Re: [Qemu-devel] [PATCH v2] curl: Operate on zero-length file

[Michael Tokarev]

08.07.2016 14:18, Tomáš Golembiovský wrote:
> Another attempt to fix the bug 1596870.
>
> When creating new disk backed by remote file accessed via HTTPS and the
> backing file has zero length, qemu-img terminates with uniformative
> error message:
>
>     qemu-img: disk.qcow2: CURL: Error opening file:
>
> While it may not make much sense to operate on empty file, other block
> backends (e.g. raw backend for regular files) seem to allow it. This
> patch fixes it for the curl backend and improves the reported error.
>
> Signed-off-by: Tomáš Golembiovský <address@hidden>
> ---
>  block/curl.c | 25 +++++++++++++++++++++----
>  1 file changed, 21 insertions(+), 4 deletions(-)
>
> diff --git a/block/curl.c b/block/curl.c
> index da9f5e8..a8cdb44 100644
> --- a/block/curl.c
> +++ b/block/curl.c
> @@ -675,11 +675,28 @@ static int curl_open(BlockDriverState *bs, QDict 
> *options, int flags,
>      curl_easy_setopt(state->curl, CURLOPT_HEADERDATA, s);
>      if (curl_easy_perform(state->curl))
>          goto out;
> -    curl_easy_getinfo(state->curl, CURLINFO_CONTENT_LENGTH_DOWNLOAD, &d);
> -    if (d)
> -        s->len = (size_t)d;
> -    else if(!s->len)
> +    if (curl_easy_getinfo(state->curl, CURLINFO_CONTENT_LENGTH_DOWNLOAD, &d)) {
>          goto out;
> +    }
> +    /* Prior CURL 7.19.4 return value of 0 could mean that the file size is not
> +     * know or the size is zero. From 7.19.4 CURL returns -1 if size is not
> +     * known and zero if it is realy zero-length file. */
> +#if LIBCURL_VERSION_NUM >= 0x071304
> +    if (d < 0) {
> +        pstrcpy(state->errmsg, CURL_ERROR_SIZE,
> +                "Server didn't report file size.");
> +        goto out;
> +    }
> +#else
> +    if (d <= 0) {
> +        pstrcpy(state->errmsg, CURL_ERROR_SIZE,
> +                "Unknown file size or zero-length file.");
> +        goto out;
> +    }
> +#endif

This is somewhat ugly ifdeffery, but ohwell..

> +    s->len = (size_t)d;
> +
>      if ((!strncasecmp(s->url, "http://";, strlen("http://";))
>          || !strncasecmp(s->url, "https://";, strlen("https://";)))
>          && !s->accept_range) {


Applied to -trivial, thank you!

/mjt