The Tuesday 17 Jun 2014 à 17:53:49 (-0400), Jeff Cody wrote :
> Currently, node_name is only filled in when done so explicitly by the
> user. If no node_name is specified, then the node name field is not
> populated.
>
> If node_names are automatically generated when not specified, that means
> that all block job operations can be done by reference to the unique
> node_name field. This eliminates ambiguity in resolving filenames
> (relative filenames, or file descriptors, symlinks, mounts, etc..) that
> qemu currently needs to deal with.
>
> If a node name is specified, then it will not be automatically
> generated for that BDS entry.
>
> If it is automatically generated, it will be prefaced with "__qemu##",
> followed by 8 characters of a unique number, followed by 8 random
> ASCII characters in the range of 'A-Z'. Some sample generated node-name
> strings:
> __qemu##00000000IAIYNXXR
> __qemu##00000002METXTRBQ
> __qemu##00000001FMBORDWG
Jeff can't we simply enforce the namespace separation with a check on the QDict
option content ?
This way we could be sure that the user can't input a node-name starting with
__qemu.
>
> The prefix is to aid in identifying it as a qemu-generated name, the
> numeric portion is to guarantee uniqueness in a given qemu session, and
> the random characters are to further avoid any accidental collisions
> with user-specified node-names.
>
> Reviewed-by: Eric Blake <ebl...@redhat.com>
> Signed-off-by: Jeff Cody <jc...@redhat.com>
> ---
> block.c | 16 +++++++++++++++-
> 1 file changed, 15 insertions(+), 1 deletion(-)
>
> diff --git a/block.c b/block.c
> index 43abe96..da32bb0 100644
> --- a/block.c
> +++ b/block.c
> @@ -843,12 +843,26 @@ static int bdrv_open_flags(BlockDriverState *bs, int
> flags)
> return open_flags;
> }
>
> +#define GEN_NODE_NAME_PREFIX "__qemu##"
> +#define GEN_NODE_NAME_MAX_LEN (sizeof(GEN_NODE_NAME_PREFIX) + 8 + 8)
> static void bdrv_assign_node_name(BlockDriverState *bs,
> const char *node_name,
> Error **errp)
> {
> + char gen_node_name[GEN_NODE_NAME_MAX_LEN];
> + static uint32_t counter; /* simple counter to guarantee uniqueness */
> +
> + /* if node_name is NULL, auto-generate a node name */
> if (!node_name) {
> - return;
> + int len;
> + snprintf(gen_node_name, GEN_NODE_NAME_MAX_LEN,
> + "%s%08x", GEN_NODE_NAME_PREFIX, counter++);
> + len = strlen(gen_node_name);
> + while (len < GEN_NODE_NAME_MAX_LEN - 1) {
> + gen_node_name[len++] = g_random_int_range('A', 'Z');
> + }
> + gen_node_name[GEN_NODE_NAME_MAX_LEN - 1] = '\0';
> + node_name = gen_node_name;
> }
>
> /* empty string node name is invalid */
> --
> 1.9.3
>
