Subject: Re: [RFC/PATCH net-next v3 3/8] flow_offload: allow user to offload tc action to net device

From: Vlad Buslov <[email-masked]>
Date: Mon, 1 Nov 2021 14:05:30 +0200

On Mon 01 Nov 2021 at 11:44, Baowen Zheng <[email-masked]> wrote:
> Thanks for your review and sorry for delay in responding.
>
> On October 30, 2021 12:59 AM, Vlad Buslov <[email-masked]> wrote:
>>On Thu 28 Oct 2021 at 14:06, Simon Horman <[email-masked]>
>>wrote:
>>> From: Baowen Zheng <[email-masked]>
>>>
>>> Use flow_indr_dev_register/flow_indr_dev_setup_offload to offload tc
>>> action.
>>>
>>> We need to call tc_cleanup_flow_action to clean up tc action entry
>>> since in tc_setup_action, some actions may hold dev refcnt, especially
>>> the mirror action.
>>>
>>> Signed-off-by: Baowen Zheng <[email-masked]>
>>> Signed-off-by: Louis Peens <[email-masked]>
>>> Signed-off-by: Simon Horman <[email-masked]>
>>> ---
>>>  include/linux/netdevice.h  |   1 +
>>>  include/net/act_api.h      |   2 +-
>>>  include/net/flow_offload.h |  17 ++++
>>>  include/net/pkt_cls.h      |  15 ++++
>>>  net/core/flow_offload.c    |  43 ++++++++--
>>>  net/sched/act_api.c        | 166
>>+++++++++++++++++++++++++++++++++++++
>>>  net/sched/cls_api.c        |  29 ++++++-
>>>  7 files changed, 260 insertions(+), 13 deletions(-)
>>>
>>> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
>>> index 3ec42495a43a..9815c3a058e9 100644
>>> --- a/include/linux/netdevice.h
>>> +++ b/include/linux/netdevice.h
>>> @@ -916,6 +916,7 @@ enum tc_setup_type {
>>>  	TC_SETUP_QDISC_TBF,
>>>  	TC_SETUP_QDISC_FIFO,
>>>  	TC_SETUP_QDISC_HTB,
>>> +	TC_SETUP_ACT,
>>>  };
>>>
>>>  /* These structures hold the attributes of bpf state that are being
>>> passed diff --git a/include/net/act_api.h b/include/net/act_api.h
>>> index b5b624c7e488..9eb19188603c 100644
>>> --- a/include/net/act_api.h
>>> +++ b/include/net/act_api.h
>>> @@ -239,7 +239,7 @@ static inline void
>>> tcf_action_inc_overlimit_qstats(struct tc_action *a)  void
>>tcf_action_update_stats(struct tc_action *a, u64 bytes, u64 packets,
>>>  			     u64 drops, bool hw);
>>>  int tcf_action_copy_stats(struct sk_buff *, struct tc_action *, int);
>>> -
>>> +int tcf_action_offload_del(struct tc_action *action);
>>
>>This doesn't seem to be used anywhere outside of act_api in this series, so
>>why is it exported?
> Thanks for bring this to us, we will fix this by moving the block of implement in act_api.c.
>>>  int tcf_action_check_ctrlact(int action, struct tcf_proto *tp,
>>>  			     struct tcf_chain **handle,
>>>  			     struct netlink_ext_ack *newchain); diff --git
>>> a/include/net/flow_offload.h b/include/net/flow_offload.h index
>>> 3961461d9c8b..aa28592fccc0 100644
>>> --- a/include/net/flow_offload.h
>>> +++ b/include/net/flow_offload.h
>>> @@ -552,6 +552,23 @@ struct flow_cls_offload {
>>>  	u32 classid;
>>>  };
>>>
>>> +enum flow_act_command {
>>> +	FLOW_ACT_REPLACE,
>>> +	FLOW_ACT_DESTROY,
>>> +	FLOW_ACT_STATS,
>>> +};
>>> +
>>> +struct flow_offload_action {
>>> +	struct netlink_ext_ack *extack; /* NULL in FLOW_ACT_STATS
>>process*/
>>> +	enum flow_act_command command;
>>> +	enum flow_action_id id;
>>> +	u32 index;
>>> +	struct flow_stats stats;
>>> +	struct flow_action action;
>>> +};
>>> +
>>> +struct flow_offload_action *flow_action_alloc(unsigned int
>>> +num_actions);
>>> +
>>>  static inline struct flow_rule *
>>>  flow_cls_offload_flow_rule(struct flow_cls_offload *flow_cmd)  { diff
>>> --git a/include/net/pkt_cls.h b/include/net/pkt_cls.h index
>>> 193f88ebf629..922775407257 100644
>>> --- a/include/net/pkt_cls.h
>>> +++ b/include/net/pkt_cls.h
>>> @@ -258,6 +258,9 @@ static inline void tcf_exts_put_net(struct tcf_exts
>>*exts)
>>>  	for (; 0; (void)(i), (void)(a), (void)(exts))  #endif
>>>
>>> +#define tcf_act_for_each_action(i, a, actions) \
>>> +	for (i = 0; i < TCA_ACT_MAX_PRIO && ((a) = actions[i]); i++)
>>> +
>>>  static inline void
>>>  tcf_exts_stats_update(const struct tcf_exts *exts,
>>>  		      u64 bytes, u64 packets, u64 drops, u64 lastuse, @@ -532,8
>>> +535,19 @@ tcf_match_indev(struct sk_buff *skb, int ifindex)
>>>  	return ifindex == skb->skb_iif;
>>>  }
>>>
>>> +#ifdef CONFIG_NET_CLS_ACT
>>>  int tc_setup_flow_action(struct flow_action *flow_action,
>>>  			 const struct tcf_exts *exts);
>>
>>Why does existing cls_api function tc_setup_flow_action() now depend on
>>CONFIG_NET_CLS_ACT?
> Originally the function tc_setup_flow_action deal with the dependence of CONFIG_NET_CLS_ACT
> By calling the macro tcf_exts_for_each_action, now we change to call the function tc_setup_action
> Then tc_setup_flow_action will refer to exts->actions, so it will depend on CONFIG_NET_CLS_ACT explicitly.
> To fix this, we have to have the ifdef in tc_setup_flow_action declaration or in the implement in cls_api.c.
> Do you think if it makes sense?

