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2cdbf41362
qemu/nbd/client.c
Eric Blake 2cdbf41362 nbd: Let server know when client gives up negotiation 
The NBD spec says that a client should send NBD_OPT_ABORT
rather than just dropping the connection, if the client doesn't
like something the server sent during option negotiation.  This
is a best-effort attempt only, and can only be done in places
where we know the server is still in sync with what we've sent,
whether or not we've read everything the server has sent.
Technically, the server then has to reply with NBD_REP_ACK, but
it's not worth complicating the client to wait around for that
reply.

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1476469998-28592-10-git-send-email-eblake@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2016-11-02 09:28:55 +01:00

771 lines
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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)
*/
/* Send an option request.
*
* The request is for option @opt, with @data containing @len bytes of
* additional payload for the request (@len may be -1 to treat @data as
* a C string; and @data may be NULL if @len is 0).
* Return 0 if successful, -1 with errp set if it is impossible to
* continue. */
static int nbd_send_option_request(QIOChannel *ioc, uint32_t opt,
uint32_t len, const char *data,
Error **errp)
{
nbd_option req;
QEMU_BUILD_BUG_ON(sizeof(req) != 16);
if (len == -1) {
req.length = len = strlen(data);
}
TRACE("Sending option request %" PRIu32", len %" PRIu32, opt, len);
stq_be_p(&req.magic, NBD_OPTS_MAGIC);
stl_be_p(&req.option, opt);
stl_be_p(&req.length, len);
if (write_sync(ioc, &req, sizeof(req)) != sizeof(req)) {
error_setg(errp, "Failed to send option request header");
return -1;
}
if (len && write_sync(ioc, (char *) data, len) != len) {
error_setg(errp, "Failed to send option request data");
return -1;
}
return 0;
}
/* Send NBD_OPT_ABORT as a courtesy to let the server know that we are
* not going to attempt further negotiation. */
static void nbd_send_opt_abort(QIOChannel *ioc)
{
/* Technically, a compliant server is supposed to reply to us; but
* older servers disconnected instead. At any rate, we're allowed
* to disconnect without waiting for the server reply, so we don't
* even care if the request makes it to the server, let alone
* waiting around for whether the server replies. */
nbd_send_option_request(ioc, NBD_OPT_ABORT, 0, NULL, NULL);
}
/* Receive the header of an option reply, which should match the given
* opt. Read through the length field, but NOT the length bytes of
* payload. Return 0 if successful, -1 with errp set if it is
* impossible to continue. */
static int nbd_receive_option_reply(QIOChannel *ioc, uint32_t opt,
nbd_opt_reply *reply, Error **errp)
{
QEMU_BUILD_BUG_ON(sizeof(*reply) != 20);
if (read_sync(ioc, reply, sizeof(*reply)) != sizeof(*reply)) {
error_setg(errp, "failed to read option reply");
nbd_send_opt_abort(ioc);
return -1;
}
be64_to_cpus(&reply->magic);
be32_to_cpus(&reply->option);
be32_to_cpus(&reply->type);
be32_to_cpus(&reply->length);
TRACE("Received option reply %" PRIx32", type %" PRIx32", len %" PRIu32,
reply->option, reply->type, reply->length);
if (reply->magic != NBD_REP_MAGIC) {
error_setg(errp, "Unexpected option reply magic");
nbd_send_opt_abort(ioc);
return -1;
}
if (reply->option != opt) {
error_setg(errp, "Unexpected option type %x expected %x",
reply->option, opt);
nbd_send_opt_abort(ioc);
return -1;
}
return 0;
}
/* If reply represents success, return 1 without further action.
