/*
   * Copyright (c) 2015 Jiri Pirko <jiri@resnulli.us>
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License as published by
   * the Free Software Foundation; either version 2 of the License, or
   * (at your option) any later version.
   */
  
  #include <linux/module.h>
  #include <linux/init.h>
  #include <linux/kernel.h>
  #include <linux/skbuff.h>
  #include <linux/rtnetlink.h>
  #include <linux/filter.h>

  #include <linux/bpf.h>

  #include <net/netlink.h>
  #include <net/pkt_sched.h>
  
  #include <linux/tc_act/tc_bpf.h>
  #include <net/tc_act/tc_bpf.h>

  #define BPF_TAB_MASK		15
  #define ACT_BPF_NAME_LEN	256
  
  struct tcf_bpf_cfg {
  	struct bpf_prog *filter;
  	struct sock_filter *bpf_ops;

  	const char *bpf_name;

  	u32 bpf_fd;
  	u16 bpf_num_ops;

  	bool is_ebpf;

  };

  static int bpf_net_id;

  static struct tc_action_ops act_bpf_ops;

  static int tcf_bpf(struct sk_buff *skb, const struct tc_action *act,

  		   struct tcf_result *res)
  {

  	bool at_ingress = skb_at_tc_ingress(skb);

  	struct tcf_bpf *prog = to_bpf(act);

  	struct bpf_prog *filter;

  	int action, filter_res;

  	tcf_lastuse_update(&prog->tcf_tm);
  	bstats_cpu_update(this_cpu_ptr(prog->common.cpu_bstats), skb);

  	rcu_read_lock();

  	filter = rcu_dereference(prog->filter);

  	if (at_ingress) {
  		__skb_push(skb, skb->mac_len);

  		bpf_compute_data_end(skb);

  		filter_res = BPF_PROG_RUN(filter, skb);

  		__skb_pull(skb, skb->mac_len);
  	} else {

  		bpf_compute_data_end(skb);

  		filter_res = BPF_PROG_RUN(filter, skb);

  	}

  	rcu_read_unlock();

  
  	/* A BPF program may overwrite the default action opcode.
  	 * Similarly as in cls_bpf, if filter_res == -1 we use the
  	 * default action specified from tc.
  	 *
  	 * In case a different well-known TC_ACT opcode has been
  	 * returned, it will overwrite the default one.
  	 *
  	 * For everything else that is unkown, TC_ACT_UNSPEC is
  	 * returned.
  	 */
  	switch (filter_res) {
  	case TC_ACT_PIPE:
  	case TC_ACT_RECLASSIFY:
  	case TC_ACT_OK:

  	case TC_ACT_REDIRECT:

  		action = filter_res;
  		break;
  	case TC_ACT_SHOT:
  		action = filter_res;

  		qstats_drop_inc(this_cpu_ptr(prog->common.cpu_qstats));

  		break;
  	case TC_ACT_UNSPEC:

  		action = prog->tcf_action;

  		break;
  	default:
  		action = TC_ACT_UNSPEC;
  		break;

  	}

  	return action;
  }

  static bool tcf_bpf_is_ebpf(const struct tcf_bpf *prog)
  {
  	return !prog->bpf_ops;
  }
  
  static int tcf_bpf_dump_bpf_info(const struct tcf_bpf *prog,
  				 struct sk_buff *skb)
  {
  	struct nlattr *nla;
  
  	if (nla_put_u16(skb, TCA_ACT_BPF_OPS_LEN, prog->bpf_num_ops))
  		return -EMSGSIZE;
  
  	nla = nla_reserve(skb, TCA_ACT_BPF_OPS, prog->bpf_num_ops *
  			  sizeof(struct sock_filter));
  	if (nla == NULL)
  		return -EMSGSIZE;
  
  	memcpy(nla_data(nla), prog->bpf_ops, nla_len(nla));
  
