RE: [RFC/PATCH net-next v3 8/8] flow_offload: validate flags of filter and actions

[Baowen Zheng <baowen.zheng@corigine.com>]

Thanks for your review and sorry for delay in responding.
On October 30, 2021 2:01 AM, Vlad Buslov wrote:
>On Thu 28 Oct 2021 at 14:06, Simon Horman <simon.horman@corigine.com>
>wrote:
>> From: Baowen Zheng <baowen.zheng@corigine.com>
>>
>> Add process to validate flags of filter and actions when adding a tc
>> filter.
>>
>> We need to prevent adding filter with flags conflicts with its actions.
>>
>> Signed-off-by: Baowen Zheng <baowen.zheng@corigine.com>
>> Signed-off-by: Louis Peens <louis.peens@corigine.com>
>> Signed-off-by: Simon Horman <simon.horman@corigine.com>
>> ---
>>  net/sched/cls_api.c      | 26 ++++++++++++++++++++++++++
>>  net/sched/cls_flower.c   |  3 ++-
>>  net/sched/cls_matchall.c |  4 ++--
>>  net/sched/cls_u32.c      |  7 ++++---
>>  4 files changed, 34 insertions(+), 6 deletions(-)
>>
>> diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c index
>> 351d93988b8b..80647da9713a 100644
>> --- a/net/sched/cls_api.c
>> +++ b/net/sched/cls_api.c
>> @@ -3025,6 +3025,29 @@ void tcf_exts_destroy(struct tcf_exts *exts)  }
>> EXPORT_SYMBOL(tcf_exts_destroy);
>>
>> +static bool tcf_exts_validate_actions(const struct tcf_exts *exts,
>> +u32 flags) { #ifdef CONFIG_NET_CLS_ACT
>> +	bool skip_sw = tc_skip_sw(flags);
>> +	bool skip_hw = tc_skip_hw(flags);
>> +	int i;
>> +
>> +	if (!(skip_sw | skip_hw))
>> +		return true;
>> +
>> +	for (i = 0; i < exts->nr_actions; i++) {
>> +		struct tc_action *a = exts->actions[i];
>> +
>> +		if ((skip_sw && tc_act_skip_hw(a->tcfa_flags)) ||
>> +		    (skip_hw && tc_act_skip_sw(a->tcfa_flags)))
>> +			return false;
>> +	}
>> +	return true;
>> +#else
>> +	return true;
>> +#endif
>> +}
>> +
>
>I know Jamal suggested to have skip_sw for actions, but it complicates the
>code and I'm still not entirely understand why it is necessary.
>After all, action can only get applied to a packet if the packet has been
>matched by some filter and filters already have skip sw/hw controls. Forgoing
>action skip_sw flag would:
>
>- Alleviate the need to validate that filter and action flags are compatible.
>(trying to offload filter that points to existing skip_hw action would just fail
>because the driver wouldn't find the action with provided id in its tables)
>
>- Remove the need to add more conditionals into TC software data path in
>patch 4.
>
>WDYT?
As we discussed with Jamal, we will keep the flag of skip_sw and we need to make
exactly match for the actions with flags and the filter specific action with index. 
>
>>  int tcf_exts_validate(struct net *net, struct tcf_proto *tp, struct nlattr **tb,
>>  		      struct nlattr *rate_tlv, struct tcf_exts *exts,
>>  		      u32 flags, struct netlink_ext_ack *extack) @@ -3066,6
>+3089,9
>> @@ int tcf_exts_validate(struct net *net, struct tcf_proto *tp, struct nlattr
>**tb,
>>  				return err;
>>  			exts->nr_actions = err;
>>  		}
>> +
>> +		if (!tcf_exts_validate_actions(exts, flags))
>> +			return -EINVAL;
>>  	}
>>  #else
>>  	if ((exts->action && tb[exts->action]) || diff --git
>> a/net/sched/cls_flower.c b/net/sched/cls_flower.c index
>> eb6345a027e1..55f89f0e393e 100644
>> --- a/net/sched/cls_flower.c
>> +++ b/net/sched/cls_flower.c
>> @@ -2035,7 +2035,8 @@ static int fl_change(struct net *net, struct sk_buff
>*in_skb,
>>  	}
>>
>>  	err = fl_set_parms(net, tp, fnew, mask, base, tb, tca[TCA_RATE],
>> -			   tp->chain->tmplt_priv, flags, extack);
>> +			   tp->chain->tmplt_priv, flags | fnew->flags,
>> +			   extack);
>
>Aren't you or-ing flags from two different ranges (TCA_CLS_FLAGS_* and
>TCA_ACT_FLAGS_*) that map to same bits, or am I missing something? This
>isn't explained in commit message so it is hard for me to understand the idea
>here.
Yes, as you said we use TCA_CLS_FLAGS_* or TCA_ACT_FLAGS_* flags to validate the action flags. 
As you know, the TCA_ACT_FLAGS_* in flags are system flags(in high 16 bits) and the TCA_CLS_FLAGS_*
are user flags(in low 16 bits), so they will not be conflict. 
But I think you suggestion also makes sense to us, do you think we need to pass a single filter flag
to make the process more clear? 
>
>>  	if (err)
>>  		goto errout;
>>
>> diff --git a/net/sched/cls_matchall.c b/net/sched/cls_matchall.c index
>> 24f0046ce0b3..00b76fbc1dce 100644
>> --- a/net/sched/cls_matchall.c
>> +++ b/net/sched/cls_matchall.c
>> @@ -226,8 +226,8 @@ static int mall_change(struct net *net, struct sk_buff
>*in_skb,
>>  		goto err_alloc_percpu;
>>  	}
>>
>> -	err = mall_set_parms(net, tp, new, base, tb, tca[TCA_RATE], flags,
>> -			     extack);
>> +	err = mall_set_parms(net, tp, new, base, tb, tca[TCA_RATE],
>> +			     flags | new->flags, extack);
>>  	if (err)
>>  		goto err_set_parms;
>>
>> diff --git a/net/sched/cls_u32.c b/net/sched/cls_u32.c index
>> 4272814487f0..fc670cc45122 100644
>> --- a/net/sched/cls_u32.c
>> +++ b/net/sched/cls_u32.c
>> @@ -895,7 +895,8 @@ static int u32_change(struct net *net, struct sk_buff
>*in_skb,
>>  			return -ENOMEM;
>>
>>  		err = u32_set_parms(net, tp, base, new, tb,
>> -				    tca[TCA_RATE], flags, extack);
>> +				    tca[TCA_RATE], flags | new->flags,
>> +				    extack);
>>
>>  		if (err) {
>>  			u32_destroy_key(new, false);
>> @@ -1060,8 +1061,8 @@ static int u32_change(struct net *net, struct
>sk_buff *in_skb,
>>  	}
>>  #endif
>>
>> -	err = u32_set_parms(net, tp, base, n, tb, tca[TCA_RATE], flags,
>> -			    extack);
>> +	err = u32_set_parms(net, tp, base, n, tb, tca[TCA_RATE],
>> +			    flags | n->flags, extack);
>>  	if (err == 0) {
>>  		struct tc_u_knode __rcu **ins;
>>  		struct tc_u_knode *pins;