NBDExport) exports = QTAILQ_HEAD_INITIALIZER(exports);
struct NBDClient {
int refcount;
void (*close)(NBDClient *client);
NBDExport *exp;
int sock;
Coroutine *recv_coroutine;
CoMutex send_lock;
Coroutine *send_coroutine;
bool can_read;
QTAILQ_ENTRY(NBDClient) next;
int nb_requests;
bool closing;
};
/* That's all folks */
static void nbd_set_handlers(NBDClient *client);
static void nbd_unset_handlers(NBDClient *client);
static void nbd_update_can_read(NBDClient *client);
ssize_t nbd_wr_sync(int fd, void *buffer, size_t size, bool do_read)
{
size_t offset = 0;
int err;
if (qemu_in_coroutine()) {
if (do_read) {
return qemu_co_recv(fd, buffer, size);
} else {
return qemu_co_send(fd, buffer, size);
}
}
while (offset < size) {
ssize_t len;
if (do_read) {
len = qemu_recv(fd, buffer + offset, size - offset, 0);
} else {
len = send(fd, buffer + offset, size - offset, 0);
}
if (len < 0) {
err = socket_error();
/* recoverable error */
if (err == EINTR || (offset > 0 && (err == EAGAIN || err == EWOULDBLOCK))) {
continue;
}
/* unrecoverable error */
return -err;
}
/* eof */
if (len == 0) {
break;
}
offset += len;
}
return offset;
}
static ssize_t read_sync(int fd, void *buffer, size_t size)
{
/* Sockets are kept in blocking mode in the negotiation phase. After
* that, a non-readable socket simply means that another thread stole
* our request/reply. Synchronization is done with recv_coroutine, so
* that this is coroutine-safe.
*/
return nbd_wr_sync(fd, buffer, size, true);
}
static ssize_t drop_sync(int fd, size_t size)
{
ssize_t ret, dropped = size;
uint8_t *buffer = g_malloc(MIN(65536, size));
while (size > 0) {
ret = read_sync(fd, buffer, MIN(65536, size));
if (ret < 0) {
g_free(buffer);
return ret;
}
assert(ret <= size);
size -= ret;
}
g_free(buffer);
return dropped;
}
static ssize_t write_sync(int fd, void *buffer, size_t size)
{
int ret;
do {
/* For writes, we do expect the socket to be writable. */
ret = nbd_wr_sync(fd, buffer, size, false);
} while (ret == -EAGAIN);
return ret;
}
/* Basic flow for negotiation
Server Client
Negotiate
or
Server Client
Negotiate #1
Option
Negotiate #2
----
followed by
Server Client
Request
Response
Request
Response
...
...
Request (type == 2)
*/
static int nbd_send_rep(int csock, uint32_t type, uint32_t opt)
{
uint64_t magic;
uint32_t len;
magic = cpu_to_be64(NBD_REP_MAGIC);
if (write_sync(csock, &magic, sizeof(magic)) != sizeof(magic)) {
LOG("write failed (rep magic)");
return -EINVAL;
}
opt = cpu_to_be32(opt);
if (write_sync(csock, &opt, sizeof(opt)) != sizeof(opt)) {
LOG("write failed (rep opt)");
return -EINVAL;
}
type = cpu_to_be32(type);
if (write_sync(csock, &type, sizeof(type)) != sizeof(type)) {
LOG("write failed (rep type)");
return -EINVAL;
}
len = cpu_to_be32(0);
if (write_sync(csock, &len, sizeof(len)) != sizeof(len)) {
LOG("write failed (rep data length)");
return -EINVAL;
}
return 0;
}
static int nbd_send_rep_list(int csock, NBDExport *exp)
{
uint64_t magic, name_len;
uint32_t opt, type, len;
name_len = strlen(exp->name);
magic = cpu_to_be64(NBD_REP_MAGIC);
if (write_sync(csock, &magic, sizeof(magic)) != sizeof(magic)) {
LOG("write failed (magic)");
return -EINVAL;
}
opt = cpu_to_be32(NBD_OPT_LIST);
