[Libvir] Proposed remote protocol (XDR source file qemud/remote_protocol.x)

Richard W.M. Jones rjones at redhat.com
Mon Apr 30 17:48:26 UTC 2007

Richard W.M. Jones wrote:
> The only problem area are the upper limits imposed on the lengths of 
> various strings and arrays.  The upper limits seem to be required for 
> safely decoding messages from untrusted sources.  Some of them however 
> would impose limits on such things as the number of CPUs supported,
and also on number of domains.

> /* For each call we may have a 'remote_CALL_args' and 'remote_CALL_ret'
>  * type.  These are omitted when they are NULL.

Instead of "NULL" that should read "void".

> struct remote_get_max_vcpus_args {
>     /* The only backend which supports this call is Xen HV, and
>      * there the type is ignored so it could be NULL.
>      */
>     remote_string type;
> };

AFAICS the 'type' parameter to GetMaxVcpus is never used.

> struct remote_domain_lookup_by_name_ret {
>     /* XXX "Not found" semantic is ill-defined. */
>     remote_nonnull_domain dom;
> };

There are various of these FooLookupByBar functions and as far as I can 
see no one has given much thought to a semantic for "Not found" which 
differs from some other error.  Am I missing something?

> struct remote_domain_get_info_ret {
>     unsigned char state;
>     unsigned hyper max_mem;
>     unsigned hyper memory;
>     unsigned short nr_virt_cpu;
>     /* XXX cpu_time is declared as unsigned long long */
>     unsigned hyper cpu_time;
> };

It wasn't clear if cpu_time, defined as unsigned long long in C, could 
be larger than 64 bits.  XDR supports 64 bits max, so if it is larger 
we'd need to send _hi and _lo hypers.


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