> 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.
Thanks for your replying, it's right. The patch only fix the situation that
IFLA_VFINFO_LIST itself
fits into 64KB but the whole netlink message would not.
