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nbd: Implement NBD_OPT_GO on server
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NBD_OPT_EXPORT_NAME is lousy: per the NBD protocol, any failure
requires us to close the connection rather than report an error.
Therefore, upstream NBD recently added NBD_OPT_GO as the improved
version of the option that does what we want [1], along with
NBD_OPT_INFO that returns the same information but does not
transition to transmission phase.

[1] https://github.com/NetworkBlockDevice/nbd/blob/extension-info/doc/proto.md

This is a first cut at the information types, and only passes the
same information already available through NBD_OPT_LIST and
NBD_OPT_EXPORT_NAME; items like NBD_INFO_BLOCK_SIZE (and thus any
use of NBD_REP_ERR_BLOCK_SIZE_REQD) are intentionally left for
later patches.

Signed-off-by: Eric Blake <[email protected]>
Message-Id: <[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>
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@ebblake @bonzini
ebblake authored and bonzini committed Jul 14, 2017
1 parent 23e099c commit f37708f
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Showing 2 changed files with 179 additions and 3 deletions.
179 changes: 176 additions & 3 deletions nbd/server.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -141,6 +141,7 @@ static int nbd_negotiate_send_rep_len(QIOChannel *ioc, uint32_t type,
trace_nbd_negotiate_send_rep_len(opt, nbd_opt_lookup(opt),
type, nbd_rep_lookup(type), len);

assert(len < NBD_MAX_BUFFER_SIZE);
magic = cpu_to_be64(NBD_REP_MAGIC);
if (nbd_write(ioc, &magic, sizeof(magic), errp) < 0) {
error_prepend(errp, "write failed (rep magic): ");
Expand Down Expand Up @@ -275,6 +276,8 @@ static int nbd_negotiate_handle_list(NBDClient *client, uint32_t length,
return nbd_negotiate_send_rep(client->ioc, NBD_REP_ACK, NBD_OPT_LIST, errp);
}

/* Send a reply to NBD_OPT_EXPORT_NAME.
* Return -errno on error, 0 on success. */
static int nbd_negotiate_handle_export_name(NBDClient *client, uint32_t length,
uint16_t myflags, bool no_zeroes,
Error **errp)
Expand Down Expand Up @@ -323,6 +326,162 @@ static int nbd_negotiate_handle_export_name(NBDClient *client, uint32_t length,
return 0;
}

/* Send a single NBD_REP_INFO, with a buffer @buf of @length bytes.
* The buffer does NOT include the info type prefix.
* Return -errno on error, 0 if ready to send more. */
static int nbd_negotiate_send_info(NBDClient *client, uint32_t opt,
uint16_t info, uint32_t length, void *buf,
Error **errp)
{
int rc;

trace_nbd_negotiate_send_info(info, nbd_info_lookup(info), length);
rc = nbd_negotiate_send_rep_len(client->ioc, NBD_REP_INFO, opt,
sizeof(info) + length, errp);
if (rc < 0) {
return rc;
}
cpu_to_be16s(&info);
if (nbd_write(client->ioc, &info, sizeof(info), errp) < 0) {
return -EIO;
}
if (nbd_write(client->ioc, buf, length, errp) < 0) {
return -EIO;
}
return 0;
}

/* Handle NBD_OPT_INFO and NBD_OPT_GO.
* Return -errno on error, 0 if ready for next option, and 1 to move
* into transmission phase. */
static int nbd_negotiate_handle_info(NBDClient *client, uint32_t length,
uint32_t opt, uint16_t myflags,
Error **errp)
{
int rc;
char name[NBD_MAX_NAME_SIZE + 1];
NBDExport *exp;
uint16_t requests;
uint16_t request;
uint32_t namelen;
bool sendname = false;
char buf[sizeof(uint64_t) + sizeof(uint16_t)];
const char *msg;

/* Client sends:
4 bytes: L, name length (can be 0)
L bytes: export name
2 bytes: N, number of requests (can be 0)
N * 2 bytes: N requests
*/
if (length < sizeof(namelen) + sizeof(requests)) {
msg = "overall request too short";
goto invalid;
}
if (nbd_read(client->ioc, &namelen, sizeof(namelen), errp) < 0) {
return -EIO;
}
be32_to_cpus(&namelen);
length -= sizeof(namelen);
if (namelen > length - sizeof(requests) || (length - namelen) % 2) {
msg = "name length is incorrect";
goto invalid;
}
if (nbd_read(client->ioc, name, namelen, errp) < 0) {
return -EIO;
}
name[namelen] = '\0';
length -= namelen;
trace_nbd_negotiate_handle_export_name_request(name);

if (nbd_read(client->ioc, &requests, sizeof(requests), errp) < 0) {
return -EIO;
}
be16_to_cpus(&requests);
length -= sizeof(requests);
trace_nbd_negotiate_handle_info_requests(requests);
if (requests != length / sizeof(request)) {
msg = "incorrect number of requests for overall length";
goto invalid;
}
while (requests--) {
if (nbd_read(client->ioc, &request, sizeof(request), errp) < 0) {
return -EIO;
}
be16_to_cpus(&request);
length -= sizeof(request);
trace_nbd_negotiate_handle_info_request(request,
nbd_info_lookup(request));
/* For now, we only care about NBD_INFO_NAME; everything else
* is either a request we don't know or something we send
* regardless of request. */
if (request == NBD_INFO_NAME) {
sendname = true;
}
}

exp = nbd_export_find(name);
if (!exp) {
return nbd_negotiate_send_rep_err(client->ioc, NBD_REP_ERR_UNKNOWN,
opt, errp, "export '%s' not present",
name);
}

