cls_cgroup.c

/*
 * net/sched/cls_cgroup.c	Control Group Classifier
 *
 *		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.
 *
 * Authors:	Thomas Graf <tgraf@suug.ch>
 */

#include <linux/module.h>
#include <linux/slab.h>
#include <linux/types.h>
#include <linux/string.h>
#include <linux/errno.h>
#include <linux/skbuff.h>
#include <linux/cgroup.h>
#include <linux/rcupdate.h>
#include <linux/fdtable.h>
#include <net/rtnetlink.h>
#include <net/pkt_cls.h>
#include <net/sock.h>
#include <net/cls_cgroup.h>

static inline struct cgroup_cls_state *css_cls_state(struct cgroup_subsys_state *css)
{
	return css ? container_of(css, struct cgroup_cls_state, css) : NULL;
}

static inline struct cgroup_cls_state *task_cls_state(struct task_struct *p)
{
	return css_cls_state(task_css(p, net_cls_subsys_id));
}

static struct cgroup_subsys_state *
cgrp_css_alloc(struct cgroup_subsys_state *parent_css)
{
	struct cgroup_cls_state *cs;

	cs = kzalloc(sizeof(*cs), GFP_KERNEL);
	if (!cs)
		return ERR_PTR(-ENOMEM);
	return &cs->css;
}

static int cgrp_css_online(struct cgroup_subsys_state *css)
{
	struct cgroup_cls_state *cs = css_cls_state(css);
	struct cgroup_cls_state *parent = css_cls_state(css_parent(css));

	if (parent)
		cs->classid = parent->classid;
	return 0;
}

static void cgrp_css_free(struct cgroup_subsys_state *css)
{
	kfree(css_cls_state(css));
}

static int update_classid(const void *v, struct file *file, unsigned n)
{
	int err;
	struct socket *sock = sock_from_file(file, &err);
	if (sock)
		sock->sk->sk_classid = (u32)(unsigned long)v;
	return 0;
}

static void cgrp_attach(struct cgroup_subsys_state *css,
			struct cgroup_taskset *tset)
{
	struct task_struct *p;
	struct cgroup_cls_state *cs = css_cls_state(css);
	void *v = (void *)(unsigned long)cs->classid;

	cgroup_taskset_for_each(p, css, tset) {
		task_lock(p);
		iterate_fd(p->files, 0, update_classid, v);
		task_unlock(p);
	}
}

static u64 read_classid(struct cgroup_subsys_state *css, struct cftype *cft)
{
	return css_cls_state(css)->classid;
}

static int write_classid(struct cgroup_subsys_state *css, struct cftype *cft,
			 u64 value)
{
	css_cls_state(css)->classid = (u32) value;
	return 0;
}

static struct cftype ss_files[] = {
	{
		.name = "classid",
		.read_u64 = read_classid,
		.write_u64 = write_classid,
	},
	{ }	/* terminate */
};

struct cgroup_subsys net_cls_subsys = {
	.name		= "net_cls",
	.css_alloc	= cgrp_css_alloc,
	.css_online	= cgrp_css_online,
	.css_free	= cgrp_css_free,
	.attach		= cgrp_attach,
	.subsys_id	= net_cls_subsys_id,
	.base_cftypes	= ss_files,
	.module		= THIS_MODULE,
};

struct cls_cgroup_head {
	u32			handle;
	struct tcf_exts		exts;
	struct tcf_ematch_tree	ematches;
};

static int cls_cgroup_classify(struct sk_buff *skb, const struct tcf_proto *tp,
			       struct tcf_result *res)
{
	struct cls_cgroup_head *head = tp->root;
	u32 classid;

	rcu_read_lock();
	classid = task_cls_state(current)->classid;
	rcu_read_unlock();

	/*
	 * Due to the nature of the classifier it is required to ignore all
	 * packets originating from softirq context as accessing `current'
	 * would lead to false results.
	 *
	 * This test assumes that all callers of dev_queue_xmit() explicitely
	 * disable bh. Knowing this, it is possible to detect softirq based
	 * calls by looking at the number of nested bh disable calls because
	 * softirqs always disables bh.
	 */
	if (in_serving_softirq()) {
		/* If there is an sk_classid we'll use that. */
		if (!skb->sk)
			return -1;
		classid = skb->sk->sk_classid;
	}

	if (!classid)
		return -1;

	if (!tcf_em_tree_match(skb, &head->ematches, NULL))
		return -1;

	res->classid = classid;
	res->class = 0;
	return tcf_exts_exec(skb, &head->exts, res);
}

static unsigned long cls_cgroup_get(struct tcf_proto *tp, u32 handle)
{
	return 0UL;
}

