net/core/netprio_cgroup.c

   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/module.h>
  15 #include <linux/slab.h>
  16 #include <linux/types.h>
  17 #include <linux/string.h>
  18 #include <linux/errno.h>
  19 #include <linux/skbuff.h>
  20 #include <linux/cgroup.h>
  21 #include <linux/rcupdate.h>
  22 #include <linux/atomic.h>
  23 #include <linux/sched/task.h>
  24
  25 #include <net/rtnetlink.h>
  26 #include <net/pkt_cls.h>
  27 #include <net/sock.h>
  28 #include <net/netprio_cgroup.h>
  29
  30 #include <linux/fdtable.h>
  31
  32 /*
  33  * netprio allocates per-net_device priomap array which is indexed by
  34  * css->id.  Limiting css ID to 16bits doesn't lose anything.
  35  */
  36 #define NETPRIO_ID_MAX          USHRT_MAX
  37
  38 #define PRIOMAP_MIN_SZ          128
  39
  40 /*
  41  * Extend @dev->priomap so that it's large enough to accommodate
  42  * @target_idx.  @dev->priomap.priomap_len > @target_idx after successful
  43  * return.  Must be called under rtnl lock.
  44  */
  45 static int extend_netdev_table(struct net_device *dev, u32 target_idx)
  46 {
  47         struct netprio_map *old, *new;
  48         size_t new_sz, new_len;
  49
  50         /* is the existing priomap large enough? */
  51         old = rtnl_dereference(dev->priomap);
  52         if (old && old->priomap_len > target_idx)
  53                 return 0;
  54
  55         /*
  56          * Determine the new size.  Let's keep it power-of-two.  We start
  57          * from PRIOMAP_MIN_SZ and double it until it's large enough to
  58          * accommodate @target_idx.
  59          */
  60         new_sz = PRIOMAP_MIN_SZ;
  61         while (true) {
  62                 new_len = (new_sz - offsetof(struct netprio_map, priomap)) /
  63                         sizeof(new->priomap[0]);
  64                 if (new_len > target_idx)
  65                         break;
  66                 new_sz *= 2;
  67                 /* overflowed? */
  68                 if (WARN_ON(new_sz < PRIOMAP_MIN_SZ))
  69                         return -ENOSPC;
  70         }
  71
  72         /* allocate & copy */
  73         new = kzalloc(new_sz, GFP_KERNEL);
  74         if (!new)
  75                 return -ENOMEM;
  76
  77         if (old)
  78                 memcpy(new->priomap, old->priomap,
  79                        old->priomap_len * sizeof(old->priomap[0]));
  80
  81         new->priomap_len = new_len;
  82
  83         /* install the new priomap */
  84         rcu_assign_pointer(dev->priomap, new);
  85         if (old)
  86                 kfree_rcu(old, rcu);
  87         return 0;
  88 }
  89
  90 /**
  91  * netprio_prio - return the effective netprio of a cgroup-net_device pair
  92  * @css: css part of the target pair
  93  * @dev: net_device part of the target pair
  94  *
  95  * Should be called under RCU read or rtnl lock.
  96  */
  97 static u32 netprio_prio(struct cgroup_subsys_state *css, struct net_device *dev)
  98 {
  99         struct netprio_map *map = rcu_dereference_rtnl(dev->priomap);
 100         int id = css->cgroup->id;
 101
 102         if (map && id < map->priomap_len)
 103                 return map->priomap[id];
 104         return 0;
 105 }
 106
 107 /**
 108  * netprio_set_prio - set netprio on a cgroup-net_device pair
 109  * @css: css part of the target pair
 110  * @dev: net_device part of the target pair
 111  * @prio: prio to set
 112  *
 113  * Set netprio to @prio on @css-@dev pair.  Should be called under rtnl
 114  * lock and may fail under memory pressure for non-zero @prio.
 115  */
 116 static int netprio_set_prio(struct cgroup_subsys_state *css,
 117                             struct net_device *dev, u32 prio)
 118 {
 119         struct netprio_map *map;
 120         int id = css->cgroup->id;
 121         int ret;
 122
 123         /* avoid extending priomap for zero writes */
 124         map = rtnl_dereference(dev->priomap);
 125         if (!prio && (!map || map->priomap_len <= id))
 126                 return 0;
 127
 128         ret = extend_netdev_table(dev, id);
 129         if (ret)
 130                 return ret;
 131
 132         map = rtnl_dereference(dev->priomap);
 133         map->priomap[id] = prio;
 134         return 0;
 135 }
 136
 137 static struct cgroup_subsys_state *
 138 cgrp_css_alloc(struct cgroup_subsys_state *parent_css)
 139 {
 140         struct cgroup_subsys_state *css;
 141
 142         css = kzalloc(sizeof(*css), GFP_KERNEL);
 143         if (!css)
 144                 return ERR_PTR(-ENOMEM);
 145
 146         return css;
 147 }
 148
 149 static int cgrp_css_online(struct cgroup_subsys_state *css)
 150 {
 151         struct cgroup_subsys_state *parent_css = css->parent;
 152         struct net_device *dev;
 153         int ret = 0;
 154
 155         if (css->id > NETPRIO_ID_MAX)
 156                 return -ENOSPC;
 157
 158         if (!parent_css)
 159                 return 0;
 160
 161         rtnl_lock();
 162         /*
 163          * Inherit prios from the parent.  As all prios are set during
 164          * onlining, there is no need to clear them on offline.
