// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * net/sched/cls_route.c        ROUTE4 classifier.
 *
 * Authors:     Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
 */

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

/*
 * 1. For now we assume that route tags < 256.
 *    It allows to use direct table lookups, instead of hash tables.
 * 2. For now we assume that "from TAG" and "fromdev DEV" statements
 *    are mutually  exclusive.
 * 3. "to TAG from ANY" has higher priority, than "to ANY from XXX"
 */
struct route4_fastmap {
        struct route4_filter            *filter;
        u32                             id;
        int                             iif;
};

struct route4_head {
        struct route4_fastmap           fastmap[16];
        struct route4_bucket __rcu      *table[256 + 1];
        struct rcu_head                 rcu;
};

struct route4_bucket {
        /* 16 FROM buckets + 16 IIF buckets + 1 wildcard bucket */
        struct route4_filter __rcu      *ht[16 + 16 + 1];
        struct rcu_head                 rcu;
};

struct route4_filter {
        struct route4_filter __rcu      *next;
        u32                     id;
        int                     iif;

        struct tcf_result       res;
        struct tcf_exts         exts;
        u32                     handle;
        struct route4_bucket    *bkt;
        struct tcf_proto        *tp;
        struct rcu_work         rwork;
};

#define ROUTE4_FAILURE ((struct route4_filter *)(-1L))

static inline int route4_fastmap_hash(u32 id, int iif)
{
        return id & 0xF;
}

static DEFINE_SPINLOCK(fastmap_lock);
static void
route4_reset_fastmap(struct route4_head *head)
{
        spin_lock_bh(&fastmap_lock);
        memset(head->fastmap, 0, sizeof(head->fastmap));
        spin_unlock_bh(&fastmap_lock);
}

static void
route4_set_fastmap(struct route4_head *head, u32 id, int iif,
                   struct route4_filter *f)
{
        int h = route4_fastmap_hash(id, iif);

        /* fastmap updates must look atomic to aling id, iff, filter */
        spin_lock_bh(&fastmap_lock);
        head->fastmap[h].id = id;
        head->fastmap[h].iif = iif;
        head->fastmap[h].filter = f;
        spin_unlock_bh(&fastmap_lock);
}

static inline int route4_hash_to(u32 id)
{
        return id & 0xFF;
}

static inline int route4_hash_from(u32 id)
{
        return (id >> 16) & 0xF;
}

static inline int route4_hash_iif(int iif)
{
        return 16 + ((iif >> 16) & 0xF);
}

static inline int route4_hash_wild(void)
{
        return 32;
}

#define ROUTE4_APPLY_RESULT()                                   \
{                                                               \
        *res = f->res;                                          \
        if (tcf_exts_has_actions(&f->exts)) {                   \
                int r = tcf_exts_exec(skb, &f->exts, res);      \
                if (r < 0) {                                    \
                        dont_cache = 1;                         \
                        continue;                               \
                }                                               \
                return r;                                       \
        } else if (!dont_cache)                                 \
                route4_set_fastmap(head, id, iif, f);           \
        return 0;                                               \
}

TC_INDIRECT_SCOPE int route4_classify(struct sk_buff *skb,
                                      const struct tcf_proto *tp,
                                      struct tcf_result *res)
{
        struct route4_head *head = rcu_dereference_bh(tp->root);
        struct dst_entry *dst;
        struct route4_bucket *b;
        struct route4_filter *f;
        u32 id, h;
        int iif, dont_cache = 0;

        dst = skb_dst(skb);
        if (!dst)
                goto failure;

        id = dst->tclassid;

        iif = inet_iif(skb);

        h = route4_fastmap_hash(id, iif);

        spin_lock(&fastmap_lock);
        if (id == head->fastmap[h].id &&
            iif == head->fastmap[h].iif &&
            (f = head->fastmap[h].filter) != NULL) {
                if (f == ROUTE4_FAILURE) {
                        spin_unlock(&fastmap_lock);
                        goto failure;
                }

