xl: Need help with overflow and error handling for vif rate support

["Mathieu Gagné" <mgagne@iweb.com>]

Hi,

I'm working a patch to add support for vif rate limiting support to 
libxl/xl. [1]

I'm especially working on using uint64_t instead of uint32_t [2] and 
adding error handling. [3]

- How should I check for overflows when multiplying 2 uint64_t together?
   - I'm currently using math.h and log. Is it the correct approach?
- How should I handle errors?
   - Should I do something similar to libxlu_disk.c?
   - Should xlu_vif_parse_rate prints an error and returns an error code?
   - If the error is from one of the "helpers", should they print an 
error too or should xlu_vif_parse_rate deals with it?

Any help would be greatly appreciated.

Regards,

[1] http://lists.xen.org/archives/html/xen-devel/2012-03/msg01596.html
[2] http://lists.xen.org/archives/html/xen-devel/2012-03/msg01627.html
[3] http://lists.xen.org/archives/html/xen-devel/2012-03/msg01738.html

-- 
Mathieu