xref: /openbmc/linux/net/core/netprio_cgroup.c (revision 8520e224)
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * net/core/netprio_cgroup.c	Priority Control Group
4  *
5  * Authors:	Neil Horman <nhorman@tuxdriver.com>
6  */
7 
8 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
9 
10 #include <linux/module.h>
11 #include <linux/slab.h>
12 #include <linux/types.h>
13 #include <linux/string.h>
14 #include <linux/errno.h>
15 #include <linux/skbuff.h>
16 #include <linux/cgroup.h>
17 #include <linux/rcupdate.h>
18 #include <linux/atomic.h>
19 #include <linux/sched/task.h>
20 
21 #include <net/rtnetlink.h>
22 #include <net/pkt_cls.h>
23 #include <net/sock.h>
24 #include <net/netprio_cgroup.h>
25 
26 #include <linux/fdtable.h>
27 
28 /*
29  * netprio allocates per-net_device priomap array which is indexed by
30  * css->id.  Limiting css ID to 16bits doesn't lose anything.
31  */
32 #define NETPRIO_ID_MAX		USHRT_MAX
33 
34 #define PRIOMAP_MIN_SZ		128
35 
36 /*
37  * Extend @dev->priomap so that it's large enough to accommodate
38  * @target_idx.  @dev->priomap.priomap_len > @target_idx after successful
39  * return.  Must be called under rtnl lock.
40  */
extend_netdev_table(struct net_device * dev,u32 target_idx)41 static int extend_netdev_table(struct net_device *dev, u32 target_idx)
42 {
43 	struct netprio_map *old, *new;
44 	size_t new_sz, new_len;
45 
46 	/* is the existing priomap large enough? */
47 	old = rtnl_dereference(dev->priomap);
48 	if (old && old->priomap_len > target_idx)
49 		return 0;
50 
51 	/*
52 	 * Determine the new size.  Let's keep it power-of-two.  We start
53 	 * from PRIOMAP_MIN_SZ and double it until it's large enough to
54 	 * accommodate @target_idx.
55 	 */
56 	new_sz = PRIOMAP_MIN_SZ;
57 	while (true) {
58 		new_len = (new_sz - offsetof(struct netprio_map, priomap)) /
59 			sizeof(new->priomap[0]);
60 		if (new_len > target_idx)
61 			break;
62 		new_sz *= 2;
63 		/* overflowed? */
64 		if (WARN_ON(new_sz < PRIOMAP_MIN_SZ))
65 			return -ENOSPC;
66 	}
67 
68 	/* allocate & copy */
69 	new = kzalloc(new_sz, GFP_KERNEL);
70 	if (!new)
71 		return -ENOMEM;
72 
73 	if (old)
74 		memcpy(new->priomap, old->priomap,
75 		       old->priomap_len * sizeof(old->priomap[0]));
76 
77 	new->priomap_len = new_len;
78 
79 	/* install the new priomap */
80 	rcu_assign_pointer(dev->priomap, new);
81 	if (old)
82 		kfree_rcu(old, rcu);
83 	return 0;
84 }
85 
86 /**
87  * netprio_prio - return the effective netprio of a cgroup-net_device pair
88  * @css: css part of the target pair
89  * @dev: net_device part of the target pair
90  *
91  * Should be called under RCU read or rtnl lock.
92  */
netprio_prio(struct cgroup_subsys_state * css,struct net_device * dev)93 static u32 netprio_prio(struct cgroup_subsys_state *css, struct net_device *dev)
94 {
95 	struct netprio_map *map = rcu_dereference_rtnl(dev->priomap);
96 	int id = css->id;
97 
98 	if (map && id < map->priomap_len)
99 		return map->priomap[id];
100 	return 0;
101 }
102 
103 /**
104  * netprio_set_prio - set netprio on a cgroup-net_device pair
105  * @css: css part of the target pair
106  * @dev: net_device part of the target pair
107  * @prio: prio to set
108  *
109  * Set netprio to @prio on @css-@dev pair.  Should be called under rtnl
110  * lock and may fail under memory pressure for non-zero @prio.
111  */
netprio_set_prio(struct cgroup_subsys_state * css,struct net_device * dev,u32 prio)112 static int netprio_set_prio(struct cgroup_subsys_state *css,
113 			    struct net_device *dev, u32 prio)
114 {
115 	struct netprio_map *map;
116 	int id = css->id;
117 	int ret;
118 
119 	/* avoid extending priomap for zero writes */
120 	map = rtnl_dereference(dev->priomap);
121 	if (!prio && (!map || map->priomap_len <= id))
122 		return 0;
123 
124 	ret = extend_netdev_table(dev, id);
125 	if (ret)
126 		return ret;
127 
128 	map = rtnl_dereference(dev->priomap);
129 	map->priomap[id] = prio;
130 	return 0;
131 }
132 
133 static struct cgroup_subsys_state *
cgrp_css_alloc(struct cgroup_subsys_state * parent_css)134 cgrp_css_alloc(struct cgroup_subsys_state *parent_css)
135 {
136 	struct cgroup_subsys_state *css;
137 
138 	css = kzalloc(sizeof(*css), GFP_KERNEL);
139 	if (!css)
140 		return ERR_PTR(-ENOMEM);
141 
142 	return css;
143 }
144 
cgrp_css_online(struct cgroup_subsys_state * css)145 static int cgrp_css_online(struct cgroup_subsys_state *css)
146 {
147 	struct cgroup_subsys_state *parent_css = css->parent;
148 	struct net_device *dev;
149 	int ret = 0;
150 
151 	if (css->id > NETPRIO_ID_MAX)
152 		return -ENOSPC;
153 
154 	if (!parent_css)
155 		return 0;
156 
157 	rtnl_lock();
158 	/*
159 	 * Inherit prios from the parent.  As all prios are set during
160 	 * onlining, there is no need to clear them on offline.