                *res = f->res;
                spin_unlock(&fastmap_lock);
                return 0;
        }
        spin_unlock(&fastmap_lock);

        h = route4_hash_to(id);

restart:
        b = rcu_dereference_bh(head->table[h]);
        if (b) {
                for (f = rcu_dereference_bh(b->ht[route4_hash_from(id)]);
                     f;
                     f = rcu_dereference_bh(f->next))
                        if (f->id == id)
                                ROUTE4_APPLY_RESULT();

                for (f = rcu_dereference_bh(b->ht[route4_hash_iif(iif)]);
                     f;
                     f = rcu_dereference_bh(f->next))
                        if (f->iif == iif)
                                ROUTE4_APPLY_RESULT();

                for (f = rcu_dereference_bh(b->ht[route4_hash_wild()]);
                     f;
                     f = rcu_dereference_bh(f->next))
                        ROUTE4_APPLY_RESULT();
        }
        if (h < 256) {
                h = 256;
                id &= ~0xFFFF;
                goto restart;
        }

        if (!dont_cache)
                route4_set_fastmap(head, id, iif, ROUTE4_FAILURE);
failure:
        return -1;
}

static inline u32 to_hash(u32 id)
{
        u32 h = id & 0xFF;

        if (id & 0x8000)
                h += 256;
        return h;
}

static inline u32 from_hash(u32 id)
{
        id &= 0xFFFF;
        if (id == 0xFFFF)
                return 32;
        if (!(id & 0x8000)) {
                if (id > 255)
                        return 256;
                return id & 0xF;
        }
        return 16 + (id & 0xF);
}

static void *route4_get(struct tcf_proto *tp, u32 handle)
{
        struct route4_head *head = rtnl_dereference(tp->root);
        struct route4_bucket *b;
        struct route4_filter *f;
        unsigned int h1, h2;

        h1 = to_hash(handle);
        if (h1 > 256)
                return NULL;

        h2 = from_hash(handle >> 16);
        if (h2 > 32)
                return NULL;

        b = rtnl_dereference(head->table[h1]);
        if (b) {
                for (f = rtnl_dereference(b->ht[h2]);
                     f;
                     f = rtnl_dereference(f->next))
                        if (f->handle == handle)
                                return f;
        }
        return NULL;
}

static int route4_init(struct tcf_proto *tp)
{
        struct route4_head *head;

        head = kzalloc_obj(struct route4_head);
        if (head == NULL)
                return -ENOBUFS;

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

static void __route4_delete_filter(struct route4_filter *f)
{
        tcf_exts_destroy(&f->exts);
        tcf_exts_put_net(&f->exts);
        kfree(f);
}

static void route4_delete_filter_work(struct work_struct *work)
{
        struct route4_filter *f = container_of(to_rcu_work(work),
                                               struct route4_filter,
                                               rwork);
        rtnl_lock();
        __route4_delete_filter(f);
        rtnl_unlock();
}

static void route4_queue_work(struct route4_filter *f)
{
        tcf_queue_work(&f->rwork, route4_delete_filter_work);
}

static void route4_destroy(struct tcf_proto *tp, bool rtnl_held,
                           struct netlink_ext_ack *extack)
{
        struct route4_head *head = rtnl_dereference(tp->root);
        int h1, h2;

        if (head == NULL)
                return;

        for (h1 = 0; h1 <= 256; h1++) {
                struct route4_bucket *b;

                b = rtnl_dereference(head->table[h1]);
                if (b) {
                        for (h2 = 0; h2 <= 32; h2++) {
                                struct route4_filter *f;

                                while ((f = rtnl_dereference(b->ht[h2])) != NULL) {
                                        struct route4_filter *next;

