Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1 | /* IP tables module for matching the value of the TTL |
| 2 | * |
| 3 | * ipt_ttl.c,v 1.5 2000/11/13 11:16:08 laforge Exp |
| 4 | * |
| 5 | * (C) 2000,2001 by Harald Welte <laforge@netfilter.org> |
| 6 | * |
| 7 | * This program is free software; you can redistribute it and/or modify |
| 8 | * it under the terms of the GNU General Public License version 2 as |
| 9 | * published by the Free Software Foundation. |
| 10 | */ |
| 11 | |
| 12 | #include <linux/module.h> |
| 13 | #include <linux/skbuff.h> |
| 14 | |
| 15 | #include <linux/netfilter_ipv4/ipt_ttl.h> |
| 16 | #include <linux/netfilter_ipv4/ip_tables.h> |
| 17 | |
| 18 | MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>"); |
| 19 | MODULE_DESCRIPTION("IP tables TTL matching module"); |
| 20 | MODULE_LICENSE("GPL"); |
| 21 | |
| 22 | static int match(const struct sk_buff *skb, const struct net_device *in, |
| 23 | const struct net_device *out, const void *matchinfo, |
| 24 | int offset, int *hotdrop) |
| 25 | { |
| 26 | const struct ipt_ttl_info *info = matchinfo; |
| 27 | |
| 28 | switch (info->mode) { |
| 29 | case IPT_TTL_EQ: |
| 30 | return (skb->nh.iph->ttl == info->ttl); |
| 31 | break; |
| 32 | case IPT_TTL_NE: |
| 33 | return (!(skb->nh.iph->ttl == info->ttl)); |
| 34 | break; |
| 35 | case IPT_TTL_LT: |
| 36 | return (skb->nh.iph->ttl < info->ttl); |
| 37 | break; |
| 38 | case IPT_TTL_GT: |
| 39 | return (skb->nh.iph->ttl > info->ttl); |
| 40 | break; |
| 41 | default: |
| 42 | printk(KERN_WARNING "ipt_ttl: unknown mode %d\n", |
| 43 | info->mode); |
| 44 | return 0; |
| 45 | } |
| 46 | |
| 47 | return 0; |
| 48 | } |
| 49 | |
| 50 | static int checkentry(const char *tablename, const struct ipt_ip *ip, |
| 51 | void *matchinfo, unsigned int matchsize, |
| 52 | unsigned int hook_mask) |
| 53 | { |
| 54 | if (matchsize != IPT_ALIGN(sizeof(struct ipt_ttl_info))) |
| 55 | return 0; |
| 56 | |
| 57 | return 1; |
| 58 | } |
| 59 | |
| 60 | static struct ipt_match ttl_match = { |
| 61 | .name = "ttl", |
| 62 | .match = &match, |
| 63 | .checkentry = &checkentry, |
| 64 | .me = THIS_MODULE, |
| 65 | }; |
| 66 | |
| 67 | static int __init init(void) |
| 68 | { |
| 69 | return ipt_register_match(&ttl_match); |
| 70 | } |
| 71 | |
| 72 | static void __exit fini(void) |
| 73 | { |
| 74 | ipt_unregister_match(&ttl_match); |
| 75 | |
| 76 | } |
| 77 | |
| 78 | module_init(init); |
| 79 | module_exit(fini); |