/*
 * net/sched/cls_tcindex.c      Packet classifier for skb->tc_index
 *
 * Written 1998,1999 by Werner Almesberger, EPFL ICA
 */

#include <linux/module.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/skbuff.h>
#include <linux/errno.h>
#include <linux/slab.h>
#include <net/act_api.h>
#include <net/netlink.h>
#include <net/pkt_cls.h>

/*
 * Passing parameters to the root seems to be done more awkwardly than really
 * necessary. At least, u32 doesn't seem to use such dirty hacks. To be
 * verified. FIXME.
 */

#define PERFECT_HASH_THRESHOLD  64      /* use perfect hash if not bigger */
#define DEFAULT_HASH_SIZE       64      /* optimized for diffserv */


struct tcindex_filter_result {
        struct tcf_exts         exts;
        struct tcf_result       res;
        struct rcu_head         rcu;
};

struct tcindex_filter {
        u16 key;
        struct tcindex_filter_result result;
        struct tcindex_filter __rcu *next;
        struct rcu_head rcu;
};


struct tcindex_data {
        struct tcindex_filter_result *perfect; /* perfect hash; NULL if none */
        struct tcindex_filter __rcu **h; /* imperfect hash; */
        struct tcf_proto *tp;
        u16 mask;               /* AND key with mask */
        u32 shift;              /* shift ANDed key to the right */
        u32 hash;               /* hash table size; 0 if undefined */
        u32 alloc_hash;         /* allocated size */
        u32 fall_through;       /* 0: only classify if explicit match */
        struct rcu_head rcu;
};

static inline int tcindex_filter_is_set(struct tcindex_filter_result *r)
{
        return tcf_exts_is_predicative(&r->exts) || r->res.classid;
}

static struct tcindex_filter_result *tcindex_lookup(struct tcindex_data *p,
                                                    u16 key)
{
        if (p->perfect) {
                struct tcindex_filter_result *f = p->perfect + key;

                return tcindex_filter_is_set(f) ? f : NULL;
        } else if (p->h) {
                struct tcindex_filter __rcu **fp;
                struct tcindex_filter *f;

                fp = &p->h[key % p->hash];
                for (f = rcu_dereference_bh_rtnl(*fp);
                     f;
                     fp = &f->next, f = rcu_dereference_bh_rtnl(*fp))
                        if (f->key == key)
                                return &f->result;
        }

        return NULL;
}


static int tcindex_classify(struct sk_buff *skb, const struct tcf_proto *tp,
                            struct tcf_result *res)
{
        struct tcindex_data *p = rcu_dereference_bh(tp->root);
        struct tcindex_filter_result *f;
        int key = (skb->tc_index & p->mask) >> p->shift;

        pr_debug("tcindex_classify(skb %p,tp %p,res %p),p %p\n",
                 skb, tp, res, p);

        f = tcindex_lookup(p, key);
        if (!f) {
                if (!p->fall_through)
                        return -1;
                res->classid = TC_H_MAKE(TC_H_MAJ(tp->q->handle), key);
                res->class = 0;
                pr_debug("alg 0x%x\n", res->classid);
                return 0;
        }
        *res = f->res;
        pr_debug("map 0x%x\n", res->classid);

        return tcf_exts_exec(skb, &f->exts, res);
}


static unsigned long tcindex_get(struct tcf_proto *tp, u32 handle)
{
        struct tcindex_data *p = rtnl_dereference(tp->root);
        struct tcindex_filter_result *r;

        pr_debug("tcindex_get(tp %p,handle 0x%08x)\n", tp, handle);
        if (p->perfect && handle >= p->alloc_hash)
                return 0;
        r = tcindex_lookup(p, handle);
        return r && tcindex_filter_is_set(r) ? (unsigned long) r : 0UL;
}

static int tcindex_init(struct tcf_proto *tp)
{
        struct tcindex_data *p;

        pr_debug("tcindex_init(tp %p)\n", tp);
        p = kzalloc(sizeof(struct tcindex_data), GFP_KERNEL);
        if (!p)
                return -ENOMEM;

        p->mask = 0xffff;
        p->hash = DEFAULT_HASH_SIZE;
        p->fall_through = 1;

