/*
 * 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 <tgraf@suug.ch>
 */

#include <linux/module.h>
#include <linux/types.h>
#include <linux/string.h>
#include <linux/errno.h>
#include <linux/skbuff.h>
#include <linux/cgroup.h>
#include <net/rtnetlink.h>
#include <net/pkt_cls.h>

struct cgroup_cls_state
{
        struct cgroup_subsys_state css;
        u32 classid;
};

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_subsys *ss,
                                                 struct cgroup *cgrp)
{
        struct cgroup_cls_state *cs;

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

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

        return &cs->css;
}

static void cgrp_destroy(struct cgroup_subsys *ss, 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,
        },
};

static int cgrp_populate(struct cgroup_subsys *ss, struct cgroup *cgrp)
{
        return cgroup_add_files(cgrp, ss, ss_files, ARRAY_SIZE(ss_files));
}

struct cgroup_subsys net_cls_subsys = {
        .name           = "net_cls",
        .create         = cgrp_create,
        .destroy        = cgrp_destroy,
        .populate       = cgrp_populate,
        .subsys_id      = net_cls_subsys_id,
};

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

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

        /*
         * 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 (softirq_count() != SOFTIRQ_OFFSET)
                return -1;

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

        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 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)
{
        return register_tcf_proto_ops(&cls_cgroup_ops);
}

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

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