Harald Welte | 703828f | 2000-10-04 15:27:07 +0000 | [diff] [blame^] | 1 | /* Shared library add-on to iptables for the TTL target |
| 2 | * (C) 2000 by Harald Welte <laforge@gnumonks.org> |
| 3 | * |
| 4 | * Version: 1.2 |
| 5 | * |
| 6 | * This program is distributed under the terms of GNU GPL |
| 7 | */ |
| 8 | #include <stdio.h> |
| 9 | #include <string.h> |
| 10 | #include <stdlib.h> |
| 11 | #include <getopt.h> |
| 12 | #include <iptables.h> |
| 13 | |
| 14 | #include <linux/netfilter_ipv4/ip_tables.h> |
| 15 | #include <linux/netfilter_ipv4/ipt_TTL.h> |
| 16 | |
| 17 | #define IPT_TTL_USED 1 |
| 18 | |
| 19 | static void init(struct ipt_entry_target *t, unsigned int *nfcache) |
| 20 | { |
| 21 | } |
| 22 | |
| 23 | static void help(void) |
| 24 | { |
| 25 | printf( |
| 26 | "TTL target v%s options\n" |
| 27 | " --ttl-set value Set TTL to <value>\n" |
| 28 | " --ttl-dec value Decrement TTL by <value>\n" |
| 29 | " --ttl-inc value Increment TTL by <value>\n" |
| 30 | , NETFILTER_VERSION); |
| 31 | } |
| 32 | |
| 33 | static int parse(int c, char **argv, int invert, unsigned int *flags, |
| 34 | const struct ipt_entry *entry, |
| 35 | struct ipt_entry_target **target) |
| 36 | { |
| 37 | struct ipt_TTL_info *info = (struct ipt_TTL_info *) (*target)->data; |
| 38 | u_int8_t value; |
| 39 | |
| 40 | if (*flags & IPT_TTL_USED) { |
| 41 | exit_error(PARAMETER_PROBLEM, |
| 42 | "Can't specify TTL option twice"); |
| 43 | } |
| 44 | |
| 45 | if (!optarg) |
| 46 | exit_error(PARAMETER_PROBLEM, |
| 47 | "TTL: You must specify a value"); |
| 48 | |
| 49 | if (check_inverse(optarg, &invert)) |
| 50 | exit_error(PARAMETER_PROBLEM, |
| 51 | "TTL: unexpected `!'"); |
| 52 | |
| 53 | value = atoi(optarg); |
| 54 | |
| 55 | switch (c) { |
| 56 | |
| 57 | case '1': |
| 58 | info->mode = IPT_TTL_SET; |
| 59 | break; |
| 60 | |
| 61 | case '2': |
| 62 | if (value == 0) { |
| 63 | exit_error(PARAMETER_PROBLEM, |
| 64 | "TTL: decreasing by 0?"); |
| 65 | } |
| 66 | |
| 67 | info->mode = IPT_TTL_DEC; |
| 68 | break; |
| 69 | |
| 70 | case '3': |
| 71 | if (value == 0) { |
| 72 | exit_error(PARAMETER_PROBLEM, |
| 73 | "TTL: increasing by 0?"); |
| 74 | } |
| 75 | |
| 76 | info->mode = IPT_TTL_INC; |
| 77 | break; |
| 78 | |
| 79 | default: |
| 80 | return 0; |
| 81 | |
| 82 | } |
| 83 | |
| 84 | info->ttl = value; |
| 85 | *flags |= IPT_TTL_USED; |
| 86 | |
| 87 | return 1; |
| 88 | } |
| 89 | |
| 90 | static void final_check(unsigned int flags) |
| 91 | { |
| 92 | if (!(flags & IPT_TTL_USED)) |
| 93 | exit_error(PARAMETER_PROBLEM, |
| 94 | "TTL: You must specify an action"); |
| 95 | } |
| 96 | |
| 97 | static void save(const struct ipt_ip *ip, |
| 98 | const struct ipt_entry_target *target) |
| 99 | { |
| 100 | const struct ipt_TTL_info *info = |
| 101 | (struct ipt_TTL_info *) target->data; |
| 102 | |
| 103 | switch (info->mode) { |
| 104 | case IPT_TTL_SET: |
| 105 | printf("--ttl-set "); |
| 106 | break; |
| 107 | case IPT_TTL_DEC: |
| 108 | printf("--ttl-dec "); |
| 109 | break; |
| 110 | |
| 111 | case IPT_TTL_INC: |
| 112 | printf("--ttl-inc "); |
| 113 | break; |
| 114 | } |
| 115 | printf("%u ", info->ttl); |
| 116 | } |
| 117 | |
| 118 | static void print(const struct ipt_ip *ip, |
| 119 | const struct ipt_entry_target *target, int numeric) |
| 120 | { |
| 121 | const struct ipt_TTL_info *info = |
| 122 | (struct ipt_TTL_info *) target->data; |
| 123 | |
| 124 | printf("TTL "); |
| 125 | switch (info->mode) { |
| 126 | case IPT_TTL_SET: |
| 127 | printf("set to "); |
| 128 | break; |
| 129 | case IPT_TTL_DEC: |
| 130 | printf("decrement by "); |
| 131 | break; |
| 132 | case IPT_TTL_INC: |
| 133 | printf("increment by "); |
| 134 | break; |
| 135 | } |
| 136 | printf("%u ", info->ttl); |
| 137 | } |
| 138 | |
| 139 | static struct option opts[] = { |
| 140 | { "ttl-set", 1, 0, '1' }, |
| 141 | { "ttl-dec", 1, 0, '2' }, |
| 142 | { "ttl-inc", 1, 0, '3' }, |
| 143 | { 0 } |
| 144 | }; |
| 145 | |
| 146 | struct iptables_target TTL = { NULL, |
| 147 | "TTL", |
| 148 | NETFILTER_VERSION, |
| 149 | IPT_ALIGN(sizeof(struct ipt_TTL_info)), |
| 150 | IPT_ALIGN(sizeof(struct ipt_TTL_info)), |
| 151 | &help, |
| 152 | &init, |
| 153 | &parse, |
| 154 | &final_check, |
| 155 | &print, |
| 156 | &save, |
| 157 | opts |
| 158 | }; |
| 159 | |
| 160 | void _init(void) |
| 161 | { |
| 162 | register_target(&TTL); |
| 163 | } |