expr/synproxy.c

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

#include "internal.h"
#include <libmnl/libmnl.h>
#include <libnftnl/expr.h>
#include <libnftnl/rule.h>

struct nftnl_expr_synproxy {
        uint16_t        mss;
        uint8_t         wscale;
        uint32_t        flags;
};

static int
nftnl_expr_synproxy_set(struct nftnl_expr *e, uint16_t type,
                        const void *data, uint32_t data_len, uint32_t byteorder)
{
        struct nftnl_expr_synproxy *synproxy = nftnl_expr_data(e);

        switch(type) {
        case NFTNL_EXPR_SYNPROXY_MSS:
                memcpy(&synproxy->mss, data, data_len);
                break;
        case NFTNL_EXPR_SYNPROXY_WSCALE:
                memcpy(&synproxy->wscale, data, data_len);
                break;
        case NFTNL_EXPR_SYNPROXY_FLAGS:
                memcpy(&synproxy->flags, data, data_len);
                break;
        }
        return 0;
}

static const void *
nftnl_expr_synproxy_get(const struct nftnl_expr *e, uint16_t type,
                        uint32_t *data_len)
{
        struct nftnl_expr_synproxy *synproxy = nftnl_expr_data(e);

        switch(type) {
        case NFTNL_EXPR_SYNPROXY_MSS:
                *data_len = sizeof(synproxy->mss);
                return &synproxy->mss;
        case NFTNL_EXPR_SYNPROXY_WSCALE:
                *data_len = sizeof(synproxy->wscale);
                return &synproxy->wscale;
        case NFTNL_EXPR_SYNPROXY_FLAGS:
                *data_len = sizeof(synproxy->flags);
                return &synproxy->flags;
        }
        return NULL;
}

static int nftnl_expr_synproxy_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_SYNPROXY_MAX) < 0)
                return MNL_CB_OK;

        switch(type) {
        case NFTNL_EXPR_SYNPROXY_MSS:
                if (mnl_attr_validate(attr, MNL_TYPE_U16) < 0)
                        abi_breakage();
                break;

        case NFTNL_EXPR_SYNPROXY_WSCALE:
                if (mnl_attr_validate(attr, MNL_TYPE_U8) < 0)
                        abi_breakage();
                break;

        case NFTNL_EXPR_SYNPROXY_FLAGS:
                if (mnl_attr_validate(attr, MNL_TYPE_U32) < 0)
                        abi_breakage();
                break;
        }

        tb[type] = attr;
        return MNL_CB_OK;
}

static void
nftnl_expr_synproxy_build(struct nlmsghdr *nlh, const struct nftnl_expr *e)
{
        struct nftnl_expr_synproxy *synproxy = nftnl_expr_data(e);

        if (e->flags & (1 << NFTNL_EXPR_SYNPROXY_MSS))
                mnl_attr_put_u16(nlh, NFTA_SYNPROXY_MSS,
                                 htons(synproxy->mss));
        if (e->flags & (1 << NFTNL_EXPR_SYNPROXY_WSCALE))
                mnl_attr_put_u8(nlh, NFTA_SYNPROXY_WSCALE,
                                synproxy->wscale);
        if (e->flags & (1 << NFTNL_EXPR_SYNPROXY_FLAGS))
                mnl_attr_put_u32(nlh, NFTA_SYNPROXY_FLAGS,
                                 htonl(synproxy->flags));
}

static int
nftnl_expr_synproxy_parse(struct nftnl_expr *e, struct nlattr *attr)
{
        struct nftnl_expr_synproxy *synproxy = nftnl_expr_data(e);
        struct nlattr *tb[NFTA_SYNPROXY_MAX + 1] = {};

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

        if (tb[NFTA_SYNPROXY_MSS]) {
                synproxy->mss = ntohs(mnl_attr_get_u16(tb[NFTA_SYNPROXY_MSS]));
                e->flags |= (1 << NFTNL_EXPR_SYNPROXY_MSS);
        }

        if (tb[NFTA_SYNPROXY_WSCALE]) {
                synproxy->wscale = mnl_attr_get_u8(tb[NFTA_SYNPROXY_WSCALE]);
                e->flags |= (1 << NFTNL_EXPR_SYNPROXY_WSCALE);
        }

        if (tb[NFTA_SYNPROXY_FLAGS]) {
                synproxy->flags = ntohl(mnl_attr_get_u32(tb[NFTA_SYNPROXY_FLAGS]));
                e->flags |= (1 << NFTNL_EXPR_SYNPROXY_FLAGS);
        }

        return 0;
}

static int
nftnl_expr_synproxy_snprintf(char *buf, size_t len,
                             uint32_t flags, const struct nftnl_expr *e)
{
        struct nftnl_expr_synproxy *synproxy = nftnl_expr_data(e);
        int ret, offset = 0;

        if (e->flags & (1 << NFTNL_EXPR_SYNPROXY_MSS) &&
            e->flags & (1 << NFTNL_EXPR_SYNPROXY_WSCALE)) {
                ret = snprintf(buf, len, "mss %u wscale %u ", synproxy->mss,
                               synproxy->wscale);
                SNPRINTF_BUFFER_SIZE(ret, len, offset);
        }

        return offset;
}

static struct attr_policy synproxy_attr_policy[__NFTNL_EXPR_SYNPROXY_MAX] = {
        [NFTNL_EXPR_SYNPROXY_MSS]    = { .maxlen = sizeof(uint16_t) },
        [NFTNL_EXPR_SYNPROXY_WSCALE] = { .maxlen = sizeof(uint8_t) },
        [NFTNL_EXPR_SYNPROXY_FLAGS]  = { .maxlen = sizeof(uint32_t) },
};

struct expr_ops expr_ops_synproxy = {
        .name           = "synproxy",
        .alloc_len      = sizeof(struct nftnl_expr_synproxy),
        .nftnl_max_attr = __NFTNL_EXPR_SYNPROXY_MAX - 1,
        .attr_policy    = synproxy_attr_policy,
        .set            = nftnl_expr_synproxy_set,
        .get            = nftnl_expr_synproxy_get,
        .parse          = nftnl_expr_synproxy_parse,
        .build          = nftnl_expr_synproxy_build,
        .output         = nftnl_expr_synproxy_snprintf,
};