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qemu/nbd/client.c
Eric Blake 7423f41782 nbd: Limit nbdflags to 16 bits 
Rather than asserting that nbdflags is within range, just give
it the correct type to begin with :)  nbdflags corresponds to
the per-export portion of NBD Protocol "transmission flags", which
is 16 bits in response to NBD_OPT_EXPORT_NAME and NBD_OPT_GO.

Furthermore, upstream NBD has never passed the global flags to
the kernel via ioctl(NBD_SET_FLAGS) (the ioctl was first
introduced in NBD 2.9.22; then a latent bug in NBD 3.1 actually
tried to OR the global flags with the transmission flags, with
the disaster that the addition of NBD_FLAG_NO_ZEROES in 3.9
caused all earlier NBD 3.x clients to treat every export as
read-only; NBD 3.10 and later intentionally clip things to 16
bits to pass only transmission flags).  Qemu should follow suit,
since the current two global flags (NBD_FLAG_FIXED_NEWSTYLE
and NBD_FLAG_NO_ZEROES) have no impact on the kernel's behavior
during transmission.

CC: qemu-stable@nongnu.org
Signed-off-by: Eric Blake <eblake@redhat.com>

Message-Id: <1469129688-22848-3-git-send-email-eblake@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2016-08-03 18:44:56 +02:00

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/*
* Copyright (C) 2005 Anthony Liguori <anthony@codemonkey.ws>
*
* Network Block Device Client Side
*
* 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 "qemu/osdep.h"
#include "qapi/error.h"
#include "nbd-internal.h"
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;
default:
TRACE("Squashing unexpected error %d to EINVAL", err);
/* fallthrough */
case NBD_EINVAL:
return EINVAL;
}
}
/* Definitions for opaque data types */
static QTAILQ_HEAD(, NBDExport) exports = QTAILQ_HEAD_INITIALIZER(exports);
/* That's all folks */
/* 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)
*/
/* If type represents success, return 1 without further action.
* If type represents an error reply, consume the rest of the packet on ioc.
* Then return 0 for unsupported (so the client can fall back to
* other approaches), or -1 with errp set for other errors.
*/
static int nbd_handle_reply_err(QIOChannel *ioc, uint32_t opt, uint32_t type,
Error **errp)
{
uint32_t len;
char *msg = NULL;
int result = -1;
if (!(type & (1 << 31))) {
return 1;
}
if (read_sync(ioc, &len, sizeof(len)) != sizeof(len)) {
error_setg(errp, "failed to read option length");
return -1;
}
len = be32_to_cpu(len);
if (len) {
if (len > NBD_MAX_BUFFER_SIZE) {
error_setg(errp, "server's error message is too long");
goto cleanup;
}
msg = g_malloc(len + 1);
if (read_sync(ioc, msg, len) != len) {
error_setg(errp, "failed to read option error message");
goto cleanup;
}
msg[len] = '\0';
}
switch (type) {
case NBD_REP_ERR_UNSUP:
TRACE("server doesn't understand request %" PRIx32
", attempting fallback", opt);
result = 0;
goto cleanup;
case NBD_REP_ERR_POLICY:
error_setg(errp, "Denied by server for option %" PRIx32, opt);
break;
case NBD_REP_ERR_INVALID:
error_setg(errp, "Invalid data length for option %" PRIx32, opt);
break;
case NBD_REP_ERR_TLS_REQD:
error_setg(errp, "TLS negotiation required before option %" PRIx32,
opt);
break;
default:
error_setg(errp, "Unknown error code when asking for option %" PRIx32,
opt);
break;
}
if (msg) {
error_append_hint(errp, "%s\n", msg);
}
cleanup:
g_free(msg);
return result;
}
static int nbd_receive_list(QIOChannel *ioc, char **name, Error **errp)
{
uint64_t magic;
uint32_t opt;
uint32_t type;
uint32_t len;
uint32_t namelen;
int error;
*name = NULL;
if (read_sync(ioc, &magic, sizeof(magic)) != sizeof(magic)) {
error_setg(errp, "failed to read list option magic");
return -1;
}
magic = be64_to_cpu(magic);
if (magic != NBD_REP_MAGIC) {
error_setg(errp, "Unexpected option list magic");
return -1;
}
if (read_sync(ioc, &opt, sizeof(opt)) != sizeof(opt)) {