if (write_sync(csock, &opt, sizeof(opt)) != sizeof(opt)) {
LOG("write failed (opt)");
return -EINVAL;
}
type = cpu_to_be32(NBD_REP_SERVER);
if (write_sync(csock, &type, sizeof(type)) != sizeof(type)) {
LOG("write failed (reply type)");
return -EINVAL;
}
len = cpu_to_be32(name_len + sizeof(len));
if (write_sync(csock, &len, sizeof(len)) != sizeof(len)) {
LOG("write failed (length)");
return -EINVAL;
}
len = cpu_to_be32(name_len);
if (write_sync(csock, &len, sizeof(len)) != sizeof(len)) {
LOG("write failed (length)");
return -EINVAL;
}
if (write_sync(csock, exp->name, name_len) != name_len) {
LOG("write failed (buffer)");
return -EINVAL;
}
return 0;
}
static int nbd_handle_list(NBDClient *client, uint32_t length)
{
int csock;
NBDExport *exp;
csock = client->sock;
if (length) {
if (drop_sync(csock, length) != length) {
return -EIO;
}
return nbd_send_rep(csock, NBD_REP_ERR_INVALID, NBD_OPT_LIST);
}
/* For each export, send a NBD_REP_SERVER reply. */
QTAILQ_FOREACH(exp, &exports, next) {
if (nbd_send_rep_list(csock, exp)) {
return -EINVAL;
}
}
/* Finish with a NBD_REP_ACK. */
return nbd_send_rep(csock, NBD_REP_ACK, NBD_OPT_LIST);
}
static int nbd_handle_export_name(NBDClient *client, uint32_t length)
{
int rc = -EINVAL, csock = client->sock;
char name[256];
/* Client sends:
[20 .. xx] export name (length bytes)
*/
TRACE("Checking length");
if (length > 255) {
LOG("Bad length received");
goto fail;
}
if (read_sync(csock, name, length) != length) {
LOG("read failed");
goto fail;
}
name[length] = '\0';
client->exp = nbd_export_find(name);
if (!client->exp) {
LOG("export not found");
goto fail;
}
QTAILQ_INSERT_TAIL(&client->exp->clients, client, next);
nbd_export_get(client->exp);
rc = 0;
fail:
return rc;
}
static int nbd_receive_options(NBDClient *client)
{
int csock = client->sock;
uint32_t flags;
/* Client sends:
[ 0 .. 3] client flags
[ 0 .. 7] NBD_OPTS_MAGIC
[ 8 .. 11] NBD option
[12 .. 15] Data length
... Rest of request
[ 0 .. 7] NBD_OPTS_MAGIC
[ 8 .. 11] Second NBD option
[12 .. 15] Data length
... Rest of request
*/
if (read_sync(csock, &flags, sizeof(flags)) != sizeof(flags)) {
LOG("read failed");
return -EIO;
}
TRACE("Checking client flags");
be32_to_cpus(&flags);
if (flags != 0 && flags != NBD_FLAG_C_FIXED_NEWSTYLE) {
LOG("Bad client flags received");
return -EIO;
}
while (1) {
int ret;
uint32_t tmp, length;
uint64_t magic;
if (read_sync(csock, &magic, sizeof(magic)) != sizeof(magic)) {
LOG("read failed");
return -EINVAL;
}
TRACE("Checking opts magic");
if (magic != be64_to_cpu(NBD_OPTS_MAGIC)) {
LOG("Bad magic received");
return -EINVAL;
}
if (read_sync(csock, &tmp, sizeof(tmp)) != sizeof(tmp)) {
LOG("read failed");
return -EINVAL;
}
if (read_sync(csock, &length, sizeof(length)) != sizeof(length)) {
LOG("read failed");
return -EINVAL;
}
length = be32_to_cpu(length);
TRACE("Checking option");
switch (be32_to_cpu(tmp)) {
case NBD_OPT_LIST:
ret = nbd_handle_list(client, length);
if (ret < 0) {
return ret;
}
break;
case NBD_OPT_ABORT:
return -EINVAL;
case NBD_OPT_EXPORT_NAME:
return nbd_handle_export_name(client, length);
default:
tmp = be32_to_cpu(tmp);
LOG("Unsupported option 0x%x", tmp);
nbd_send_rep(client->sock, NBD_REP_ERR_UNSUP, tmp);
return -EINVAL;
}
}
}
