diff options
Diffstat (limited to 'net/ipv6')
| -rw-r--r-- | net/ipv6/netfilter/Kconfig | 16 | ||||
| -rw-r--r-- | net/ipv6/netfilter/Makefile | 1 | ||||
| -rw-r--r-- | net/ipv6/netfilter/ip6t_HL.c | 118 |
3 files changed, 135 insertions, 0 deletions
diff --git a/net/ipv6/netfilter/Kconfig b/net/ipv6/netfilter/Kconfig index 8a10c2d..216fbe1a 100644 --- a/net/ipv6/netfilter/Kconfig +++ b/net/ipv6/netfilter/Kconfig @@ -239,6 +239,22 @@ config IP6_NF_TARGET_MARK To compile it as a module, choose M here. If unsure, say N. +config IP6_NF_TARGET_HL + tristate 'HL (hoplimit) target support' + depends on IP6_NF_MANGLE + help + This option adds a `HL' target, which enables the user to decrement + the hoplimit value of the IPv6 header or set it to a given (lower) + value. + + While it is safe to decrement the hoplimit value, this option also + enables functionality to increment and set the hoplimit value of the + IPv6 header to arbitrary values. This is EXTREMELY DANGEROUS since + you can easily create immortal packets that loop forever on the + network. + + To compile it as a module, choose M here. If unsure, say N. + #dep_tristate ' LOG target support' CONFIG_IP6_NF_TARGET_LOG $CONFIG_IP6_NF_IPTABLES config IP6_NF_RAW tristate 'raw table support (required for TRACE)' diff --git a/net/ipv6/netfilter/Makefile b/net/ipv6/netfilter/Makefile index 70f6ba6..bd9a16a 100644 --- a/net/ipv6/netfilter/Makefile +++ b/net/ipv6/netfilter/Makefile @@ -20,6 +20,7 @@ obj-$(CONFIG_IP6_NF_MATCH_PHYSDEV) += ip6t_physdev.o obj-$(CONFIG_IP6_NF_FILTER) += ip6table_filter.o obj-$(CONFIG_IP6_NF_MANGLE) += ip6table_mangle.o obj-$(CONFIG_IP6_NF_TARGET_MARK) += ip6t_MARK.o +obj-$(CONFIG_IP6_NF_TARGET_HL) += ip6t_HL.o obj-$(CONFIG_IP6_NF_QUEUE) += ip6_queue.o obj-$(CONFIG_IP6_NF_TARGET_LOG) += ip6t_LOG.o obj-$(CONFIG_IP6_NF_RAW) += ip6table_raw.o diff --git a/net/ipv6/netfilter/ip6t_HL.c b/net/ipv6/netfilter/ip6t_HL.c new file mode 100644 index 0000000..8f5549b --- /dev/null +++ b/net/ipv6/netfilter/ip6t_HL.c @@ -0,0 +1,118 @@ +/* + * Hop Limit modification target for ip6tables + * Maciej Soltysiak <solt@dns.toxicfilms.tv> + * Based on HW's TTL module + * + * This software is distributed under the terms of GNU GPL + */ + +#include <linux/module.h> +#include <linux/skbuff.h> +#include <linux/ip.h> + +#include <linux/netfilter_ipv6/ip6_tables.h> +#include <linux/netfilter_ipv6/ip6t_HL.h> + +MODULE_AUTHOR("Maciej Soltysiak <solt@dns.toxicfilms.tv>"); +MODULE_DESCRIPTION("IP tables Hop Limit modification module"); +MODULE_LICENSE("GPL"); + +static unsigned int ip6t_hl_target(struct sk_buff **pskb, + const struct net_device *in, + const struct net_device *out, + unsigned int hooknum, + const void *targinfo, void *userinfo) +{ + struct ipv6hdr *ip6h; + const struct ip6t_HL_info *info = targinfo; + u_int16_t diffs[2]; + int new_hl; + + if (!skb_make_writable(pskb, (*pskb)->len)) + return NF_DROP; + + ip6h = (*pskb)->nh.ipv6h; + + 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; + } + + if (new_hl != ip6h->hop_limit) { + diffs[0] = htons(((unsigned)ip6h->hop_limit) << 8) ^ 0xFFFF; + ip6h->hop_limit = new_hl; + diffs[1] = htons(((unsigned)ip6h->hop_limit) << 8); + } + + return IP6T_CONTINUE; +} + +static int ip6t_hl_checkentry(const char *tablename, + const struct ip6t_entry *e, + void *targinfo, + unsigned int targinfosize, + unsigned int hook_mask) +{ + struct ip6t_HL_info *info = targinfo; + + if (targinfosize != IP6T_ALIGN(sizeof(struct ip6t_HL_info))) { + printk(KERN_WARNING "ip6t_HL: targinfosize %u != %Zu\n", + targinfosize, + IP6T_ALIGN(sizeof(struct ip6t_HL_info))); + return 0; + } + + if (strcmp(tablename, "mangle")) { + printk(KERN_WARNING "ip6t_HL: can only be called from " + "\"mangle\" table, not \"%s\"\n", tablename); + return 0; + } + + if (info->mode > IP6T_HL_MAXMODE) { + printk(KERN_WARNING "ip6t_HL: invalid or unknown Mode %u\n", + info->mode); + return 0; + } + + 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 0; + } + + return 1; +} + +static struct ip6t_target ip6t_HL = { + .name = "HL", + .target = ip6t_hl_target, + .checkentry = ip6t_hl_checkentry, + .me = THIS_MODULE +}; + +static int __init init(void) +{ + return ip6t_register_target(&ip6t_HL); +} + +static void __exit fini(void) +{ + ip6t_unregister_target(&ip6t_HL); +} + +module_init(init); +module_exit(fini); |