error_setg(errp, "failed to read list option");
return -1;
}
opt = be32_to_cpu(opt);
if (opt != NBD_OPT_LIST) {
error_setg(errp, "Unexpected option type %" PRIx32 " expected %x",
opt, NBD_OPT_LIST);
return -1;
}
if (read_sync(ioc, &type, sizeof(type)) != sizeof(type)) {
error_setg(errp, "failed to read list option type");
return -1;
}
type = be32_to_cpu(type);
error = nbd_handle_reply_err(ioc, opt, type, errp);
if (error <= 0) {
return error;
}
if (read_sync(ioc, &len, sizeof(len)) != sizeof(len)) {
error_setg(errp, "failed to read option length");
return -1;
}
len = be32_to_cpu(len);
if (type == NBD_REP_ACK) {
if (len != 0) {
error_setg(errp, "length too long for option end");
return -1;
}
} else if (type == NBD_REP_SERVER) {
if (len < sizeof(namelen) || len > NBD_MAX_BUFFER_SIZE) {
error_setg(errp, "incorrect option length");
return -1;
}
if (read_sync(ioc, &namelen, sizeof(namelen)) != sizeof(namelen)) {
error_setg(errp, "failed to read option name length");
return -1;
}
namelen = be32_to_cpu(namelen);
len -= sizeof(namelen);
if (len < namelen) {
error_setg(errp, "incorrect option name length");
return -1;
}
if (namelen > NBD_MAX_NAME_SIZE) {
error_setg(errp, "export name length too long %" PRIu32, namelen);
return -1;
}
*name = g_new0(char, namelen + 1);
if (read_sync(ioc, *name, namelen) != namelen) {
error_setg(errp, "failed to read export name");
g_free(*name);
*name = NULL;
return -1;
}
(*name)[namelen] = '\0';
len -= namelen;
if (len) {
char *buf = g_malloc(len + 1);
if (read_sync(ioc, buf, len) != len) {
error_setg(errp, "failed to read export description");
g_free(*name);
g_free(buf);
*name = NULL;
return -1;
}
buf[len] = '\0';
TRACE("Ignoring export description: %s", buf);
g_free(buf);
}
} else {
error_setg(errp, "Unexpected reply type %" PRIx32 " expected %x",
type, NBD_REP_SERVER);
return -1;
}
return 1;
}
static int nbd_receive_query_exports(QIOChannel *ioc,
const char *wantname,
Error **errp)
{
uint64_t magic = cpu_to_be64(NBD_OPTS_MAGIC);
uint32_t opt = cpu_to_be32(NBD_OPT_LIST);
uint32_t length = 0;
bool foundExport = false;
TRACE("Querying export list");
if (write_sync(ioc, &magic, sizeof(magic)) != sizeof(magic)) {
error_setg(errp, "Failed to send list option magic");
return -1;
}
if (write_sync(ioc, &opt, sizeof(opt)) != sizeof(opt)) {
error_setg(errp, "Failed to send list option number");
return -1;
}
if (write_sync(ioc, &length, sizeof(length)) != sizeof(length)) {
error_setg(errp, "Failed to send list option length");
return -1;
}
TRACE("Reading available export names");
while (1) {
char *name = NULL;
int ret = nbd_receive_list(ioc, &name, errp);
if (ret < 0) {
g_free(name);
name = NULL;
return -1;
}
if (ret == 0) {
/* Server doesn't support export listing, so
* we will just assume an export with our
* wanted name exists */
foundExport = true;
break;
}
if (name == NULL) {
TRACE("End of export name list");
break;
}
if (g_str_equal(name, wantname)) {
foundExport = true;
TRACE("Found desired export name '%s'", name);
} else {
TRACE("Ignored export name '%s'", name);
}
g_free(name);
}
if (!foundExport) {
error_setg(errp, "No export with name '%s' available", wantname);
return -1;
}
return 0;
}
static QIOChannel *nbd_receive_starttls(QIOChannel *ioc,
QCryptoTLSCreds *tlscreds,
const char *hostname, Error **errp)
{
uint64_t magic = cpu_to_be64(NBD_OPTS_MAGIC);
uint32_t opt = cpu_to_be32(NBD_OPT_STARTTLS);
uint32_t length = 0;
uint32_t type;
QIOChannelTLS *tioc;
struct NBDTLSHandshakeData data = { 0 };
TRACE("Requesting TLS from server");
if (write_sync(ioc, &magic, sizeof(magic)) != sizeof(magic)) {
error_setg(errp, "Failed to send option magic");
return NULL;
}
if (write_sync(ioc, &opt, sizeof(opt)) != sizeof(opt)) {
error_setg(errp, "Failed to send option number");
return NULL;
}
if (write_sync(ioc, &length, sizeof(length)) != sizeof(length)) {
