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 | ||
| 6709dbbb | 15 | #include <linux/netfilter/x_tables.h> |
| 5f2c3b91 HW |
16 | #include <linux/netfilter_ipv4/ipt_TTL.h> |
| 17 | ||
| 18 | MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>"); | |
| 2ae15b64 | 19 | MODULE_DESCRIPTION("Xtables: IPv4 TTL field modification target"); |
| 5f2c3b91 HW |
20 | MODULE_LICENSE("GPL"); |
| 21 | ||
| e905a9ed | 22 | static unsigned int |
| d3c5ee6d JE |
23 | ttl_tg(struct sk_buff *skb, const struct net_device *in, |
| 24 | const struct net_device *out, unsigned int hooknum, | |
| 25 | const struct xt_target *target, const void *targinfo) | |
| 5f2c3b91 HW |
26 | { |
| 27 | struct iphdr *iph; | |
| 28 | const struct ipt_TTL_info *info = targinfo; | |
| 5f2c3b91 HW |
29 | int new_ttl; |
| 30 | ||
| 3db05fea | 31 | if (!skb_make_writable(skb, skb->len)) |
| 5f2c3b91 HW |
32 | return NF_DROP; |
| 33 | ||
| 3db05fea | 34 | iph = ip_hdr(skb); |
| 5f2c3b91 HW |
35 | |
| 36 | switch (info->mode) { | |
| 37 | case IPT_TTL_SET: | |
| 38 | new_ttl = info->ttl; | |
| 39 | break; | |
| 40 | case IPT_TTL_INC: | |
| 41 | new_ttl = iph->ttl + info->ttl; | |
| 42 | if (new_ttl > 255) | |
| 43 | new_ttl = 255; | |
| 44 | break; | |
| 45 | case IPT_TTL_DEC: | |
| 46 | new_ttl = iph->ttl - info->ttl; | |
| 47 | if (new_ttl < 0) | |
| 48 | new_ttl = 0; | |
| 49 | break; | |
| 50 | default: | |
| 51 | new_ttl = iph->ttl; | |
| 52 | break; | |
| 53 | } | |
| 54 | ||
| 55 | if (new_ttl != iph->ttl) { | |
| be0ea7d5 PM |
56 | csum_replace2(&iph->check, htons(iph->ttl << 8), |
| 57 | htons(new_ttl << 8)); | |
| 5f2c3b91 | 58 | iph->ttl = new_ttl; |
| 5f2c3b91 HW |
59 | } |
| 60 | ||
| 6709dbbb | 61 | return XT_CONTINUE; |
| 5f2c3b91 HW |
62 | } |
| 63 | ||
| d3c5ee6d JE |
64 | static bool |
| 65 | ttl_tg_check(const char *tablename, const void *e, | |
| 66 | const struct xt_target *target, void *targinfo, | |
| 67 | unsigned int hook_mask) | |
| 5f2c3b91 | 68 | { |
| a47362a2 | 69 | const struct ipt_TTL_info *info = targinfo; |
| 5f2c3b91 | 70 | |
| 5f2c3b91 | 71 | if (info->mode > IPT_TTL_MAXMODE) { |
| e905a9ed | 72 | printk(KERN_WARNING "ipt_TTL: invalid or unknown Mode %u\n", |
| 5f2c3b91 | 73 | info->mode); |
| e1931b78 | 74 | return false; |
| 5f2c3b91 | 75 | } |
| 7c4e36bc | 76 | if (info->mode != IPT_TTL_SET && info->ttl == 0) |
| e1931b78 JE |
77 | return false; |
| 78 | return true; | |
| 5f2c3b91 HW |
79 | } |
| 80 | ||
| d3c5ee6d | 81 | static struct xt_target ttl_tg_reg __read_mostly = { |
| 5f2c3b91 | 82 | .name = "TTL", |
| 6709dbbb | 83 | .family = AF_INET, |
| d3c5ee6d | 84 | .target = ttl_tg, |
| 1d5cd909 PM |
85 | .targetsize = sizeof(struct ipt_TTL_info), |
| 86 | .table = "mangle", | |
| d3c5ee6d | 87 | .checkentry = ttl_tg_check, |
| 5f2c3b91 HW |
88 | .me = THIS_MODULE, |
| 89 | }; | |
| 90 | ||
| d3c5ee6d | 91 | static int __init ttl_tg_init(void) |
| 5f2c3b91 | 92 | { |
| d3c5ee6d | 93 | return xt_register_target(&ttl_tg_reg); |
| 5f2c3b91 HW |
94 | } |
| 95 | ||
| d3c5ee6d | 96 | static void __exit ttl_tg_exit(void) |
| 5f2c3b91 | 97 | { |
| d3c5ee6d | 98 | xt_unregister_target(&ttl_tg_reg); |
| 5f2c3b91 HW |
99 | } |
| 100 | ||
| d3c5ee6d JE |
101 | module_init(ttl_tg_init); |
| 102 | module_exit(ttl_tg_exit); |