        rcu_assign_pointer(tp->root, p);
        return 0;
}

static void tcindex_destroy_rexts(struct rcu_head *head)
{
        struct tcindex_filter_result *r;

        r = container_of(head, struct tcindex_filter_result, rcu);
        tcf_exts_destroy(&r->exts);
}

static void tcindex_destroy_fexts(struct rcu_head *head)
{
        struct tcindex_filter *f = container_of(head, struct tcindex_filter,
                                                rcu);

        tcf_exts_destroy(&f->result.exts);
        kfree(f);
}

static int tcindex_delete(struct tcf_proto *tp, unsigned long arg, bool *last)
{
        struct tcindex_data *p = rtnl_dereference(tp->root);
        struct tcindex_filter_result *r = (struct tcindex_filter_result *) arg;
        struct tcindex_filter __rcu **walk;
        struct tcindex_filter *f = NULL;

        pr_debug("tcindex_delete(tp %p,arg 0x%lx),p %p\n", tp, arg, p);
        if (p->perfect) {
                if (!r->res.class)
                        return -ENOENT;
        } else {
                int i;

                for (i = 0; i < p->hash; i++) {
                        walk = p->h + i;
                        for (f = rtnl_dereference(*walk); f;
                             walk = &f->next, f = rtnl_dereference(*walk)) {
                                if (&f->result == r)
                                        goto found;
                        }
                }
                return -ENOENT;

found:
                rcu_assign_pointer(*walk, rtnl_dereference(f->next));
        }
        tcf_unbind_filter(tp, &r->res);
        /* all classifiers are required to call tcf_exts_destroy() after rcu
         * grace period, since converted-to-rcu actions are relying on that
         * in cleanup() callback
         */
        if (f)
                call_rcu(&f->rcu, tcindex_destroy_fexts);
        else
                call_rcu(&r->rcu, tcindex_destroy_rexts);

        *last = false;
        return 0;
}

static int tcindex_destroy_element(struct tcf_proto *tp,
                                   unsigned long arg,
                                   struct tcf_walker *walker)
{
        bool last;

        return tcindex_delete(tp, arg, &last);
}

static void __tcindex_destroy(struct rcu_head *head)
{
        struct tcindex_data *p = container_of(head, struct tcindex_data, rcu);

        kfree(p->perfect);
        kfree(p->h);
        kfree(p);
}

static inline int
valid_perfect_hash(struct tcindex_data *p)
{
        return  p->hash > (p->mask >> p->shift);
}

static const struct nla_policy tcindex_policy[TCA_TCINDEX_MAX + 1] = {
        [TCA_TCINDEX_HASH]              = { .type = NLA_U32 },
        [TCA_TCINDEX_MASK]              = { .type = NLA_U16 },
        [TCA_TCINDEX_SHIFT]             = { .type = NLA_U32 },
        [TCA_TCINDEX_FALL_THROUGH]      = { .type = NLA_U32 },
        [TCA_TCINDEX_CLASSID]           = { .type = NLA_U32 },
};

static int tcindex_filter_result_init(struct tcindex_filter_result *r)
{
        memset(r, 0, sizeof(*r));
        return tcf_exts_init(&r->exts, TCA_TCINDEX_ACT, TCA_TCINDEX_POLICE);
}

static void __tcindex_partial_destroy(struct rcu_head *head)
{
        struct tcindex_data *p = container_of(head, struct tcindex_data, rcu);

        kfree(p->perfect);
        kfree(p);
}

static void tcindex_free_perfect_hash(struct tcindex_data *cp)
{
        int i;

        for (i = 0; i < cp->hash; i++)
                tcf_exts_destroy(&cp->perfect[i].exts);
        kfree(cp->perfect);
}

static int tcindex_alloc_perfect_hash(struct tcindex_data *cp)
{
        int i, err = 0;

        cp->perfect = kcalloc(cp->hash, sizeof(struct tcindex_filter_result),
                              GFP_KERNEL);
        if (!cp->perfect)
                return -ENOMEM;

        for (i = 0; i < cp->hash; i++) {
                err = tcf_exts_init(&cp->perfect[i].exts,
                                    TCA_TCINDEX_ACT, TCA_TCINDEX_POLICE);
                if (err < 0)
                        goto errout;
        }