 165          */
 166         for_each_netdev(&init_net, dev) {
 167                 u32 prio = netprio_prio(parent_css, dev);
 168
 169                 ret = netprio_set_prio(css, dev, prio);
 170                 if (ret)
 171                         break;
 172         }
 173         rtnl_unlock();
 174         return ret;
 175 }
 176
 177 static void cgrp_css_free(struct cgroup_subsys_state *css)
 178 {
 179         kfree(css);
 180 }
 181
 182 static u64 read_prioidx(struct cgroup_subsys_state *css, struct cftype *cft)
 183 {
 184         return css->cgroup->id;
 185 }
 186
 187 static int read_priomap(struct seq_file *sf, void *v)
 188 {
 189         struct net_device *dev;
 190
 191         rcu_read_lock();
 192         for_each_netdev_rcu(&init_net, dev)
 193                 seq_printf(sf, "%s %u\n", dev->name,
 194                            netprio_prio(seq_css(sf), dev));
 195         rcu_read_unlock();
 196         return 0;
 197 }
 198
 199 static ssize_t write_priomap(struct kernfs_open_file *of,
 200                              char *buf, size_t nbytes, loff_t off)
 201 {
 202         char devname[IFNAMSIZ + 1];
 203         struct net_device *dev;
 204         u32 prio;
 205         int ret;
 206
 207         if (sscanf(buf, "%"__stringify(IFNAMSIZ)"s %u", devname, &prio) != 2)
 208                 return -EINVAL;
 209
 210         dev = dev_get_by_name(&init_net, devname);
 211         if (!dev)
 212                 return -ENODEV;
 213
 214         cgroup_sk_alloc_disable();
 215
 216         rtnl_lock();
 217
 218         ret = netprio_set_prio(of_css(of), dev, prio);
 219
 220         rtnl_unlock();
 221         dev_put(dev);
 222         return ret ?: nbytes;
 223 }
 224
 225 static int update_netprio(const void *v, struct file *file, unsigned n)
 226 {
 227         int err;
 228         struct socket *sock = sock_from_file(file, &err);
 229         if (sock) {
 230                 spin_lock(&cgroup_sk_update_lock);
 231                 sock_cgroup_set_prioidx(&sock->sk->sk_cgrp_data,
 232                                         (unsigned long)v);
 233                 spin_unlock(&cgroup_sk_update_lock);
 234         }
 235         return 0;
 236 }
 237
 238 static void net_prio_attach(struct cgroup_taskset *tset)
 239 {
 240         struct task_struct *p;
 241         struct cgroup_subsys_state *css;
 242
 243         cgroup_taskset_for_each(p, css, tset) {
 244                 void *v = (void *)(unsigned long)css->cgroup->id;
 245
 246                 task_lock(p);
 247                 iterate_fd(p->files, 0, update_netprio, v);
 248                 task_unlock(p);
 249         }
 250 }
 251
 252 static struct cftype ss_files[] = {
 253         {
 254                 .name = "prioidx",
 255                 .read_u64 = read_prioidx,
 256         },
 257         {
 258                 .name = "ifpriomap",
 259                 .seq_show = read_priomap,
 260                 .write = write_priomap,
 261         },
 262         { }     /* terminate */
 263 };
 264
 265 struct cgroup_subsys net_prio_cgrp_subsys = {
 266         .css_alloc      = cgrp_css_alloc,
 267         .css_online     = cgrp_css_online,
 268         .css_free       = cgrp_css_free,
 269         .attach         = net_prio_attach,
 270         .legacy_cftypes = ss_files,
 271 };
 272
 273 static int netprio_device_event(struct notifier_block *unused,
 274                                 unsigned long event, void *ptr)
 275 {
 276         struct net_device *dev = netdev_notifier_info_to_dev(ptr);
 277         struct netprio_map *old;
 278
 279         /*
 280          * Note this is called with rtnl_lock held so we have update side
 281          * protection on our rcu assignments
 282          */
 283
 284         switch (event) {
 285         case NETDEV_UNREGISTER:
 286                 old = rtnl_dereference(dev->priomap);
 287                 RCU_INIT_POINTER(dev->priomap, NULL);
 288                 if (old)
 289                         kfree_rcu(old, rcu);
 290                 break;
 291         }
 292         return NOTIFY_DONE;
 293 }
 294
 295 static struct notifier_block netprio_device_notifier = {
 296         .notifier_call = netprio_device_event
 297 };
 298
 299 static int __init init_cgroup_netprio(void)
 300 {
 301         register_netdevice_notifier(&netprio_device_notifier);
 302         return 0;
 303 }
 304
 305 subsys_initcall(init_cgroup_netprio);
 306 MODULE_LICENSE("GPL v2");