diff options
Diffstat (limited to 'net/netfilter/xt_HL.c')
| -rw-r--r-- | net/netfilter/xt_HL.c | 171 |
1 files changed, 171 insertions, 0 deletions
diff --git a/net/netfilter/xt_HL.c b/net/netfilter/xt_HL.c new file mode 100644 index 000000000000..10e789e2d12a --- /dev/null +++ b/net/netfilter/xt_HL.c @@ -0,0 +1,171 @@ +/* + * TTL modification target for IP tables + * (C) 2000,2005 by Harald Welte <laforge@netfilter.org> + * + * Hop Limit modification target for ip6tables + * Maciej Soltysiak <solt@dns.toxicfilms.tv> + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2 as + * published by the Free Software Foundation. + */ + +#include <linux/module.h> +#include <linux/skbuff.h> +#include <linux/ip.h> +#include <linux/ipv6.h> +#include <net/checksum.h> + +#include <linux/netfilter/x_tables.h> +#include <linux/netfilter_ipv4/ipt_TTL.h> +#include <linux/netfilter_ipv6/ip6t_HL.h> + +MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>"); +MODULE_AUTHOR("Maciej Soltysiak <solt@dns.toxicfilms.tv>"); +MODULE_DESCRIPTION("Xtables: Hoplimit/TTL Limit field modification target"); +MODULE_LICENSE("GPL"); + +static unsigned int +ttl_tg(struct sk_buff *skb, const struct xt_target_param *par) +{ + struct iphdr *iph; + const struct ipt_TTL_info *info = par->targinfo; + int new_ttl; + + if (!skb_make_writable(skb, skb->len)) + return NF_DROP; + + iph = ip_hdr(skb); + + switch (info->mode) { + case IPT_TTL_SET: + new_ttl = info->ttl; + break; + case IPT_TTL_INC: + new_ttl = iph->ttl + info->ttl; + if (new_ttl > 255) + new_ttl = 255; + break; + case IPT_TTL_DEC: + new_ttl = iph->ttl - info->ttl; + if (new_ttl < 0) + new_ttl = 0; + break; + default: + new_ttl = iph->ttl; + break; + } + + if (new_ttl != iph->ttl) { + csum_replace2(&iph->check, htons(iph->ttl << 8), + htons(new_ttl << 8)); + iph->ttl = new_ttl; + } + + return XT_CONTINUE; +} + +static unsigned int +hl_tg6(struct sk_buff *skb, const struct xt_target_param *par) +{ + struct ipv6hdr *ip6h; + const struct ip6t_HL_info *info = par->targinfo; + int new_hl; + + if (!skb_make_writable(skb, skb->len)) + return NF_DROP; + + ip6h = ipv6_hdr(skb); + + switch (info->mode) { + case IP6T_HL_SET: + new_hl = info->hop_limit; + break; + case IP6T_HL_INC: + new_hl = ip6h->hop_limit + info->hop_limit; + if (new_hl > 255) + new_hl = 255; + break; + case IP6T_HL_DEC: + new_hl = ip6h->hop_limit - info->hop_limit; + if (new_hl < 0) + new_hl = 0; + break; + default: + new_hl = ip6h->hop_limit; + break; + } + + ip6h->hop_limit = new_hl; + + return XT_CONTINUE; +} + +static bool ttl_tg_check(const struct xt_tgchk_param *par) +{ + const struct ipt_TTL_info *info = par->targinfo; + + if (info->mode > IPT_TTL_MAXMODE) { + printk(KERN_WARNING "ipt_TTL: invalid or unknown Mode %u\n", + info->mode); + return false; + } + if (info->mode != IPT_TTL_SET && info->ttl == 0) + return false; + return true; +} + +static bool hl_tg6_check(const struct xt_tgchk_param *par) +{ + const struct ip6t_HL_info *info = par->targinfo; + + if (info->mode > IP6T_HL_MAXMODE) { + printk(KERN_WARNING "ip6t_HL: invalid or unknown Mode %u\n", + info->mode); + return false; + } + if (info->mode != IP6T_HL_SET && info->hop_limit == 0) { + printk(KERN_WARNING "ip6t_HL: increment/decrement doesn't " + "make sense with value 0\n"); + return false; + } + return true; +} + +static struct xt_target hl_tg_reg[] __read_mostly = { + { + .name = "TTL", + .revision = 0, + .family = NFPROTO_IPV4, + .target = ttl_tg, + .targetsize = sizeof(struct ipt_TTL_info), + .table = "mangle", + .checkentry = ttl_tg_check, + .me = THIS_MODULE, + }, + { + .name = "HL", + .revision = 0, + .family = NFPROTO_IPV6, + .target = hl_tg6, + .targetsize = sizeof(struct ip6t_HL_info), + .table = "mangle", + .checkentry = hl_tg6_check, + .me = THIS_MODULE, + }, +}; + +static int __init hl_tg_init(void) +{ + return xt_register_targets(hl_tg_reg, ARRAY_SIZE(hl_tg_reg)); +} + +static void __exit hl_tg_exit(void) +{ + xt_unregister_targets(hl_tg_reg, ARRAY_SIZE(hl_tg_reg)); +} + +module_init(hl_tg_init); +module_exit(hl_tg_exit); +MODULE_ALIAS("ipt_TTL"); +MODULE_ALIAS("ip6t_HL"); |