/usr/src/xtables-addons-2.12/extensions/libxt_ipv4options.c is in xtables-addons-dkms 2.12-0.1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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* "ipv4options" match extension for iptables
* Copyright © Jan Engelhardt, 2009
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License; either
* version 2 of the License, or any later version, as published by the
* Free Software Foundation.
*/
#include <getopt.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <string.h>
#include <xtables.h>
#include "xt_ipv4options.h"
#include "compat_user.h"
/*
* Overview from http://www.networksorcery.com/enp/protocol/ip.htm
* Not providing strings for options that seem to be most distant in the past.
*/
static const char *const v4opt_names[32] = {
[ 1] = "nop",
[ 2] = "security", /* RFC 1108 */
[ 3] = "lsrr", /* RFC 791 */
[ 4] = "timestamp", /* RFC 781, 791 */
[ 7] = "record-route", /* RFC 791 */
[ 9] = "ssrr", /* RFC 791 */
[11] = "mtu-probe", /* RFC 1063 */
[12] = "mtu-reply", /* RFC 1063 */
[18] = "traceroute", /* RFC 1393 */
[20] = "router-alert", /* RFC 2113 */
};
static void ipv4options_mt_help(void)
{
printf(
"ipv4options match options:\n"
"--flags [!]symbol[,...] Match presence/absence (!) of option\n"
" (either by name or number)\n"
"--any Interpret --flags as OR-combined\n\n");
}
static const struct option ipv4options_mt_opts[] = {
{.name = "flags", .has_arg = true, .val = 'f'},
{.name = "any", .has_arg = false, .val = 'a'},
{NULL},
};
static void ipv4options_parse_flagspec(struct xt_ipv4options_mtinfo1 *info,
char *arg)
{
unsigned int i, opt;
bool inv;
char *p;
while (true) {
p = strchr(arg, ',');
if (p != NULL)
*p = '\0';
inv = false;
opt = 0;
if (*arg == '!') {
inv = true;
++arg;
}
for (i = 1; i < 32;++i)
if (v4opt_names[i] != NULL &&
strcmp(v4opt_names[i], arg) == 0) {
opt = i;
break;
}
if (opt == 0 &&
!xtables_strtoui(arg, NULL, &opt, 0, UINT8_MAX))
xtables_error(PARAMETER_PROBLEM,
"ipv4options: Bad option value \"%s\"", arg);
if (opt == 0)
xtables_error(PARAMETER_PROBLEM,
"ipv4options: Option value may not be zero");
info->map |= (1 << opt);
if (inv)
info->invert |= (1 << opt);
if (p == NULL)
break;
arg = p + 1;
}
}
static int ipv4options_mt_parse(int c, char **argv, int invert,
unsigned int *flags, const void *entry, struct xt_entry_match **match)
{
struct xt_ipv4options_mtinfo1 *info = (void *)(*match)->data;
switch (c) {
case 'a': /* --any */
xtables_param_act(XTF_NO_INVERT, "ipv4options", "--any", invert);
info->flags |= XT_V4OPTS_ANY;
return true;
case 'f': /* --flags */
xtables_param_act(XTF_NO_INVERT, "ipv4options", "--flags", invert);
ipv4options_parse_flagspec(info, optarg);
return true;
}
return false;
}
/* no checking of *flags - no IPv4 options is also valid */
static void ipv4options_print_flags(const struct xt_ipv4options_mtinfo1 *info,
bool numeric)
{
uint32_t tmp = info->map;
unsigned int i;
for (i = 1; i < 32; ++i)
if (tmp & (1 << i)) {
if (info->invert & (1 << i))
printf("!");
if (!numeric && v4opt_names[i] != NULL)
printf("%s", v4opt_names[i]);
else
printf("%u", i);
tmp &= ~(1 << i);
if (tmp)
printf(",");
}
}
static void ipv4options_mt_save(const void *ip,
const struct xt_entry_match *match)
{
const struct xt_ipv4options_mtinfo1 *info = (void *)match->data;
if (info->map != 0) {
printf(" --flags ");
ipv4options_print_flags(info, true);
}
if (info->flags & XT_V4OPTS_ANY)
printf(" --any");
printf(" ");
}
static void ipv4options_mt_print(const void *ip,
const struct xt_entry_match *match, int numeric)
{
printf(" -m ipv4options");
ipv4options_mt_save(ip, match);
}
static struct xtables_match ipv4options_mt_reg = {
.version = XTABLES_VERSION,
.name = "ipv4options",
.revision = 1,
.family = NFPROTO_IPV4,
.size = XT_ALIGN(sizeof(struct xt_ipv4options_mtinfo1)),
.userspacesize = XT_ALIGN(sizeof(struct xt_ipv4options_mtinfo1)),
.help = ipv4options_mt_help,
.parse = ipv4options_mt_parse,
.print = ipv4options_mt_print,
.save = ipv4options_mt_save,
.extra_opts = ipv4options_mt_opts,
};
static __attribute__((constructor)) void ipv4options_mt_ldr(void)
{
xtables_register_match(&ipv4options_mt_reg);
}
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