On 8 Apr 2016, at 23:05, Eric Blake <ebl...@redhat.com> wrote:
> The server has a nice helper function nbd_negotiate_drop_sync()
> which lets it easily ignore fluff from the client (such as the
> payload to an unknown option request). We can't quite make it
> common, since it depends on nbd_negotiate_read() which handles
> coroutine magic, but we can copy the idea into the client where
> we have places where we want to ignore data (such as the
> description tacked on the end of NBD_REP_SERVER).
>
> Signed-off-by: Eric Blake <ebl...@redhat.com>
Reviewed-by: Alex Bligh <a...@alex.org.uk>
> ---
> nbd/client.c | 45 ++++++++++++++++++++++++++++++++-------------
> 1 file changed, 32 insertions(+), 13 deletions(-)
>
> diff --git a/nbd/client.c b/nbd/client.c
> index 07b8d2e..b2dfc11 100644
> --- a/nbd/client.c
> +++ b/nbd/client.c
> @@ -75,6 +75,32 @@ static QTAILQ_HEAD(, NBDExport) exports =
> QTAILQ_HEAD_INITIALIZER(exports);
>
> */
>
> +/* Discard length bytes from channel. Return -errno on failure, or
> + * the amount of bytes consumed. */
> +static ssize_t drop_sync(QIOChannel *ioc, size_t size)
> +{
> + ssize_t ret, dropped = size;
> + char small[1024];
> + char *buffer;
> +
> + buffer = sizeof(small) < size ? small : g_malloc(MIN(65536, size));
> + while (size > 0) {
> + ret = read_sync(ioc, buffer, MIN(65536, size));
> + if (ret < 0) {
> + goto cleanup;
> + }
> + assert(ret <= size);
> + size -= ret;
> + }
> + ret = dropped;
> +
> + cleanup:
> + if (buffer != small) {
> + g_free(buffer);
> + }
> + return ret;
> +}
> +
> /* Send an option request. Return 0 if successful, -1 with errp set if
> * it is impossible to continue. */
> static int nbd_send_option_request(QIOChannel *ioc, uint32_t opt,
> @@ -255,18 +281,11 @@ static int nbd_receive_list(QIOChannel *ioc, char
> **name, Error **errp)
> }
> (*name)[namelen] = '\0';
> len -= namelen;
> - if (len) {
> - char *buf = g_malloc(len + 1);
> - if (read_sync(ioc, buf, len) != len) {
> - error_setg(errp, "failed to read export description");
> - g_free(*name);
> - g_free(buf);
> - *name = NULL;
> - return -1;
> - }
> - buf[len] = '\0';
> - TRACE("Ignoring export description: %s", buf);
> - g_free(buf);
> + if (drop_sync(ioc, len) != len) {
> + error_setg(errp, "failed to read export description");
> + g_free(*name);
> + *name = NULL;
> + return -1;
> }
> } else {
> error_setg(errp, "Unexpected reply type %" PRIx32 " expected %x",
> @@ -539,7 +558,7 @@ int nbd_receive_negotiate(QIOChannel *ioc, const char
> *name, uint32_t *flags,
> goto fail;
> }
>
> - if (read_sync(ioc, &buf, 124) != 124) {
> + if (drop_sync(ioc, 124) != 124) {
> error_setg(errp, "Failed to read reserved block");
> goto fail;
> }
> --
> 2.5.5
>
>
--
Alex Bligh
