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9344e5f554
qemu/nbd/client.c
Daniel P. Berrange 9344e5f554 nbd: always query export list in fixed new style protocol 
With the new style protocol, the NBD client will currenetly
send NBD_OPT_EXPORT_NAME as the first (and indeed only)
option it wants. The problem is that the NBD protocol spec
does not allow for returning an error message with the
NBD_OPT_EXPORT_NAME option. So if the server mandates use
of TLS, the client will simply see an immediate connection
close after issuing NBD_OPT_EXPORT_NAME which is not user
friendly.

To improve this situation, if we have the fixed new style
protocol, we can sent NBD_OPT_LIST as the first option
to query the list of server exports. We can check for our
named export in this list and raise an error if it is not
found, instead of going ahead and sending NBD_OPT_EXPORT_NAME
with a name that we know will be rejected.

This improves the error reporting both in the case that the
server required TLS, and in the case that the client requested
export name does not exist on the server.

If the server does not support NBD_OPT_LIST, we just ignore
that and carry on with NBD_OPT_EXPORT_NAME as before.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Message-Id: <1455129674-17255-12-git-send-email-berrange@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2016-02-16 17:16:11 +01:00

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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 "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;
case NBD_EINVAL:
default:
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)
*/
static int nbd_handle_reply_err(uint32_t opt, uint32_t type, Error **errp)
{
if (!(type & (1 << 31))) {
return 0;
}
switch (type) {
case NBD_REP_ERR_UNSUP:
error_setg(errp, "Unsupported option type %x", opt);
break;
case NBD_REP_ERR_INVALID:
error_setg(errp, "Invalid data length for option %x", opt);
break;
default:
error_setg(errp, "Unknown error code when asking for option %x", opt);
break;
}
return -1;
}
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;
*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 %x 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);
if (type == NBD_REP_ERR_UNSUP) {
return 0;
}
if (nbd_handle_reply_err(opt, type, errp) < 0) {
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 (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 (read_sync(ioc, &namelen, sizeof(namelen)) != sizeof(namelen)) {
error_setg(errp, "failed to read option name length");
return -1;
}
namelen = be32_to_cpu(namelen);
if (len != (namelen + sizeof(namelen))) {
error_setg(errp, "incorrect option mame length");
return -1;
}
if (namelen > 255) {
error_setg(errp, "export name length too long %d", 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';
} else {
error_setg(errp, "Unexpected reply type %x 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;
}
int nbd_receive_negotiate(QIOChannel *ioc, const char *name, uint32_t *flags,
off_t *size, Error **errp)
{
char buf[256];
uint64_t magic, s;
int rc;
TRACE("Receiving negotiation.");
rc = -EINVAL;
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;
uint16_t exportflags;
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);
*flags = globalflags << 16;
TRACE("Global flags are %x", 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 (!name) {
error_setg(errp, "Server requires an export name");
goto fail;
}
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);
TRACE("Size is %" PRIu64, *size);
if (read_sync(ioc, &exportflags, sizeof(exportflags)) !=
sizeof(exportflags)) {
error_setg(errp, "Failed to read export flags");
goto fail;
}
exportflags = be16_to_cpu(exportflags);
*flags |= exportflags;
TRACE("Export flags are %x", exportflags);
} else if (magic == NBD_CLIENT_MAGIC) {
if (name) {
error_setg(errp, "Server does not support export names");
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, flags, sizeof(*flags)) != sizeof(*flags)) {
error_setg(errp, "Failed to read export flags");
goto fail;
}
*flags = be32_to_cpup(flags);
} else {
error_setg(errp, "Bad magic received");
goto fail;
}
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, uint32_t flags, off_t size)
{
TRACE("Setting NBD socket");
if (ioctl(fd, NBD_SET_SOCK, 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, (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_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, QIOChannelSocket *ioc, uint32_t flags, off_t size)
{
return -ENOTSUP;
}
int nbd_client(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;
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(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 = 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;
}
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