/*
   * Berkeley Packet Filter based traffic classifier
   *
   * Might be used to classify traffic through flexible, user-defined and
   * possibly JIT-ed BPF filters for traffic control as an alternative to
   * ematches.
   *
   * (C) 2013 Daniel Borkmann <dborkman@redhat.com>
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License version 2 as
   * published by the Free Software Foundation.
   */
  
  #include <linux/module.h>
  #include <linux/types.h>
  #include <linux/skbuff.h>
  #include <linux/filter.h>
  #include <net/rtnetlink.h>
  #include <net/pkt_cls.h>
  #include <net/sock.h>
  
  MODULE_LICENSE("GPL");
  MODULE_AUTHOR("Daniel Borkmann <dborkman@redhat.com>");
  MODULE_DESCRIPTION("TC BPF based classifier");
  
  struct cls_bpf_head {
  	struct list_head plist;
  	u32 hgen;
  };
  
  struct cls_bpf_prog {
  	struct sk_filter *filter;
  	struct sock_filter *bpf_ops;
  	struct tcf_exts exts;
  	struct tcf_result res;
  	struct list_head link;
  	u32 handle;
  	u16 bpf_len;
  };
  
  static const struct nla_policy bpf_policy[TCA_BPF_MAX + 1] = {
  	[TCA_BPF_CLASSID]	= { .type = NLA_U32 },
  	[TCA_BPF_OPS_LEN]	= { .type = NLA_U16 },
  	[TCA_BPF_OPS]		= { .type = NLA_BINARY,
  				    .len = sizeof(struct sock_filter) * BPF_MAXINSNS },
  };

  static int cls_bpf_classify(struct sk_buff *skb, const struct tcf_proto *tp,
  			    struct tcf_result *res)
  {
  	struct cls_bpf_head *head = tp->root;
  	struct cls_bpf_prog *prog;
  	int ret;
  
  	list_for_each_entry(prog, &head->plist, link) {
  		int filter_res = SK_RUN_FILTER(prog->filter, skb);
  
  		if (filter_res == 0)
  			continue;
  
  		*res = prog->res;
  		if (filter_res != -1)
  			res->classid = filter_res;
  
  		ret = tcf_exts_exec(skb, &prog->exts, res);
  		if (ret < 0)
  			continue;
  
  		return ret;
  	}
  
  	return -1;
  }
  
  static int cls_bpf_init(struct tcf_proto *tp)
  {
  	struct cls_bpf_head *head;
  
  	head = kzalloc(sizeof(*head), GFP_KERNEL);
  	if (head == NULL)
  		return -ENOBUFS;
  
  	INIT_LIST_HEAD(&head->plist);
  	tp->root = head;
  
  	return 0;
  }
  
  static void cls_bpf_delete_prog(struct tcf_proto *tp, struct cls_bpf_prog *prog)
  {
  	tcf_unbind_filter(tp, &prog->res);
  	tcf_exts_destroy(tp, &prog->exts);
  
  	sk_unattached_filter_destroy(prog->filter);
  
  	kfree(prog->bpf_ops);
  	kfree(prog);
  }
  
  static int cls_bpf_delete(struct tcf_proto *tp, unsigned long arg)
  {
  	struct cls_bpf_head *head = tp->root;
  	struct cls_bpf_prog *prog, *todel = (struct cls_bpf_prog *) arg;
  
  	list_for_each_entry(prog, &head->plist, link) {
  		if (prog == todel) {
  			tcf_tree_lock(tp);
  			list_del(&prog->link);
  			tcf_tree_unlock(tp);
  
  			cls_bpf_delete_prog(tp, prog);
  			return 0;
  		}
  	}
  
  	return -ENOENT;
  }
  
  static void cls_bpf_destroy(struct tcf_proto *tp)
  {
  	struct cls_bpf_head *head = tp->root;
  	struct cls_bpf_prog *prog, *tmp;
  
  	list_for_each_entry_safe(prog, tmp, &head->plist, link) {
  		list_del(&prog->link);
  		cls_bpf_delete_prog(tp, prog);
  	}
  
  	kfree(head);
  }
  
  static unsigned long cls_bpf_get(struct tcf_proto *tp, u32 handle)
  {
  	struct cls_bpf_head *head = tp->root;
  	struct cls_bpf_prog *prog;
  	unsigned long ret = 0UL;
  
