Re: [PATCH net 2/4] s390/qeth: don't use obsolete dst entry

David Miller
2019-06-03T19:43:51Z

From: Julian Wiedmann <jwi@linux.ibm.com>
Date: Mon, 3 Jun 2019 17:04:44 +0200

> While qeth_l3 uses netif_keep_dst() to hold onto the dst, a skb's dst
> may still have been obsoleted (via dst_dev_put()) by the time that we
> end up using it. The dst then points to the loopback interface, which
> means the neighbour lookup in qeth_l3_get_cast_type() determines a bogus
> cast type of RTN_BROADCAST.
> For IQD interfaces this causes us to place such skbs on the wrong
> HW queue, resulting in TX errors.
>
> Fix-up the various call sites to check whether the dst is obsolete, and
> fall back accordingly.
>
> Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>

Please use "dst_check()".

Some routes have DST_OBSOLETE_FORCE_CHK set on them from the very beginning
so that uses of the route are forced through the dst->ops->check() method.

Simply use dst_check() and then you can just retain the 'rt == NULL' logic
as-is.

Thanks.