1/*
  2 * net/core/netprio_cgroup.c	Priority Control Group
  3 *
  4 *		This program is free software; you can redistribute it and/or
  5 *		modify it under the terms of the GNU General Public License
  6 *		as published by the Free Software Foundation; either version
  7 *		2 of the License, or (at your option) any later version.
  8 *
  9 * Authors:	Neil Horman <nhorman@tuxdriver.com>
 10 */
 11
 12#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 13
 14#include <linux/module.h>
 15#include <linux/slab.h>
 16#include <linux/types.h>
 17#include <linux/string.h>
 18#include <linux/errno.h>
 19#include <linux/skbuff.h>
 20#include <linux/cgroup.h>
 21#include <linux/rcupdate.h>
 22#include <linux/atomic.h>
 23#include <net/rtnetlink.h>
 24#include <net/pkt_cls.h>
 25#include <net/sock.h>
 26#include <net/netprio_cgroup.h>
 27
 28#include <linux/fdtable.h>
 29
 30#define PRIOMAP_MIN_SZ		128
 31
 32/*
 33 * Extend @dev->priomap so that it's large enough to accommodate
 34 * @target_idx.  @dev->priomap.priomap_len > @target_idx after successful
 35 * return.  Must be called under rtnl lock.
 36 */
 37static int extend_netdev_table(struct net_device *dev, u32 target_idx)
 38{
 39	struct netprio_map *old, *new;
 40	size_t new_sz, new_len;
 41
 42	/* is the existing priomap large enough? */
 43	old = rtnl_dereference(dev->priomap);
 44	if (old && old->priomap_len > target_idx)
 45		return 0;
 46
 47	/*
 48	 * Determine the new size.  Let's keep it power-of-two.  We start
 49	 * from PRIOMAP_MIN_SZ and double it until it's large enough to
 50	 * accommodate @target_idx.
 51	 */
 52	new_sz = PRIOMAP_MIN_SZ;
 53	while (true) {
 54		new_len = (new_sz - offsetof(struct netprio_map, priomap)) /
 55			sizeof(new->priomap[0]);
 56		if (new_len > target_idx)
 57			break;
 58		new_sz *= 2;
 59		/* overflowed? */
 60		if (WARN_ON(new_sz < PRIOMAP_MIN_SZ))
 61			return -ENOSPC;
 62	}
 63
 64	/* allocate & copy */
 65	new = kzalloc(new_sz, GFP_KERNEL);
 66	if (!new)
 67		return -ENOMEM;
 68
 69	if (old)
 70		memcpy(new->priomap, old->priomap,
 71		       old->priomap_len * sizeof(old->priomap[0]));
 72
 73	new->priomap_len = new_len;
 74
 75	/* install the new priomap */
 76	rcu_assign_pointer(dev->priomap, new);
 77	if (old)
 78		kfree_rcu(old, rcu);
 79	return 0;
 80}
 81
 82/**
 83 * netprio_prio - return the effective netprio of a cgroup-net_device pair
 84 * @css: css part of the target pair
 85 * @dev: net_device part of the target pair
 86 *
 87 * Should be called under RCU read or rtnl lock.
 88 */
 89static u32 netprio_prio(struct cgroup_subsys_state *css, struct net_device *dev)
 90{
 91	struct netprio_map *map = rcu_dereference_rtnl(dev->priomap);
 92	int id = css->cgroup->id;
 93
 94	if (map && id < map->priomap_len)
 95		return map->priomap[id];
 96	return 0;
 97}
 98
 99/**
100 * netprio_set_prio - set netprio on a cgroup-net_device pair
101 * @css: css part of the target pair
102 * @dev: net_device part of the target pair
103 * @prio: prio to set
104 *
105 * Set netprio to @prio on @css-@dev pair.  Should be called under rtnl
106 * lock and may fail under memory pressure for non-zero @prio.
107 */
108static int netprio_set_prio(struct cgroup_subsys_state *css,
109			    struct net_device *dev, u32 prio)
110{
111	struct netprio_map *map;
112	int id = css->cgroup->id;
113	int ret;
114
115	/* avoid extending priomap for zero writes */
116	map = rtnl_dereference(dev->priomap);
117	if (!prio && (!map || map->priomap_len <= id))
118		return 0;
119
120	ret = extend_netdev_table(dev, id);
121	if (ret)
122		return ret;
123
124	map = rtnl_dereference(dev->priomap);
125	map->priomap[id] = prio;
126	return 0;
127}
128
129static struct cgroup_subsys_state *
130cgrp_css_alloc(struct cgroup_subsys_state *parent_css)
131{
132	struct cgroup_subsys_state *css;
133
134	css = kzalloc(sizeof(*css), GFP_KERNEL);
135	if (!css)
136		return ERR_PTR(-ENOMEM);
137
138	return css;
139}
140
141static int cgrp_css_online(struct cgroup_subsys_state *css)
142{
143	struct cgroup_subsys_state *parent_css = css_parent(css);
144	struct net_device *dev;
145	int ret = 0;
146
147	if (!parent_css)
148		return 0;
149
150	rtnl_lock();
151	/*
152	 * Inherit prios from the parent.  As all prios are set during
153	 * onlining, there is no need to clear them on offline.