        return 0;

errout:
        tcindex_free_perfect_hash(cp);
        return err;
}

static int
tcindex_set_parms(struct net *net, struct tcf_proto *tp, unsigned long base,
                  u32 handle, struct tcindex_data *p,
                  struct tcindex_filter_result *r, struct nlattr **tb,
                  struct nlattr *est, bool ovr)
{
        struct tcindex_filter_result new_filter_result, *old_r = r;
        struct tcindex_filter_result cr;
        struct tcindex_data *cp = NULL, *oldp;
        struct tcindex_filter *f = NULL; /* make gcc behave */
        int err, balloc = 0;
        struct tcf_exts e;

        err = tcf_exts_init(&e, TCA_TCINDEX_ACT, TCA_TCINDEX_POLICE);
        if (err < 0)
                return err;
        err = tcf_exts_validate(net, tp, tb, est, &e, ovr);
        if (err < 0)
                goto errout;

        err = -ENOMEM;
        /* tcindex_data attributes must look atomic to classifier/lookup so
         * allocate new tcindex data and RCU assign it onto root. Keeping
         * perfect hash and hash pointers from old data.
         */
        cp = kzalloc(sizeof(*cp), GFP_KERNEL);
        if (!cp)
                goto errout;

        cp->mask = p->mask;
        cp->shift = p->shift;
        cp->hash = p->hash;
        cp->alloc_hash = p->alloc_hash;
        cp->fall_through = p->fall_through;
        cp->tp = tp;

        if (p->perfect) {
                int i;

                if (tcindex_alloc_perfect_hash(cp) < 0)
                        goto errout;
                for (i = 0; i < cp->hash; i++)
                        cp->perfect[i].res = p->perfect[i].res;
                balloc = 1;
        }
        cp->h = p->h;

        err = tcindex_filter_result_init(&new_filter_result);
        if (err < 0)
                goto errout1;
        err = tcindex_filter_result_init(&cr);
        if (err < 0)
                goto errout1;
        if (old_r)
                cr.res = r->res;

        if (tb[TCA_TCINDEX_HASH])
                cp->hash = nla_get_u32(tb[TCA_TCINDEX_HASH]);

        if (tb[TCA_TCINDEX_MASK])
                cp->mask = nla_get_u16(tb[TCA_TCINDEX_MASK]);

        if (tb[TCA_TCINDEX_SHIFT])
                cp->shift = nla_get_u32(tb[TCA_TCINDEX_SHIFT]);

        err = -EBUSY;

        /* Hash already allocated, make sure that we still meet the
         * requirements for the allocated hash.
         */
        if (cp->perfect) {
                if (!valid_perfect_hash(cp) ||
                    cp->hash > cp->alloc_hash)
                        goto errout_alloc;
        } else if (cp->h && cp->hash != cp->alloc_hash) {
                goto errout_alloc;
        }

        err = -EINVAL;
        if (tb[TCA_TCINDEX_FALL_THROUGH])
                cp->fall_through = nla_get_u32(tb[TCA_TCINDEX_FALL_THROUGH]);

        if (!cp->hash) {
                /* Hash not specified, use perfect hash if the upper limit
                 * of the hashing index is below the threshold.
                 */
                if ((cp->mask >> cp->shift) < PERFECT_HASH_THRESHOLD)
                        cp->hash = (cp->mask >> cp->shift) + 1;
                else
                        cp->hash = DEFAULT_HASH_SIZE;
        }

        if (!cp->perfect && !cp->h)
                cp->alloc_hash = cp->hash;

        /* Note: this could be as restrictive as if (handle & ~(mask >> shift))
         * but then, we'd fail handles that may become valid after some future
         * mask change. While this is extremely unlikely to ever matter,
         * the check below is safer (and also more backwards-compatible).
         */
        if (cp->perfect || valid_perfect_hash(cp))
                if (handle >= cp->alloc_hash)
                        goto errout_alloc;


        err = -ENOMEM;
        if (!cp->perfect && !cp->h) {
                if (valid_perfect_hash(cp)) {
                        if (tcindex_alloc_perfect_hash(cp) < 0)
                                goto errout_alloc;
                        balloc = 1;
                } else {
                        struct tcindex_filter __rcu **hash;

