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 */
41static 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(to: new->priomap, from: old->priomap,
75 len: 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 */
93static 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 */
112static 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, target_idx: id);
125 if (ret)
126 return ret;
127
128 map = rtnl_dereference(dev->priomap);
129 map->priomap[id] = prio;
130 return 0;
131}
132
133static struct cgroup_subsys_state *
134cgrp_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(error: -ENOMEM);
141
142 return css;
143}
144
145static 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(css: 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
173static void cgrp_css_free(struct cgroup_subsys_state *css)
174{
175 kfree(objp: css);
176}
177
178static u64 read_prioidx(struct cgroup_subsys_state *css, struct cftype *cft)
179{
180 return css->id;
181}
182
183static 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(m: sf, fmt: "%s %u\n", dev->name,
190 netprio_prio(css: seq_css(seq: sf), dev));
191 rcu_read_unlock();
192 return 0;
193}
194
195static 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(net: &init_net, name: devname);
207 if (!dev)
208 return -ENODEV;
209
210 rtnl_lock();
211
212 ret = netprio_set_prio(css: of_css(of), dev, prio);
213
214 rtnl_unlock();
215 dev_put(dev);
216 return ret ?: nbytes;
217}
218
219static 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(skcd: &sock->sk->sk_cgrp_data,
225 prioidx: (unsigned long)v);
226 return 0;
227}
228
229static 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
243static 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
256struct 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
264static 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(info: 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
286static struct notifier_block netprio_device_notifier = {
287 .notifier_call = netprio_device_event
288};
289
290static int __init init_cgroup_netprio(void)
291{
292 register_netdevice_notifier(nb: &netprio_device_notifier);
293 return 0;
294}
295subsys_initcall(init_cgroup_netprio);
296