154	 */
155	for_each_netdev(&init_net, dev) {
156		u32 prio = netprio_prio(parent_css, dev);
157
158		ret = netprio_set_prio(css, dev, prio);
159		if (ret)
160			break;
161	}
162	rtnl_unlock();
163	return ret;
164}
165
166static void cgrp_css_free(struct cgroup_subsys_state *css)
167{
168	kfree(css);
169}
170
171static u64 read_prioidx(struct cgroup_subsys_state *css, struct cftype *cft)
172{
173	return css->cgroup->id;
174}
175
176static int read_priomap(struct seq_file *sf, void *v)
177{
178	struct net_device *dev;
179
180	rcu_read_lock();
181	for_each_netdev_rcu(&init_net, dev)
182		seq_printf(sf, "%s %u\n", dev->name,
183			   netprio_prio(seq_css(sf), dev));
184	rcu_read_unlock();
185	return 0;
186}
187
188static int write_priomap(struct cgroup_subsys_state *css, struct cftype *cft,
189			 char *buffer)
190{
191	char devname[IFNAMSIZ + 1];
192	struct net_device *dev;
193	u32 prio;
194	int ret;
195
196	if (sscanf(buffer, "%"__stringify(IFNAMSIZ)"s %u", devname, &prio) != 2)
197		return -EINVAL;
198
199	dev = dev_get_by_name(&init_net, devname);
200	if (!dev)
201		return -ENODEV;
202
203	rtnl_lock();
204
205	ret = netprio_set_prio(css, dev, prio);
206
207	rtnl_unlock();
208	dev_put(dev);
209	return ret;
210}
211
212static int update_netprio(const void *v, struct file *file, unsigned n)
213{
214	int err;
215	struct socket *sock = sock_from_file(file, &err);
216	if (sock)
217		sock->sk->sk_cgrp_prioidx = (u32)(unsigned long)v;
218	return 0;
219}
220
221static void net_prio_attach(struct cgroup_subsys_state *css,
222			    struct cgroup_taskset *tset)
223{
224	struct task_struct *p;
225	void *v = (void *)(unsigned long)css->cgroup->id;
226
227	cgroup_taskset_for_each(p, tset) {
228		task_lock(p);
229		iterate_fd(p->files, 0, update_netprio, v);
230		task_unlock(p);
231	}
232}
233
234static struct cftype ss_files[] = {
235	{
236		.name = "prioidx",
237		.read_u64 = read_prioidx,
238	},
239	{
240		.name = "ifpriomap",
241		.seq_show = read_priomap,
242		.write_string = write_priomap,
243	},
244	{ }	/* terminate */
245};
246
247struct cgroup_subsys net_prio_cgrp_subsys = {
248	.css_alloc	= cgrp_css_alloc,
249	.css_online	= cgrp_css_online,
250	.css_free	= cgrp_css_free,
251	.attach		= net_prio_attach,
252	.base_cftypes	= ss_files,
253};
254
255static int netprio_device_event(struct notifier_block *unused,
256				unsigned long event, void *ptr)
257{
258	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
259	struct netprio_map *old;
260
261	/*
262	 * Note this is called with rtnl_lock held so we have update side
263	 * protection on our rcu assignments
264	 */
265
266	switch (event) {
267	case NETDEV_UNREGISTER:
268		old = rtnl_dereference(dev->priomap);
269		RCU_INIT_POINTER(dev->priomap, NULL);
270		if (old)
271			kfree_rcu(old, rcu);
272		break;
273	}
274	return NOTIFY_DONE;
275}
276
277static struct notifier_block netprio_device_notifier = {
278	.notifier_call = netprio_device_event
279};
280
281static int __init init_cgroup_netprio(void)
282{
283	register_netdevice_notifier(&netprio_device_notifier);
284	return 0;
285}
286
287subsys_initcall(init_cgroup_netprio);
288MODULE_LICENSE("GPL v2");