netprio_cgroup.c

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/*
 * net/core/netprio_cgroup.c    Priority Control Group
 *
 *      This program is free software; you can redistribute it and/or
 *      modify it under the terms of the GNU General Public License
 *      as published by the Free Software Foundation; either version
 *      2 of the License, or (at your option) any later version.
 *
 * Authors: Neil Horman <[email protected]>
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/slab.h>
#include <linux/types.h>
#include <linux/string.h>
#include <linux/errno.h>
#include <linux/skbuff.h>
#include <linux/cgroup.h>
#include <linux/rcupdate.h>
#include <linux/atomic.h>
#include <net/rtnetlink.h>
#include <net/pkt_cls.h>
#include <net/sock.h>
#include <net/netprio_cgroup.h>

#include <linux/fdtable.h>

#define PRIOIDX_SZ 128

static unsigned long prioidx_map[PRIOIDX_SZ];
static DEFINE_SPINLOCK(prioidx_map_lock);
static atomic_t max_prioidx = ATOMIC_INIT(0);

static inline struct cgroup_netprio_state *cgrp_netprio_state(struct cgroup *cgrp)
{
    return container_of(cgroup_subsys_state(cgrp, net_prio_subsys_id),
                struct cgroup_netprio_state, css);
}

static int get_prioidx(u32 *prio)
{
    unsigned long flags;
    u32 prioidx;

    spin_lock_irqsave(&prioidx_map_lock, flags);
    prioidx = find_first_zero_bit(prioidx_map, sizeof(unsigned long) * PRIOIDX_SZ);
    if (prioidx == sizeof(unsigned long) * PRIOIDX_SZ) {
        spin_unlock_irqrestore(&prioidx_map_lock, flags);
        return -ENOSPC;
    }
    set_bit(prioidx, prioidx_map);
    if (atomic_read(&max_prioidx) < prioidx)
        atomic_set(&max_prioidx, prioidx);
    spin_unlock_irqrestore(&prioidx_map_lock, flags);
    *prio = prioidx;
    return 0;
}

static void put_prioidx(u32 idx)
{
    unsigned long flags;

    spin_lock_irqsave(&prioidx_map_lock, flags);
    clear_bit(idx, prioidx_map);
    spin_unlock_irqrestore(&prioidx_map_lock, flags);
}

static int extend_netdev_table(struct net_device *dev, u32 new_len)
{
    size_t new_size = sizeof(struct netprio_map) +
               ((sizeof(u32) * new_len));
    struct netprio_map *new_priomap = kzalloc(new_size, GFP_KERNEL);
    struct netprio_map *old_priomap;

    old_priomap  = rtnl_dereference(dev->priomap);

    if (!new_priomap) {
        pr_warn("Unable to alloc new priomap!\n");
        return -ENOMEM;
    }

    if (old_priomap)
        memcpy(new_priomap->priomap, old_priomap->priomap,
               old_priomap->priomap_len *
               sizeof(old_priomap->priomap[0]));

    new_priomap->priomap_len = new_len;

    rcu_assign_pointer(dev->priomap, new_priomap);
    if (old_priomap)
        kfree_rcu(old_priomap, rcu);
    return 0;
}

static int write_update_netdev_table(struct net_device *dev)
{
    int ret = 0;
    u32 max_len;
    struct netprio_map *map;

    max_len = atomic_read(&max_prioidx) + 1;
    map = rtnl_dereference(dev->priomap);
    if (!map || map->priomap_len < max_len)
        ret = extend_netdev_table(dev, max_len);

    return ret;
}

static struct cgroup_subsys_state *cgrp_create(struct cgroup *cgrp)
{
    struct cgroup_netprio_state *cs;
    int ret = -EINVAL;

    cs = kzalloc(sizeof(*cs), GFP_KERNEL);
    if (!cs)
        return ERR_PTR(-ENOMEM);

    if (cgrp->parent && cgrp_netprio_state(cgrp->parent)->prioidx)
        goto out;

    ret = get_prioidx(&cs->prioidx);
    if (ret < 0) {
        pr_warn("No space in priority index array\n");
        goto out;
    }

    return &cs->css;
out:
    kfree(cs);
    return ERR_PTR(ret);
}

static void cgrp_destroy(struct cgroup *cgrp)
{
    struct cgroup_netprio_state *cs;
    struct net_device *dev;
    struct netprio_map *map;

    cs = cgrp_netprio_state(cgrp);
    rtnl_lock();
    for_each_netdev(&init_net, dev) {
        map = rtnl_dereference(dev->priomap);
        if (map && cs->prioidx < map->priomap_len)
            map->priomap[cs->prioidx] = 0;
    }
    rtnl_unlock();
    put_prioidx(cs->prioidx);
    kfree(cs);
}

static u64 read_prioidx(struct cgroup *cgrp, struct cftype *cft)
{
    return (u64)cgrp_netprio_state(cgrp)->prioidx;
}

static int read_priomap(struct cgroup *cont, struct cftype *cft,
            struct cgroup_map_cb *cb)
{
    struct net_device *dev;
    u32 prioidx = cgrp_netprio_state(cont)->prioidx;
    u32 priority;
    struct netprio_map *map;