                        hash = kcalloc(cp->hash,
                                       sizeof(struct tcindex_filter *),
                                       GFP_KERNEL);

                        if (!hash)
                                goto errout_alloc;

                        cp->h = hash;
                        balloc = 2;
                }
        }

        if (cp->perfect)
                r = cp->perfect + handle;
        else
                r = tcindex_lookup(cp, handle) ? : &new_filter_result;

        if (r == &new_filter_result) {
                f = kzalloc(sizeof(*f), GFP_KERNEL);
                if (!f)
                        goto errout_alloc;
                f->key = handle;
                f->next = NULL;
                err = tcindex_filter_result_init(&f->result);
                if (err < 0) {
                        kfree(f);
                        goto errout_alloc;
                }
        }

        if (tb[TCA_TCINDEX_CLASSID]) {
                cr.res.classid = nla_get_u32(tb[TCA_TCINDEX_CLASSID]);
                tcf_bind_filter(tp, &cr.res, base);
        }

        if (old_r)
                tcf_exts_change(tp, &r->exts, &e);
        else
                tcf_exts_change(tp, &cr.exts, &e);

        if (old_r && old_r != r) {
                err = tcindex_filter_result_init(old_r);
                if (err < 0) {
                        kfree(f);
                        goto errout_alloc;
                }
        }

        oldp = p;
        r->res = cr.res;
        rcu_assign_pointer(tp->root, cp);

        if (r == &new_filter_result) {
                struct tcindex_filter *nfp;
                struct tcindex_filter __rcu **fp;

                tcf_exts_change(tp, &f->result.exts, &r->exts);

                fp = cp->h + (handle % cp->hash);
                for (nfp = rtnl_dereference(*fp);
                     nfp;
                     fp = &nfp->next, nfp = rtnl_dereference(*fp))
                                ; /* nothing */

                rcu_assign_pointer(*fp, f);
        }

        if (oldp)
                call_rcu(&oldp->rcu, __tcindex_partial_destroy);
        return 0;

errout_alloc:
        if (balloc == 1)
                tcindex_free_perfect_hash(cp);
        else if (balloc == 2)
                kfree(cp->h);
errout1:
        tcf_exts_destroy(&cr.exts);
        tcf_exts_destroy(&new_filter_result.exts);
errout:
        kfree(cp);
        tcf_exts_destroy(&e);
        return err;
}

static int
tcindex_change(struct net *net, struct sk_buff *in_skb,
               struct tcf_proto *tp, unsigned long base, u32 handle,
               struct nlattr **tca, unsigned long *arg, bool ovr)
{
        struct nlattr *opt = tca[TCA_OPTIONS];
        struct nlattr *tb[TCA_TCINDEX_MAX + 1];
        struct tcindex_data *p = rtnl_dereference(tp->root);
        struct tcindex_filter_result *r = (struct tcindex_filter_result *) *arg;
        int err;

        pr_debug("tcindex_change(tp %p,handle 0x%08x,tca %p,arg %p),opt %p,"
            "p %p,r %p,*arg 0x%lx\n",
            tp, handle, tca, arg, opt, p, r, arg ? *arg : 0L);

        if (!opt)
                return 0;

        err = nla_parse_nested(tb, TCA_TCINDEX_MAX, opt, tcindex_policy, NULL);
        if (err < 0)
                return err;

        return tcindex_set_parms(net, tp, base, handle, p, r, tb,
                                 tca[TCA_RATE], ovr);
}

static void tcindex_walk(struct tcf_proto *tp, struct tcf_walker *walker)
{
        struct tcindex_data *p = rtnl_dereference(tp->root);
        struct tcindex_filter *f, *next;
        int i;

