net/core/netprio_cgroup.c

   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         rtnl_lock();
 211
 212         ret = netprio_set_prio(of_css(of), dev, prio);
 213
 214         rtnl_unlock();
 215         dev_put(dev);
 216         return ret ?: nbytes;
 217 }
 218
 219 static 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(&sock->sk->sk_cgrp_data,
 225                                         (unsigned long)v);
 226         return 0;
 227 }
 228
 229 static 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
 243 static 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
 256 struct 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
 264 static 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(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
 286 static struct notifier_block netprio_device_notifier = {
 287         .notifier_call = netprio_device_event
 288 };
 289
 290 static int __init init_cgroup_netprio(void)
 291 {
 292         register_netdevice_notifier(&netprio_device_notifier);
 293         return 0;
 294 }
 295 subsys_initcall(init_cgroup_netprio);