Since we already have multiple of such ifdefs in cls_api I don't think
having more is an issue, but I also don't think we need to ifdef this
function in both pkt_cls.h and cls_api.c. Unless I'm missing something
you can either:

- Make tc_setup_flow_action() inline in pkt_cls.h and remove its
definition from cls_api.c since tc_setup_action() is also exported.

- Move ifdef check inside function definition in cls_api.c (return 0, if
config is not defined), which will allows you to remove ifdef from
pkt_cls.h.

WDYT?

>>> +#else
>>> +static inline int tc_setup_flow_action(struct flow_action *flow_action,
>>> +				       const struct tcf_exts *exts) {
>>> +	return 0;
>>> +}
>>> +#endif
>>> +
>>> +int tc_setup_action(struct flow_action *flow_action,
>>> +		    struct tc_action *actions[]);
>>>  void tc_cleanup_flow_action(struct flow_action *flow_action);
>>>
> ...
>>>  #ifdef CONFIG_INET
>>>  DEFINE_STATIC_KEY_FALSE(tcf_frag_xmit_count);
>>> @@ -148,6 +161,7 @@ static int __tcf_action_put(struct tc_action *p, bool
>>bind)
>>>  		idr_remove(&idrinfo->action_idr, p->tcfa_index);
>>>  		mutex_unlock(&idrinfo->lock);
>>>
>>> +		tcf_action_offload_del(p);
>>>  		tcf_action_cleanup(p);
>>>  		return 1;
>>>  	}
>>> @@ -341,6 +355,7 @@ static int tcf_idr_release_unsafe(struct tc_action *p)
>>>  		return -EPERM;
>>>
>>>  	if (refcount_dec_and_test(&p->tcfa_refcnt)) {
>>> +		tcf_action_offload_del(p);
>>>  		idr_remove(&p->idrinfo->action_idr, p->tcfa_index);
>>>  		tcf_action_cleanup(p);
>>>  		return ACT_P_DELETED;
>>> @@ -452,6 +467,7 @@ static int tcf_idr_delete_index(struct tcf_idrinfo
>>*idrinfo, u32 index)
>>>  						p->tcfa_index));
>>>  			mutex_unlock(&idrinfo->lock);
>>>
>>> +			tcf_action_offload_del(p);
>>
>>tcf_action_offload_del() and tcf_action_cleanup() seem to be always called
>>together. Consider moving the call to tcf_action_offload_del() into
>>tcf_action_cleanup().
>>
> Thanks, we will consider to move tcf_action_offload_del() inside of tcf_action_cleanup.
>>>  			tcf_action_cleanup(p);
>>>  			module_put(owner);
>>>  			return 0;
>>> @@ -1061,6 +1077,154 @@ struct tc_action *tcf_action_init_1(struct net
>>*net, struct tcf_proto *tp,
>>>  	return ERR_PTR(err);
>>>  }
>>>
> ...
>>> +/* offload the tc command after inserted */ static int
>>> +tcf_action_offload_add(struct tc_action *action,
>>> +				  struct netlink_ext_ack *extack) {
>>> +	struct tc_action *actions[TCA_ACT_MAX_PRIO] = {
>>> +		[0] = action,
>>> +	};
>>> +	struct flow_offload_action *fl_action;
>>> +	int err = 0;
>>> +
>>> +	fl_action = flow_action_alloc(tcf_act_num_actions_single(action));
>>> +	if (!fl_action)
>>> +		return -EINVAL;
>>
>>Failed alloc-like functions usually result -ENOMEM.
>>
> Thanks, we will fix this in V4 patch.
>>> +
>>> +	err = flow_action_init(fl_action, action, FLOW_ACT_REPLACE, extack);
>>> +	if (err)
>>> +		goto fl_err;
>>> +
>>> +	err = tc_setup_action(&fl_action->action, actions);
>>> +	if (err) {
>>> +		NL_SET_ERR_MSG_MOD(extack,
>>> +				   "Failed to setup tc actions for offload\n");
>>> +		goto fl_err;
>>> +	}
>>> +
>>> +	err = tcf_action_offload_cmd(fl_action, extack);
>>> +	tc_cleanup_flow_action(&fl_action->action);
>>> +
>>> +fl_err:
>>> +	kfree(fl_action);
>>> +
>>> +	return err;
>>> +}
>>> +
>>> +int tcf_action_offload_del(struct tc_action *action) {
