linux/net/core/netprio_cgroup.c
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   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/slab.h>
  15#include <linux/types.h>
  16#include <linux/string.h>
  17#include <linux/errno.h>
  18#include <linux/skbuff.h>
  19#include <linux/cgroup.h>
  20#include <linux/rcupdate.h>
  21#include <linux/atomic.h>
  22#include <net/rtnetlink.h>
  23#include <net/pkt_cls.h>
  24#include <net/sock.h>
  25#include <net/netprio_cgroup.h>
  26
  27#include <linux/fdtable.h>
  28
  29/*
  30 * netprio allocates per-net_device priomap array which is indexed by
  31 * css->id.  Limiting css ID to 16bits doesn't lose anything.
  32 */
  33#define NETPRIO_ID_MAX          USHRT_MAX
  34
  35#define PRIOMAP_MIN_SZ          128
  36
  37/*
  38 * Extend @dev->priomap so that it's large enough to accommodate
  39 * @target_idx.  @dev->priomap.priomap_len > @target_idx after successful
  40 * return.  Must be called under rtnl lock.
  41 */
  42static int extend_netdev_table(struct net_device *dev, u32 target_idx)
  43{
  44        struct netprio_map *old, *new;
  45        size_t new_sz, new_len;
  46
  47        /* is the existing priomap large enough? */
  48        old = rtnl_dereference(dev->priomap);
  49        if (old && old->priomap_len > target_idx)
  50                return 0;
  51
  52        /*
  53         * Determine the new size.  Let's keep it power-of-two.  We start
  54         * from PRIOMAP_MIN_SZ and double it until it's large enough to
  55         * accommodate @target_idx.
  56         */
  57        new_sz = PRIOMAP_MIN_SZ;
  58        while (true) {
  59                new_len = (new_sz - offsetof(struct netprio_map, priomap)) /
  60                        sizeof(new->priomap[0]);
  61                if (new_len > target_idx)
  62                        break;
  63                new_sz *= 2;
  64                /* overflowed? */
  65                if (WARN_ON(new_sz < PRIOMAP_MIN_SZ))
  66                        return -ENOSPC;
  67        }
  68
  69        /* allocate & copy */
  70        new = kzalloc(new_sz, GFP_KERNEL);
  71        if (!new)
  72                return -ENOMEM;
  73
  74        if (old)
  75                memcpy(new->priomap, old->priomap,
  76                       old->priomap_len * sizeof(old->priomap[0]));
  77
  78        new->priomap_len = new_len;
  79
  80        /* install the new priomap */
  81        rcu_assign_pointer(dev->priomap, new);
  82        if (old)
  83                kfree_rcu(old, rcu);
  84        return 0;
  85}
  86
  87/**
  88 * netprio_prio - return the effective netprio of a cgroup-net_device pair
  89 * @css: css part of the target pair
  90 * @dev: net_device part of the target pair
  91 *
  92 * Should be called under RCU read or rtnl lock.
  93 */
  94static u32 netprio_prio(struct cgroup_subsys_state *css, struct net_device *dev)
  95{
  96        struct netprio_map *map = rcu_dereference_rtnl(dev->priomap);
  97        int id = css->cgroup->id;
  98
  99        if (map && id < map->priomap_len)
 100                return map->priomap[id];
 101        return 0;
 102}
 103
 104/**
 105 * netprio_set_prio - set netprio on a cgroup-net_device pair
 106 * @css: css part of the target pair
 107 * @dev: net_device part of the target pair
 108 * @prio: prio to set
 109 *
 110 * Set netprio to @prio on @css-@dev pair.  Should be called under rtnl
 111 * lock and may fail under memory pressure for non-zero @prio.
