[Libguestfs] [nbdkit PATCH] vddk: advise user on obscure thumbprint mismatch error condition

[Laszlo Ersek]

On 05/17/22 10:09, Richard W.M. Jones wrote:
> On Tue, May 17, 2022 at 10:02:28AM +0200, Laszlo Ersek wrote:
>> If the thumbprint parameter is wrong, it's only reported in
>> VixDiskLib_Open(), and then with the non-descript VIX_E_FAIL error code.
>> If the user typed or cut-and-pasted the thumbprint incorrectly, said
>> "Unkown error" message is not helpful for fixing the nbkit command line.
> 
> ^^ Typo: Unknown

Thanks; fixed.

> 
>> Hint at the thumbprint as the potential culprit.
>>
>> Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1905772
>> Signed-off-by: Laszlo Ersek <lersek at redhat.com>
>> ---
>>  plugins/vddk/vddk-structs.h |  1 +
>>  plugins/vddk/vddk.c         | 20 ++++++++++++++++++++
>>  2 files changed, 21 insertions(+)
>>
>> diff --git a/plugins/vddk/vddk-structs.h b/plugins/vddk/vddk-structs.h
>> index 799c4aecc5b8..4c7c6fe2e4fc 100644
>> --- a/plugins/vddk/vddk-structs.h
>> +++ b/plugins/vddk/vddk-structs.h
>> @@ -43,6 +43,7 @@
>>  
>>  typedef uint64_t VixError;
>>  #define VIX_OK 0
>> +#define VIX_E_FAIL 1
>>  #define VIX_E_NOT_SUPPORTED 6
>>  #define VIX_ASYNC 25000
>>  
>> diff --git a/plugins/vddk/vddk.c b/plugins/vddk/vddk.c
>> index 2ea071d641e6..dbd3fdbe09af 100644
>> --- a/plugins/vddk/vddk.c
>> +++ b/plugins/vddk/vddk.c
>> @@ -769,6 +769,26 @@ vddk_open (int readonly)
>>    VDDK_CALL_END (VixDiskLib_Open, 0);
>>    if (err != VIX_OK) {
>>      VDDK_ERROR (err, "VixDiskLib_Open: %s", filename);
>> +
>> +    /* Attempt to advise the user on the extremely helpful "Unknown error"
>> +     * result of VixDiskLib_Open().  The one reason we've seen for this error
>> +     * mode is a thumbprint mismatch (RHBZ#1905772).  Note that:
>> +     *
>> +     * (1) The thumbprint (as a part of "h->params") is passed to
>> +     *     VixDiskLib_ConnectEx() above, but the fingerprint mismatch is
>> +     *     detected only inside VixDiskLib_Open().
>> +     *
>> +     * (2) "thumb_print" may be NULL -- vddk_config_complete() is correct not to
>> +     *     require a non-NULL "thumb_print" for a remote connection; the sample
>> +     *     program "vixDiskLibSample.cpp" in vddk-7.0.3 explicitly permits
>> +     *     "-thumb" to be absent.
>> +     */
>> +    if (is_remote && err == VIX_E_FAIL)
>> +      nbdkit_error ("Please verify whether the \"thumbprint\" parameter (%s) "
>> +                    "matches the SHA1 fingerprint of the remote VMware "
>> +                    "server.  Refer to nbdkit-vddk-plugin(1) section "
>> +                    "\"THUMBPRINTS\" for details.",
>> +                    thumb_print == NULL ? "not specified" : thumb_print);
>>      goto err2;
>>    }
> 
> Seems fine, ACK

Commit ce6d20eee4f3.

Thanks!
Laszlo