// SPDX-License-Identifier: GPL-2.0-only

  /*
   * net/sched/act_sample.c - Packet sampling tc action
   * Copyright (c) 2017 Yotam Gigi <yotamg@mellanox.com>

   */
  
  #include <linux/types.h>
  #include <linux/kernel.h>
  #include <linux/string.h>
  #include <linux/errno.h>
  #include <linux/skbuff.h>
  #include <linux/rtnetlink.h>
  #include <linux/module.h>
  #include <linux/init.h>
  #include <linux/gfp.h>
  #include <net/net_namespace.h>
  #include <net/netlink.h>
  #include <net/pkt_sched.h>
  #include <linux/tc_act/tc_sample.h>
  #include <net/tc_act/tc_sample.h>
  #include <net/psample.h>

  #include <net/pkt_cls.h>

  
  #include <linux/if_arp.h>

  static unsigned int sample_net_id;
  static struct tc_action_ops act_sample_ops;
  
  static const struct nla_policy sample_policy[TCA_SAMPLE_MAX + 1] = {
  	[TCA_SAMPLE_PARMS]		= { .len = sizeof(struct tc_sample) },
  	[TCA_SAMPLE_RATE]		= { .type = NLA_U32 },
  	[TCA_SAMPLE_TRUNC_SIZE]		= { .type = NLA_U32 },
  	[TCA_SAMPLE_PSAMPLE_GROUP]	= { .type = NLA_U32 },
  };
  
  static int tcf_sample_init(struct net *net, struct nlattr *nla,
  			   struct nlattr *est, struct tc_action **a, int ovr,

  			   int bind, bool rtnl_held, struct tcf_proto *tp,

  			   u32 flags, struct netlink_ext_ack *extack)

  {
  	struct tc_action_net *tn = net_generic(net, sample_net_id);
  	struct nlattr *tb[TCA_SAMPLE_MAX + 1];
  	struct psample_group *psample_group;

  	u32 psample_group_num, rate, index;

  	struct tcf_chain *goto_ch = NULL;

  	struct tc_sample *parm;
  	struct tcf_sample *s;
  	bool exists = false;

  	int ret, err;

  
  	if (!nla)
  		return -EINVAL;

  	ret = nla_parse_nested_deprecated(tb, TCA_SAMPLE_MAX, nla,
  					  sample_policy, NULL);

  	if (ret < 0)
  		return ret;
  	if (!tb[TCA_SAMPLE_PARMS] || !tb[TCA_SAMPLE_RATE] ||
  	    !tb[TCA_SAMPLE_PSAMPLE_GROUP])
  		return -EINVAL;
  
  	parm = nla_data(tb[TCA_SAMPLE_PARMS]);

  	index = parm->index;
  	err = tcf_idr_check_alloc(tn, &index, a, bind);

  	if (err < 0)
  		return err;
  	exists = err;

  	if (exists && bind)
  		return 0;
  
  	if (!exists) {

  		ret = tcf_idr_create(tn, index, est, a,

  				     &act_sample_ops, bind, true, 0);

  		if (ret) {

  			tcf_idr_cleanup(tn, index);

  			return ret;

  		}

  		ret = ACT_P_CREATED;

  	} else if (!ovr) {

  		tcf_idr_release(*a, bind);

  		return -EEXIST;

  	}

  	err = tcf_action_check_ctrlact(parm->action, tp, &goto_ch, extack);
  	if (err < 0)
  		goto release_idr;

  	rate = nla_get_u32(tb[TCA_SAMPLE_RATE]);
  	if (!rate) {
  		NL_SET_ERR_MSG(extack, "invalid sample rate");
  		err = -EINVAL;
  		goto put_chain;
  	}

  	psample_group_num = nla_get_u32(tb[TCA_SAMPLE_PSAMPLE_GROUP]);
  	psample_group = psample_group_get(net, psample_group_num);

  	if (!psample_group) {

  		err = -ENOMEM;
  		goto put_chain;