        pr_debug("tcindex_walk(tp %p,walker %p),p %p\n", tp, walker, p);
        if (p->perfect) {
                for (i = 0; i < p->hash; i++) {
                        if (!p->perfect[i].res.class)
                                continue;
                        if (walker->count >= walker->skip) {
                                if (walker->fn(tp,
                                    (unsigned long) (p->perfect+i), walker)
                                     < 0) {
                                        walker->stop = 1;
                                        return;
                                }
                        }
                        walker->count++;
                }
        }
        if (!p->h)
                return;
        for (i = 0; i < p->hash; i++) {
                for (f = rtnl_dereference(p->h[i]); f; f = next) {
                        next = rtnl_dereference(f->next);
                        if (walker->count >= walker->skip) {
                                if (walker->fn(tp, (unsigned long) &f->result,
                                    walker) < 0) {
                                        walker->stop = 1;
                                        return;
                                }
                        }
                        walker->count++;
                }
        }
}

static void tcindex_destroy(struct tcf_proto *tp)
{
        struct tcindex_data *p = rtnl_dereference(tp->root);
        struct tcf_walker walker;

        pr_debug("tcindex_destroy(tp %p),p %p\n", tp, p);
        walker.count = 0;
        walker.skip = 0;
        walker.fn = tcindex_destroy_element;
        tcindex_walk(tp, &walker);

        call_rcu(&p->rcu, __tcindex_destroy);
}


static int tcindex_dump(struct net *net, struct tcf_proto *tp, unsigned long fh,
                        struct sk_buff *skb, struct tcmsg *t)
{
        struct tcindex_data *p = rtnl_dereference(tp->root);
        struct tcindex_filter_result *r = (struct tcindex_filter_result *) fh;
        struct nlattr *nest;

        pr_debug("tcindex_dump(tp %p,fh 0x%lx,skb %p,t %p),p %p,r %p\n",
                 tp, fh, skb, t, p, r);
        pr_debug("p->perfect %p p->h %p\n", p->perfect, p->h);

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

        if (!fh) {
                t->tcm_handle = ~0; /* whatever ... */
                if (nla_put_u32(skb, TCA_TCINDEX_HASH, p->hash) ||
                    nla_put_u16(skb, TCA_TCINDEX_MASK, p->mask) ||
                    nla_put_u32(skb, TCA_TCINDEX_SHIFT, p->shift) ||
                    nla_put_u32(skb, TCA_TCINDEX_FALL_THROUGH, p->fall_through))
                        goto nla_put_failure;
                nla_nest_end(skb, nest);
        } else {
                if (p->perfect) {
                        t->tcm_handle = r - p->perfect;
                } else {
                        struct tcindex_filter *f;
                        struct tcindex_filter __rcu **fp;
                        int i;

                        t->tcm_handle = 0;
                        for (i = 0; !t->tcm_handle && i < p->hash; i++) {
                                fp = &p->h[i];
                                for (f = rtnl_dereference(*fp);
                                     !t->tcm_handle && f;
                                     fp = &f->next, f = rtnl_dereference(*fp)) {
                                        if (&f->result == r)
                                                t->tcm_handle = f->key;
                                }
                        }
                }
                pr_debug("handle = %d\n", t->tcm_handle);
                if (r->res.class &&
                    nla_put_u32(skb, TCA_TCINDEX_CLASSID, r->res.classid))
                        goto nla_put_failure;

                if (tcf_exts_dump(skb, &r->exts) < 0)
                        goto nla_put_failure;
                nla_nest_end(skb, nest);

                if (tcf_exts_dump_stats(skb, &r->exts) < 0)
                        goto nla_put_failure;
        }

        return skb->len;

nla_put_failure:
        nla_nest_cancel(skb, nest);
        return -1;
}

static struct tcf_proto_ops cls_tcindex_ops __read_mostly = {
        .kind           =       "tcindex",
        .classify       =       tcindex_classify,
        .init           =       tcindex_init,
        .destroy        =       tcindex_destroy,
        .get            =       tcindex_get,
        .change         =       tcindex_change,
        .delete         =       tcindex_delete,
        .walk           =       tcindex_walk,
        .dump           =       tcindex_dump,
        .owner          =       THIS_MODULE,
};

static int __init init_tcindex(void)
{
        return register_tcf_proto_ops(&cls_tcindex_ops);
}

static void __exit exit_tcindex(void)
{
        unregister_tcf_proto_ops(&cls_tcindex_ops);
}

module_init(init_tcindex)
module_exit(exit_tcindex)
MODULE_LICENSE("GPL");