projects / deliverable / linux.git / blame
| Commit | Line | Data |
|---|---|---|
| 5f2c3b91 HW |
1 | /* TTL modification target for IP tables |
| 2 | * (C) 2000,2005 by Harald Welte <laforge@netfilter.org> | |
| 3 | * | |
| 4 | * This program is free software; you can redistribute it and/or modify | |
| 5 | * it under the terms of the GNU General Public License version 2 as | |
| 6 | * published by the Free Software Foundation. | |
| 7 | * | |
| 8 | */ | |
| 9 | ||
| 10 | #include <linux/module.h> | |
| 11 | #include <linux/skbuff.h> | |
| 12 | #include <linux/ip.h> | |
| 13 | #include <net/checksum.h> | |
| 14 | ||
| 15 | #include <linux/netfilter_ipv4/ip_tables.h> | |
| 16 | #include <linux/netfilter_ipv4/ipt_TTL.h> | |
| 17 | ||
| 18 | MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>"); | |
| 19 | MODULE_DESCRIPTION("IP tables TTL modification module"); | |
| 20 | MODULE_LICENSE("GPL"); | |
| 21 | ||
| 22 | static unsigned int | |
| c4986734 PM |
23 | ipt_ttl_target(struct sk_buff **pskb, |
| 24 | const struct net_device *in, const struct net_device *out, | |
| 25 | unsigned int hooknum, const struct xt_target *target, | |
| fe1cb108 | 26 | const void *targinfo) |
| 5f2c3b91 HW |
27 | { |
| 28 | struct iphdr *iph; | |
| 29 | const struct ipt_TTL_info *info = targinfo; | |
| 5f2c3b91 HW |
30 | int new_ttl; |
| 31 | ||
| 32 | if (!skb_make_writable(pskb, (*pskb)->len)) | |
| 33 | return NF_DROP; | |
| 34 | ||
| 35 | iph = (*pskb)->nh.iph; | |
| 36 | ||
| 37 | switch (info->mode) { | |
| 38 | case IPT_TTL_SET: | |
| 39 | new_ttl = info->ttl; | |
| 40 | break; | |
| 41 | case IPT_TTL_INC: | |
| 42 | new_ttl = iph->ttl + info->ttl; | |
| 43 | if (new_ttl > 255) | |
| 44 | new_ttl = 255; | |
| 45 | break; | |
| 46 | case IPT_TTL_DEC: | |
| 47 | new_ttl = iph->ttl - info->ttl; | |
| 48 | if (new_ttl < 0) | |
| 49 | new_ttl = 0; | |
| 50 | break; | |
| 51 | default: | |
| 52 | new_ttl = iph->ttl; | |
| 53 | break; | |
| 54 | } | |
| 55 | ||
| 56 | if (new_ttl != iph->ttl) { | |
| ca39df6c PM |
57 | iph->check = nf_csum_update(ntohs((iph->ttl << 8)) ^ 0xFFFF, |
| 58 | ntohs(new_ttl << 8), | |
| da878c8e | 59 | iph->check); |
| 5f2c3b91 | 60 | iph->ttl = new_ttl; |
| 5f2c3b91 HW |
61 | } |
| 62 | ||
| 63 | return IPT_CONTINUE; | |
| 64 | } | |
| 65 | ||
| 66 | static int ipt_ttl_checkentry(const char *tablename, | |
| 2e4e6a17 | 67 | const void *e, |
| c4986734 | 68 | const struct xt_target *target, |
| 5f2c3b91 | 69 | void *targinfo, |
| 5f2c3b91 HW |
70 | unsigned int hook_mask) |
| 71 | { | |
| 72 | struct ipt_TTL_info *info = targinfo; | |
| 73 | ||
| 5f2c3b91 HW |
74 | if (info->mode > IPT_TTL_MAXMODE) { |
| 75 | printk(KERN_WARNING "ipt_TTL: invalid or unknown Mode %u\n", | |
| 76 | info->mode); | |
| 77 | return 0; | |
| 78 | } | |
| 5f2c3b91 HW |
79 | if ((info->mode != IPT_TTL_SET) && (info->ttl == 0)) |
| 80 | return 0; | |
| 5f2c3b91 HW |
81 | return 1; |
| 82 | } | |
| 83 | ||
| 84 | static struct ipt_target ipt_TTL = { | |
| 85 | .name = "TTL", | |
| 86 | .target = ipt_ttl_target, | |
| 1d5cd909 PM |
87 | .targetsize = sizeof(struct ipt_TTL_info), |
| 88 | .table = "mangle", | |
| 5f2c3b91 HW |
89 | .checkentry = ipt_ttl_checkentry, |
| 90 | .me = THIS_MODULE, | |
| 91 | }; | |
| 92 | ||
| 65b4b4e8 | 93 | static int __init ipt_ttl_init(void) |
| 5f2c3b91 HW |
94 | { |
| 95 | return ipt_register_target(&ipt_TTL); | |
| 96 | } | |
| 97 | ||
| 65b4b4e8 | 98 | static void __exit ipt_ttl_fini(void) |
| 5f2c3b91 HW |
99 | { |
| 100 | ipt_unregister_target(&ipt_TTL); | |
| 101 | } | |
| 102 | ||
| 65b4b4e8 AM |
103 | module_init(ipt_ttl_init); |
| 104 | module_exit(ipt_ttl_fini); |