  	return 0;
  }
  
  static int tcf_bpf_dump_ebpf_info(const struct tcf_bpf *prog,
  				  struct sk_buff *skb)
  {
  	if (nla_put_u32(skb, TCA_ACT_BPF_FD, prog->bpf_fd))
  		return -EMSGSIZE;
  
  	if (prog->bpf_name &&
  	    nla_put_string(skb, TCA_ACT_BPF_NAME, prog->bpf_name))
  		return -EMSGSIZE;
  
  	return 0;
  }
  
  static int tcf_bpf_dump(struct sk_buff *skb, struct tc_action *act,

  			int bind, int ref)
  {
  	unsigned char *tp = skb_tail_pointer(skb);

  	struct tcf_bpf *prog = to_bpf(act);

  	struct tc_act_bpf opt = {

  		.index   = prog->tcf_index,
  		.refcnt  = prog->tcf_refcnt - ref,
  		.bindcnt = prog->tcf_bindcnt - bind,
  		.action  = prog->tcf_action,

  	};

  	struct tcf_t tm;
  	int ret;

  
  	if (nla_put(skb, TCA_ACT_BPF_PARMS, sizeof(opt), &opt))
  		goto nla_put_failure;

  	if (tcf_bpf_is_ebpf(prog))
  		ret = tcf_bpf_dump_ebpf_info(prog, skb);
  	else
  		ret = tcf_bpf_dump_bpf_info(prog, skb);
  	if (ret)

  		goto nla_put_failure;

  	tcf_tm_dump(&tm, &prog->tcf_tm);

  	if (nla_put_64bit(skb, TCA_ACT_BPF_TM, sizeof(tm), &tm,
  			  TCA_ACT_BPF_PAD))

  		goto nla_put_failure;

  	return skb->len;
  
  nla_put_failure:
  	nlmsg_trim(skb, tp);
  	return -1;
  }
  
  static const struct nla_policy act_bpf_policy[TCA_ACT_BPF_MAX + 1] = {
  	[TCA_ACT_BPF_PARMS]	= { .len = sizeof(struct tc_act_bpf) },

  	[TCA_ACT_BPF_FD]	= { .type = NLA_U32 },

  	[TCA_ACT_BPF_NAME]	= { .type = NLA_NUL_STRING,
  				    .len = ACT_BPF_NAME_LEN },

  	[TCA_ACT_BPF_OPS_LEN]	= { .type = NLA_U16 },
  	[TCA_ACT_BPF_OPS]	= { .type = NLA_BINARY,
  				    .len = sizeof(struct sock_filter) * BPF_MAXINSNS },
  };

  static int tcf_bpf_init_from_ops(struct nlattr **tb, struct tcf_bpf_cfg *cfg)

  {

  	struct sock_filter *bpf_ops;

  	struct sock_fprog_kern fprog_tmp;

  	struct bpf_prog *fp;

  	u16 bpf_size, bpf_num_ops;

  	int ret;

  	bpf_num_ops = nla_get_u16(tb[TCA_ACT_BPF_OPS_LEN]);
  	if (bpf_num_ops	> BPF_MAXINSNS || bpf_num_ops == 0)
  		return -EINVAL;
  
  	bpf_size = bpf_num_ops * sizeof(*bpf_ops);

  	if (bpf_size != nla_len(tb[TCA_ACT_BPF_OPS]))
  		return -EINVAL;

  	bpf_ops = kzalloc(bpf_size, GFP_KERNEL);

  	if (bpf_ops == NULL)

  		return -ENOMEM;
  
  	memcpy(bpf_ops, nla_data(tb[TCA_ACT_BPF_OPS]), bpf_size);

  	fprog_tmp.len = bpf_num_ops;
  	fprog_tmp.filter = bpf_ops;

  	ret = bpf_prog_create(&fp, &fprog_tmp);
  	if (ret < 0) {
  		kfree(bpf_ops);
  		return ret;
  	}