                                        next = rtnl_dereference(f->next);
                                        RCU_INIT_POINTER(b->ht[h2], next);
                                        tcf_unbind_filter(tp, &f->res);
                                        if (tcf_exts_get_net(&f->exts))
                                                route4_queue_work(f);
                                        else
                                                __route4_delete_filter(f);
                                }
                        }
                        RCU_INIT_POINTER(head->table[h1], NULL);
                        kfree_rcu(b, rcu);
                }
        }
        kfree_rcu(head, rcu);
}

static int route4_delete(struct tcf_proto *tp, void *arg, bool *last,
                         bool rtnl_held, struct netlink_ext_ack *extack)
{
        struct route4_head *head = rtnl_dereference(tp->root);
        struct route4_filter *f = arg;
        struct route4_filter __rcu **fp;
        struct route4_filter *nf;
        struct route4_bucket *b;
        unsigned int h = 0;
        int i, h1;

        if (!head || !f)
                return -EINVAL;

        h = f->handle;
        b = f->bkt;

        fp = &b->ht[from_hash(h >> 16)];
        for (nf = rtnl_dereference(*fp); nf;
             fp = &nf->next, nf = rtnl_dereference(*fp)) {
                if (nf == f) {
                        /* unlink it */
                        RCU_INIT_POINTER(*fp, rtnl_dereference(f->next));

                        /* Remove any fastmap lookups that might ref filter
                         * notice we unlink'd the filter so we can't get it
                         * back in the fastmap.
                         */
                        route4_reset_fastmap(head);

                        /* Delete it */
                        tcf_unbind_filter(tp, &f->res);
                        tcf_exts_get_net(&f->exts);
                        tcf_queue_work(&f->rwork, route4_delete_filter_work);

                        /* Strip RTNL protected tree */
                        for (i = 0; i <= 32; i++) {
                                struct route4_filter *rt;

                                rt = rtnl_dereference(b->ht[i]);
                                if (rt)
                                        goto out;
                        }

                        /* OK, session has no flows */
                        RCU_INIT_POINTER(head->table[to_hash(h)], NULL);
                        kfree_rcu(b, rcu);
                        break;
                }
        }

out:
        *last = true;
        for (h1 = 0; h1 <= 256; h1++) {
                if (rcu_access_pointer(head->table[h1])) {
                        *last = false;
                        break;
                }
        }

        return 0;
}

static const struct nla_policy route4_policy[TCA_ROUTE4_MAX + 1] = {
        [TCA_ROUTE4_CLASSID]    = { .type = NLA_U32 },
        [TCA_ROUTE4_TO]         = NLA_POLICY_MAX(NLA_U32, 0xFF),
        [TCA_ROUTE4_FROM]       = NLA_POLICY_MAX(NLA_U32, 0xFF),
        [TCA_ROUTE4_IIF]        = NLA_POLICY_MAX(NLA_U32, 0x7FFF),
};

static int route4_set_parms(struct net *net, struct tcf_proto *tp,
                            unsigned long base, struct route4_filter *f,
                            u32 handle, struct route4_head *head,
                            struct nlattr **tb, struct nlattr *est, int new,
                            u32 flags, struct netlink_ext_ack *extack)
{
        u32 id = 0, to = 0, nhandle = 0x8000;
        struct route4_filter *fp;
        unsigned int h1;
        struct route4_bucket *b;
        int err;

        err = tcf_exts_validate(net, tp, tb, est, &f->exts, flags, extack);
        if (err < 0)
                return err;

        if (tb[TCA_ROUTE4_TO]) {
                if (new && handle & 0x8000) {
                        NL_SET_ERR_MSG(extack, "Invalid handle");
                        return -EINVAL;
                }
                to = nla_get_u32(tb[TCA_ROUTE4_TO]);
                nhandle = to;
        }

        if (tb[TCA_ROUTE4_FROM] && tb[TCA_ROUTE4_IIF]) {
                NL_SET_ERR_MSG_ATTR(extack, tb[TCA_ROUTE4_FROM],
                                    "'from' and 'fromif' are mutually exclusive");
                return -EINVAL;
        }

        if (tb[TCA_ROUTE4_FROM]) {
                id = nla_get_u32(tb[TCA_ROUTE4_FROM]);
                nhandle |= id << 16;
        } else if (tb[TCA_ROUTE4_IIF]) {
                id = nla_get_u32(tb[TCA_ROUTE4_IIF]);
                nhandle |= (id | 0x8000) << 16;
        } else
                nhandle |= 0xFFFF << 16;

