Home | History | Annotate | Download | only in extensions 
      1 /* Shared library add-on to iptables for the TTL target
      2  * (C) 2000 by Harald Welte <laforge (at) gnumonks.org>
      3  *
      4  * This program is distributed under the terms of GNU GPL
      5  */
      6 #include <stdio.h>
      7 #include <xtables.h>
      8 #include <linux/netfilter_ipv4/ipt_TTL.h>
      9 
     10 enum {
     11 	O_TTL_SET = 0,
     12 	O_TTL_INC,
     13 	O_TTL_DEC,
     14 	F_TTL_SET = 1 << O_TTL_SET,
     15 	F_TTL_INC = 1 << O_TTL_INC,
     16 	F_TTL_DEC = 1 << O_TTL_DEC,
     17 	F_ANY     = F_TTL_SET | F_TTL_INC | F_TTL_DEC,
     18 };
     19 
     20 #define s struct ipt_TTL_info
     21 static const struct xt_option_entry TTL_opts[] = {
     22 	{.name = "ttl-set", .type = XTTYPE_UINT8, .id = O_TTL_SET,
     23 	 .excl = F_ANY, .flags = XTOPT_PUT, XTOPT_POINTER(s, ttl)},
     24 	{.name = "ttl-dec", .type = XTTYPE_UINT8, .id = O_TTL_DEC,
     25 	 .excl = F_ANY, .flags = XTOPT_PUT, XTOPT_POINTER(s, ttl),
     26 	 .min = 1},
     27 	{.name = "ttl-inc", .type = XTTYPE_UINT8, .id = O_TTL_INC,
     28 	 .excl = F_ANY, .flags = XTOPT_PUT, XTOPT_POINTER(s, ttl),
     29 	 .min = 1},
     30 	XTOPT_TABLEEND,
     31 };
     32 #undef s
     33 
     34 static void TTL_help(void)
     35 {
     36 	printf(
     37 "TTL target options\n"
     38 "  --ttl-set value		Set TTL to <value 0-255>\n"
     39 "  --ttl-dec value		Decrement TTL by <value 1-255>\n"
     40 "  --ttl-inc value		Increment TTL by <value 1-255>\n");
     41 }
     42 
     43 static void TTL_parse(struct xt_option_call *cb)
     44 {
     45 	struct ipt_TTL_info *info = cb->data;
     46 
     47 	xtables_option_parse(cb);
     48 	switch (cb->entry->id) {
     49 	case O_TTL_SET:
     50 		info->mode = IPT_TTL_SET;
     51 		break;
     52 	case O_TTL_DEC:
     53 		info->mode = IPT_TTL_DEC;
     54 		break;
     55 	case O_TTL_INC:
     56 		info->mode = IPT_TTL_INC;
     57 		break;
     58 	}
     59 }
     60 
     61 static void TTL_check(struct xt_fcheck_call *cb)
     62 {
     63 	if (!(cb->xflags & F_ANY))
     64 		xtables_error(PARAMETER_PROBLEM,
     65 				"TTL: You must specify an action");
     66 }
     67 
     68 static void TTL_save(const void *ip, const struct xt_entry_target *target)
     69 {
     70 	const struct ipt_TTL_info *info =
     71 		(struct ipt_TTL_info *) target->data;
     72 
     73 	switch (info->mode) {
     74 		case IPT_TTL_SET:
     75 			printf(" --ttl-set");
     76 			break;
     77 		case IPT_TTL_DEC:
     78 			printf(" --ttl-dec");
     79 			break;
     80 
     81 		case IPT_TTL_INC:
     82 			printf(" --ttl-inc");
     83 			break;
     84 	}
     85 	printf(" %u", info->ttl);
     86 }
     87 
     88 static void TTL_print(const void *ip, const struct xt_entry_target *target,
     89                       int numeric)
     90 {
     91 	const struct ipt_TTL_info *info =
     92 		(struct ipt_TTL_info *) target->data;
     93 
     94 	printf(" TTL ");
     95 	switch (info->mode) {
     96 		case IPT_TTL_SET:
     97 			printf("set to");
     98 			break;
     99 		case IPT_TTL_DEC:
    100 			printf("decrement by");
    101 			break;
    102 		case IPT_TTL_INC:
    103 			printf("increment by");
    104 			break;
    105 	}
    106 	printf(" %u", info->ttl);
    107 }
    108 
    109 static struct xtables_target ttl_tg_reg = {
    110 	.name		= "TTL",
    111 	.version	= XTABLES_VERSION,
    112 	.family		= NFPROTO_IPV4,
    113 	.size		= XT_ALIGN(sizeof(struct ipt_TTL_info)),
    114 	.userspacesize	= XT_ALIGN(sizeof(struct ipt_TTL_info)),
    115 	.help		= TTL_help,
    116 	.print		= TTL_print,
    117 	.save		= TTL_save,
    118 	.x6_parse	= TTL_parse,
    119 	.x6_fcheck	= TTL_check,
    120 	.x6_options	= TTL_opts,
    121 };
    122 
    123 void _init(void)
    124 {
    125 	xtables_register_target(&ttl_tg_reg);
    126 }
    127