static int nbd_send_negotiate(NBDClient *client)
{
int csock = client->sock;
char buf[8 + 8 + 8 + 128];
int rc;
const int myflags = (NBD_FLAG_HAS_FLAGS | NBD_FLAG_SEND_TRIM |
NBD_FLAG_SEND_FLUSH | NBD_FLAG_SEND_FUA);
/* Negotiation header without options:
[ 0 .. 7] passwd ("NBDMAGIC")
[ 8 .. 15] magic (NBD_CLIENT_MAGIC)
[16 .. 23] size
[24 .. 25] server flags (0)
[26 .. 27] export flags
[28 .. 151] reserved (0)
Negotiation header with options, part 1:
[ 0 .. 7] passwd ("NBDMAGIC")
[ 8 .. 15] magic (NBD_OPTS_MAGIC)
[16 .. 17] server flags (0)
part 2 (after options are sent):
[18 .. 25] size
[26 .. 27] export flags
[28 .. 151] reserved (0)
*/
qemu_set_block(csock);
rc = -EINVAL;
TRACE("Beginning negotiation.");
memset(buf, 0, sizeof(buf));
memcpy(buf, "NBDMAGIC", 8);
if (client->exp) {
assert ((client->exp->nbdflags & ~65535) == 0);
cpu_to_be64w((uint64_t*)(buf + 8), NBD_CLIENT_MAGIC);
cpu_to_be64w((uint64_t*)(buf + 16), client->exp->size);
cpu_to_be16w((uint16_t*)(buf + 26), client->exp->nbdflags | myflags);
} else {
cpu_to_be64w((uint64_t*)(buf + 8), NBD_OPTS_MAGIC);
cpu_to_be16w((uint16_t *)(buf + 16), NBD_FLAG_FIXED_NEWSTYLE);
}
if (client->exp) {
if (write_sync(csock, buf, sizeof(buf)) != sizeof(buf)) {
LOG("write failed");
goto fail;
}
} else {
if (write_sync(csock, buf, 18) != 18) {
LOG("write failed");
goto fail;
}
rc = nbd_receive_options(client);
if (rc != 0) {
LOG("option negotiation failed");
goto fail;
}
assert ((client->exp->nbdflags & ~65535) == 0);
cpu_to_be64w((uint64_t*)(buf + 18), client->exp->size);
cpu_to_be16w((uint16_t*)(buf + 26), client->exp->nbdflags | myflags);
if (write_sync(csock, buf + 18, sizeof(buf) - 18) != sizeof(buf) - 18) {
LOG("write failed");
goto fail;
}
}
TRACE("Negotiation succeeded.");
rc = 0;
fail:
qemu_set_nonblock(csock);
return rc;
}
int nbd_receive_negotiate(int csock, const char *name, uint32_t *flags,
off_t *size, Error **errp)
{
char buf[256];
uint64_t magic, s;
uint16_t tmp;
int rc;
TRACE("Receiving negotiation.");
rc = -EINVAL;
if (read_sync(csock, buf, 8) != 8) {
error_setg(errp, "Failed to read data");
goto fail;
}
buf[8] = '\0';
if (strlen(buf) == 0) {
error_setg(errp, "Server connection closed unexpectedly");
goto fail;
}
TRACE("Magic is %c%c%c%c%c%c%c%c",
qemu_isprint(buf[0]) ? buf[0] : '.',
qemu_isprint(buf[1]) ? buf[1] : '.',
qemu_isprint(buf[2]) ? buf[2] : '.',
qemu_isprint(buf[3]) ? buf[3] : '.',
qemu_isprint(buf[4]) ? buf[4] : '.',
qemu_isprint(buf[5]) ? buf[5] : '.',
qemu_isprint(buf[6]) ? buf[6] : '.',
qemu_isprint(buf[7]) ? buf[7] : '.');
if (memcmp(buf, "NBDMAGIC", 8) != 0) {
error_setg(errp, "Invalid magic received");
goto fail;
}
if (read_sync(csock, &magic, sizeof(magic)) != sizeof(magic)) {
error_setg(errp, "Failed to read magic");
goto fail;
}
magic = be64_to_cpu(magic);
TRACE("Magic is 0x%" PRIx64, magic);
if (name) {
uint32_t reserved = 0;
uint32_t opt;
uint32_t namesize;
TRACE("Checking magic (opts_magic)");
if (magic != NBD_OPTS_MAGIC) {
if (magic == NBD_CLIENT_MAGIC) {
error_setg(errp, "Server does not support export names");
} else {
error_setg(errp, "Bad magic received");
}
goto fail;
}
if (read_sync(csock, &tmp, sizeof(tmp)) != sizeof(tmp)) {
error_setg(errp, "Failed to read server flags");