    rcu_read_lock();
    for_each_netdev_rcu(&init_net, dev) {
        map = rcu_dereference(dev->priomap);
        priority = (map && prioidx < map->priomap_len) ? map->priomap[prioidx] : 0;
        cb->fill(cb, dev->name, priority);
    }
    rcu_read_unlock();
    return 0;
}

static int write_priomap(struct cgroup *cgrp, struct cftype *cft,
             const char *buffer)
{
    char *devname = kstrdup(buffer, GFP_KERNEL);
    int ret = -EINVAL;
    u32 prioidx = cgrp_netprio_state(cgrp)->prioidx;
    unsigned long priority;
    char *priostr;
    struct net_device *dev;
    struct netprio_map *map;

    if (!devname)
        return -ENOMEM;

    /*
     * Minimally sized valid priomap string
     */
    if (strlen(devname) < 3)
        goto out_free_devname;

    priostr = strstr(devname, " ");
    if (!priostr)
        goto out_free_devname;

    /*
     *Separate the devname from the associated priority
     *and advance the priostr pointer to the priority value
     */
    *priostr = '\0';
    priostr++;

    /*
     * If the priostr points to NULL, we're at the end of the passed
     * in string, and its not a valid write
     */
    if (*priostr == '\0')
        goto out_free_devname;

    ret = kstrtoul(priostr, 10, &priority);
    if (ret < 0)
        goto out_free_devname;

    ret = -ENODEV;

    dev = dev_get_by_name(&init_net, devname);
    if (!dev)
        goto out_free_devname;

    rtnl_lock();
    ret = write_update_netdev_table(dev);
    if (ret < 0)
        goto out_put_dev;

    map = rtnl_dereference(dev->priomap);
    if (map)
        map->priomap[prioidx] = priority;

out_put_dev:
    rtnl_unlock();
    dev_put(dev);

out_free_devname:
    kfree(devname);
    return ret;
}

static int update_netprio(const void *v, struct file *file, unsigned n)
{
    int err;
    struct socket *sock = sock_from_file(file, &err);
    if (sock)
        sock->sk->sk_cgrp_prioidx = (u32)(unsigned long)v;
    return 0;
}

void net_prio_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
{
    struct task_struct *p;
    void *v;

    cgroup_taskset_for_each(p, cgrp, tset) {
        task_lock(p);
        v = (void *)(unsigned long)task_netprioidx(p);
        iterate_fd(p->files, 0, update_netprio, v);
        task_unlock(p);
    }
}

static struct cftype ss_files[] = {
    {
        .name = "prioidx",
        .read_u64 = read_prioidx,
    },
    {
        .name = "ifpriomap",
        .read_map = read_priomap,
        .write_string = write_priomap,
    },
    { } /* terminate */
};

struct cgroup_subsys net_prio_subsys = {
    .name       = "net_prio",
    .create     = cgrp_create,
    .destroy    = cgrp_destroy,
    .attach     = net_prio_attach,
    .subsys_id  = net_prio_subsys_id,
    .base_cftypes   = ss_files,
    .module     = THIS_MODULE,

    /*
     * net_prio has artificial limit on the number of cgroups and
     * disallows nesting making it impossible to co-mount it with other
     * hierarchical subsystems.  Remove the artificially low PRIOIDX_SZ
     * limit and properly nest configuration such that children follow
     * their parents' configurations by default and are allowed to
     * override and remove the following.
     */
    .broken_hierarchy = true,
};

static int netprio_device_event(struct notifier_block *unused,
                unsigned long event, void *ptr)
{
    struct net_device *dev = ptr;
    struct netprio_map *old;

    /*
     * Note this is called with rtnl_lock held so we have update side
     * protection on our rcu assignments
     */

    switch (event) {
    case NETDEV_UNREGISTER:
        old = rtnl_dereference(dev->priomap);
        RCU_INIT_POINTER(dev->priomap, NULL);
        if (old)
            kfree_rcu(old, rcu);
        break;
    }
    return NOTIFY_DONE;
}

static struct notifier_block netprio_device_notifier = {
    .notifier_call = netprio_device_event
};

static int __init init_cgroup_netprio(void)
{
    int ret;

    ret = cgroup_load_subsys(&net_prio_subsys);
    if (ret)
        goto out;

    register_netdevice_notifier(&netprio_device_notifier);

out:
    return ret;
}

static void __exit exit_cgroup_netprio(void)
{
    struct netprio_map *old;
    struct net_device *dev;

    unregister_netdevice_notifier(&netprio_device_notifier);

    cgroup_unload_subsys(&net_prio_subsys);

    rtnl_lock();
    for_each_netdev(&init_net, dev) {
        old = rtnl_dereference(dev->priomap);
        RCU_INIT_POINTER(dev->priomap, NULL);
        if (old)
            kfree_rcu(old, rcu);
    }
    rtnl_unlock();
}

module_init(init_cgroup_netprio);
module_exit(exit_cgroup_netprio);
MODULE_LICENSE("GPL v2");