cls_cgroup.c

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/*
 * net/sched/cls_cgroup.c   Control Group Classifier
 *
 *      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: Thomas Graf <[email protected]>
 */

#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 <net/rtnetlink.h>
#include <net/pkt_cls.h>
#include <net/sock.h>
#include <net/cls_cgroup.h>

static inline struct cgroup_cls_state *cgrp_cls_state(struct cgroup *cgrp)
{
    return container_of(cgroup_subsys_state(cgrp, net_cls_subsys_id),
                struct cgroup_cls_state, css);
}

static inline struct cgroup_cls_state *task_cls_state(struct task_struct *p)
{
    return container_of(task_subsys_state(p, net_cls_subsys_id),
                struct cgroup_cls_state, css);
}

static struct cgroup_subsys_state *cgrp_create(struct cgroup *cgrp)
{
    struct cgroup_cls_state *cs;

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

    if (cgrp->parent)
        cs->classid = cgrp_cls_state(cgrp->parent)->classid;

    return &cs->css;
}

static void cgrp_destroy(struct cgroup *cgrp)
{
    kfree(cgrp_cls_state(cgrp));
}

static u64 read_classid(struct cgroup *cgrp, struct cftype *cft)
{
    return cgrp_cls_state(cgrp)->classid;
}

static int write_classid(struct cgroup *cgrp, struct cftype *cft, u64 value)
{
    cgrp_cls_state(cgrp)->classid = (u32) value;
    return 0;
}

static struct cftype ss_files[] = {
    {
        .name = "classid",
        .read_u64 = read_classid,
        .write_u64 = write_classid,
    },
    { } /* terminate */
};

struct cgroup_subsys net_cls_subsys = {
    .name       = "net_cls",
    .create     = cgrp_create,
    .destroy    = cgrp_destroy,
    .subsys_id  = net_cls_subsys_id,
    .base_cftypes   = ss_files,
    .module     = THIS_MODULE,

    /*
     * While net_cls cgroup has the rudimentary hierarchy support of
     * inheriting the parent's classid on cgroup creation, it doesn't
     * properly propagates config changes in ancestors to their
     * descendents.  A child should follow the parent's configuration
     * but be allowed to override it.  Fix it and remove the following.
     */
    .broken_hierarchy = true,
};

struct cls_cgroup_head {
    u32         handle;
    struct tcf_exts     exts;
    struct tcf_ematch_tree  ematches;
};

static int cls_cgroup_classify(struct sk_buff *skb, const struct tcf_proto *tp,
                   struct tcf_result *res)
{
    struct cls_cgroup_head *head = tp->root;
    u32 classid;

    rcu_read_lock();
    classid = task_cls_state(current)->classid;
    rcu_read_unlock();

    /*
     * Due to the nature of the classifier it is required to ignore all
     * packets originating from softirq context as accessing `current'
     * would lead to false results.
     *
     * This test assumes that all callers of dev_queue_xmit() explicitely
     * disable bh. Knowing this, it is possible to detect softirq based
     * calls by looking at the number of nested bh disable calls because
     * softirqs always disables bh.
     */
    if (in_serving_softirq()) {
        /* If there is an sk_classid we'll use that. */
        if (!skb->sk)
            return -1;
        classid = skb->sk->sk_classid;
    }

    if (!classid)
        return -1;

    if (!tcf_em_tree_match(skb, &head->ematches, NULL))
        return -1;

    res->classid = classid;
    res->class = 0;
    return tcf_exts_exec(skb, &head->exts, res);
}

static unsigned long cls_cgroup_get(struct tcf_proto *tp, u32 handle)
{
    return 0UL;
}

static void cls_cgroup_put(struct tcf_proto *tp, unsigned long f)
{
}

static int cls_cgroup_init(struct tcf_proto *tp)
{
    return 0;
}

static const struct tcf_ext_map cgroup_ext_map = {
    .action = TCA_CGROUP_ACT,
    .police = TCA_CGROUP_POLICE,
};

static const struct nla_policy cgroup_policy[TCA_CGROUP_MAX + 1] = {
    [TCA_CGROUP_EMATCHES]   = { .type = NLA_NESTED },
};