goto fail;
}
*flags = be16_to_cpu(tmp) << 16;
/* reserved for future use */
if (write_sync(csock, &reserved, sizeof(reserved)) !=
sizeof(reserved)) {
error_setg(errp, "Failed to read reserved field");
goto fail;
}
/* write the export name */
magic = cpu_to_be64(magic);
if (write_sync(csock, &magic, sizeof(magic)) != sizeof(magic)) {
error_setg(errp, "Failed to send export name magic");
goto fail;
}
opt = cpu_to_be32(NBD_OPT_EXPORT_NAME);
if (write_sync(csock, &opt, sizeof(opt)) != sizeof(opt)) {
error_setg(errp, "Failed to send export name option number");
goto fail;
}
namesize = cpu_to_be32(strlen(name));
if (write_sync(csock, &namesize, sizeof(namesize)) !=
sizeof(namesize)) {
error_setg(errp, "Failed to send export name length");
goto fail;
}
if (write_sync(csock, (char*)name, strlen(name)) != strlen(name)) {
error_setg(errp, "Failed to send export name");
goto fail;
}
} else {
TRACE("Checking magic (cli_magic)");
if (magic != NBD_CLIENT_MAGIC) {
if (magic == NBD_OPTS_MAGIC) {
error_setg(errp, "Server requires an export name");
} else {
error_setg(errp, "Bad magic received");
}
goto fail;
}
}
if (read_sync(csock, &s, sizeof(s)) != sizeof(s)) {
error_setg(errp, "Failed to read export length");
goto fail;
}
*size = be64_to_cpu(s);
TRACE("Size is %" PRIu64, *size);
if (!name) {
if (read_sync(csock, flags, sizeof(*flags)) != sizeof(*flags)) {
error_setg(errp, "Failed to read export flags");
goto fail;
}
*flags = be32_to_cpup(flags);
} else {
if (read_sync(csock, &tmp, sizeof(tmp)) != sizeof(tmp)) {
error_setg(errp, "Failed to read export flags");
goto fail;
}
*flags |= be16_to_cpu(tmp);
}
if (read_sync(csock, &buf, 124) != 124) {
error_setg(errp, "Failed to read reserved block");
goto fail;
}
rc = 0;
fail:
return rc;
}
#ifdef __linux__
int nbd_init(int fd, int csock, uint32_t flags, off_t size)
{
TRACE("Setting NBD socket");
if (ioctl(fd, NBD_SET_SOCK, csock) < 0) {
int serrno = errno;
LOG("Failed to set NBD socket");
return -serrno;
}
TRACE("Setting block size to %lu", (unsigned long)BDRV_SECTOR_SIZE);
if (ioctl(fd, NBD_SET_BLKSIZE, (size_t)BDRV_SECTOR_SIZE) < 0) {
int serrno = errno;
LOG("Failed setting NBD block size");
return -serrno;
}
TRACE("Setting size to %zd block(s)", (size_t)(size / BDRV_SECTOR_SIZE));
if (ioctl(fd, NBD_SET_SIZE_BLOCKS, (size_t)(size / BDRV_SECTOR_SIZE)) < 0) {
int serrno = errno;
LOG("Failed setting size (in blocks)");
return -serrno;
}
if (ioctl(fd, NBD_SET_FLAGS, flags) < 0) {
if (errno == ENOTTY) {
int read_only = (flags & NBD_FLAG_READ_ONLY) != 0;
TRACE("Setting readonly attribute");
if (ioctl(fd, BLKROSET, (unsigned long) &read_only) < 0) {
int serrno = errno;
LOG("Failed setting read-only attribute");
return -serrno;
}
} else {
int serrno = errno;
LOG("Failed setting flags");
return -serrno;
}
}
TRACE("Negotiation ended");
return 0;
}
int nbd_disconnect(int fd)
{
ioctl(fd, NBD_CLEAR_QUE);
ioctl(fd, NBD_DISCONNECT);
ioctl(fd, NBD_CLEAR_SOCK);
return 0;
}
int nbd_client(int fd)
{
int ret;
int serrno;
TRACE("Doing NBD loop");
ret = ioctl(fd, NBD_DO_IT);
if (ret < 0 && errno == EPIPE) {
/* NBD_DO_IT normally returns EPIPE when someone has disconnected
* the socket via NBD_DISCONNECT. We do not want to return 1 in
* that case.
