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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 */
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 */
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 */
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 *
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
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
173 static void cgrp_css_free(struct cgroup_subsys_state *css)
174 {
175 kfree(css);
176 }
177
178 static u64 read_prioidx(struct cgroup_subsys_state *css, struct cftype *cft)
179 {
180 return css->id;
181 }
182
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
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 cgroup_sk_alloc_disable();
211
212 rtnl_lock();
213
214 ret = netprio_set_prio(of_css(of), dev, prio);
215
216 rtnl_unlock();
217 dev_put(dev);
218 return ret ?: nbytes;
219 }
220
221 static int update_netprio(const void *v, struct file *file, unsigned n)
222 {
223 int err;
224 struct socket *sock = sock_from_file(file, &err);
225 if (sock) {
226 spin_lock(&cgroup_sk_update_lock);
227 sock_cgroup_set_prioidx(&sock->sk->sk_cgrp_data,
228 (unsigned long)v);
229 spin_unlock(&cgroup_sk_update_lock);
230 }
231 return 0;
232 }
233
234 static void net_prio_attach(struct cgroup_taskset *tset)
235 {
236 struct task_struct *p;
237 struct cgroup_subsys_state *css;
238
239 cgroup_taskset_for_each(p, css, tset) {
240 void *v = (void *)(unsigned long)css->id;
241
242 task_lock(p);
243 iterate_fd(p->files, 0, update_netprio, v);
244 task_unlock(p);
245 }
246 }
247
248 static struct cftype ss_files[] = {
249 {
250 .name = "prioidx",
251 .read_u64 = read_prioidx,
252 },
253 {
254 .name = "ifpriomap",
255 .seq_show = read_priomap,
256 .write = write_priomap,
257 },
258 { } /* terminate */
259 };
260
261 struct cgroup_subsys net_prio_cgrp_subsys = {
262 .css_alloc = cgrp_css_alloc,
263 .css_online = cgrp_css_online,
264 .css_free = cgrp_css_free,
265 .attach = net_prio_attach,
266 .legacy_cftypes = ss_files,
267 };
268
269 static int netprio_device_event(struct notifier_block *unused,
270 unsigned long event, void *ptr)
271 {
272 struct net_device *dev = netdev_notifier_info_to_dev(ptr);
273 struct netprio_map *old;
274
275 /*
276 * Note this is called with rtnl_lock held so we have update side
277 * protection on our rcu assignments
278 */
279
280 switch (event) {
281 case NETDEV_UNREGISTER:
282 old = rtnl_dereference(dev->priomap);
283 RCU_INIT_POINTER(dev->priomap, NULL);
284 if (old)
285 kfree_rcu(old, rcu);
286 break;
287 }
288 return NOTIFY_DONE;
289 }
290
291 static struct notifier_block netprio_device_notifier = {
292 .notifier_call = netprio_device_event
293 };
294
295 static int __init init_cgroup_netprio(void)
296 {
297 register_netdevice_notifier(&netprio_device_notifier);
298 return 0;
299 }
300 subsys_initcall(init_cgroup_netprio);