  	cfg->bpf_ops = bpf_ops;
  	cfg->bpf_num_ops = bpf_num_ops;
  	cfg->filter = fp;

  	cfg->is_ebpf = false;

  
  	return 0;
  }
  
  static int tcf_bpf_init_from_efd(struct nlattr **tb, struct tcf_bpf_cfg *cfg)
  {
  	struct bpf_prog *fp;
  	char *name = NULL;
  	u32 bpf_fd;
  
  	bpf_fd = nla_get_u32(tb[TCA_ACT_BPF_FD]);

  	fp = bpf_prog_get_type(bpf_fd, BPF_PROG_TYPE_SCHED_ACT);

  	if (IS_ERR(fp))
  		return PTR_ERR(fp);

  	if (tb[TCA_ACT_BPF_NAME]) {
  		name = kmemdup(nla_data(tb[TCA_ACT_BPF_NAME]),
  			       nla_len(tb[TCA_ACT_BPF_NAME]),
  			       GFP_KERNEL);
  		if (!name) {
  			bpf_prog_put(fp);
  			return -ENOMEM;
  		}
  	}
  
  	cfg->bpf_fd = bpf_fd;
  	cfg->bpf_name = name;
  	cfg->filter = fp;

  	cfg->is_ebpf = true;

  
  	return 0;
  }

  static void tcf_bpf_cfg_cleanup(const struct tcf_bpf_cfg *cfg)
  {
  	if (cfg->is_ebpf)
  		bpf_prog_put(cfg->filter);
  	else
  		bpf_prog_destroy(cfg->filter);
  
  	kfree(cfg->bpf_ops);
  	kfree(cfg->bpf_name);
  }
  
  static void tcf_bpf_prog_fill_cfg(const struct tcf_bpf *prog,
  				  struct tcf_bpf_cfg *cfg)
  {
  	cfg->is_ebpf = tcf_bpf_is_ebpf(prog);

  	/* updates to prog->filter are prevented, since it's called either
  	 * with rtnl lock or during final cleanup in rcu callback
  	 */
  	cfg->filter = rcu_dereference_protected(prog->filter, 1);

  
  	cfg->bpf_ops = prog->bpf_ops;
  	cfg->bpf_name = prog->bpf_name;
  }

  static int tcf_bpf_init(struct net *net, struct nlattr *nla,

  			struct nlattr *est, struct tc_action **act,

  			int replace, int bind)
  {

  	struct tc_action_net *tn = net_generic(net, bpf_net_id);

  	struct nlattr *tb[TCA_ACT_BPF_MAX + 1];

  	struct tcf_bpf_cfg cfg, old;

  	struct tc_act_bpf *parm;
  	struct tcf_bpf *prog;

  	bool is_bpf, is_ebpf;

  	int ret, res = 0;

  
  	if (!nla)
  		return -EINVAL;
  
  	ret = nla_parse_nested(tb, TCA_ACT_BPF_MAX, nla, act_bpf_policy);
  	if (ret < 0)
  		return ret;

  	if (!tb[TCA_ACT_BPF_PARMS])

  		return -EINVAL;
  
  	parm = nla_data(tb[TCA_ACT_BPF_PARMS]);

  	if (!tcf_hash_check(tn, parm->index, act, bind)) {
  		ret = tcf_hash_create(tn, parm->index, est, act,

  				      &act_bpf_ops, bind, true);

  		if (ret < 0)

  			return ret;

  		res = ACT_P_CREATED;

  	} else {

  		/* Don't override defaults. */

  		if (bind)

  			return 0;

  		tcf_hash_release(*act, bind);

  		if (!replace)
  			return -EEXIST;

