On Fri, Oct 16, 2020 at 10:02:38AM +0800, zhudi wrote:
> "ip addr show" command execute error when we have a physical
> network card with number of VFs larger than 247.
>
> The return value of if_nlmsg_size() in rtnl_calcit() will exceed
> range of u16 data type when any network cards has a larger number of
> VFs. rtnl_vfinfo_size() will significant increase needed dump size when
> the value of num_vfs is larger.
>
> Eventually we get a wrong value of min_ifinfo_dump_size because of overflow
> which decides the memory size needed by netlink dump and netlink_dump()
> will return -EMSGSIZE because of not enough memory was allocated.
>
> So fix it by promoting min_dump_alloc data type to u32 to
> avoid data overflow and it's also align with the data type of
> struct netlink_callback{}.min_dump_alloc which is assigned by
> return value of rtnl_calcit()
Unfortunately this is only part of the problem. For a NIC with so many
VFs (not sure if exactly 247 but it's close to that), IFLA_VFINFO_LIST
nested attribute itself would be over 64KB long which is not possible as
attribute size is u16.
So we should rather fail in such case (except when IFLA_VFINFO_LIST
itself fits into 64KB but the whole netlink message would not) and
provide an alternative way to get information about all VFs.
Michal