        if (handle && new) {
                nhandle |= handle & 0x7F00;
                if (nhandle != handle) {
                        NL_SET_ERR_MSG_FMT(extack,
                                           "Handle mismatch constructed: %x (expected: %x)",
                                           handle, nhandle);
                        return -EINVAL;
                }
        }

        if (!nhandle) {
                NL_SET_ERR_MSG(extack, "Replacing with handle of 0 is invalid");
                return -EINVAL;
        }

        h1 = to_hash(nhandle);
        b = rtnl_dereference(head->table[h1]);
        if (!b) {
                b = kzalloc_obj(struct route4_bucket);
                if (b == NULL)
                        return -ENOBUFS;

                rcu_assign_pointer(head->table[h1], b);
        } else {
                unsigned int h2 = from_hash(nhandle >> 16);

                for (fp = rtnl_dereference(b->ht[h2]);
                     fp;
                     fp = rtnl_dereference(fp->next))
                        if (fp->handle == f->handle)
                                return -EEXIST;
        }

        if (tb[TCA_ROUTE4_TO])
                f->id = to;

        if (tb[TCA_ROUTE4_FROM])
                f->id = to | id<<16;
        else if (tb[TCA_ROUTE4_IIF])
                f->iif = id;

        f->handle = nhandle;
        f->bkt = b;
        f->tp = tp;

        if (tb[TCA_ROUTE4_CLASSID]) {
                f->res.classid = nla_get_u32(tb[TCA_ROUTE4_CLASSID]);
                tcf_bind_filter(tp, &f->res, base);
        }

        return 0;
}

static int route4_change(struct net *net, struct sk_buff *in_skb,
                         struct tcf_proto *tp, unsigned long base, u32 handle,
                         struct nlattr **tca, void **arg, u32 flags,
                         struct netlink_ext_ack *extack)
{
        struct route4_head *head = rtnl_dereference(tp->root);
        struct route4_filter __rcu **fp;
        struct route4_filter *fold, *f1, *pfp, *f = NULL;
        struct route4_bucket *b;
        struct nlattr *tb[TCA_ROUTE4_MAX + 1];
        unsigned int h, th;
        int err;
        bool new = true;

        if (!handle) {
                NL_SET_ERR_MSG(extack, "Creating with handle of 0 is invalid");
                return -EINVAL;
        }

        if (NL_REQ_ATTR_CHECK(extack, NULL, tca, TCA_OPTIONS)) {
                NL_SET_ERR_MSG_MOD(extack, "Missing options");
                return -EINVAL;
        }

        err = nla_parse_nested_deprecated(tb, TCA_ROUTE4_MAX, tca[TCA_OPTIONS],
                                          route4_policy, NULL);
        if (err < 0)
                return err;

        fold = *arg;
        if (fold && fold->handle != handle)
                        return -EINVAL;

        err = -ENOBUFS;
        f = kzalloc_obj(struct route4_filter);
        if (!f)
                goto errout;

        err = tcf_exts_init(&f->exts, net, TCA_ROUTE4_ACT, TCA_ROUTE4_POLICE);
        if (err < 0)
                goto errout;

        if (fold) {
                f->id = fold->id;
                f->iif = fold->iif;
                f->handle = fold->handle;

                f->tp = fold->tp;
                f->bkt = fold->bkt;
                new = false;
        }

        err = route4_set_parms(net, tp, base, f, handle, head, tb,
                               tca[TCA_RATE], new, flags, extack);
        if (err < 0)
                goto errout;

        h = from_hash(f->handle >> 16);
        fp = &f->bkt->ht[h];
        for (pfp = rtnl_dereference(*fp);
             (f1 = rtnl_dereference(*fp)) != NULL;
             fp = &f1->next)
                if (f->handle < f1->handle)
                        break;

        tcf_block_netif_keep_dst(tp->chain->block);
        rcu_assign_pointer(f->next, f1);
        rcu_assign_pointer(*fp, f);

