// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * net/sched/em_cmp.c   Simple packet data comparison ematch
 *
 * Authors:     Thomas Graf <tgraf@suug.ch>
 */

#include <linux/module.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/skbuff.h>
#include <linux/tc_ematch/tc_em_cmp.h>
#include <linux/unaligned.h>
#include <net/pkt_cls.h>

static inline int cmp_needs_transformation(struct tcf_em_cmp *cmp)
{
        return unlikely(cmp->flags & TCF_EM_CMP_TRANS);
}

static int em_cmp_match(struct sk_buff *skb, struct tcf_ematch *em,
                        struct tcf_pkt_info *info)
{
        struct tcf_em_cmp *cmp = (struct tcf_em_cmp *) em->data;
        unsigned char *ptr = tcf_get_base_ptr(skb, cmp->layer);
        u32 val = 0;

        if (!ptr)
                return 0;
        ptr += cmp->off;
        if (!tcf_valid_offset(skb, ptr, cmp->align))
                return 0;

        switch (cmp->align) {
        case TCF_EM_ALIGN_U8:
                val = *ptr;
                break;

        case TCF_EM_ALIGN_U16:
                val = get_unaligned_be16(ptr);

                if (cmp_needs_transformation(cmp))
                        val = be16_to_cpu(val);
                break;

        case TCF_EM_ALIGN_U32:
                /* Worth checking boundaries? The branching seems
                 * to get worse. Visit again.
                 */
                val = get_unaligned_be32(ptr);

                if (cmp_needs_transformation(cmp))
                        val = be32_to_cpu(val);
                break;

        default:
                return 0;
        }

        if (cmp->mask)
                val &= cmp->mask;

        switch (cmp->opnd) {
        case TCF_EM_OPND_EQ:
                return val == cmp->val;
        case TCF_EM_OPND_LT:
                return val < cmp->val;
        case TCF_EM_OPND_GT:
                return val > cmp->val;
        }

        return 0;
}

static struct tcf_ematch_ops em_cmp_ops = {
        .kind     = TCF_EM_CMP,
        .datalen  = sizeof(struct tcf_em_cmp),
        .match    = em_cmp_match,
        .owner    = THIS_MODULE,
        .link     = LIST_HEAD_INIT(em_cmp_ops.link)
};

static int __init init_em_cmp(void)
{
        return tcf_em_register(&em_cmp_ops);
}

static void __exit exit_em_cmp(void)
{
        tcf_em_unregister(&em_cmp_ops);
}

MODULE_DESCRIPTION("ematch classifier for basic data types(8/16/32 bit) against skb data");
MODULE_LICENSE("GPL");

module_init(init_em_cmp);
module_exit(exit_em_cmp);

MODULE_ALIAS_TCF_EMATCH(TCF_EM_CMP);