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#include <stdio.h>
#include <xtables.h>
#include <linux/netfilter/xt_tcpmss.h>
enum {
O_TCPMSS = 0,
};
static void tcpmss_help(void)
{
printf(
"tcpmss match options:\n"
"[!] --mss value[:value] Match TCP MSS range.\n"
" (only valid for TCP SYN or SYN/ACK packets)\n");
}
static const struct xt_option_entry tcpmss_opts[] = {
{.name = "mss", .id = O_TCPMSS, .type = XTTYPE_UINT16RC,
.flags = XTOPT_MAND | XTOPT_INVERT},
XTOPT_TABLEEND,
};
static void tcpmss_parse(struct xt_option_call *cb)
{
struct xt_tcpmss_match_info *mssinfo = cb->data;
xtables_option_parse(cb);
mssinfo->mss_min = cb->val.u16_range[0];
mssinfo->mss_max = mssinfo->mss_min;
if (cb->nvals == 2) {
mssinfo->mss_max = cb->val.u16_range[1];
if (mssinfo->mss_max < mssinfo->mss_min)
xtables_error(PARAMETER_PROBLEM,
"tcpmss: invalid range given");
}
if (cb->invert)
mssinfo->invert = 1;
}
static void
tcpmss_print(const void *ip, const struct xt_entry_match *match, int numeric)
{
const struct xt_tcpmss_match_info *info = (void *)match->data;
printf(" tcpmss match %s", info->invert ? "!" : "");
if (info->mss_min == info->mss_max)
printf("%u", info->mss_min);
else
printf("%u:%u", info->mss_min, info->mss_max);
}
static void tcpmss_save(const void *ip, const struct xt_entry_match *match)
{
const struct xt_tcpmss_match_info *info = (void *)match->data;
printf("%s --mss ", info->invert ? " !" : "");
if (info->mss_min == info->mss_max)
printf("%u", info->mss_min);
else
printf("%u:%u", info->mss_min, info->mss_max);
}
static struct xtables_match tcpmss_match = {
.family = NFPROTO_UNSPEC,
.name = "tcpmss",
.version = XTABLES_VERSION,
.size = XT_ALIGN(sizeof(struct xt_tcpmss_match_info)),
.userspacesize = XT_ALIGN(sizeof(struct xt_tcpmss_match_info)),
.help = tcpmss_help,
.print = tcpmss_print,
.save = tcpmss_save,
.x6_parse = tcpmss_parse,
.x6_options = tcpmss_opts,
};
void _init(void)
{
xtables_register_match(&tcpmss_match);
}
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