        if (fold) {
                th = to_hash(fold->handle);
                h = from_hash(fold->handle >> 16);
                b = rtnl_dereference(head->table[th]);
                if (b) {
                        fp = &b->ht[h];
                        for (pfp = rtnl_dereference(*fp); pfp;
                             fp = &pfp->next, pfp = rtnl_dereference(*fp)) {
                                if (pfp == fold) {
                                        rcu_assign_pointer(*fp, fold->next);
                                        break;
                                }
                        }
                }
        }

        route4_reset_fastmap(head);
        *arg = f;
        if (fold) {
                tcf_unbind_filter(tp, &fold->res);
                tcf_exts_get_net(&fold->exts);
                tcf_queue_work(&fold->rwork, route4_delete_filter_work);
        }
        return 0;

errout:
        if (f)
                tcf_exts_destroy(&f->exts);
        kfree(f);
        return err;
}

static void route4_walk(struct tcf_proto *tp, struct tcf_walker *arg,
                        bool rtnl_held)
{
        struct route4_head *head = rtnl_dereference(tp->root);
        unsigned int h, h1;

        if (head == NULL || arg->stop)
                return;

        for (h = 0; h <= 256; h++) {
                struct route4_bucket *b = rtnl_dereference(head->table[h]);

                if (b) {
                        for (h1 = 0; h1 <= 32; h1++) {
                                struct route4_filter *f;

                                for (f = rtnl_dereference(b->ht[h1]);
                                     f;
                                     f = rtnl_dereference(f->next)) {
                                        if (!tc_cls_stats_dump(tp, arg, f))
                                                return;
                                }
                        }
                }
        }
}

static int route4_dump(struct net *net, struct tcf_proto *tp, void *fh,
                       struct sk_buff *skb, struct tcmsg *t, bool rtnl_held)
{
        struct route4_filter *f = fh;
        struct nlattr *nest;
        u32 id;

        if (f == NULL)
                return skb->len;

        t->tcm_handle = f->handle;

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

        if (!(f->handle & 0x8000)) {
                id = f->id & 0xFF;
                if (nla_put_u32(skb, TCA_ROUTE4_TO, id))
                        goto nla_put_failure;
        }
        if (f->handle & 0x80000000) {
                if ((f->handle >> 16) != 0xFFFF &&
                    nla_put_u32(skb, TCA_ROUTE4_IIF, f->iif))
                        goto nla_put_failure;
        } else {
                id = f->id >> 16;
                if (nla_put_u32(skb, TCA_ROUTE4_FROM, id))
                        goto nla_put_failure;
        }
        if (f->res.classid &&
            nla_put_u32(skb, TCA_ROUTE4_CLASSID, f->res.classid))
                goto nla_put_failure;

        if (tcf_exts_dump(skb, &f->exts) < 0)
                goto nla_put_failure;

        nla_nest_end(skb, nest);

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

        return skb->len;

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

static void route4_bind_class(void *fh, u32 classid, unsigned long cl, void *q,
                              unsigned long base)
{
        struct route4_filter *f = fh;

        tc_cls_bind_class(classid, cl, q, &f->res, base);
}

static struct tcf_proto_ops cls_route4_ops __read_mostly = {
        .kind           =       "route",
        .classify       =       route4_classify,
        .init           =       route4_init,
        .destroy        =       route4_destroy,
        .get            =       route4_get,
        .change         =       route4_change,
        .delete         =       route4_delete,
        .walk           =       route4_walk,
        .dump           =       route4_dump,
        .bind_class     =       route4_bind_class,
        .owner          =       THIS_MODULE,
};
MODULE_ALIAS_NET_CLS("route");

static int __init init_route4(void)
{
        return register_tcf_proto_ops(&cls_route4_ops);
}

static void __exit exit_route4(void)
{
        unregister_tcf_proto_ops(&cls_route4_ops);
}

module_init(init_route4)
module_exit(exit_route4)
MODULE_DESCRIPTION("Routing table realm based TC classifier");
MODULE_LICENSE("GPL");