/* Don't bother sending NBD_INFO_NAME unless client requested it */
if (sendname) {
rc = nbd_negotiate_send_info(client, opt, NBD_INFO_NAME, length, name,
errp);
if (rc < 0) {
return rc;
}
}

/* Send NBD_INFO_DESCRIPTION only if available, regardless of
* client request */
if (exp->description) {
size_t len = strlen(exp->description);

rc = nbd_negotiate_send_info(client, opt, NBD_INFO_DESCRIPTION,
len, exp->description, errp);
if (rc < 0) {
return rc;
}
}

/* Send NBD_INFO_EXPORT always */
trace_nbd_negotiate_new_style_size_flags(exp->size,
exp->nbdflags | myflags);
stq_be_p(buf, exp->size);
stw_be_p(buf + 8, exp->nbdflags | myflags);
rc = nbd_negotiate_send_info(client, opt, NBD_INFO_EXPORT,
sizeof(buf), buf, errp);
if (rc < 0) {
return rc;
}

/* Final reply */
rc = nbd_negotiate_send_rep(client->ioc, NBD_REP_ACK, opt, errp);
if (rc < 0) {
return rc;
}

if (opt == NBD_OPT_GO) {
client->exp = exp;
QTAILQ_INSERT_TAIL(&client->exp->clients, client, next);
nbd_export_get(client->exp);
rc = 1;
}
return rc;

invalid:
if (nbd_drop(client->ioc, length, errp) < 0) {
return -EIO;
}
return nbd_negotiate_send_rep_err(client->ioc, NBD_REP_ERR_INVALID, opt,
errp, "%s", msg);
}


/* Handle NBD_OPT_STARTTLS. Return NULL to drop connection, or else the
* new channel for all further (now-encrypted) communication. */
static QIOChannel *nbd_negotiate_handle_starttls(NBDClient *client,
Expand Down Expand Up @@ -380,7 +539,8 @@ static QIOChannel *nbd_negotiate_handle_starttls(NBDClient *client,
}

/* nbd_negotiate_options
* Process all NBD_OPT_* client option commands.
* Process all NBD_OPT_* client option commands, during fixed newstyle
* negotiation.
* Return:
* -errno on error, errp is set
* 0 on successful negotiation, errp is not set
Expand All @@ -397,7 +557,7 @@ static int nbd_negotiate_options(NBDClient *client, uint16_t myflags,
/* Client sends:
[ 0 .. 3] client flags
Then we loop until NBD_OPT_EXPORT_NAME:
Then we loop until NBD_OPT_EXPORT_NAME or NBD_OPT_GO:
[ 0 .. 7] NBD_OPTS_MAGIC
[ 8 .. 11] NBD option
[12 .. 15] Data length
Expand Down Expand Up @@ -524,6 +684,19 @@ static int nbd_negotiate_options(NBDClient *client, uint16_t myflags,
myflags, no_zeroes,
errp);

case NBD_OPT_INFO:
case NBD_OPT_GO:
ret = nbd_negotiate_handle_info(client, length, option,
myflags, errp);
if (ret == 1) {
assert(option == NBD_OPT_GO);
return 0;
}
if (ret) {
return ret;
}
break;

case NBD_OPT_STARTTLS:
if (nbd_drop(client->ioc, length, errp) < 0) {
return -EIO;
Expand Down Expand Up @@ -606,7 +779,7 @@ static coroutine_fn int nbd_negotiate(NBDClient *client, Error **errp)
[ 0 .. 7] passwd ("NBDMAGIC")
[ 8 .. 15] magic (NBD_OPTS_MAGIC)
[16 .. 17] server flags (0)
....options sent, ending in NBD_OPT_EXPORT_NAME....
....options sent, ending in NBD_OPT_EXPORT_NAME or NBD_OPT_GO....
*/

qio_channel_set_blocking(client->ioc, false, NULL);
Expand Down
3 changes: 3 additions & 0 deletions nbd/trace-events
View file
Original file line number Diff line number Diff line change
Expand Up @@ -33,6 +33,9 @@ nbd_negotiate_send_rep_err(const char *msg) "sending error message \"%s\""
nbd_negotiate_send_rep_list(const char *name, const char *desc) "Advertising export name '%s' description '%s'"
nbd_negotiate_handle_export_name(void) "Checking length"
nbd_negotiate_handle_export_name_request(const char *name) "Client requested export '%s'"
nbd_negotiate_send_info(int info, const char *name, uint32_t length) "Sending NBD_REP_INFO type %d (%s) with remaining length %" PRIu32
nbd_negotiate_handle_info_requests(int requests) "Client requested %d items of info"
nbd_negotiate_handle_info_request(int request, const char *name) "Client requested info %d (%s)"
nbd_negotiate_handle_starttls(void) "Setting up TLS"
nbd_negotiate_handle_starttls_handshake(void) "Starting TLS handshake"
nbd_negotiate_options_flags(uint32_t flags) "Received client flags 0x%" PRIx32
Expand Down

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