Subject: Re: [PATCH v4 04/10] flow_offload: allow user to offload tc action to net device

From: Vlad Buslov <[email-masked]>
Date: Fri, 19 Nov 2021 21:05:44 +0200

On Thu 18 Nov 2021 at 15:07, 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/flow_offload.h |  17 ++++
>  include/net/pkt_cls.h      |  12 +++
>  net/core/flow_offload.c    |  43 ++++++++--
>  net/sched/act_api.c        | 164 +++++++++++++++++++++++++++++++++++++
>  net/sched/cls_api.c        |  31 ++++++-
>  6 files changed, 256 insertions(+), 12 deletions(-)
>
> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> index 4f4a299e92de..ae189fcff3c6 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/flow_offload.h b/include/net/flow_offload.h
> index f6970213497a..15662cad5bca 100644
> --- a/include/net/flow_offload.h
> +++ b/include/net/flow_offload.h
> @@ -551,6 +551,23 @@ 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..14d098a887d0 100644
> --- a/include/net/pkt_cls.h
> +++ b/include/net/pkt_cls.h
> @@ -258,6 +258,14 @@ 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 bool tc_act_bind(u32 flags)
> +{
> +	return !!(flags & TCA_ACT_FLAGS_BIND);
> +}
> +
>  static inline void
>  tcf_exts_stats_update(const struct tcf_exts *exts,
>  		      u64 bytes, u64 packets, u64 drops, u64 lastuse,
> @@ -534,6 +542,9 @@ tcf_match_indev(struct sk_buff *skb, int ifindex)
>  
>  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[]);
>  void tc_cleanup_flow_action(struct flow_action *flow_action);
>  
>  int tc_setup_cb_call(struct tcf_block *block, enum tc_setup_type type,
> @@ -554,6 +565,7 @@ int tc_setup_cb_reoffload(struct tcf_block *block, struct tcf_proto *tp,
>  			  enum tc_setup_type type, void *type_data,
>  			  void *cb_priv, u32 *flags, unsigned int *in_hw_count);
>  unsigned int tcf_exts_num_actions(struct tcf_exts *exts);
> +unsigned int tcf_act_num_actions_single(struct tc_action *act);
>  
>  #ifdef CONFIG_NET_CLS_ACT
>  int tcf_qevent_init(struct tcf_qevent *qe, struct Qdisc *sch,
> diff --git a/net/core/flow_offload.c b/net/core/flow_offload.c
> index 6beaea13564a..6676431733ef 100644
> --- a/net/core/flow_offload.c
> +++ b/net/core/flow_offload.c
> @@ -27,6 +27,27 @@ struct flow_rule *flow_rule_alloc(unsigned int num_actions)
>  }
>  EXPORT_SYMBOL(flow_rule_alloc);
>  
> +struct flow_offload_action *flow_action_alloc(unsigned int num_actions)
> +{
> +	struct flow_offload_action *fl_action;
> +	int i;
> +
> +	fl_action = kzalloc(struct_size(fl_action, action.entries, num_actions),
> +			    GFP_KERNEL);
> +	if (!fl_action)
> +		return NULL;
> +
> +	fl_action->action.num_entries = num_actions;
> +	/* Pre-fill each action hw_stats with DONT_CARE.
