cls_tcindex.c

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/*
 * 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, const 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 sk_buff *in_skb,
           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 ... */
        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;
            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))
            goto nla_put_failure;

        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");