*/
ret = 0;
}
serrno = errno;
TRACE("NBD loop returned %d: %s", ret, strerror(serrno));
TRACE("Clearing NBD queue");
ioctl(fd, NBD_CLEAR_QUE);
TRACE("Clearing NBD socket");
ioctl(fd, NBD_CLEAR_SOCK);
errno = serrno;
return ret;
}
#else
int nbd_init(int fd, int csock, uint32_t flags, off_t size)
{
return -ENOTSUP;
}
int nbd_disconnect(int fd)
{
return -ENOTSUP;
}
int nbd_client(int fd)
{
return -ENOTSUP;
}
#endif
ssize_t nbd_send_request(int csock, struct nbd_request *request)
{
uint8_t buf[NBD_REQUEST_SIZE];
ssize_t ret;
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: "
"{ .from = %" PRIu64", .len = %u, .handle = %" PRIu64", .type=%i}",
request->from, request->len, request->handle, request->type);
ret = write_sync(csock, buf, sizeof(buf));
if (ret < 0) {
return ret;
}
if (ret != sizeof(buf)) {
LOG("writing to socket failed");
return -EINVAL;
}
return 0;
}
static ssize_t nbd_receive_request(int csock, struct nbd_request *request)
{
uint8_t buf[NBD_REQUEST_SIZE];
uint32_t magic;
ssize_t ret;
ret = read_sync(csock, buf, sizeof(buf));
if (ret < 0) {
return ret;
}
if (ret != sizeof(buf)) {
LOG("read failed");
return -EINVAL;
}
/* Request
[ 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);
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, request->type, request->from, request->len);
if (magic != NBD_REQUEST_MAGIC) {
LOG("invalid magic (got 0x%x)", magic);
return -EINVAL;
}
return 0;
}
ssize_t nbd_receive_reply(int csock, struct nbd_reply *reply)
{
uint8_t buf[NBD_REPLY_SIZE];
uint32_t magic;
ssize_t ret;
ret = read_sync(csock, buf, sizeof(buf));
if (ret < 0) {
return ret;
}
if (ret != sizeof(buf)) {
LOG("read failed");
return -EINVAL;
}
/* 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));
reply->error = nbd_errno_to_system_errno(reply->error);
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);
return -EINVAL;
}
return 0;
}
static ssize_t nbd_send_reply(int csock, struct nbd_reply *reply)
{
uint8_t buf[NBD_REPLY_SIZE];
ssize_t ret;
reply->error = system_errno_to_nbd_errno(reply->error);
/* 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");
ret = write_sync(csock, buf, sizeof(buf));
if (ret < 0) {
return ret;
}
if (ret != sizeof(buf)) {
LOG("writing to socket failed");
return -EINVAL;
}
return 0;
}
#define MAX_NBD_REQUESTS 16
void nbd_client_get(NBDClient *client)
{
client->refcount++;
}
void nbd_client_put(NBDClient *client)
{
if (--client->refcount == 0) {
/* The last reference should be dropped by client->close,
* which is called by client_close.
*/
assert(client->closing);
nbd_unset_handlers(client);
close(client->sock);
client->sock = -1;
if (client->exp) {
QTAILQ_REMOVE(&client->exp->clients, client, next);
nbd_export_put(client->exp);
}
g_free(client);
}
}
static void client_close(NBDClient *client)
{
if (client->closing) {
return;
}
client->closing = true;
/* Force requests to finish. They will drop their own references,
* then we'll close the socket and free the NBDClient.
