nbd\_can\_meta\_context(3) LIBNBD nbd\_can\_meta\_context(3)

# [NAME](#NAME)

nbd\_can\_meta\_context - does the server support a specific meta context?

# [SYNOPSIS](#SYNOPSIS)

```
 #include <libnbd.h>
 int nbd_can_meta_context (
       struct nbd_handle *h, const char *metacontext
     );
```

# [DESCRIPTION](#DESCRIPTION)

Returns true if the server supports the given meta context (see [**nbd\_add\_meta\_context**(3)](/man/os/libnbd/nbd_add_meta_context.3)). Returns false if the server does not. It is possible for this command to fail if meta contexts were requested but there is a missing or failed attempt at NBD\_OPT\_SET\_META\_CONTEXT during option negotiation.

If the server supports block status filtering (see [**nbd\_can\_block\_status\_payload**(3)](/man/os/libnbd/nbd_can_block_status_payload.3), this function must return true for any filter name passed to [**nbd\_block\_status\_filter**(3)](/man/os/libnbd/nbd_block_status_filter.3).

The single parameter is the name of the metadata context, for example "LIBNBD\_CONTEXT\_BASE\_ALLOCATION". **&lt;libnbd.h&gt;** includes defined constants for well-known namespace contexts beginning with "LIBNBD\_CONTEXT\_", but you are free to pass in other contexts.

This call does not block, because it returns data that is saved in the handle from the NBD protocol handshake.

# [RETURN VALUE](#RETURN_VALUE)

This call returns a boolean value.

# [ERRORS](#ERRORS)

On error -1 is returned.

Refer to "ERROR HANDLING" in [**libnbd**(3)](/man/os/libnbd/libnbd.3) for how to get further details of the error.

The following parameters must not be NULL: "h", "metacontext". For more information see "Non-NULL parameters" in [**libnbd**(3)](/man/os/libnbd/libnbd.3).

# [HANDLE STATE](#HANDLE_STATE)

nbd\_can\_meta\_context can be called when the handle is in the following states:

```
 ┌─────────────────────────────────────┬─────────────────────────┐
 │ Handle created, before connecting   │ ❌ error                │
 │ Connecting                          │ ❌ error                │
 │ Connecting & handshaking (opt_mode) │ ✅ allowed              │
 │ Connected to the server             │ ✅ allowed              │
 │ Connection shut down                │ ✅ allowed              │
 │ Handle dead                         │ ❌ error                │
 └─────────────────────────────────────┴─────────────────────────┘
```

# [VERSION](#VERSION)

This function first appeared in libnbd 1.0.

If you need to test if this function is available at compile time check if the following macro is defined:

```
 #define LIBNBD_HAVE_NBD_CAN_META_CONTEXT 1
```

# [SEE ALSO](#SEE_ALSO)

[**nbd\_add\_meta\_context**(3)](/man/os/libnbd/nbd_add_meta_context.3), [**nbd\_aio\_block\_status\_64**(3)](/man/os/libnbd/nbd_aio_block_status_64.3), [**nbd\_block\_status\_64**(3)](/man/os/libnbd/nbd_block_status_64.3), [**nbd\_block\_status\_filter**(3)](/man/os/libnbd/nbd_block_status_filter.3), [**nbd\_can\_block\_status\_payload**(3)](/man/os/libnbd/nbd_can_block_status_payload.3), [**nbd\_create**(3)](/man/os/libnbd/nbd_create.3), [**nbd\_opt\_info**(3)](/man/os/libnbd/nbd_opt_info.3), [**nbd\_opt\_set\_meta\_context**(3)](/man/os/libnbd/nbd_opt_set_meta_context.3), [**nbd\_set\_request\_meta\_context**(3)](/man/os/libnbd/nbd_set_request_meta_context.3), "Flag calls" in [**libnbd**(3)](/man/os/libnbd/libnbd.3), [**libnbd**(3)](/man/os/libnbd/libnbd.3).

# [AUTHORS](#AUTHORS)

Eric Blake

Richard W.M. Jones

# [COPYRIGHT](#COPYRIGHT)

Copyright Red Hat

# [LICENSE](#LICENSE)

This library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.

This library 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 Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License along with this library; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

2026-10-11 libnbd-1.25.7

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Document: nbd_can_meta_context(3) from libnbd 1.25.7-r3 (Chainguard OS)