> +	 * Caller can override this if it wants stats for a given action.
> +	 */
> +	for (i = 0; i < num_actions; i++)
> +		fl_action->action.entries[i].hw_stats = FLOW_ACTION_HW_STATS_DONT_CARE;
> +
> +	return fl_action;
> +}
> +EXPORT_SYMBOL(flow_action_alloc);
> +
>  #define FLOW_DISSECTOR_MATCH(__rule, __type, __out)				\
>  	const struct flow_match *__m = &(__rule)->match;			\
>  	struct flow_dissector *__d = (__m)->dissector;				\
> @@ -549,19 +570,25 @@ int flow_indr_dev_setup_offload(struct net_device *dev,	struct Qdisc *sch,
>  				void (*cleanup)(struct flow_block_cb *block_cb))
>  {
>  	struct flow_indr_dev *this;
> +	u32 count = 0;
> +	int err;
>  
>  	mutex_lock(&flow_indr_block_lock);
> +	if (bo) {
> +		if (bo->command == FLOW_BLOCK_BIND)
> +			indir_dev_add(data, dev, sch, type, cleanup, bo);
> +		else if (bo->command == FLOW_BLOCK_UNBIND)
> +			indir_dev_remove(data);
> +	}
>  
> -	if (bo->command == FLOW_BLOCK_BIND)
> -		indir_dev_add(data, dev, sch, type, cleanup, bo);
> -	else if (bo->command == FLOW_BLOCK_UNBIND)
> -		indir_dev_remove(data);
> -
> -	list_for_each_entry(this, &flow_block_indr_dev_list, list)
> -		this->cb(dev, sch, this->cb_priv, type, bo, data, cleanup);
> +	list_for_each_entry(this, &flow_block_indr_dev_list, list) {
> +		err = this->cb(dev, sch, this->cb_priv, type, bo, data, cleanup);
> +		if (!err)
> +			count++;
> +	}
>  
>  	mutex_unlock(&flow_indr_block_lock);
>  
> -	return list_empty(&bo->cb_list) ? -EOPNOTSUPP : 0;
> +	return (bo && list_empty(&bo->cb_list)) ? -EOPNOTSUPP : count;
>  }
>  EXPORT_SYMBOL(flow_indr_dev_setup_offload);
> diff --git a/net/sched/act_api.c b/net/sched/act_api.c
> index 3258da3d5bed..c3d08b710661 100644
> --- a/net/sched/act_api.c
> +++ b/net/sched/act_api.c
> @@ -21,6 +21,19 @@
>  #include <net/pkt_cls.h>
>  #include <net/act_api.h>
>  #include <net/netlink.h>
> +#include <net/tc_act/tc_pedit.h>
> +#include <net/tc_act/tc_mirred.h>
> +#include <net/tc_act/tc_vlan.h>
> +#include <net/tc_act/tc_tunnel_key.h>
> +#include <net/tc_act/tc_csum.h>
> +#include <net/tc_act/tc_gact.h>
> +#include <net/tc_act/tc_police.h>
> +#include <net/tc_act/tc_sample.h>
> +#include <net/tc_act/tc_skbedit.h>
> +#include <net/tc_act/tc_ct.h>
> +#include <net/tc_act/tc_mpls.h>
> +#include <net/tc_act/tc_gate.h>
> +#include <net/flow_offload.h>
>  
>  #ifdef CONFIG_INET
>  DEFINE_STATIC_KEY_FALSE(tcf_frag_xmit_count);
> @@ -129,8 +142,157 @@ static void free_tcf(struct tc_action *p)
>  	kfree(p);
>  }
>  
> +static int flow_action_init(struct flow_offload_action *fl_action,
> +			    struct tc_action *act,
> +			    enum flow_act_command cmd,
> +			    struct netlink_ext_ack *extack)
> +{
> +	if (!fl_action)
> +		return -EINVAL;