161 	 */
162 	for_each_netdev(&init_net, dev) {
163 		u32 prio = netprio_prio(parent_css, dev);
164 
165 		ret = netprio_set_prio(css, dev, prio);
166 		if (ret)
167 			break;
168 	}
169 	rtnl_unlock();
170 	return ret;
171 }
172 
cgrp_css_free(struct cgroup_subsys_state * css)173 static void cgrp_css_free(struct cgroup_subsys_state *css)
174 {
175 	kfree(css);
176 }
177 
read_prioidx(struct cgroup_subsys_state * css,struct cftype * cft)178 static u64 read_prioidx(struct cgroup_subsys_state *css, struct cftype *cft)
179 {
180 	return css->id;
181 }
182 
read_priomap(struct seq_file * sf,void * v)183 static int read_priomap(struct seq_file *sf, void *v)
184 {
185 	struct net_device *dev;
186 
187 	rcu_read_lock();
188 	for_each_netdev_rcu(&init_net, dev)
189 		seq_printf(sf, "%s %u\n", dev->name,
190 			   netprio_prio(seq_css(sf), dev));
191 	rcu_read_unlock();
192 	return 0;
193 }
194 
write_priomap(struct kernfs_open_file * of,char * buf,size_t nbytes,loff_t off)195 static ssize_t write_priomap(struct kernfs_open_file *of,
196 			     char *buf, size_t nbytes, loff_t off)
197 {
198 	char devname[IFNAMSIZ + 1];
199 	struct net_device *dev;
200 	u32 prio;
201 	int ret;
202 
203 	if (sscanf(buf, "%"__stringify(IFNAMSIZ)"s %u", devname, &prio) != 2)
204 		return -EINVAL;
205 
206 	dev = dev_get_by_name(&init_net, devname);
207 	if (!dev)
208 		return -ENODEV;
209 
210 	rtnl_lock();
211 
212 	ret = netprio_set_prio(of_css(of), dev, prio);
213 
214 	rtnl_unlock();
215 	dev_put(dev);
216 	return ret ?: nbytes;
217 }
218 
update_netprio(const void * v,struct file * file,unsigned n)219 static int update_netprio(const void *v, struct file *file, unsigned n)
220 {
221 	struct socket *sock = sock_from_file(file);
222 
223 	if (sock)
224 		sock_cgroup_set_prioidx(&sock->sk->sk_cgrp_data,
225 					(unsigned long)v);
226 	return 0;
227 }
228 
net_prio_attach(struct cgroup_taskset * tset)229 static void net_prio_attach(struct cgroup_taskset *tset)
230 {
231 	struct task_struct *p;
232 	struct cgroup_subsys_state *css;
233 
234 	cgroup_taskset_for_each(p, css, tset) {
235 		void *v = (void *)(unsigned long)css->id;
236 
237 		task_lock(p);
238 		iterate_fd(p->files, 0, update_netprio, v);
239 		task_unlock(p);
240 	}
241 }
242 
243 static struct cftype ss_files[] = {
244 	{
245 		.name = "prioidx",
246 		.read_u64 = read_prioidx,
247 	},
248 	{
249 		.name = "ifpriomap",
250 		.seq_show = read_priomap,
251 		.write = write_priomap,
252 	},
253 	{ }	/* terminate */
254 };
255 
256 struct cgroup_subsys net_prio_cgrp_subsys = {
257 	.css_alloc	= cgrp_css_alloc,
258 	.css_online	= cgrp_css_online,
259 	.css_free	= cgrp_css_free,
260 	.attach		= net_prio_attach,
261 	.legacy_cftypes	= ss_files,
262 };
263 
netprio_device_event(struct notifier_block * unused,unsigned long event,void * ptr)264 static int netprio_device_event(struct notifier_block *unused,
265 				unsigned long event, void *ptr)
266 {
267 	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
268 	struct netprio_map *old;
269 
270 	/*
271 	 * Note this is called with rtnl_lock held so we have update side
272 	 * protection on our rcu assignments
273 	 */
274 
275 	switch (event) {
276 	case NETDEV_UNREGISTER:
277 		old = rtnl_dereference(dev->priomap);
278 		RCU_INIT_POINTER(dev->priomap, NULL);
279 		if (old)
280 			kfree_rcu(old, rcu);
281 		break;
282 	}
283 	return NOTIFY_DONE;
284 }
285 
286 static struct notifier_block netprio_device_notifier = {
287 	.notifier_call = netprio_device_event
288 };
289 
init_cgroup_netprio(void)290 static int __init init_cgroup_netprio(void)
291 {
292 	register_netdevice_notifier(&netprio_device_notifier);
293 	return 0;
294 }
295 subsys_initcall(init_cgroup_netprio);
296