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/* Shared library add-on to iptables to add TCPMSS target support.
*
* Copyright (c) 2000 Marc Boucher
*/
#include "config.h"
#include <stdio.h>
#include <xtables.h>
#include <netinet/ip.h>
#include <linux/netfilter/xt_TCPMSS.h>
enum {
O_SET_MSS = 0,
O_CLAMP_MSS,
};
struct mssinfo {
struct xt_entry_target t;
struct xt_tcpmss_info mss;
};
static void __TCPMSS_help(int hdrsize)
{
printf(
"TCPMSS target mutually-exclusive options:\n"
" --set-mss value explicitly set MSS option to specified value\n"
" --clamp-mss-to-pmtu automatically clamp MSS value to (path_MTU - %d)\n",
hdrsize);
}
static void TCPMSS_help(void)
{
__TCPMSS_help(sizeof(struct iphdr));
}
static void TCPMSS_help6(void)
{
__TCPMSS_help(SIZEOF_STRUCT_IP6_HDR);
}
static const struct xt_option_entry TCPMSS4_opts[] = {
{.name = "set-mss", .id = O_SET_MSS, .type = XTTYPE_UINT16,
.min = 0, .max = UINT16_MAX - sizeof(struct iphdr),
.flags = XTOPT_PUT, XTOPT_POINTER(struct xt_tcpmss_info, mss)},
{.name = "clamp-mss-to-pmtu", .id = O_CLAMP_MSS, .type = XTTYPE_NONE},
XTOPT_TABLEEND,
};
static const struct xt_option_entry TCPMSS6_opts[] = {
{.name = "set-mss", .id = O_SET_MSS, .type = XTTYPE_UINT16,
.min = 0, .max = UINT16_MAX - SIZEOF_STRUCT_IP6_HDR,
.flags = XTOPT_PUT, XTOPT_POINTER(struct xt_tcpmss_info, mss)},
{.name = "clamp-mss-to-pmtu", .id = O_CLAMP_MSS, .type = XTTYPE_NONE},
XTOPT_TABLEEND,
};
static void TCPMSS_parse(struct xt_option_call *cb)
{
struct xt_tcpmss_info *mssinfo = cb->data;
xtables_option_parse(cb);
if (cb->entry->id == O_CLAMP_MSS)
mssinfo->mss = XT_TCPMSS_CLAMP_PMTU;
}
static void TCPMSS_check(struct xt_fcheck_call *cb)
{
if (cb->xflags == 0)
xtables_error(PARAMETER_PROBLEM,
"TCPMSS target: At least one parameter is required");
}
static void TCPMSS_print(const void *ip, const struct xt_entry_target *target,
int numeric)
{
const struct xt_tcpmss_info *mssinfo =
(const struct xt_tcpmss_info *)target->data;
if(mssinfo->mss == XT_TCPMSS_CLAMP_PMTU)
printf(" TCPMSS clamp to PMTU");
else
printf(" TCPMSS set %u", mssinfo->mss);
}
static void TCPMSS_save(const void *ip, const struct xt_entry_target *target)
{
const struct xt_tcpmss_info *mssinfo =
(const struct xt_tcpmss_info *)target->data;
if(mssinfo->mss == XT_TCPMSS_CLAMP_PMTU)
printf(" --clamp-mss-to-pmtu");
else
printf(" --set-mss %u", mssinfo->mss);
}
static int TCPMSS_xlate(struct xt_xlate *xl,
const struct xt_xlate_tg_params *params)
{
const struct xt_tcpmss_info *mssinfo =
(const struct xt_tcpmss_info *)params->target->data;
if (mssinfo->mss == XT_TCPMSS_CLAMP_PMTU)
xt_xlate_add(xl, "tcp option maxseg size set rt mtu");
else
xt_xlate_add(xl, "tcp option maxseg size set %d", mssinfo->mss);
return 1;
}
static struct xtables_target tcpmss_tg_reg[] = {
{
.family = NFPROTO_IPV4,
.name = "TCPMSS",
.version = XTABLES_VERSION,
.size = XT_ALIGN(sizeof(struct xt_tcpmss_info)),
.userspacesize = XT_ALIGN(sizeof(struct xt_tcpmss_info)),
.help = TCPMSS_help,
.print = TCPMSS_print,
.save = TCPMSS_save,
.x6_parse = TCPMSS_parse,
.x6_fcheck = TCPMSS_check,
.x6_options = TCPMSS4_opts,
.xlate = TCPMSS_xlate,
},
{
.family = NFPROTO_IPV6,
.name = "TCPMSS",
.version = XTABLES_VERSION,
.size = XT_ALIGN(sizeof(struct xt_tcpmss_info)),
.userspacesize = XT_ALIGN(sizeof(struct xt_tcpmss_info)),
.help = TCPMSS_help6,
.print = TCPMSS_print,
.save = TCPMSS_save,
.x6_parse = TCPMSS_parse,
.x6_fcheck = TCPMSS_check,
.x6_options = TCPMSS6_opts,
},
};
void _init(void)
{
xtables_register_targets(tcpmss_tg_reg, ARRAY_SIZE(tcpmss_tg_reg));
}
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