static void cls_cgroup_put(struct tcf_proto *tp, unsigned long f)
{
}

static int cls_cgroup_init(struct tcf_proto *tp)
{
	return 0;
}

static const struct nla_policy cgroup_policy[TCA_CGROUP_MAX + 1] = {
	[TCA_CGROUP_EMATCHES]	= { .type = NLA_NESTED },
};

static int cls_cgroup_change(struct net *net, struct sk_buff *in_skb,
			     struct tcf_proto *tp, unsigned long base,
			     u32 handle, struct nlattr **tca,
			     unsigned long *arg)
{
	struct nlattr *tb[TCA_CGROUP_MAX + 1];
	struct cls_cgroup_head *head = tp->root;
	struct tcf_ematch_tree t;
	struct tcf_exts e;
	int err;

	if (!tca[TCA_OPTIONS])
		return -EINVAL;

	if (head == NULL) {
		if (!handle)
			return -EINVAL;

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

		tcf_exts_init(&head->exts, TCA_CGROUP_ACT, TCA_CGROUP_POLICE);
		head->handle = handle;

		tcf_tree_lock(tp);
		tp->root = head;
		tcf_tree_unlock(tp);
	}

	if (handle != head->handle)
		return -ENOENT;

	err = nla_parse_nested(tb, TCA_CGROUP_MAX, tca[TCA_OPTIONS],
			       cgroup_policy);
	if (err < 0)
		return err;

	tcf_exts_init(&e, TCA_CGROUP_ACT, TCA_CGROUP_POLICE);
	err = tcf_exts_validate(net, tp, tb, tca[TCA_RATE], &e);
	if (err < 0)
		return err;

	err = tcf_em_tree_validate(tp, tb[TCA_CGROUP_EMATCHES], &t);
	if (err < 0)
		return err;

	tcf_exts_change(tp, &head->exts, &e);
	tcf_em_tree_change(tp, &head->ematches, &t);

	return 0;
}

static void cls_cgroup_destroy(struct tcf_proto *tp)
{
	struct cls_cgroup_head *head = tp->root;

	if (head) {
		tcf_exts_destroy(tp, &head->exts);
		tcf_em_tree_destroy(tp, &head->ematches);
		kfree(head);
	}
}

static int cls_cgroup_delete(struct tcf_proto *tp, unsigned long arg)
{
	return -EOPNOTSUPP;
}

static void cls_cgroup_walk(struct tcf_proto *tp, struct tcf_walker *arg)
{
	struct cls_cgroup_head *head = tp->root;

	if (arg->count < arg->skip)
		goto skip;

	if (arg->fn(tp, (unsigned long) head, arg) < 0) {
		arg->stop = 1;
		return;
	}
skip:
	arg->count++;
}

static int cls_cgroup_dump(struct tcf_proto *tp, unsigned long fh,
			   struct sk_buff *skb, struct tcmsg *t)
{
	struct cls_cgroup_head *head = tp->root;
	unsigned char *b = skb_tail_pointer(skb);
	struct nlattr *nest;

	t->tcm_handle = head->handle;

	nest = nla_nest_start(skb, TCA_OPTIONS);
	if (nest == NULL)
		goto nla_put_failure;

	if (tcf_exts_dump(skb, &head->exts) < 0 ||
	    tcf_em_tree_dump(skb, &head->ematches, TCA_CGROUP_EMATCHES) < 0)
		goto nla_put_failure;

	nla_nest_end(skb, nest);

	if (tcf_exts_dump_stats(skb, &head->exts) < 0)
		goto nla_put_failure;

	return skb->len;

nla_put_failure:
	nlmsg_trim(skb, b);
	return -1;
}

static struct tcf_proto_ops cls_cgroup_ops __read_mostly = {
	.kind		=	"cgroup",
	.init		=	cls_cgroup_init,
	.change		=	cls_cgroup_change,
	.classify	=	cls_cgroup_classify,
	.destroy	=	cls_cgroup_destroy,
	.get		=	cls_cgroup_get,
	.put		=	cls_cgroup_put,
	.delete		=	cls_cgroup_delete,
	.walk		=	cls_cgroup_walk,
	.dump		=	cls_cgroup_dump,
	.owner		=	THIS_MODULE,
};

static int __init init_cgroup_cls(void)
{
	int ret;

	ret = cgroup_load_subsys(&net_cls_subsys);
	if (ret)
		goto out;

	ret = register_tcf_proto_ops(&cls_cgroup_ops);
	if (ret)
		cgroup_unload_subsys(&net_cls_subsys);

out:
	return ret;
}

static void __exit exit_cgroup_cls(void)
{
	unregister_tcf_proto_ops(&cls_cgroup_ops);

	cgroup_unload_subsys(&net_cls_subsys);
}

module_init(init_cgroup_cls);
module_exit(exit_cgroup_cls);
MODULE_LICENSE("GPL");