error_setg(errp, "Failed to send option length");
return NULL;
}
TRACE("Getting TLS reply from server1");
if (read_sync(ioc, &magic, sizeof(magic)) != sizeof(magic)) {
error_setg(errp, "failed to read option magic");
return NULL;
}
magic = be64_to_cpu(magic);
if (magic != NBD_REP_MAGIC) {
error_setg(errp, "Unexpected option magic");
return NULL;
}
TRACE("Getting TLS reply from server2");
if (read_sync(ioc, &opt, sizeof(opt)) != sizeof(opt)) {
error_setg(errp, "failed to read option");
return NULL;
}
opt = be32_to_cpu(opt);
if (opt != NBD_OPT_STARTTLS) {
error_setg(errp, "Unexpected option type %" PRIx32 " expected %x",
opt, NBD_OPT_STARTTLS);
return NULL;
}
TRACE("Getting TLS reply from server");
if (read_sync(ioc, &type, sizeof(type)) != sizeof(type)) {
error_setg(errp, "failed to read option type");
return NULL;
}
type = be32_to_cpu(type);
if (type != NBD_REP_ACK) {
error_setg(errp, "Server rejected request to start TLS %" PRIx32,
type);
return NULL;
}
TRACE("Getting TLS reply from server");
if (read_sync(ioc, &length, sizeof(length)) != sizeof(length)) {
error_setg(errp, "failed to read option length");
return NULL;
}
length = be32_to_cpu(length);
if (length != 0) {
error_setg(errp, "Start TLS response was not zero %" PRIu32,
length);
return NULL;
}
TRACE("TLS request approved, setting up TLS");
tioc = qio_channel_tls_new_client(ioc, tlscreds, hostname, errp);
if (!tioc) {
return NULL;
}
data.loop = g_main_loop_new(g_main_context_default(), FALSE);
TRACE("Starting TLS handshake");
qio_channel_tls_handshake(tioc,
nbd_tls_handshake,
&data,
NULL);
if (!data.complete) {
g_main_loop_run(data.loop);
}
g_main_loop_unref(data.loop);
if (data.error) {
error_propagate(errp, data.error);
object_unref(OBJECT(tioc));
return NULL;
}
return QIO_CHANNEL(tioc);
}
int nbd_receive_negotiate(QIOChannel *ioc, const char *name, uint16_t *flags,
QCryptoTLSCreds *tlscreds, const char *hostname,
QIOChannel **outioc,
off_t *size, Error **errp)
{
char buf[256];
uint64_t magic, s;
int rc;
TRACE("Receiving negotiation tlscreds=%p hostname=%s.",
tlscreds, hostname ? hostname : "<null>");
rc = -EINVAL;
if (outioc) {
*outioc = NULL;
}
if (tlscreds && !outioc) {
error_setg(errp, "Output I/O channel required for TLS");
goto fail;
}
if (read_sync(ioc, 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(ioc, &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 (magic == NBD_OPTS_MAGIC) {
uint32_t clientflags = 0;
uint32_t opt;
uint32_t namesize;
uint16_t globalflags;
bool fixedNewStyle = false;
if (read_sync(ioc, &globalflags, sizeof(globalflags)) !=
sizeof(globalflags)) {
error_setg(errp, "Failed to read server flags");
goto fail;
}
globalflags = be16_to_cpu(globalflags);
TRACE("Global flags are %" PRIx32, globalflags);
if (globalflags & NBD_FLAG_FIXED_NEWSTYLE) {
fixedNewStyle = true;
TRACE("Server supports fixed new style");
clientflags |= NBD_FLAG_C_FIXED_NEWSTYLE;
}
/* client requested flags */
clientflags = cpu_to_be32(clientflags);
if (write_sync(ioc, &clientflags, sizeof(clientflags)) !=
sizeof(clientflags)) {
error_setg(errp, "Failed to send clientflags field");
goto fail;
}
if (tlscreds) {
if (fixedNewStyle) {
*outioc = nbd_receive_starttls(ioc, tlscreds, hostname, errp);
if (!*outioc) {
goto fail;
}
ioc = *outioc;
} else {
error_setg(errp, "Server does not support STARTTLS");
goto fail;
}
}
if (!name) {
TRACE("Using default NBD export name \"\"");
name = "";
}
if (fixedNewStyle) {
/* Check our desired export is present in the
* server export list. Since NBD_OPT_EXPORT_NAME
* cannot return an error message, running this
* query gives us good error reporting if the
* server required TLS
*/
if (nbd_receive_query_exports(ioc, name, errp) < 0) {
goto fail;
}
}
/* write the export name */
magic = cpu_to_be64(magic);
if (write_sync(ioc, &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(ioc, &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(ioc, &namesize, sizeof(namesize)) !=
