[v2,17/22] nbd/client: Pull out oldstyle size determination

Another refactoring creating nbd_negotiate_finish_oldstyle()
for further reuse during 'qemu-nbd --list'.

Signed-off-by: Eric Blake <eblake@redhat.com>
---
v2: new patch [Vladimir]
---
 nbd/client.c | 49 ++++++++++++++++++++++++++++++++-----------------
 1 file changed, 32 insertions(+), 17 deletions(-)

On Sat, Dec 15, 2018 at 07:53:19AM -0600, Eric Blake wrote:
> Another refactoring creating nbd_negotiate_finish_oldstyle()
> for further reuse during 'qemu-nbd --list'.
> 
> Signed-off-by: Eric Blake <eblake@redhat.com>
> ---
> v2: new patch [Vladimir]
> ---
>  nbd/client.c | 49 ++++++++++++++++++++++++++++++++-----------------
>  1 file changed, 32 insertions(+), 17 deletions(-)
> 
> diff --git a/nbd/client.c b/nbd/client.c
> index 8b0ae20fae8..4bdfba43068 100644
> --- a/nbd/client.c
> +++ b/nbd/client.c
> @@ -811,7 +811,7 @@ static int nbd_negotiate_simple_meta_context(QIOChannel *ioc,
>   * Start the handshake to the server.  After a positive return, the server
>   * is ready to accept additional NBD_OPT requests.
>   * Returns: negative errno: failure talking to server
> - *          0: server is oldstyle, client must still parse export size
> + *          0: server is oldstyle, must call nbd_negotiate_finish_oldstyle
>   *          1: server is newstyle, but can only accept EXPORT_NAME
>   *          2: server is newstyle, but lacks structured replies
>   *          3: server is newstyle and set up for structured replies
> @@ -916,6 +916,36 @@ static int nbd_start_negotiate(QIOChannel *ioc, QCryptoTLSCreds *tlscreds,
>      }
>  }
> 
> +/*
> + * nbd_negotiate_finish_oldstyle:
> + * Populate @info with the size and export flags from an oldstyle server,
> + * but does not consume 124 bytes of reserved zero padding.
> + * Returns 0 on success, -1 with @errp set on failure
> + */
> +static int nbd_negotiate_finish_oldstyle(QIOChannel *ioc, NBDExportInfo *info,
> +                                         Error **errp)
> +{
> +    uint32_t oldflags;
> +
> +    if (nbd_read(ioc, &info->size, sizeof(info->size), errp) < 0) {
> +        error_prepend(errp, "Failed to read export length: ");
> +        return -EINVAL;
> +    }
> +    info->size = be64_to_cpu(info->size);
> +
> +    if (nbd_read(ioc, &oldflags, sizeof(oldflags), errp) < 0) {
> +        error_prepend(errp, "Failed to read export flags: ");
> +        return -EINVAL;
> +    }
> +    oldflags = be32_to_cpu(oldflags);
> +    if (oldflags & ~0xffff) {
> +        error_setg(errp, "Unexpected export flags %0x" PRIx32, oldflags);
> +        return -EINVAL;
> +    }
> +    info->flags = oldflags;
> +    return 0;
> +}
> +
>  /*
>   * nbd_receive_negotiate:
>   * Connect to server, complete negotiation, and move into transmission phase.
> @@ -929,7 +959,6 @@ int nbd_receive_negotiate(QIOChannel *ioc, QCryptoTLSCreds *tlscreds,
>      int result;
>      bool zeroes = true;
>      bool base_allocation = info->base_allocation;
> -    uint32_t oldflags;
> 
>      assert(info->name);
>      trace_nbd_receive_negotiate_name(info->name);
> @@ -1002,23 +1031,9 @@ int nbd_receive_negotiate(QIOChannel *ioc, QCryptoTLSCreds *tlscreds,
>              error_setg(errp, "Server does not support non-empty export names");
>              return -EINVAL;
>          }
> -
> -        if (nbd_read(ioc, &info->size, sizeof(info->size), errp) < 0) {
> -            error_prepend(errp, "Failed to read export length: ");
> +        if (nbd_negotiate_finish_oldstyle(ioc, info, errp) < 0) {
>              return -EINVAL;
>          }
> -        info->size = be64_to_cpu(info->size);
> -
> -        if (nbd_read(ioc, &oldflags, sizeof(oldflags), errp) < 0) {
> -            error_prepend(errp, "Failed to read export flags: ");
> -            return -EINVAL;
> -        }
> -        oldflags = be32_to_cpu(oldflags);
> -        if (oldflags & ~0xffff) {
> -            error_setg(errp, "Unexpected export flags %0x" PRIx32, oldflags);
> -            return -EINVAL;
> -        }
> -        info->flags = oldflags;
>          break;
>      default:
>          return result;

Straightforward refactoring, so:

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

Rich.