  	if (head == NULL)
  		return 0UL;
  
  	list_for_each_entry(prog, &head->plist, link) {
  		if (prog->handle == handle) {
  			ret = (unsigned long) prog;
  			break;
  		}
  	}
  
  	return ret;
  }
  
  static void cls_bpf_put(struct tcf_proto *tp, unsigned long f)
  {
  }
  
  static int cls_bpf_modify_existing(struct net *net, struct tcf_proto *tp,
  				   struct cls_bpf_prog *prog,
  				   unsigned long base, struct nlattr **tb,

  				   struct nlattr *est, bool ovr)

  {
  	struct sock_filter *bpf_ops, *bpf_old;
  	struct tcf_exts exts;

  	struct sock_fprog_kern tmp;

  	struct sk_filter *fp, *fp_old;
  	u16 bpf_size, bpf_len;
  	u32 classid;
  	int ret;
  
  	if (!tb[TCA_BPF_OPS_LEN] || !tb[TCA_BPF_OPS] || !tb[TCA_BPF_CLASSID])
  		return -EINVAL;

  	tcf_exts_init(&exts, TCA_BPF_ACT, TCA_BPF_POLICE);

  	ret = tcf_exts_validate(net, tp, tb, est, &exts, ovr);

  	if (ret < 0)
  		return ret;
  
  	classid = nla_get_u32(tb[TCA_BPF_CLASSID]);
  	bpf_len = nla_get_u16(tb[TCA_BPF_OPS_LEN]);
  	if (bpf_len > BPF_MAXINSNS || bpf_len == 0) {
  		ret = -EINVAL;
  		goto errout;
  	}
  
  	bpf_size = bpf_len * sizeof(*bpf_ops);
  	bpf_ops = kzalloc(bpf_size, GFP_KERNEL);
  	if (bpf_ops == NULL) {
  		ret = -ENOMEM;
  		goto errout;
  	}
  
  	memcpy(bpf_ops, nla_data(tb[TCA_BPF_OPS]), bpf_size);
  
  	tmp.len = bpf_len;

  	tmp.filter = bpf_ops;

  
  	ret = sk_unattached_filter_create(&fp, &tmp);
  	if (ret)
  		goto errout_free;
  
  	tcf_tree_lock(tp);
  	fp_old = prog->filter;
  	bpf_old = prog->bpf_ops;
  
  	prog->bpf_len = bpf_len;
  	prog->bpf_ops = bpf_ops;
  	prog->filter = fp;
  	prog->res.classid = classid;
  	tcf_tree_unlock(tp);
  
  	tcf_bind_filter(tp, &prog->res, base);
  	tcf_exts_change(tp, &prog->exts, &exts);
  
  	if (fp_old)
  		sk_unattached_filter_destroy(fp_old);
  	if (bpf_old)
  		kfree(bpf_old);
  
  	return 0;
  
  errout_free:
  	kfree(bpf_ops);
  errout:
  	tcf_exts_destroy(tp, &exts);
  	return ret;
  }
  
  static u32 cls_bpf_grab_new_handle(struct tcf_proto *tp,
  				   struct cls_bpf_head *head)
  {
  	unsigned int i = 0x80000000;
  
  	do {
  		if (++head->hgen == 0x7FFFFFFF)
  			head->hgen = 1;
  	} while (--i > 0 && cls_bpf_get(tp, head->hgen));
  	if (i == 0)
  		pr_err("Insufficient number of handles
  ");
  
  	return i;
  }
  
  static int cls_bpf_change(struct net *net, struct sk_buff *in_skb,
  			  struct tcf_proto *tp, unsigned long base,
  			  u32 handle, struct nlattr **tca,

  			  unsigned long *arg, bool ovr)

  {
  	struct cls_bpf_head *head = tp->root;
  	struct cls_bpf_prog *prog = (struct cls_bpf_prog *) *arg;
  	struct nlattr *tb[TCA_BPF_MAX + 1];
  	int ret;
  
  	if (tca[TCA_OPTIONS] == NULL)
  		return -EINVAL;
  
  	ret = nla_parse_nested(tb, TCA_BPF_MAX, tca[TCA_OPTIONS], bpf_policy);
  	if (ret < 0)
  		return ret;
  
  	if (prog != NULL) {
  		if (handle && prog->handle != handle)
  			return -EINVAL;
  		return cls_bpf_modify_existing(net, tp, prog, base, tb,

  					       tca[TCA_RATE], ovr);

