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

Julian Wiedmann
2019-06-04T08:04:07Z

On 03.06.19 21:43, David Miller wrote:
> 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 Fix-up the various call sites to check whether the dst is obsolete, and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.
>
Alright - I was hesitant to go down that path in the context of a driver,
but looks like rt6_get_cookie() should do the trick. v2 coming up... thanks.