Multiple functions in this patch verify action argument that seemingly
can't be NULL neither in this change nor in the following ones in
series. Any particular motivation for this?

> +
> +	fl_action->extack = extack;
> +	fl_action->command = cmd;
> +	fl_action->index = act->tcfa_index;
> +
> +	if (is_tcf_gact_ok(act)) {
> +		fl_action->id = FLOW_ACTION_ACCEPT;
> +	} else if (is_tcf_gact_shot(act)) {
> +		fl_action->id = FLOW_ACTION_DROP;
> +	} else if (is_tcf_gact_trap(act)) {
> +		fl_action->id = FLOW_ACTION_TRAP;
> +	} else if (is_tcf_gact_goto_chain(act)) {
> +		fl_action->id = FLOW_ACTION_GOTO;
> +	} else if (is_tcf_mirred_egress_redirect(act)) {
> +		fl_action->id = FLOW_ACTION_REDIRECT;
> +	} else if (is_tcf_mirred_egress_mirror(act)) {
> +		fl_action->id = FLOW_ACTION_MIRRED;
> +	} else if (is_tcf_mirred_ingress_redirect(act)) {
> +		fl_action->id = FLOW_ACTION_REDIRECT_INGRESS;
> +	} else if (is_tcf_mirred_ingress_mirror(act)) {
> +		fl_action->id = FLOW_ACTION_MIRRED_INGRESS;
> +	} else if (is_tcf_vlan(act)) {
> +		switch (tcf_vlan_action(act)) {
> +		case TCA_VLAN_ACT_PUSH:
> +			fl_action->id = FLOW_ACTION_VLAN_PUSH;
> +			break;
> +		case TCA_VLAN_ACT_POP:
> +			fl_action->id = FLOW_ACTION_VLAN_POP;
> +			break;
> +		case TCA_VLAN_ACT_MODIFY:
> +			fl_action->id = FLOW_ACTION_VLAN_MANGLE;
> +			break;
> +		default:
> +			return -EOPNOTSUPP;
> +		}
> +	} else if (is_tcf_tunnel_set(act)) {
> +		fl_action->id = FLOW_ACTION_TUNNEL_ENCAP;
> +	} else if (is_tcf_tunnel_release(act)) {
> +		fl_action->id = FLOW_ACTION_TUNNEL_DECAP;
> +	} else if (is_tcf_csum(act)) {
> +		fl_action->id = FLOW_ACTION_CSUM;
> +	} else if (is_tcf_skbedit_mark(act)) {
> +		fl_action->id = FLOW_ACTION_MARK;
> +	} else if (is_tcf_sample(act)) {
> +		fl_action->id = FLOW_ACTION_SAMPLE;
> +	} else if (is_tcf_police(act)) {
> +		fl_action->id = FLOW_ACTION_POLICE;
> +	} else if (is_tcf_ct(act)) {
> +		fl_action->id = FLOW_ACTION_CT;
> +	} else if (is_tcf_mpls(act)) {
> +		switch (tcf_mpls_action(act)) {
> +		case TCA_MPLS_ACT_PUSH:
> +			fl_action->id = FLOW_ACTION_MPLS_PUSH;
> +			break;
> +		case TCA_MPLS_ACT_POP:
> +			fl_action->id = FLOW_ACTION_MPLS_POP;
> +			break;
> +		case TCA_MPLS_ACT_MODIFY:
> +			fl_action->id = FLOW_ACTION_MPLS_MANGLE;
> +			break;
> +		default:
> +			return -EOPNOTSUPP;
> +		}
> +	} else if (is_tcf_skbedit_ptype(act)) {
> +		fl_action->id = FLOW_ACTION_PTYPE;
> +	} else if (is_tcf_skbedit_priority(act)) {
> +		fl_action->id = FLOW_ACTION_PRIORITY;
> +	} else if (is_tcf_gate(act)) {
> +		fl_action->id = FLOW_ACTION_GATE;
> +	} else {
> +		return -EOPNOTSUPP;
> +	}
> +
> +	return 0;
> +}
> +
> +static int tcf_action_offload_cmd(struct flow_offload_action *fl_act,
> +				  struct netlink_ext_ack *extack)
> +{
> +	int err;
> +
> +	if (IS_ERR(fl_act))
> +		return PTR_ERR(fl_act);

Ditto.

> +
> +	err = flow_indr_dev_setup_offload(NULL, NULL, TC_SETUP_ACT,
> +					  fl_act, NULL, NULL);
> +	if (err < 0)
> +		return err;
> +
> +	return 0;
> +}
> +
> +/* 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 -ENOMEM;
> +
> +	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;
> +}
> +
> +static int tcf_action_offload_del(struct tc_action *action)
> +{
> +	struct flow_offload_action fl_act;

This is the only usage of uninitialized flow_offload_action instance.
Since there is no reference driver implementation, it is not clear to me
whether this is intentional because flow_action_init() is guaranteed to
initialize all data that is necessary for delete, or just an omission.

> +	int err = 0;
> +
> +	if (!action)
> +		return -EINVAL;

Seemingly redundant check again.

> +
> +	err = flow_action_init(&fl_act, action, FLOW_ACT_DESTROY, NULL);
> +	if (err)
> +		return err;
> +
> +	return tcf_action_offload_cmd(&fl_act, NULL);
> +}
> +
>  static void tcf_action_cleanup(struct tc_action *p)
>  {
> +	tcf_action_offload_del(p);
>  	if (p->ops->cleanup)
>  		p->ops->cleanup(p);
>  
> @@ -1103,6 +1265,8 @@ 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 (!tc_act_bind(flags))
> +			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 d9d6ff0bf361..55fa48999d43 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];
> @@ -3724,6 +3724,20 @@ int tc_setup_flow_action(struct flow_action *flow_action,
>  	spin_unlock_bh(&act->tcfa_lock);
>  	goto err_out;
>  }
> +EXPORT_SYMBOL(tc_setup_action);
> +
> +int tc_setup_flow_action(struct flow_action *flow_action,
> +			 const struct tcf_exts *exts)
> +{
> +#ifdef CONFIG_NET_CLS_ACT
> +	if (!exts)
> +		return 0;
> +
> +	return tc_setup_action(flow_action, exts->actions);
> +#else
> +	return 0;
> +#endif
> +}
>  EXPORT_SYMBOL(tc_setup_flow_action);
>  
>  unsigned int tcf_exts_num_actions(struct tcf_exts *exts)
> @@ -3742,6 +3756,15 @@ 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,