/*
 * 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 */


#define PRIV(tp)        ((struct tcindex_data *) (tp)->root)


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

struct tcindex_filter {
        u16 key;
        struct tcindex_filter_result result;
        struct tcindex_filter *next;
};


struct tcindex_data {
        struct tcindex_filter_result *perfect; /* perfect hash; NULL if none */
        struct tcindex_filter **h; /* imperfect hash; only used if !perfect;
                                      NULL if unused */
        u16 mask;               /* AND key with mask */
        int shift;              /* shift ANDed key to the right */
        int hash;               /* hash table size; 0 if undefined */
        int alloc_hash;         /* allocated size */
        int fall_through;       /* 0: only classify if explicit match */
};

static const struct tcf_ext_map tcindex_ext_map = {
        .police = TCA_TCINDEX_POLICE,
        .action = TCA_TCINDEX_ACT
};

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)
{
        struct tcindex_filter *f;

        if (p->perfect)
                return tcindex_filter_is_set(p->perfect + key) ?
                        p->perfect + key : NULL;
        else if (p->h) {
                for (f = p->h[key % p->hash]; f; f = f->next)
                        if (f->key == key)
                                return &f->result;
        }

        return NULL;
}


static int tcindex_classify(struct sk_buff *skb, struct tcf_proto *tp,
                            struct tcf_result *res)
{
        struct tcindex_data *p = PRIV(tp);
        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 = PRIV(tp);
        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 void tcindex_put(struct tcf_proto *tp, unsigned long f)
{
        pr_debug("tcindex_put(tp %p,f 0x%lx)\n", tp, f);
}


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;

        tp->root = p;
        return 0;
}


static int
__tcindex_delete(struct tcf_proto *tp, unsigned long arg, int lock)
{
        struct tcindex_data *p = PRIV(tp);
        struct tcindex_filter_result *r = (struct tcindex_filter_result *) arg;
        struct tcindex_filter *f = NULL;

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

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

found:
                f = *walk;
                if (lock)
                        tcf_tree_lock(tp);
                *walk = f->next;
                if (lock)
                        tcf_tree_unlock(tp);
        }
        tcf_unbind_filter(tp, &r->res);
        tcf_exts_destroy(tp, &r->exts);
        kfree(f);
        return 0;
}

static int tcindex_delete(struct tcf_proto *tp, unsigned long arg)
{
        return __tcindex_delete(tp, arg, 1);
}

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

        err = tcf_exts_validate(tp, tb, est, &e, &tcindex_ext_map);
        if (err < 0)
                return err;

        memcpy(&cp, p, sizeof(cp));
        memset(&new_filter_result, 0, sizeof(new_filter_result));

        if (old_r)
                memcpy(&cr, r, sizeof(cr));
        else
                memset(&cr, 0, sizeof(cr));

        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;
        } else if (cp.h && cp.hash != cp.alloc_hash)
                goto errout;

        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;


        err = -ENOMEM;
        if (!cp.perfect && !cp.h) {
                if (valid_perfect_hash(&cp)) {
                        cp.perfect = kcalloc(cp.hash, sizeof(*r), GFP_KERNEL);
                        if (!cp.perfect)
                                goto errout;
                        balloc = 1;
                } else {
                        cp.h = kcalloc(cp.hash, sizeof(f), GFP_KERNEL);
                        if (!cp.h)
                                goto errout;
                        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;
        }

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

        tcf_exts_change(tp, &cr.exts, &e);

        tcf_tree_lock(tp);
        if (old_r && old_r != r)
                memset(old_r, 0, sizeof(*old_r));

        memcpy(p, &cp, sizeof(cp));
        memcpy(r, &cr, sizeof(cr));

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

                f->key = handle;
                f->result = new_filter_result;
                f->next = NULL;
                for (fp = p->h+(handle % p->hash); *fp; fp = &(*fp)->next)
                        /* nothing */;
                *fp = f;
        }
        tcf_tree_unlock(tp);

        return 0;

errout_alloc:
        if (balloc == 1)
                kfree(cp.perfect);
        else if (balloc == 2)
                kfree(cp.h);
errout:
        tcf_exts_destroy(tp, &e);
        return err;
}

static int
tcindex_change(struct tcf_proto *tp, unsigned long base, u32 handle,
               struct nlattr **tca, unsigned long *arg)
{
        struct nlattr *opt = tca[TCA_OPTIONS];
        struct nlattr *tb[TCA_TCINDEX_MAX + 1];
        struct tcindex_data *p = PRIV(tp);
        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);
        if (err < 0)
                return err;

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


static void tcindex_walk(struct tcf_proto *tp, struct tcf_walker *walker)
{
        struct tcindex_data *p = PRIV(tp);
        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 = p->h[i]; f; f = next) {
                        next = f->next;
                        if (walker->count >= walker->skip) {
                                if (walker->fn(tp, (unsigned long) &f->result,
                                    walker) < 0) {
                                        walker->stop = 1;
                                        return;
                                }
                        }
                        walker->count++;
                }
        }
}


static int tcindex_destroy_element(struct tcf_proto *tp,
    unsigned long arg, struct tcf_walker *walker)
{
        return __tcindex_delete(tp, arg, 0);
}


static void tcindex_destroy(struct tcf_proto *tp)
{
        struct tcindex_data *p = PRIV(tp);
        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);
        kfree(p->perfect);
        kfree(p->h);
        kfree(p);
        tp->root = NULL;
}


static int tcindex_dump(struct tcf_proto *tp, unsigned long fh,
    struct sk_buff *skb, struct tcmsg *t)
{
        struct tcindex_data *p = PRIV(tp);
        struct tcindex_filter_result *r = (struct tcindex_filter_result *) fh;
        unsigned char *b = skb_tail_pointer(skb);
        struct nlattr *nest;

        pr_debug("tcindex_dump(tp %p,fh 0x%lx,skb %p,t %p),p %p,r %p,b %p\n",
                 tp, fh, skb, t, p, r, b);
        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 ... */
                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);
                nla_nest_end(skb, nest);
        } else {
                if (p->perfect) {
                        t->tcm_handle = r-p->perfect;
                } else {
                        struct tcindex_filter *f;
                        int i;

                        t->tcm_handle = 0;
                        for (i = 0; !t->tcm_handle && i < p->hash; i++) {
                                for (f = p->h[i]; !t->tcm_handle && f;
                                     f = f->next) {
                                        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);

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

                if (tcf_exts_dump_stats(skb, &r->exts, &tcindex_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_tcindex_ops __read_mostly = {
        .kind           =       "tcindex",
        .classify       =       tcindex_classify,
        .init           =       tcindex_init,
        .destroy        =       tcindex_destroy,
        .get            =       tcindex_get,
        .put            =       tcindex_put,
        .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");