Subject: Re: [patch net-next v8 08/14] net: sched: add rt netlink message type for block get

From: Jiri Pirko <[email-masked]>
Date: Mon, 15 Jan 2018 18:27:02 +0100

Mon, Jan 15, 2018 at 06:21:44PM CET, [email-masked] wrote:
>On 1/15/18 10:08 AM, David Ahern wrote:
>> On 1/15/18 10:03 AM, Jiri Pirko wrote:
>>> Mon, Jan 15, 2018 at 05:56:31PM CET, [email-masked] wrote:
>>>> On 1/12/18 8:46 AM, Jiri Pirko wrote:
>>>>> From: Jiri Pirko <[email-masked]>
>>>>>
>>>>> Add simple block get operation which primary purpose is to check the
>>>>> block existence by block index.
>>>>>
>>>>> Signed-off-by: Jiri Pirko <[email-masked]>
>>>>> ---
>>>>> v6->v7:
>>>>> - new patch
>>>>> ---
>>>>>  include/uapi/linux/rtnetlink.h |  6 ++++
>>>>>  net/sched/cls_api.c            | 64 ++++++++++++++++++++++++++++++++++++++++++
>>>>>  security/selinux/nlmsgtab.c    |  5 +++-
>>>>>  3 files changed, 74 insertions(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/include/uapi/linux/rtnetlink.h b/include/uapi/linux/rtnetlink.h
>>>>> index da878f2..4b1f626 100644
>>>>> --- a/include/uapi/linux/rtnetlink.h
>>>>> +++ b/include/uapi/linux/rtnetlink.h
>>>>> @@ -150,6 +150,12 @@ enum {
>>>>>  	RTM_NEWCACHEREPORT = 96,
>>>>>  #define RTM_NEWCACHEREPORT RTM_NEWCACHEREPORT
>>>>>  
>>>>> +	RTM_NEWBLOCK = 100,
>>>>> +#define RTM_NEWBLOCK RTM_NEWBLOCK
>>>>> +	RTM_DELBLOCK,
>>>>> +#define RTM_DELBLOCK RTM_DELBLOCK
>>>>> +	RTM_GETBLOCK,
>>>>> +#define RTM_GETBLOCK RTM_GETBLOCK
>>>>>  	__RTM_MAX,
>>>>>  #define RTM_MAX		(((__RTM_MAX + 3) & ~3) - 1)
>>>>>  };
>>>>> diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
>>>>> index d687e58..14e4f20 100644
>>>>> --- a/net/sched/cls_api.c
>>>>> +++ b/net/sched/cls_api.c
>>>>> @@ -1553,6 +1553,69 @@ int tc_setup_cb_call(struct tcf_block *block, struct tcf_exts *exts,
>>>>>  }
>>>>>  EXPORT_SYMBOL(tc_setup_cb_call);
>>>>>  
>>>>> +static int block_notify_fill(struct net *net, struct sk_buff *skb,
>>>>> +			     struct tcf_block *block, u32 portid, u32 seq,
>>>>> +			     u16 flags, int event)
>>>>> +{
>>>>> +	struct nlmsghdr *nlh;
>>>>> +	struct tcmsg *tcm;
>>>>> +
>>>>> +	nlh = nlmsg_put(skb, portid, seq, event, sizeof(*tcm), flags);
>>>>> +	if (!nlh)
>>>>> +		return -EMSGSIZE;
>>>>> +	tcm = nlmsg_data(nlh);
>>>>> +	memset(tcm, 0, sizeof(*tcm));
>>>>> +	tcm->tcm_family = AF_UNSPEC;
>>>>> +	tcm->tcm_ifindex = TCM_IFINDEX_MAGIC_BLOCK;
>>>>> +	tcm->tcm_block_index = block->index;
>>>>> +	return 0;
>>>>> +}
>>>>
>>>> Why can't this be done with RTM_GETQDISC?
>>>
>>> I don't follow. Could you please describe a bit more what do you think?
>> 
>> Why are you adding RTM_{NEW,GET,DEL}BLOCK? Can't you get the same
>> information using RTM_GETQDISC and updating it to check for the
>> 'tcm_ifindex == TCM_IFINDEX_MAGIC_BLOCK' path

I might, but it bould be an ugly hack. I would use cmd that is used to
manipulate qdisc to some entirely different purpose. That does not make
any sense to me :(

>> 
>
>The above question is because a user specifies a shared block in a
>'qdisc add'.

Qdisc and block is a different entity

>
>Alternatively, what about RTM_GETTFILTER? You already update
>tc_ctl_tfilter to check for TCM_IFINDEX_MAGIC_BLOCK

The object is still filter! Only the handle is different. You cannot
compare that, sorry.

>
>My main question is why can't existing RTM_ commands be used?