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/* Shared library add-on to iptables to add TCPMSS target support.
*
* Copyright (c) 2000 Marc Boucher
*/
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <getopt.h>
#include <iptables.h>
#include <linux/netfilter_ipv4/ip_tables.h>
#include <linux/netfilter_ipv4/ipt_TCPMSS.h>
struct mssinfo {
struct ipt_entry_target t;
struct ipt_tcpmss_info mss;
};
/* Function which prints out usage message. */
static void
help(void)
{
printf(
"TCPMSS target v%s 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 - 40)\n",
IPTABLES_VERSION);
}
static struct option opts[] = {
{ "set-mss", 1, 0, '1' },
{ "clamp-mss-to-pmtu", 0, 0, '2' },
{ 0 }
};
/* Initialize the target. */
static void
init(struct ipt_entry_target *t, unsigned int *nfcache)
{
}
/* Function which parses command options; returns true if it
ate an option */
static int
parse(int c, char **argv, int invert, unsigned int *flags,
const struct ipt_entry *entry,
struct ipt_entry_target **target)
{
struct ipt_tcpmss_info *mssinfo
= (struct ipt_tcpmss_info *)(*target)->data;
switch (c) {
unsigned int mssval;
case '1':
if (*flags)
exit_error(PARAMETER_PROBLEM,
"TCPMSS target: Only one option may be specified");
if (string_to_number(optarg, 0, 65535 - 40, &mssval) == -1)
exit_error(PARAMETER_PROBLEM, "Bad TCPMSS value `%s'", optarg);
mssinfo->mss = mssval;
*flags = 1;
break;
case '2':
if (*flags)
exit_error(PARAMETER_PROBLEM,
"TCPMSS target: Only one option may be specified");
mssinfo->mss = IPT_TCPMSS_CLAMP_PMTU;
*flags = 1;
break;
default:
return 0;
}
return 1;
}
static void
final_check(unsigned int flags)
{
if (!flags)
exit_error(PARAMETER_PROBLEM,
"TCPMSS target: At least one parameter is required");
}
/* Prints out the targinfo. */
static void
print(const struct ipt_ip *ip,
const struct ipt_entry_target *target,
int numeric)
{
const struct ipt_tcpmss_info *mssinfo =
(const struct ipt_tcpmss_info *)target->data;
if(mssinfo->mss == IPT_TCPMSS_CLAMP_PMTU)
printf("TCPMSS clamp to PMTU ");
else
printf("TCPMSS set %u ", mssinfo->mss);
}
/* Saves the union ipt_targinfo in parsable form to stdout. */
static void
save(const struct ipt_ip *ip, const struct ipt_entry_target *target)
{
const struct ipt_tcpmss_info *mssinfo =
(const struct ipt_tcpmss_info *)target->data;
if(mssinfo->mss == IPT_TCPMSS_CLAMP_PMTU)
printf("--clamp-mss-to-pmtu ");
else
printf("--set-mss %u ", mssinfo->mss);
}
static struct iptables_target mss = {
.next = NULL,
.name = "TCPMSS",
.version = IPTABLES_VERSION,
.size = IPT_ALIGN(sizeof(struct ipt_tcpmss_info)),
.userspacesize = IPT_ALIGN(sizeof(struct ipt_tcpmss_info)),
.help = &help,
.init = &init,
.parse = &parse,
.final_check = &final_check,
.print = &print,
.save = &save,
.extra_opts = opts
};
void _init(void)
{
register_target(&mss);
}
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