12.01.2019 20:58, Eric Blake wrote:
> Another refactoring creating nbd_negotiate_finish_oldstyle()
> for further reuse during 'qemu-nbd --list'.
>
> Signed-off-by: Eric Blake <ebl...@redhat.com>
> Message-Id: <20181215135324.152629-18-ebl...@redhat.com>
> Reviewed-by: Richard W.M. Jones <rjo...@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com>
Hmm, looking at this, I found that nbd_start_negotiate() has very unusual
semantics
for @zeroes field, without any comment about it:
It must be set to true before calling, and nbd_start_negotiate may set it to
true.
I think better is not to rely on caller initialization and set zeroes to true
at the
beginning of nbd_start_negotiate().
> ---
> nbd/client.c | 49 ++++++++++++++++++++++++++++++++-----------------
> 1 file changed, 32 insertions(+), 17 deletions(-)
>
> diff --git a/nbd/client.c b/nbd/client.c
> index 5053433ea5e..620fbb5ef01 100644
> --- a/nbd/client.c
> +++ b/nbd/client.c
> @@ -818,7 +818,7 @@ 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
> @@ -923,6 +923,36 @@ 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.
> @@ -936,7 +966,6 @@ 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);
> @@ -1009,23 +1038,9 @@ 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;
>
--
Best regards,
Vladimir