  	}

  
  	s = to_sample(*a);
  
  	spin_lock_bh(&s->tcf_lock);

  	goto_ch = tcf_action_set_ctrlact(*a, parm->action, goto_ch);

  	s->rate = rate;

  	s->psample_group_num = psample_group_num;

  	psample_group = rcu_replace_pointer(s->psample_group, psample_group,
  					    lockdep_is_held(&s->tcf_lock));

  
  	if (tb[TCA_SAMPLE_TRUNC_SIZE]) {
  		s->truncate = true;
  		s->trunc_size = nla_get_u32(tb[TCA_SAMPLE_TRUNC_SIZE]);
  	}

  	spin_unlock_bh(&s->tcf_lock);

  
  	if (psample_group)
  		psample_group_put(psample_group);

  	if (goto_ch)
  		tcf_chain_put_by_act(goto_ch);

  	return ret;

  put_chain:
  	if (goto_ch)
  		tcf_chain_put_by_act(goto_ch);
  release_idr:
  	tcf_idr_release(*a, bind);
  	return err;

  }

  static void tcf_sample_cleanup(struct tc_action *a)

  {

  	struct tcf_sample *s = to_sample(a);

  	struct psample_group *psample_group;

  	/* last reference to action, no need to lock */
  	psample_group = rcu_dereference_protected(s->psample_group, 1);

  	RCU_INIT_POINTER(s->psample_group, NULL);

  	if (psample_group)
  		psample_group_put(psample_group);

  }

  static bool tcf_sample_dev_ok_push(struct net_device *dev)
  {
  	switch (dev->type) {
  	case ARPHRD_TUNNEL:
  	case ARPHRD_TUNNEL6:
  	case ARPHRD_SIT:
  	case ARPHRD_IPGRE:

  	case ARPHRD_IP6GRE:

  	case ARPHRD_VOID:
  	case ARPHRD_NONE:
  		return false;
  	default:
  		return true;
  	}
  }
  
  static int tcf_sample_act(struct sk_buff *skb, const struct tc_action *a,
  			  struct tcf_result *res)
  {
  	struct tcf_sample *s = to_sample(a);
  	struct psample_group *psample_group;
  	int retval;
  	int size;
  	int iif;
  	int oif;
  
  	tcf_lastuse_update(&s->tcf_tm);
  	bstats_cpu_update(this_cpu_ptr(s->common.cpu_bstats), skb);
  	retval = READ_ONCE(s->tcf_action);

  	psample_group = rcu_dereference_bh(s->psample_group);

  
  	/* randomly sample packets according to rate */
  	if (psample_group && (prandom_u32() % s->rate == 0)) {
  		if (!skb_at_tc_ingress(skb)) {
  			iif = skb->skb_iif;
  			oif = skb->dev->ifindex;
  		} else {
  			iif = skb->dev->ifindex;
  			oif = 0;
  		}
  
  		/* on ingress, the mac header gets popped, so push it back */
  		if (skb_at_tc_ingress(skb) && tcf_sample_dev_ok_push(skb->dev))
  			skb_push(skb, skb->mac_len);
  
  		size = s->truncate ? s->trunc_size : skb->len;
  		psample_sample_packet(psample_group, skb, size, iif, oif,
  				      s->rate);
  
  		if (skb_at_tc_ingress(skb) && tcf_sample_dev_ok_push(skb->dev))
  			skb_pull(skb, skb->mac_len);
  	}

  	return retval;
  }
  
  static int tcf_sample_dump(struct sk_buff *skb, struct tc_action *a,
  			   int bind, int ref)
  {
  	unsigned char *b = skb_tail_pointer(skb);
  	struct tcf_sample *s = to_sample(a);
  	struct tc_sample opt = {
  		.index      = s->tcf_index,

  		.refcnt     = refcount_read(&s->tcf_refcnt) - ref,
  		.bindcnt    = atomic_read(&s->tcf_bindcnt) - bind,