* If reply represents an error, consume the optional payload 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, nbd_opt_reply *reply,
Error **errp)
{
char *msg = NULL;
int result = -1;
if (!(reply->type & (1 << 31))) {
return 1;
}
if (reply->length) {
if (reply->length > NBD_MAX_BUFFER_SIZE) {
error_setg(errp, "server's error message is too long");
goto cleanup;
}
msg = g_malloc(reply->length + 1);
if (read_sync(ioc, msg, reply->length) != reply->length) {
error_setg(errp, "failed to read option error message");
goto cleanup;
}
msg[reply->length] = '\0';
}
switch (reply->type) {
case NBD_REP_ERR_UNSUP:
TRACE("server doesn't understand request %" PRIx32
", attempting fallback", reply->option);
result = 0;
goto cleanup;
case NBD_REP_ERR_POLICY:
error_setg(errp, "Denied by server for option %" PRIx32,
reply->option);
break;
case NBD_REP_ERR_INVALID:
error_setg(errp, "Invalid data length for option %" PRIx32,
reply->option);
break;
case NBD_REP_ERR_TLS_REQD:
error_setg(errp, "TLS negotiation required before option %" PRIx32,
reply->option);
break;
default:
error_setg(errp, "Unknown error code when asking for option %" PRIx32,
reply->option);
break;
}
if (msg) {
error_append_hint(errp, "%s\n", msg);
}
cleanup:
g_free(msg);
if (result < 0) {
nbd_send_opt_abort(ioc);
}
return result;
}
static int nbd_receive_list(QIOChannel *ioc, char **name, Error **errp)
{
nbd_opt_reply reply;
uint32_t len;
uint32_t namelen;
int error;
*name = NULL;
if (nbd_receive_option_reply(ioc, NBD_OPT_LIST, &reply, errp) < 0) {
return -1;
}
error = nbd_handle_reply_err(ioc, &reply, errp);
if (error <= 0) {
return error;
}
len = reply.length;
if (reply.type == NBD_REP_ACK) {
if (len != 0) {
error_setg(errp, "length too long for option end");
nbd_send_opt_abort(ioc);
return -1;
}
} else if (reply.type == NBD_REP_SERVER) {
if (len < sizeof(namelen) || len > NBD_MAX_BUFFER_SIZE) {
error_setg(errp, "incorrect option length %" PRIu32, len);
nbd_send_opt_abort(ioc);
return -1;
}
if (read_sync(ioc, &namelen, sizeof(namelen)) != sizeof(namelen)) {
error_setg(errp, "failed to read option name length");
nbd_send_opt_abort(ioc);
return -1;
}
namelen = be32_to_cpu(namelen);
len -= sizeof(namelen);
if (len < namelen) {
error_setg(errp, "incorrect option name length");
nbd_send_opt_abort(ioc);
return -1;
}
if (namelen > NBD_MAX_NAME_SIZE) {
error_setg(errp, "export name length too long %" PRIu32, namelen);
nbd_send_opt_abort(ioc);
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;
nbd_send_opt_abort(ioc);
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;
nbd_send_opt_abort(ioc);
return -1;
}
buf[len] = '\0';
TRACE("Ignoring export description: %s", buf);
g_free(buf);
}
} else {
error_setg(errp, "Unexpected reply type %" PRIx32 " expected %x",
reply.type, NBD_REP_SERVER);
nbd_send_opt_abort(ioc);
return -1;
}
return 1;
}
static int nbd_receive_query_exports(QIOChannel *ioc,
const char *wantname,
Error **errp)
{
bool foundExport = false;
TRACE("Querying export list");
if (nbd_send_option_request(ioc, NBD_OPT_LIST, 0, NULL, errp) < 0) {
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);
nbd_send_opt_abort(ioc);
return -1;
}
return 0;
}
static QIOChannel *nbd_receive_starttls(QIOChannel *ioc,
QCryptoTLSCreds *tlscreds,
const char *hostname, Error **errp)
{
nbd_opt_reply reply;
QIOChannelTLS *tioc;
struct NBDTLSHandshakeData data = { 0 };
TRACE("Requesting TLS from server");
if (nbd_send_option_request(ioc, NBD_OPT_STARTTLS, 0, NULL, errp) < 0) {
return NULL;
}
TRACE("Getting TLS reply from server");
if (nbd_receive_option_reply(ioc, NBD_OPT_STARTTLS, &reply, errp) < 0) {
return NULL;
}
if (reply.type != NBD_REP_ACK) {
error_setg(errp, "Server rejected request to start TLS %" PRIx32,
reply.type);
nbd_send_opt_abort(ioc);
return NULL;
}
if (reply.length != 0) {
error_setg(errp, "Start TLS response was not zero %" PRIu32,
reply.length);
nbd_send_opt_abort(ioc);
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;
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 request */
if (nbd_send_option_request(ioc, NBD_OPT_EXPORT_NAME, -1, name,
errp) < 0) {
goto fail;
}
/* Read the response */
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, NBDRequest *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, NBDReply *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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