  	}
  
  	prog = kzalloc(sizeof(*prog), GFP_KERNEL);
  	if (prog == NULL)
  		return -ENOBUFS;

  	tcf_exts_init(&prog->exts, TCA_BPF_ACT, TCA_BPF_POLICE);

  	if (handle == 0)
  		prog->handle = cls_bpf_grab_new_handle(tp, head);
  	else
  		prog->handle = handle;
  	if (prog->handle == 0) {
  		ret = -EINVAL;
  		goto errout;
  	}

  	ret = cls_bpf_modify_existing(net, tp, prog, base, tb, tca[TCA_RATE], ovr);

  	if (ret < 0)
  		goto errout;
  
  	tcf_tree_lock(tp);
  	list_add(&prog->link, &head->plist);
  	tcf_tree_unlock(tp);
  
  	*arg = (unsigned long) prog;
  
  	return 0;
  errout:
  	if (*arg == 0UL && prog)
  		kfree(prog);
  
  	return ret;
  }

  static int cls_bpf_dump(struct net *net, struct tcf_proto *tp, unsigned long fh,

  			struct sk_buff *skb, struct tcmsg *tm)
  {
  	struct cls_bpf_prog *prog = (struct cls_bpf_prog *) fh;
  	struct nlattr *nest, *nla;
  
  	if (prog == NULL)
  		return skb->len;
  
  	tm->tcm_handle = prog->handle;
  
  	nest = nla_nest_start(skb, TCA_OPTIONS);
  	if (nest == NULL)
  		goto nla_put_failure;
  
  	if (nla_put_u32(skb, TCA_BPF_CLASSID, prog->res.classid))
  		goto nla_put_failure;
  	if (nla_put_u16(skb, TCA_BPF_OPS_LEN, prog->bpf_len))
  		goto nla_put_failure;
  
  	nla = nla_reserve(skb, TCA_BPF_OPS, prog->bpf_len *
  			  sizeof(struct sock_filter));
  	if (nla == NULL)
  		goto nla_put_failure;

  	memcpy(nla_data(nla), prog->bpf_ops, nla_len(nla));

  	if (tcf_exts_dump(skb, &prog->exts) < 0)

  		goto nla_put_failure;
  
  	nla_nest_end(skb, nest);

  	if (tcf_exts_dump_stats(skb, &prog->exts) < 0)

  		goto nla_put_failure;
  
  	return skb->len;
  
  nla_put_failure:
  	nla_nest_cancel(skb, nest);
  	return -1;
  }
  
  static void cls_bpf_walk(struct tcf_proto *tp, struct tcf_walker *arg)
  {
  	struct cls_bpf_head *head = tp->root;
  	struct cls_bpf_prog *prog;
  
  	list_for_each_entry(prog, &head->plist, link) {
  		if (arg->count < arg->skip)
  			goto skip;
  		if (arg->fn(tp, (unsigned long) prog, arg) < 0) {
  			arg->stop = 1;
  			break;
  		}
  skip:
  		arg->count++;
  	}
  }
  
  static struct tcf_proto_ops cls_bpf_ops __read_mostly = {
  	.kind		=	"bpf",
  	.owner		=	THIS_MODULE,
  	.classify	=	cls_bpf_classify,
  	.init		=	cls_bpf_init,
  	.destroy	=	cls_bpf_destroy,
  	.get		=	cls_bpf_get,
  	.put		=	cls_bpf_put,
  	.change		=	cls_bpf_change,
  	.delete		=	cls_bpf_delete,
  	.walk		=	cls_bpf_walk,
  	.dump		=	cls_bpf_dump,
  };
  
  static int __init cls_bpf_init_mod(void)
  {
  	return register_tcf_proto_ops(&cls_bpf_ops);
  }
  
  static void __exit cls_bpf_exit_mod(void)
  {
  	unregister_tcf_proto_ops(&cls_bpf_ops);
  }
  
  module_init(cls_bpf_init_mod);
  module_exit(cls_bpf_exit_mod);