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nbd/server: Enable initial support for extended headers

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Time to start supporting clients that request extended headers.  Now
we can finally reach the code added across several previous patches.

Even though the NBD spec has been altered to allow us to accept
NBD_CMD_READ larger than the max payload size (provided our response
is a hole or broken up over more than one data chunk), we are not
planning to take advantage of that, and continue to cap NBD_CMD_READ
to 32M regardless of header size.

For NBD_CMD_WRITE_ZEROES and NBD_CMD_TRIM, the block layer already
supports 64-bit operations without any effort on our part.  For
NBD_CMD_BLOCK_STATUS, the client's length is a hint, and the previous
patch took care of implementing the required
NBD_REPLY_TYPE_BLOCK_STATUS_EXT.

We do not yet support clients that want to do request payload
filtering of NBD_CMD_BLOCK_STATUS; that will be added in later
patches, but is not essential for qemu as a client since qemu only
requests the single context base:allocation.

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Message-ID: <20230925192229.3186470-19-eblake@redhat.com>
This commit is contained in:
Eric Blake 2023-09-25 14:22:35 -05:00
parent bcc16cc19e
commit 9c1d261437
2 changed files with 22 additions and 0 deletions
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21
nbd/server.c
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@ -482,6 +482,10 @@ static int nbd_negotiate_handle_export_name(NBDClient *client, bool no_zeroes,
[10 .. 133] reserved (0) [unless no_zeroes]
*/
trace_nbd_negotiate_handle_export_name();
if (client->mode >= NBD_MODE_EXTENDED) {
error_setg(errp, "Extended headers already negotiated");
return -EINVAL;
}
if (client->optlen > NBD_MAX_STRING_SIZE) {
error_setg(errp, "Bad length received");
return -EINVAL;
@ -1264,6 +1268,10 @@ static int nbd_negotiate_options(NBDClient *client, Error **errp)
case NBD_OPT_STRUCTURED_REPLY:
if (length) {
ret = nbd_reject_length(client, false, errp);
} else if (client->mode >= NBD_MODE_EXTENDED) {
ret = nbd_negotiate_send_rep_err(
client, NBD_REP_ERR_EXT_HEADER_REQD, errp,
"extended headers already negotiated");
} else if (client->mode >= NBD_MODE_STRUCTURED) {
ret = nbd_negotiate_send_rep_err(
client, NBD_REP_ERR_INVALID, errp,
@ -1280,6 +1288,19 @@ static int nbd_negotiate_options(NBDClient *client, Error **errp)
errp);
break;
case NBD_OPT_EXTENDED_HEADERS:
if (length) {
ret = nbd_reject_length(client, false, errp);
} else if (client->mode >= NBD_MODE_EXTENDED) {
ret = nbd_negotiate_send_rep_err(
client, NBD_REP_ERR_INVALID, errp,
"extended headers already negotiated");
} else {
ret = nbd_negotiate_send_rep(client, NBD_REP_ACK, errp);
client->mode = NBD_MODE_EXTENDED;
}
break;
default:
ret = nbd_opt_drop(client, NBD_REP_ERR_UNSUP, errp,
"Unsupported option %" PRIu32 " (%s)",