Re: [Qemu-devel] [PATCH v2 19/22] nbd/client: Add meta contexts to nbd_receive_export_list()

["Richard W.M. Jones" <rjones@redhat.com>]

On Sat, Dec 15, 2018 at 07:53:21AM -0600, Eric Blake wrote:
> We want to be able to detect whether a given qemu NBD server is
> exposing the right export(s) and dirty bitmaps, at least for
> regression testing.  We could use 'nbd-client -l' from the upstream
> NBD project to list exports, but it's annoying to rely on
> out-of-tree binaries; furthermore, nbd-client doesn't necessarily
> know about all of the qemu NBD extensions.  Thus, we plan on adding
> a new mode to qemu-nbd that merely sniffs all possible information
> from the server during handshake phase, then disconnects and dumps
> the information.
> 
> This patch continues the work of the previous patch, by adding the
> ability to track the list of available meta contexts into
> NBDExportInfo.  It benefits from the recent refactoring patches
> with a new nbd_list_meta_contexts() that reuses much of the same
> framework as setting a meta context.
> 
> Signed-off-by: Eric Blake <eblake@redhat.com>
> 
> ---
> v2: new patch to split out collection of meta context collection
> s/free/g_free/ [Vladimir]
> ---
>  include/block/nbd.h |  2 ++
>  nbd/client.c        | 41 +++++++++++++++++++++++++++++++++++++++--
>  2 files changed, 41 insertions(+), 2 deletions(-)
> 
> diff --git a/include/block/nbd.h b/include/block/nbd.h
> index 09d2157efe0..6d9fbb941d7 100644
> --- a/include/block/nbd.h
> +++ b/include/block/nbd.h
> @@ -284,6 +284,8 @@ struct NBDExportInfo {
> 
>      /* Set by server results during nbd_receive_export_list() */
>      char *description;
> +    int n_contexts;
> +    char **contexts;
>  };
>  typedef struct NBDExportInfo NBDExportInfo;
> 
> diff --git a/nbd/client.c b/nbd/client.c
> index 0e6c575ccad..d392b5e8bee 100644
> --- a/nbd/client.c
> +++ b/nbd/client.c
> @@ -808,6 +808,36 @@ static int nbd_negotiate_simple_meta_context(QIOChannel *ioc,
>      }
>  }
> 
> +/*
> + * nbd_list_meta_contexts:
> + * Request the server to list all meta contexts for export @info->name.
> + * return 0 if list is complete (even if empty),
> + *        -1 with errp set for any other error
> + */
> +static int nbd_list_meta_contexts(QIOChannel *ioc,
> +                                  NBDExportInfo *info,
> +                                  Error **errp)
> +{
> +    int ret;
> +
> +    if (nbd_send_one_meta_context(ioc, NBD_OPT_LIST_META_CONTEXT,
> +                                  info->name, NULL, errp) < 0) {
> +        return -1;
> +    }
> +
> +    while (1) {
> +        char *context;
> +
> +        ret = nbd_receive_one_meta_context(ioc, NBD_OPT_LIST_META_CONTEXT,
> +                                           &context, NULL, errp);
> +        if (ret <= 0) {
> +            return ret;
> +        }
> +        info->contexts = g_renew(char *, info->contexts, ++info->n_contexts);
> +        info->contexts[info->n_contexts - 1] = context;
> +    }
> +}
> +
>  /*
>   * nbd_start_negotiate:
>   * Start the handshake to the server.  After a positive return, the server
> @@ -1054,7 +1084,7 @@ int nbd_receive_negotiate(QIOChannel *ioc, QCryptoTLSCreds *tlscreds,
>  /* Clean up result of nbd_receive_export_list */
>  void nbd_free_export_list(NBDExportInfo *info, int count)
>  {
> -    int i;
> +    int i, j;
> 
>      if (!info) {
>          return;
> @@ -1063,6 +1093,10 @@ void nbd_free_export_list(NBDExportInfo *info, int count)
>      for (i = 0; i < count; i++) {
>          g_free(info[i].name);
>          g_free(info[i].description);
> +        for (j = 0; j < info[i].n_contexts; j++) {
> +            g_free(info[i].contexts[j]);
> +        }
> +        g_free(info[i].contexts);
>      }
>      g_free(info);
>  }
> @@ -1130,7 +1164,10 @@ int nbd_receive_export_list(QIOChannel *ioc, QCryptoTLSCreds *tlscreds,
>                  break;
>              }
> 
> -            /* TODO: Grab meta contexts */
> +            if (result == 3 &&
> +                nbd_list_meta_contexts(ioc, &array[i], errp) < 0) {
> +                goto out;
> +            }
>          }
> 
>          /* Send NBD_OPT_ABORT as a courtesy before hanging up */
> -- 
> 2.17.2

Reviewed-by: Richard W.M. Jones <rjones@redhat.com>

Rich.

-- 
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