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b626b51a67
qemu/nbd/client.c
Eric Blake b626b51a67 nbd: Treat flags vs. command type as separate fields 
Current upstream NBD documents that requests have a 16-bit flags,
followed by a 16-bit type integer; although older versions mentioned
only a 32-bit field with masking to find flags.  Since the protocol
is in network order (big-endian over the wire), the ABI is unchanged;
but dealing with the flags as a separate field rather than masking
will make it easier to add support for upcoming NBD extensions that
increase the number of both flags and commands.

Improve some comments in nbd.h based on the current upstream
NBD protocol (https://github.com/yoe/nbd/blob/master/doc/proto.md),
and touch some nearby code to keep checkpatch.pl happy.

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1476469998-28592-3-git-send-email-eblake@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2016-11-02 09:28:55 +01:00

780 lines
22 KiB
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/*
* Copyright (C) 2016 Red Hat, Inc.
* 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;
}
qio_channel_set_name(QIO_CHANNEL(tioc), "nbd-client-tls");
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
", .flags = %" PRIx16 ", .type = %" PRIu16 " }",
request->from, request->len, request->handle,
request->flags, request->type);
stl_be_p(buf, NBD_REQUEST_MAGIC);
stw_be_p(buf + 4, request->flags);
stw_be_p(buf + 6, 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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