/*
   * 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 tcf_bpf(struct sk_buff *skb, const struct tc_action *act,
  		   struct tcf_result *res)
  {
  	struct tcf_bpf *prog = act->priv;
  	struct bpf_prog *filter;
  	int action, filter_res;
  	bool at_ingress = G_TC_AT(skb->tc_verd) & AT_INGRESS;
  
  	if (unlikely(!skb_mac_header_was_set(skb)))
  		return TC_ACT_UNSPEC;
  
  	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);
  		filter_res = BPF_PROG_RUN(filter, skb);
  		__skb_pull(skb, skb->mac_len);
  	} else {
  		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 = act->priv;
  	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;
  
  	tm.install = jiffies_to_clock_t(jiffies - prog->tcf_tm.install);
  	tm.lastuse = jiffies_to_clock_t(jiffies - prog->tcf_tm.lastuse);
  	tm.expires = jiffies_to_clock_t(prog->tcf_tm.expires);
  
  	if (nla_put(skb, TCA_ACT_BPF_TM, sizeof(tm), &tm))
  		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(bpf_fd);
  	if (IS_ERR(fp))
  		return PTR_ERR(fp);
  
  	if (fp->type != BPF_PROG_TYPE_SCHED_ACT) {
  		bpf_prog_put(fp);
  		return -EINVAL;
  	}
  
  	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 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(parm->index, act, bind)) {
  		ret = tcf_hash_create(parm->index, est, act,
  				      sizeof(*prog), 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(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(act->priv, &tmp);
  	tcf_bpf_cfg_cleanup(&tmp);
  }
  
  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,
  };
  
  static int __init bpf_init_module(void)
  {
  	return tcf_register_action(&act_bpf_ops, BPF_TAB_MASK);
  }
  
  static void __exit bpf_cleanup_module(void)
  {
  	tcf_unregister_action(&act_bpf_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");