 112 */
 113static int netprio_set_prio(struct cgroup_subsys_state *css,
 114                            struct net_device *dev, u32 prio)
 115{
 116        struct netprio_map *map;
 117        int id = css->cgroup->id;
 118        int ret;
 119
 120        /* avoid extending priomap for zero writes */
 121        map = rtnl_dereference(dev->priomap);
 122        if (!prio && (!map || map->priomap_len <= id))
 123                return 0;
 124
 125        ret = extend_netdev_table(dev, id);
 126        if (ret)
 127                return ret;
 128
 129        map = rtnl_dereference(dev->priomap);
 130        map->priomap[id] = prio;
 131        return 0;
 132}
 133
 134static struct cgroup_subsys_state *
 135cgrp_css_alloc(struct cgroup_subsys_state *parent_css)
 136{
 137        struct cgroup_subsys_state *css;
 138
 139        css = kzalloc(sizeof(*css), GFP_KERNEL);
 140        if (!css)
 141                return ERR_PTR(-ENOMEM);
 142
 143        return css;
 144}
 145
 146static int cgrp_css_online(struct cgroup_subsys_state *css)
 147{
 148        struct cgroup_subsys_state *parent_css = css->parent;
 149        struct net_device *dev;
 150        int ret = 0;
 151
 152        if (css->id > NETPRIO_ID_MAX)
 153                return -ENOSPC;
 154
 155        if (!parent_css)
 156                return 0;
 157
 158        rtnl_lock();
 159        /*
 160         * Inherit prios from the parent.  As all prios are set during
 161         * onlining, there is no need to clear them on offline.
 162         */
 163        for_each_netdev(&init_net, dev) {
 164                u32 prio = netprio_prio(parent_css, dev);
 165
 166                ret = netprio_set_prio(css, dev, prio);
 167                if (ret)
 168                        break;
 169        }
 170        rtnl_unlock();
 171        return ret;
 172}
 173
 174static void cgrp_css_free(struct cgroup_subsys_state *css)
 175{
 176        kfree(css);
 177}
 178
 179static u64 read_prioidx(struct cgroup_subsys_state *css, struct cftype *cft)
 180{
 181        return css->cgroup->id;
 182}
 183
 184static int read_priomap(struct seq_file *sf, void *v)
 185{
 186        struct net_device *dev;
 187
 188        rcu_read_lock();
 189        for_each_netdev_rcu(&init_net, dev)
 190                seq_printf(sf, "%s %u\n", dev->name,
 191                           netprio_prio(seq_css(sf), dev));
 192        rcu_read_unlock();
 193        return 0;
 194}
 195
 196static ssize_t write_priomap(struct kernfs_open_file *of,
 197                             char *buf, size_t nbytes, loff_t off)
 198{
 199        char devname[IFNAMSIZ + 1];
 200        struct net_device *dev;
 201        u32 prio;
 202        int ret;
 203
 204        if (sscanf(buf, "%"__stringify(IFNAMSIZ)"s %u", devname, &prio) != 2)
 205                return -EINVAL;
 206
 207        dev = dev_get_by_name(&init_net, devname);
 208        if (!dev)
 209                return -ENODEV;
 210
 211        cgroup_sk_alloc_disable();
 212
 213        rtnl_lock();
 214
 215        ret = netprio_set_prio(of_css(of), dev, prio);
 216
 217        rtnl_unlock();
 218        dev_put(dev);
 219        return ret ?: nbytes;
 220}
 221
 222static int update_netprio(const void *v, struct file *file, unsigned n)
 223{
 224        int err;
 225        struct socket *sock = sock_from_file(file, &err);
 226        if (sock) {
 227                spin_lock(&cgroup_sk_update_lock);
 228                sock_cgroup_set_prioidx(&sock->sk->sk_cgrp_data,
 229                                        (unsigned long)v);
 230                spin_unlock(&cgroup_sk_update_lock);
 231        }
 232        return 0;
 233}
 234
 235static void net_prio_attach(struct cgroup_taskset *tset)
 236{
 237        struct task_struct *p;
 238        struct cgroup_subsys_state *css;
 239
 240        cgroup_taskset_for_each(p, css, tset) {
 241                void *v = (void *)(unsigned long)css->cgroup->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}
 301
 302subsys_initcall(init_cgroup_netprio);
 303MODULE_LICENSE("GPL v2");
 304