>>> +	struct flow_offload_action fl_act;
>>> +	int err = 0;
>>> +
>>> +	if (!action)
>>> +		return -EINVAL;
>>> +
>>> +	err = flow_action_init(&fl_act, action, FLOW_ACT_DESTROY, NULL);
>>> +	if (err)
>>> +		return err;
>>> +
>>> +	return tcf_action_offload_cmd(&fl_act, NULL); }
>>> +
>>>  /* Returns numbers of initialized actions or negative error. */
>>>
>>>  int tcf_action_init(struct net *net, struct tcf_proto *tp, struct
>>> nlattr *nla, @@ -1103,6 +1267,8 @@ int tcf_action_init(struct net *net,
>>struct tcf_proto *tp, struct nlattr *nla,
>>>  		sz += tcf_action_fill_size(act);
>>>  		/* Start from index 0 */
>>>  		actions[i - 1] = act;
>>> +		if (!(flags & TCA_ACT_FLAGS_BIND))
>>> +			tcf_action_offload_add(act, extack);
>>>  	}
>>>
>>>  	/* We have to commit them all together, because if any error
>>> happened in diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
>>> index 2ef8f5a6205a..351d93988b8b 100644
>>> --- a/net/sched/cls_api.c
>>> +++ b/net/sched/cls_api.c
>>> @@ -3544,8 +3544,8 @@ static enum flow_action_hw_stats
>>tc_act_hw_stats(u8 hw_stats)
>>>  	return hw_stats;
>>>  }
>>>
>>> -int tc_setup_flow_action(struct flow_action *flow_action,
>>> -			 const struct tcf_exts *exts)
>>> +int tc_setup_action(struct flow_action *flow_action,
>>> +		    struct tc_action *actions[])
>>>  {
>>>  	struct tc_action *act;
>>>  	int i, j, k, err = 0;
>>> @@ -3554,11 +3554,11 @@ int tc_setup_flow_action(struct flow_action
>>*flow_action,
>>>  	BUILD_BUG_ON(TCA_ACT_HW_STATS_IMMEDIATE !=
>>FLOW_ACTION_HW_STATS_IMMEDIATE);
>>>  	BUILD_BUG_ON(TCA_ACT_HW_STATS_DELAYED !=
>>> FLOW_ACTION_HW_STATS_DELAYED);
>>>
>>> -	if (!exts)
>>> +	if (!actions)
>>>  		return 0;
>>>
>>>  	j = 0;
>>> -	tcf_exts_for_each_action(i, act, exts) {
>>> +	tcf_act_for_each_action(i, act, actions) {
>>>  		struct flow_action_entry *entry;
>>>
>>>  		entry = &flow_action->entries[j];
>>> @@ -3725,7 +3725,19 @@ int tc_setup_flow_action(struct flow_action
>>*flow_action,
>>>  	spin_unlock_bh(&act->tcfa_lock);
>>>  	goto err_out;
>>>  }
>>> +EXPORT_SYMBOL(tc_setup_action);
>>> +
>>> +#ifdef CONFIG_NET_CLS_ACT
>>
>>Maybe just move tc_setup_action() to act_api and ifdef its definition in
>>pkt_cls.h instead of existing tc_setup_flow_action()?
> As explanation above, after the change, tc_setup_flow_action will call function of 
> tc_setup_action and refer to exts->actions, so just move tc_setup_action can not
> fix this problem.

Got it.

>>> +int tc_setup_flow_action(struct flow_action *flow_action,
>>> +			 const struct tcf_exts *exts)
>>> +{
>>> +	if (!exts)
>>> +		return 0;
>>> +
>>> +	return tc_setup_action(flow_action, exts->actions); }
>>>  EXPORT_SYMBOL(tc_setup_flow_action);
>>> +#endif
>>>
>>>  unsigned int tcf_exts_num_actions(struct tcf_exts *exts)  { @@
>>> -3743,6 +3755,15 @@ unsigned int tcf_exts_num_actions(struct tcf_exts
>>> *exts)  }  EXPORT_SYMBOL(tcf_exts_num_actions);
>>>
>>> +unsigned int tcf_act_num_actions_single(struct tc_action *act) {
>>> +	if (is_tcf_pedit(act))
>>> +		return tcf_pedit_nkeys(act);
>>> +	else
>>> +		return 1;
>>> +}
>>> +EXPORT_SYMBOL(tcf_act_num_actions_single);
>>> +
>>>  #ifdef CONFIG_NET_CLS_ACT
>>>  static int tcf_qevent_parse_block_index(struct nlattr *block_index_attr,
>>>  					u32 *p_block_index,