linux/net/core/netprio_cgroup.c
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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 */
  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(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 */
  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, 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(-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(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(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(sf, "%s %u\n", dev->name,
 190                           netprio_prio(seq_css(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(&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
 221static int update_netprio(const void *v, struct file *file, unsigned n)
 222{
 223        struct socket *sock = sock_from_file(file);
 224        if (sock) {
 225                spin_lock(&cgroup_sk_update_lock);
 226                sock_cgroup_set_prioidx(&sock->sk->sk_cgrp_data,
 227                                        (unsigned long)v);
 228                spin_unlock(&cgroup_sk_update_lock);
 229        }
 230        return 0;
 231}
 232
 233static void net_prio_attach(struct cgroup_taskset *tset)
 234{
 235        struct task_struct *p;
 236        struct cgroup_subsys_state *css;
 237
 238        cgroup_sk_alloc_disable();
 239
 240        cgroup_taskset_for_each(p, css, tset) {
 241                void *v = (void *)(unsigned long)css->id;
 242
 243                task_lock(p);
 244                iterate_fd(p->files, 0, update_netprio, v);
 245                task_unlock(p);
 246        }
 247}
 248
 249static struct cftype ss_files[] = {
 250        {
 251                .name = "prioidx",
 252                .read_u64 = read_prioidx,
 253        },
 254        {
 255                .name = "ifpriomap",
 256                .seq_show = read_priomap,
 257                .write = write_priomap,
 258        },
 259        { }     /* terminate */
 260};
 261
 262struct cgroup_subsys net_prio_cgrp_subsys = {
 263        .css_alloc      = cgrp_css_alloc,
 264        .css_online     = cgrp_css_online,
 265        .css_free       = cgrp_css_free,
 266        .attach         = net_prio_attach,
 267        .legacy_cftypes = ss_files,
 268};
 269
 270static int netprio_device_event(struct notifier_block *unused,
 271                                unsigned long event, void *ptr)
 272{
 273        struct net_device *dev = netdev_notifier_info_to_dev(ptr);
 274        struct netprio_map *old;
 275
 276        /*
 277         * Note this is called with rtnl_lock held so we have update side
 278         * protection on our rcu assignments
 279         */
 280
 281        switch (event) {
 282        case NETDEV_UNREGISTER:
 283                old = rtnl_dereference(dev->priomap);
 284                RCU_INIT_POINTER(dev->priomap, NULL);
 285                if (old)
 286                        kfree_rcu(old, rcu);
 287                break;
 288        }
 289        return NOTIFY_DONE;
 290}
 291
 292static struct notifier_block netprio_device_notifier = {
 293        .notifier_call = netprio_device_event
 294};
 295
 296static int __init init_cgroup_netprio(void)
 297{
 298        register_netdevice_notifier(&netprio_device_notifier);
 299        return 0;
 300}
 301subsys_initcall(init_cgroup_netprio);
 302