static int cls_cgroup_change(struct sk_buff *in_skb,
                 struct tcf_proto *tp, unsigned long base,
                 u32 handle, struct nlattr **tca,
                 unsigned long *arg)
{
    struct nlattr *tb[TCA_CGROUP_MAX + 1];
    struct cls_cgroup_head *head = tp->root;
    struct tcf_ematch_tree t;
    struct tcf_exts e;
    int err;

    if (!tca[TCA_OPTIONS])
        return -EINVAL;

    if (head == NULL) {
        if (!handle)
            return -EINVAL;

        head = kzalloc(sizeof(*head), GFP_KERNEL);
        if (head == NULL)
            return -ENOBUFS;

        head->handle = handle;

        tcf_tree_lock(tp);
        tp->root = head;
        tcf_tree_unlock(tp);
    }

    if (handle != head->handle)
        return -ENOENT;

    err = nla_parse_nested(tb, TCA_CGROUP_MAX, tca[TCA_OPTIONS],
                   cgroup_policy);
    if (err < 0)
        return err;

    err = tcf_exts_validate(tp, tb, tca[TCA_RATE], &e, &cgroup_ext_map);
    if (err < 0)
        return err;

    err = tcf_em_tree_validate(tp, tb[TCA_CGROUP_EMATCHES], &t);
    if (err < 0)
        return err;

    tcf_exts_change(tp, &head->exts, &e);
    tcf_em_tree_change(tp, &head->ematches, &t);

    return 0;
}

static void cls_cgroup_destroy(struct tcf_proto *tp)
{
    struct cls_cgroup_head *head = tp->root;

    if (head) {
        tcf_exts_destroy(tp, &head->exts);
        tcf_em_tree_destroy(tp, &head->ematches);
        kfree(head);
    }
}

static int cls_cgroup_delete(struct tcf_proto *tp, unsigned long arg)
{
    return -EOPNOTSUPP;
}

static void cls_cgroup_walk(struct tcf_proto *tp, struct tcf_walker *arg)
{
    struct cls_cgroup_head *head = tp->root;

    if (arg->count < arg->skip)
        goto skip;

    if (arg->fn(tp, (unsigned long) head, arg) < 0) {
        arg->stop = 1;
        return;
    }
skip:
    arg->count++;
}

static int cls_cgroup_dump(struct tcf_proto *tp, unsigned long fh,
               struct sk_buff *skb, struct tcmsg *t)
{
    struct cls_cgroup_head *head = tp->root;
    unsigned char *b = skb_tail_pointer(skb);
    struct nlattr *nest;

    t->tcm_handle = head->handle;

    nest = nla_nest_start(skb, TCA_OPTIONS);
    if (nest == NULL)
        goto nla_put_failure;

    if (tcf_exts_dump(skb, &head->exts, &cgroup_ext_map) < 0 ||
        tcf_em_tree_dump(skb, &head->ematches, TCA_CGROUP_EMATCHES) < 0)
        goto nla_put_failure;

    nla_nest_end(skb, nest);

    if (tcf_exts_dump_stats(skb, &head->exts, &cgroup_ext_map) < 0)
        goto nla_put_failure;

    return skb->len;

nla_put_failure:
    nlmsg_trim(skb, b);
    return -1;
}

static struct tcf_proto_ops cls_cgroup_ops __read_mostly = {
    .kind       =   "cgroup",
    .init       =   cls_cgroup_init,
    .change     =   cls_cgroup_change,
    .classify   =   cls_cgroup_classify,
    .destroy    =   cls_cgroup_destroy,
    .get        =   cls_cgroup_get,
    .put        =   cls_cgroup_put,
    .delete     =   cls_cgroup_delete,
    .walk       =   cls_cgroup_walk,
    .dump       =   cls_cgroup_dump,
    .owner      =   THIS_MODULE,
};

static int __init init_cgroup_cls(void)
{
    int ret;

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

    ret = register_tcf_proto_ops(&cls_cgroup_ops);
    if (ret)
        cgroup_unload_subsys(&net_cls_subsys);

out:
    return ret;
}

static void __exit exit_cgroup_cls(void)
{
    unregister_tcf_proto_ops(&cls_cgroup_ops);

    cgroup_unload_subsys(&net_cls_subsys);
}

module_init(init_cgroup_cls);
module_exit(exit_cgroup_cls);
MODULE_LICENSE("GPL");