  	};
  	struct tcf_t t;

  	spin_lock_bh(&s->tcf_lock);

  	opt.action = s->tcf_action;

  	if (nla_put(skb, TCA_SAMPLE_PARMS, sizeof(opt), &opt))
  		goto nla_put_failure;
  
  	tcf_tm_dump(&t, &s->tcf_tm);
  	if (nla_put_64bit(skb, TCA_SAMPLE_TM, sizeof(t), &t, TCA_SAMPLE_PAD))
  		goto nla_put_failure;
  
  	if (nla_put_u32(skb, TCA_SAMPLE_RATE, s->rate))
  		goto nla_put_failure;
  
  	if (s->truncate)
  		if (nla_put_u32(skb, TCA_SAMPLE_TRUNC_SIZE, s->trunc_size))
  			goto nla_put_failure;
  
  	if (nla_put_u32(skb, TCA_SAMPLE_PSAMPLE_GROUP, s->psample_group_num))
  		goto nla_put_failure;

  	spin_unlock_bh(&s->tcf_lock);

  	return skb->len;
  
  nla_put_failure:

  	spin_unlock_bh(&s->tcf_lock);

  	nlmsg_trim(skb, b);
  	return -1;
  }
  
  static int tcf_sample_walker(struct net *net, struct sk_buff *skb,
  			     struct netlink_callback *cb, int type,

  			     const struct tc_action_ops *ops,
  			     struct netlink_ext_ack *extack)

  {
  	struct tc_action_net *tn = net_generic(net, sample_net_id);

  	return tcf_generic_walker(tn, skb, cb, type, ops, extack);

  }

  static int tcf_sample_search(struct net *net, struct tc_action **a, u32 index)

  {
  	struct tc_action_net *tn = net_generic(net, sample_net_id);

  	return tcf_idr_search(tn, a, index);

  }

  static void tcf_psample_group_put(void *priv)
  {
  	struct psample_group *group = priv;
  
  	psample_group_put(group);
  }
  
  static struct psample_group *
  tcf_sample_get_group(const struct tc_action *a,
  		     tc_action_priv_destructor *destructor)
  {
  	struct tcf_sample *s = to_sample(a);
  	struct psample_group *group;

  	group = rcu_dereference_protected(s->psample_group,
  					  lockdep_is_held(&s->tcf_lock));
  	if (group) {
  		psample_group_take(group);
  		*destructor = tcf_psample_group_put;
  	}

  
  	return group;
  }

  static struct tc_action_ops act_sample_ops = {
  	.kind	  = "sample",

  	.id	  = TCA_ID_SAMPLE,

  	.owner	  = THIS_MODULE,
  	.act	  = tcf_sample_act,
  	.dump	  = tcf_sample_dump,
  	.init	  = tcf_sample_init,
  	.cleanup  = tcf_sample_cleanup,
  	.walk	  = tcf_sample_walker,
  	.lookup	  = tcf_sample_search,

  	.get_psample_group = tcf_sample_get_group,

  	.size	  = sizeof(struct tcf_sample),
  };
  
  static __net_init int sample_init_net(struct net *net)
  {
  	struct tc_action_net *tn = net_generic(net, sample_net_id);

  	return tc_action_net_init(net, tn, &act_sample_ops);

  }

  static void __net_exit sample_exit_net(struct list_head *net_list)

  {

  	tc_action_net_exit(net_list, sample_net_id);

  }
  
  static struct pernet_operations sample_net_ops = {
  	.init = sample_init_net,

  	.exit_batch = sample_exit_net,

  	.id   = &sample_net_id,
  	.size = sizeof(struct tc_action_net),
  };
  
  static int __init sample_init_module(void)
  {
  	return tcf_register_action(&act_sample_ops, &sample_net_ops);
  }
  
  static void __exit sample_cleanup_module(void)
  {
  	tcf_unregister_action(&act_sample_ops, &sample_net_ops);
  }
  
  module_init(sample_init_module);
  module_exit(sample_cleanup_module);

  MODULE_AUTHOR("Yotam Gigi <yotam.gi@gmail.com>");

  MODULE_DESCRIPTION("Packet sampling action");
  MODULE_LICENSE("GPL v2");