*/
shutdown(client->sock, 2);
/* Also tell the client, so that they release their reference. */
if (client->close) {
client->close(client);
}
}
static NBDRequest *nbd_request_get(NBDClient *client)
{
NBDRequest *req;
assert(client->nb_requests <= MAX_NBD_REQUESTS - 1);
client->nb_requests++;
nbd_update_can_read(client);
req = g_slice_new0(NBDRequest);
nbd_client_get(client);
req->client = client;
return req;
}
static void nbd_request_put(NBDRequest *req)
{
NBDClient *client = req->client;
if (req->data) {
qemu_vfree(req->data);
}
g_slice_free(NBDRequest, req);
client->nb_requests--;
nbd_update_can_read(client);
nbd_client_put(client);
}
static void blk_aio_attached(AioContext *ctx, void *opaque)
{
NBDExport *exp = opaque;
NBDClient *client;
TRACE("Export %s: Attaching clients to AIO context %p\n", exp->name, ctx);
exp->ctx = ctx;
QTAILQ_FOREACH(client, &exp->clients, next) {
nbd_set_handlers(client);
}
}
static void blk_aio_detach(void *opaque)
{
NBDExport *exp = opaque;
NBDClient *client;
TRACE("Export %s: Detaching clients from AIO context %p\n", exp->name, exp->ctx);
QTAILQ_FOREACH(client, &exp->clients, next) {
nbd_unset_handlers(client);
}
exp->ctx = NULL;
}
NBDExport *nbd_export_new(BlockBackend *blk, off_t dev_offset, off_t size,
uint32_t nbdflags, void (*close)(NBDExport *),
Error **errp)
{
NBDExport *exp = g_malloc0(sizeof(NBDExport));
exp->refcount = 1;
QTAILQ_INIT(&exp->clients);
exp->blk = blk;
exp->dev_offset = dev_offset;
exp->nbdflags = nbdflags;
exp->size = size < 0 ? blk_getlength(blk) : size;
if (exp->size < 0) {
error_setg_errno(errp, -exp->size,
"Failed to determine the NBD export's length");
goto fail;
}
exp->size -= exp->size % BDRV_SECTOR_SIZE;
exp->close = close;
exp->ctx = blk_get_aio_context(blk);
blk_ref(blk);
blk_add_aio_context_notifier(blk, blk_aio_attached, blk_aio_detach, exp);
/*
* NBD exports are used for non-shared storage migration. Make sure
* that BDRV_O_INCOMING is cleared and the image is ready for write
* access since the export could be available before migration handover.
*/
blk_invalidate_cache(blk, NULL);
return exp;
fail:
g_free(exp);
return NULL;
}
NBDExport *nbd_export_find(const char *name)
{
NBDExport *exp;
QTAILQ_FOREACH(exp, &exports, next) {
if (strcmp(name, exp->name) == 0) {
return exp;
}
}
return NULL;
}
void nbd_export_set_name(NBDExport *exp, const char *name)
{
if (exp->name == name) {
return;
}
nbd_export_get(exp);
if (exp->name != NULL) {
g_free(exp->name);
exp->name = NULL;
QTAILQ_REMOVE(&exports, exp, next);
nbd_export_put(exp);
}
if (name != NULL) {
nbd_export_get(exp);
exp->name = g_strdup(name);
QTAILQ_INSERT_TAIL(&exports, exp, next);
}
nbd_export_put(exp);
}
void nbd_export_close(NBDExport *exp)
{
NBDClient *client, *next;
nbd_export_get(exp);
QTAILQ_FOREACH_SAFE(client, &exp->clients, next, next) {
client_close(client);
}
nbd_export_set_name(exp, NULL);
nbd_export_put(exp);
if (exp->blk) {
blk_remove_aio_context_notifier(exp->blk, blk_aio_attached,
blk_aio_detach, exp);
blk_unref(exp->blk);
exp->blk = NULL;
}
}
void nbd_export_get(NBDExport *exp)
{
assert(exp->refcount > 0);
exp->refcount++;
}
void nbd_export_put(NBDExport *exp)
{
assert(exp->refcount > 0);
if (exp->refcount == 1) {
nbd_export_close(exp);
}
if (--exp->refcount == 0) {
assert(exp->name == NULL);