sizeof(namesize)) {
error_setg(errp, "Failed to send export name length");
goto fail;
}
if (write_sync(ioc, (char *)name, strlen(name)) != strlen(name)) {
error_setg(errp, "Failed to send export name");
goto fail;
}
if (read_sync(ioc, &s, sizeof(s)) != sizeof(s)) {
error_setg(errp, "Failed to read export length");
goto fail;
}
*size = be64_to_cpu(s);
if (read_sync(ioc, flags, sizeof(*flags)) != sizeof(*flags)) {
error_setg(errp, "Failed to read export flags");
goto fail;
}
be16_to_cpus(flags);
} else if (magic == NBD_CLIENT_MAGIC) {
uint32_t oldflags;
if (name) {
error_setg(errp, "Server does not support export names");
goto fail;
}
if (tlscreds) {
error_setg(errp, "Server does not support STARTTLS");
goto fail;
}
if (read_sync(ioc, &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 (read_sync(ioc, &oldflags, sizeof(oldflags)) != sizeof(oldflags)) {
error_setg(errp, "Failed to read export flags");
goto fail;
}
be32_to_cpus(&oldflags);
if (oldflags & ~0xffff) {
error_setg(errp, "Unexpected export flags %0x" PRIx32, oldflags);
goto fail;
}
*flags = oldflags;
} else {
error_setg(errp, "Bad magic received");
goto fail;
}
TRACE("Size is %" PRIu64 ", export flags %" PRIx16, *size, *flags);
if (read_sync(ioc, &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, QIOChannelSocket *sioc, uint16_t flags, off_t size)
{
unsigned long sectors = size / BDRV_SECTOR_SIZE;
if (size / BDRV_SECTOR_SIZE != sectors) {
LOG("Export size %lld too large for 32-bit kernel", (long long) size);
return -E2BIG;
}
TRACE("Setting NBD socket");
if (ioctl(fd, NBD_SET_SOCK, (unsigned long) sioc->fd) < 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, (unsigned long)BDRV_SECTOR_SIZE) < 0) {
int serrno = errno;
LOG("Failed setting NBD block size");
return -serrno;
}
TRACE("Setting size to %lu block(s)", sectors);
if (size % BDRV_SECTOR_SIZE) {
TRACE("Ignoring trailing %d bytes of export",
(int) (size % BDRV_SECTOR_SIZE));
}
if (ioctl(fd, NBD_SET_SIZE_BLOCKS, sectors) < 0) {
int serrno = errno;
LOG("Failed setting size (in blocks)");
return -serrno;
}
if (ioctl(fd, NBD_SET_FLAGS, (unsigned long) 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_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;
}
int nbd_disconnect(int fd)
{
ioctl(fd, NBD_CLEAR_QUE);
ioctl(fd, NBD_DISCONNECT);
ioctl(fd, NBD_CLEAR_SOCK);
return 0;
}
#else
int nbd_init(int fd, QIOChannelSocket *ioc, uint16_t flags, off_t size)
{
return -ENOTSUP;
}
int nbd_client(int fd)
{
return -ENOTSUP;
}
int nbd_disconnect(int fd)
{
return -ENOTSUP;
}
#endif
ssize_t nbd_send_request(QIOChannel *ioc, struct nbd_request *request)
{
uint8_t buf[NBD_REQUEST_SIZE];
ssize_t ret;
TRACE("Sending request to server: "
"{ .from = %" PRIu64", .len = %" PRIu32 ", .handle = %" PRIu64
", .type=%" PRIu32 " }",
request->from, request->len, request->handle, request->type);
stl_be_p(buf, NBD_REQUEST_MAGIC);
stl_be_p(buf + 4, request->type);
stq_be_p(buf + 8, request->handle);
stq_be_p(buf + 16, request->from);
stl_be_p(buf + 24, request->len);
ret = write_sync(ioc, buf, sizeof(buf));
if (ret < 0) {
return ret;
}
if (ret != sizeof(buf)) {
LOG("writing to socket failed");
return -EINVAL;
}
return 0;
}
ssize_t nbd_receive_reply(QIOChannel *ioc, struct nbd_reply *reply)
{
uint8_t buf[NBD_REPLY_SIZE];
uint32_t magic;
ssize_t ret;
ret = read_sync(ioc, 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 = ldl_be_p(buf);
reply->error = ldl_be_p(buf + 4);
reply->handle = ldq_be_p(buf + 8);
reply->error = nbd_errno_to_system_errno(reply->error);
TRACE("Got reply: { magic = 0x%" PRIx32 ", .error = % " PRId32
", handle = %" PRIu64" }",
magic, reply->error, reply->handle);
if (magic != NBD_REPLY_MAGIC) {
LOG("invalid magic (got 0x%" PRIx32 ")", magic);
return -EINVAL;
}
return 0;
}
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