On Thu, Sep 21, 2023 at 03:58:05PM -0500, Eric Blake wrote:
> As previous patches showed, the NBD spec does not yet forbid a server
> sending us a size that does not fit in int64_t. We should gracefully
> handle this during nbdinfo, rather than giving up early.
>
> With the same one-line hack to qemu to set the most significant bit of
> the export size, output changes from pre-patch:
>
> $ ./run nbdinfo nbd://localhost
> /home/eblake/libnbd/info/.libs/nbdinfo: nbd_get_size: server claims size
> 9223372036854781440 which does not fit in signed result: Value too large for
> defined data type
> qemu-nbd: option negotiation failed: Failed to read opts magic: Unexpected
> end-of-file before all data were read
>
> to post-patch:
>
> $ ./run nbdinfo nbd://localhost
> protocol: newstyle-fixed without TLS, using extended packets
> ...
> block_size_maximum: 33554432
>
> or
>
> $ ./run nbdinfo nbd://localhost --json
> {
> "protocol": "newstyle-fixed",
> ...
> "block_size_maximum": 33554432,
> "export-size-str": "unavailable"
> } ]
> }
>
> Sadly, since writing a server with such large export sizes requires a
> one-off hack, I don't see the point in adding a unit test.
>
> Signed-off-by: Eric Blake <ebl...@redhat.com>
> ---
> info/show.c | 25 +++++++++++++------------
> 1 file changed, 13 insertions(+), 12 deletions(-)
>
> diff --git a/info/show.c b/info/show.c
> index a71d837e..3d80545e 100644
> --- a/info/show.c
> +++ b/info/show.c
> @@ -46,7 +46,7 @@ show_one_export (struct nbd_handle *nbd, const char *desc,
> bool first, bool last)
> {
> int64_t i, size;
> - char size_str[HUMAN_SIZE_LONGEST];
> + char size_str[HUMAN_SIZE_LONGEST] = "unavailable";
> bool human_size_flag;
> char *export_name = NULL;
> char *export_desc = NULL;
> @@ -89,13 +89,10 @@ show_one_export (struct nbd_handle *nbd, const char *desc,
> return false;
> }
> size = nbd_get_size (nbd);
> - if (size == -1) {
> - fprintf (stderr, "%s: %s\n", progname, nbd_get_error ());
> - exit (EXIT_FAILURE);
> + if (size >= 0) {
> + human_size (size_str, size, &human_size_flag);
> }
>
> - human_size (size_str, size, &human_size_flag);
> -
> if (uri_is_meaningful ())
> uri = nbd_get_uri (nbd);
>
> @@ -130,7 +127,8 @@ show_one_export (struct nbd_handle *nbd, const char *desc,
> show_context = true;
>
> /* Get content last, as it moves the connection out of negotiating */
> - content = get_content (nbd, size);
> + if (size >= 0)
> + content = get_content (nbd, size);
>
> if (!json_output) {
> ansi_colour (ANSI_FG_BOLD_BLACK, fp);
> @@ -140,10 +138,12 @@ show_one_export (struct nbd_handle *nbd, const char
> *desc,
> fprintf (fp, ":\n");
> if (desc && *desc)
> fprintf (fp, "\tdescription: %s\n", desc);
> - if (human_size_flag)
> - fprintf (fp, "\texport-size: %" PRIi64 " (%s)\n", size, size_str);
> - else
> - fprintf (fp, "\texport-size: %" PRIi64 "\n", size);
> + if (size >= 0) {
> + if (human_size_flag)
> + fprintf (fp, "\texport-size: %" PRIi64 " (%s)\n", size, size_str);
> + else
> + fprintf (fp, "\texport-size: %" PRIi64 "\n", size);
> + }
> if (content)
> fprintf (fp, "\tcontent: %s\n", content);
> if (uri)
> @@ -273,7 +273,8 @@ show_one_export (struct nbd_handle *nbd, const char *desc,
> block_maximum);
>
> /* Put this one at the end because of the stupid comma thing in JSON. */
> - fprintf (fp, "\t\"export-size\": %" PRIi64 ",\n", size);
> + if (size >= 0)
> + fprintf (fp, "\t\"export-size\": %" PRIi64 ",\n", size);
> fprintf (fp, "\t\"export-size-str\": \"%s\"\n", size_str);
>
> if (last)
Reviewed-by: Richard W.M. Jones <rjo...@redhat.com>
--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
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