if (exp->close) {
exp->close(exp);
}
g_free(exp);
}
}
BlockBackend *nbd_export_get_blockdev(NBDExport *exp)
{
return exp->blk;
}
void nbd_export_close_all(void)
{
NBDExport *exp, *next;
QTAILQ_FOREACH_SAFE(exp, &exports, next, next) {
nbd_export_close(exp);
}
}
static ssize_t nbd_co_send_reply(NBDRequest *req, struct nbd_reply *reply,
int len)
{
NBDClient *client = req->client;
int csock = client->sock;
ssize_t rc, ret;
qemu_co_mutex_lock(&client->send_lock);
client->send_coroutine = qemu_coroutine_self();
nbd_set_handlers(client);
if (!len) {
rc = nbd_send_reply(csock, reply);
} else {
socket_set_cork(csock, 1);
rc = nbd_send_reply(csock, reply);
if (rc >= 0) {
ret = qemu_co_send(csock, req->data, len);
if (ret != len) {
rc = -EIO;
}
}
socket_set_cork(csock, 0);
}
client->send_coroutine = NULL;
nbd_set_handlers(client);
qemu_co_mutex_unlock(&client->send_lock);
return rc;
}
static ssize_t nbd_co_receive_request(NBDRequest *req, struct nbd_request *request)
{
NBDClient *client = req->client;
int csock = client->sock;
uint32_t command;
ssize_t rc;
client->recv_coroutine = qemu_coroutine_self();
nbd_update_can_read(client);
rc = nbd_receive_request(csock, request);
if (rc < 0) {
if (rc != -EAGAIN) {
rc = -EIO;
}
goto out;
}
if (request->len > NBD_MAX_BUFFER_SIZE) {
LOG("len (%u) is larger than max len (%u)",
request->len, NBD_MAX_BUFFER_SIZE);
rc = -EINVAL;
goto out;
}
if ((request->from + request->len) < request->from) {
LOG("integer overflow detected! "
"you're probably being attacked");
rc = -EINVAL;
goto out;
}
TRACE("Decoding type");
command = request->type & NBD_CMD_MASK_COMMAND;
if (command == NBD_CMD_READ || command == NBD_CMD_WRITE) {
req->data = blk_blockalign(client->exp->blk, request->len);
}
if (command == NBD_CMD_WRITE) {
TRACE("Reading %u byte(s)", request->len);
if (qemu_co_recv(csock, req->data, request->len) != request->len) {
LOG("reading from socket failed");
rc = -EIO;
goto out;
}
}
rc = 0;
out:
client->recv_coroutine = NULL;
nbd_update_can_read(client);
return rc;
}
static void nbd_trip(void *opaque)
{
NBDClient *client = opaque;
NBDExport *exp = client->exp;
NBDRequest *req;
struct nbd_request request;
struct nbd_reply reply;
ssize_t ret;
uint32_t command;
TRACE("Reading request.");
if (client->closing) {
return;
}
req = nbd_request_get(client);
ret = nbd_co_receive_request(req, &request);
if (ret == -EAGAIN) {
goto done;
}
if (ret == -EIO) {
goto out;
}
reply.handle = request.handle;
reply.error = 0;
if (ret < 0) {
reply.error = -ret;
goto error_reply;
}
command = request.type & NBD_CMD_MASK_COMMAND;
if (command != NBD_CMD_DISC && (request.from + request.len) > exp->size) {
LOG("From: %" PRIu64 ", Len: %u, Size: %" PRIu64
", Offset: %" PRIu64 "\n",
request.from, request.len,
(uint64_t)exp->size, (uint64_t)exp->dev_offset);
LOG("requested operation past EOF--bad client?");
goto invalid_request;
}
switch (command) {
case NBD_CMD_READ:
TRACE("Request type is READ");
if (request.type & NBD_CMD_FLAG_FUA) {
ret = blk_co_flush(exp->blk);
if (ret < 0) {
LOG("flush failed");
reply.error = -ret;
goto error_reply;
}
}
ret = blk_read(exp->blk,
(request.from + exp->dev_offset) / BDRV_SECTOR_SIZE,
req->data, request.len / BDRV_SECTOR_SIZE);
if (ret < 0) {
LOG("reading from file failed");
reply.error = -ret;