  	}

  	is_bpf = tb[TCA_ACT_BPF_OPS_LEN] && tb[TCA_ACT_BPF_OPS];
  	is_ebpf = tb[TCA_ACT_BPF_FD];
  
  	if ((!is_bpf && !is_ebpf) || (is_bpf && is_ebpf)) {
  		ret = -EINVAL;
  		goto out;
  	}
  
  	memset(&cfg, 0, sizeof(cfg));
  
  	ret = is_bpf ? tcf_bpf_init_from_ops(tb, &cfg) :
  		       tcf_bpf_init_from_efd(tb, &cfg);
  	if (ret < 0)
  		goto out;

  	prog = to_bpf(*act);

  	ASSERT_RTNL();

  	if (res != ACT_P_CREATED)

  		tcf_bpf_prog_fill_cfg(prog, &old);

  	prog->bpf_ops = cfg.bpf_ops;
  	prog->bpf_name = cfg.bpf_name;
  
  	if (cfg.bpf_num_ops)
  		prog->bpf_num_ops = cfg.bpf_num_ops;
  	if (cfg.bpf_fd)
  		prog->bpf_fd = cfg.bpf_fd;
  
  	prog->tcf_action = parm->action;

  	rcu_assign_pointer(prog->filter, cfg.filter);

  	if (res == ACT_P_CREATED) {

  		tcf_hash_insert(tn, *act);

  	} else {
  		/* make sure the program being replaced is no longer executing */
  		synchronize_rcu();

  		tcf_bpf_cfg_cleanup(&old);

  	}

  	return res;
  out:
  	if (res == ACT_P_CREATED)

  		tcf_hash_cleanup(*act, est);

  	return ret;
  }

  static void tcf_bpf_cleanup(struct tc_action *act, int bind)

  {

  	struct tcf_bpf_cfg tmp;

  	tcf_bpf_prog_fill_cfg(to_bpf(act), &tmp);

  	tcf_bpf_cfg_cleanup(&tmp);

  }

  static int tcf_bpf_walker(struct net *net, struct sk_buff *skb,
  			  struct netlink_callback *cb, int type,

  			  const struct tc_action_ops *ops)

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

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

  }

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

  {
  	struct tc_action_net *tn = net_generic(net, bpf_net_id);
  
  	return tcf_hash_search(tn, a, index);
  }

  static struct tc_action_ops act_bpf_ops __read_mostly = {
  	.kind		=	"bpf",
  	.type		=	TCA_ACT_BPF,
  	.owner		=	THIS_MODULE,
  	.act		=	tcf_bpf,
  	.dump		=	tcf_bpf_dump,
  	.cleanup	=	tcf_bpf_cleanup,
  	.init		=	tcf_bpf_init,

  	.walk		=	tcf_bpf_walker,
  	.lookup		=	tcf_bpf_search,

  	.size		=	sizeof(struct tcf_bpf),

  };
  
  static __net_init int bpf_init_net(struct net *net)
  {
  	struct tc_action_net *tn = net_generic(net, bpf_net_id);
  
  	return tc_action_net_init(tn, &act_bpf_ops, BPF_TAB_MASK);
  }
  
  static void __net_exit bpf_exit_net(struct net *net)
  {
  	struct tc_action_net *tn = net_generic(net, bpf_net_id);
  
  	tc_action_net_exit(tn);
  }
  
  static struct pernet_operations bpf_net_ops = {
  	.init = bpf_init_net,
  	.exit = bpf_exit_net,
  	.id   = &bpf_net_id,
  	.size = sizeof(struct tc_action_net),

  };
  
  static int __init bpf_init_module(void)
  {

  	return tcf_register_action(&act_bpf_ops, &bpf_net_ops);

  }
  
  static void __exit bpf_cleanup_module(void)
  {

  	tcf_unregister_action(&act_bpf_ops, &bpf_net_ops);

  }
  
  module_init(bpf_init_module);
  module_exit(bpf_cleanup_module);
  
  MODULE_AUTHOR("Jiri Pirko <jiri@resnulli.us>");
  MODULE_DESCRIPTION("TC BPF based action");
  MODULE_LICENSE("GPL v2");