cmp.c

/* SPDX-License-Identifier: GPL-2.0-or-later */
/*
 * (C) 2012 by Pablo Neira Ayuso <pablo@netfilter.org>
 *
 * This code has been sponsored by Sophos Astaro <http://www.sophos.com>
 */

#include "internal.h"

#include <stdio.h>
#include <stdint.h>
#include <string.h>
#include <arpa/inet.h>
#include <errno.h>

#include <libmnl/libmnl.h>
#include <linux/netfilter/nf_tables.h>
#include <libnftnl/expr.h>
#include <libnftnl/rule.h>

struct nftnl_expr_cmp {
        union nftnl_data_reg    data;
        enum nft_registers      sreg;
        enum nft_cmp_ops        op;
};

static int
nftnl_expr_cmp_set(struct nftnl_expr *e, uint16_t type,
                   const void *data, uint32_t data_len, uint32_t byteorder)
{
        struct nftnl_expr_cmp *cmp = nftnl_expr_data(e);

        switch(type) {
        case NFTNL_EXPR_CMP_SREG:
                memcpy(&cmp->sreg, data, data_len);
                break;
        case NFTNL_EXPR_CMP_OP:
                memcpy(&cmp->op, data, data_len);
                break;
        case NFTNL_EXPR_CMP_DATA:
                return nftnl_data_cpy(&cmp->data, data,
                                      data_len, byteorder, NULL);
        }
        return 0;
}

static const void *
nftnl_expr_cmp_get(const struct nftnl_expr *e, uint16_t type,
                      uint32_t *data_len)
{
        struct nftnl_expr_cmp *cmp = nftnl_expr_data(e);

        switch(type) {
        case NFTNL_EXPR_CMP_SREG:
                *data_len = sizeof(cmp->sreg);
                return &cmp->sreg;
        case NFTNL_EXPR_CMP_OP:
                *data_len = sizeof(cmp->op);
                return &cmp->op;
        case NFTNL_EXPR_CMP_DATA:
                *data_len = cmp->data.len;
                return &cmp->data.val;
        }
        return NULL;
}

static int nftnl_expr_cmp_cb(const struct nlattr *attr, void *data)
{
        const struct nlattr **tb = data;
        int type = mnl_attr_get_type(attr);

        if (mnl_attr_type_valid(attr, NFTA_CMP_MAX) < 0)
                return MNL_CB_OK;

        switch(type) {
        case NFTA_CMP_SREG:
        case NFTA_CMP_OP:
                if (mnl_attr_validate(attr, MNL_TYPE_U32) < 0)
                        abi_breakage();
                break;
        case NFTA_CMP_DATA:
                if (mnl_attr_validate(attr, MNL_TYPE_BINARY) < 0)
                        abi_breakage();
                break;
        }

        tb[type] = attr;
        return MNL_CB_OK;
}

static void
nftnl_expr_cmp_build(struct nlmsghdr *nlh, const struct nftnl_expr *e)
{
        struct nftnl_expr_cmp *cmp = nftnl_expr_data(e);

        if (e->flags & (1 << NFTNL_EXPR_CMP_SREG))
                mnl_attr_put_u32(nlh, NFTA_CMP_SREG, htonl(cmp->sreg));
        if (e->flags & (1 << NFTNL_EXPR_CMP_OP))
                mnl_attr_put_u32(nlh, NFTA_CMP_OP, htonl(cmp->op));
        if (e->flags & (1 << NFTNL_EXPR_CMP_DATA)) {
                struct nlattr *nest;

                nest = mnl_attr_nest_start(nlh, NFTA_CMP_DATA);
                mnl_attr_put(nlh, NFTA_DATA_VALUE, cmp->data.len, cmp->data.val);
                mnl_attr_nest_end(nlh, nest);
        }
}

static int
nftnl_expr_cmp_parse(struct nftnl_expr *e, struct nlattr *attr)
{
        struct nftnl_expr_cmp *cmp = nftnl_expr_data(e);
        struct nlattr *tb[NFTA_CMP_MAX+1] = {};
        int ret = 0;

        if (mnl_attr_parse_nested(attr, nftnl_expr_cmp_cb, tb) < 0)
                return -1;

        if (tb[NFTA_CMP_SREG]) {
                cmp->sreg = ntohl(mnl_attr_get_u32(tb[NFTA_CMP_SREG]));
                e->flags |= (1 << NFTA_CMP_SREG);
        }
        if (tb[NFTA_CMP_OP]) {
                cmp->op = ntohl(mnl_attr_get_u32(tb[NFTA_CMP_OP]));
                e->flags |= (1 << NFTA_CMP_OP);
        }
        if (tb[NFTA_CMP_DATA]) {
                ret = nftnl_parse_data(&cmp->data, tb[NFTA_CMP_DATA], NULL);
                e->flags |= (1 << NFTA_CMP_DATA);
        }

        return ret;
}

static const char *expr_cmp_str[] = {
        [NFT_CMP_EQ]    = "eq",
        [NFT_CMP_NEQ]   = "neq",
        [NFT_CMP_LT]    = "lt",
        [NFT_CMP_LTE]   = "lte",
        [NFT_CMP_GT]    = "gt",
        [NFT_CMP_GTE]   = "gte",
};

static const char *cmp2str(uint32_t op)
{
        if (op > NFT_CMP_GTE)
                return "unknown";

        return expr_cmp_str[op];
}

static int
nftnl_expr_cmp_snprintf(char *buf, size_t remain,
                        uint32_t flags, const struct nftnl_expr *e)
{
        struct nftnl_expr_cmp *cmp = nftnl_expr_data(e);
        int offset = 0, ret;

        ret = snprintf(buf, remain, "%s reg %u ",
                       cmp2str(cmp->op), cmp->sreg);
        SNPRINTF_BUFFER_SIZE(ret, remain, offset);

        ret = nftnl_data_reg_snprintf(buf + offset, remain, &cmp->data,
                                      0, DATA_VALUE);
        SNPRINTF_BUFFER_SIZE(ret, remain, offset);

        ret = snprintf(buf + offset, remain, " ");
        SNPRINTF_BUFFER_SIZE(ret, remain, offset);

        return offset;
}

static struct attr_policy cmp_attr_policy[__NFTNL_EXPR_CMP_MAX] = {
        [NFTNL_EXPR_CMP_SREG] = { .maxlen = sizeof(uint32_t) },
        [NFTNL_EXPR_CMP_OP]   = { .maxlen = sizeof(uint32_t) },
        [NFTNL_EXPR_CMP_DATA] = { .maxlen = NFT_DATA_VALUE_MAXLEN }
};

struct expr_ops expr_ops_cmp = {
        .name           = "cmp",
        .alloc_len      = sizeof(struct nftnl_expr_cmp),
        .nftnl_max_attr = __NFTNL_EXPR_CMP_MAX - 1,
        .attr_policy    = cmp_attr_policy,
        .set            = nftnl_expr_cmp_set,
        .get            = nftnl_expr_cmp_get,
        .parse          = nftnl_expr_cmp_parse,
        .build          = nftnl_expr_cmp_build,
        .output         = nftnl_expr_cmp_snprintf,
};