goto error_reply;
}
TRACE("Read %u byte(s)", request.len);
if (nbd_co_send_reply(req, &reply, request.len) < 0)
goto out;
break;
case NBD_CMD_WRITE:
TRACE("Request type is WRITE");
if (exp->nbdflags & NBD_FLAG_READ_ONLY) {
TRACE("Server is read-only, return error");
reply.error = EROFS;
goto error_reply;
}
TRACE("Writing to device");
ret = blk_write(exp->blk,
(request.from + exp->dev_offset) / BDRV_SECTOR_SIZE,
req->data, request.len / BDRV_SECTOR_SIZE);
if (ret < 0) {
LOG("writing to file failed");
reply.error = -ret;
goto error_reply;
}
if (request.type & NBD_CMD_FLAG_FUA) {
ret = blk_co_flush(exp->blk);
if (ret < 0) {
LOG("flush failed");
reply.error = -ret;
goto error_reply;
}
}
if (nbd_co_send_reply(req, &reply, 0) < 0) {
goto out;
}
break;
case NBD_CMD_DISC:
TRACE("Request type is DISCONNECT");
errno = 0;
goto out;
case NBD_CMD_FLUSH:
TRACE("Request type is FLUSH");
ret = blk_co_flush(exp->blk);
if (ret < 0) {
LOG("flush failed");
reply.error = -ret;
}
if (nbd_co_send_reply(req, &reply, 0) < 0) {
goto out;
}
break;
case NBD_CMD_TRIM:
TRACE("Request type is TRIM");
ret = blk_co_discard(exp->blk, (request.from + exp->dev_offset)
/ BDRV_SECTOR_SIZE,
request.len / BDRV_SECTOR_SIZE);
if (ret < 0) {
LOG("discard failed");
reply.error = -ret;
}
if (nbd_co_send_reply(req, &reply, 0) < 0) {
goto out;
}
break;
default:
LOG("invalid request type (%u) received", request.type);
invalid_request:
reply.error = EINVAL;
error_reply:
if (nbd_co_send_reply(req, &reply, 0) < 0) {
goto out;
}
break;
}
TRACE("Request/Reply complete");
done:
nbd_request_put(req);
return;
out:
nbd_request_put(req);
client_close(client);
}
static void nbd_read(void *opaque)
{
NBDClient *client = opaque;
if (client->recv_coroutine) {
qemu_coroutine_enter(client->recv_coroutine, NULL);
} else {
qemu_coroutine_enter(qemu_coroutine_create(nbd_trip), client);
}
}
static void nbd_restart_write(void *opaque)
{
NBDClient *client = opaque;
qemu_coroutine_enter(client->send_coroutine, NULL);
}
static void nbd_set_handlers(NBDClient *client)
{
if (client->exp && client->exp->ctx) {
aio_set_fd_handler(client->exp->ctx, client->sock,
client->can_read ? nbd_read : NULL,
client->send_coroutine ? nbd_restart_write : NULL,
client);
}
}
static void nbd_unset_handlers(NBDClient *client)
{
if (client->exp && client->exp->ctx) {
aio_set_fd_handler(client->exp->ctx, client->sock, NULL, NULL, NULL);
}
}
static void nbd_update_can_read(NBDClient *client)
{
bool can_read = client->recv_coroutine ||
client->nb_requests < MAX_NBD_REQUESTS;
if (can_read != client->can_read) {
client->can_read = can_read;
nbd_set_handlers(client);
/* There is no need to invoke aio_notify(), since aio_set_fd_handler()
* in nbd_set_handlers() will have taken care of that */
}
}
NBDClient *nbd_client_new(NBDExport *exp, int csock,
void (*close)(NBDClient *))
{
NBDClient *client;
client = g_malloc0(sizeof(NBDClient));
client->refcount = 1;
client->exp = exp;
client->sock = csock;
client->can_read = true;
if (nbd_send_negotiate(client)) {
g_free(client);
return NULL;
}
client->close = close;
qemu_co_mutex_init(&client->send_lock);
nbd_set_handlers(client);
if (exp) {
QTAILQ_INSERT_TAIL(&exp->clients, client, next);
nbd_export_get(exp);
}
return client;
}
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