Re: [Libguestfs] [libnbd PATCH v2 6/6] info: Tolerate missing size

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 <eblake(a)redhat.com&gt; --- 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)