On Sat, Jan 30, 2016 at 10:34:32AM -0800, Eric Dumazet wrote:
> On Sat, 2016-01-30 at 13:19 -0500, Jarod Wilson wrote:
> > The netdev_stats_to_stats64 function copies the deprecated
> > net_device_stats format stats into rtnl_link_stats64 for legacy support
> > purposes, but with the BUILD_BUG_ON as it was, it wasn't possible to
> > extend rtnl_link_stats64 without also extending net_device_stats. Relax
> > the BUILD_BUG_ON to only require that rtnl_link_stats64 is larger, and
> > zero out all the stat counters that aren't present in net_device_stats.
> >
> > CC: Eric Dumazet <eduma...@google.com>
> > CC: netdev@vger.kernel.org
> > Signed-off-by: Jarod Wilson <ja...@redhat.com>
> > ---
> > Re-re-sending, hopefully getting the patch to the right list this time.
> >
> > net/core/dev.c | 13 +++++++++----
> > 1 file changed, 9 insertions(+), 4 deletions(-)
> >
> > diff --git a/net/core/dev.c b/net/core/dev.c
> > index 8cba3d8..575a7df 100644
> > --- a/net/core/dev.c
> > +++ b/net/core/dev.c
> > @@ -7253,25 +7253,30 @@ void netdev_run_todo(void)
> > }
> > }
> >
> > -/* Convert net_device_stats to rtnl_link_stats64. They have the same
> > - * fields in the same order, with only the type differing.
> > +/* Convert net_device_stats to rtnl_link_stats64. rtnl_link_stats64 has
> > + * all the same fields in the same order as net_device_stats, with only
> > + * the type differing, but rtnl_link_stats64 may have additional fields
> > + * at the end for newer counters.
> > */
> > void netdev_stats_to_stats64(struct rtnl_link_stats64 *stats64,
> > const struct net_device_stats *netdev_stats)
> > {
> > #if BITS_PER_LONG == 64
> > - BUILD_BUG_ON(sizeof(*stats64) != sizeof(*netdev_stats));
> > + BUILD_BUG_ON(sizeof(*stats64) < sizeof(*netdev_stats));
> > memcpy(stats64, netdev_stats, sizeof(*stats64));
> > #else
> > size_t i, n = sizeof(*stats64) / sizeof(u64);
> > const unsigned long *src = (const unsigned long *)netdev_stats;
> > u64 *dst = (u64 *)stats64;
> >
> > - BUILD_BUG_ON(sizeof(*netdev_stats) / sizeof(unsigned long) !=
> > + BUILD_BUG_ON(sizeof(*netdev_stats) / sizeof(unsigned long) >
> > sizeof(*stats64) / sizeof(u64));
> > for (i = 0; i < n; i++)
> > dst[i] = src[i];
> > #endif
> > + /* zero out counters that only exist in rtnl_link_stats64 */
> > + memset((char *)stats64 + sizeof(*netdev_stats), 0,
> > + sizeof(*stats64) - sizeof(*netdev_stats));
>
> Are you sure it works on 32bit arches ?
Ew, no, it won't work correctly on 32-bit. The for loop is going to copy
data into dst from beyond the end of netdev_stats, and the range looks
like it won't be right either, only half of the added stats64 space will
get zeroed out. Okay, I'll fix that up correctly.
--
Jarod Wilson
ja...@redhat.com
