diff options
Diffstat (limited to 'kernel/linux/net/bridge/netfilter/ebt_isnat.c')
-rw-r--r-- | kernel/linux/net/bridge/netfilter/ebt_isnat.c | 122 |
1 files changed, 122 insertions, 0 deletions
diff --git a/kernel/linux/net/bridge/netfilter/ebt_isnat.c b/kernel/linux/net/bridge/netfilter/ebt_isnat.c new file mode 100644 index 0000000..7f2f844 --- /dev/null +++ b/kernel/linux/net/bridge/netfilter/ebt_isnat.c @@ -0,0 +1,122 @@ +/* + * ebt_isnat + * + * Authors: + * Grzegorz Borowiak <grzes@gnu.univ.gda.pl> + * + * September, 2003 + * + */ + +#include <linux/netfilter_bridge/ebtables.h> +#include <linux/netfilter_bridge/ebt_inat.h> +#include <linux/module.h> +#include <linux/ip.h> +#include <linux/if_arp.h> +#include <linux/types.h> +#include <net/sock.h> + +static int get_ip_src(const struct sk_buff *skb, uint32_t *addr) +{ + if (skb->mac.ethernet->h_proto == __constant_htons(ETH_P_IP)) { + *addr = skb->nh.iph->saddr; + return 1; + } + if (skb->mac.ethernet->h_proto == __constant_htons(ETH_P_ARP)) { + + uint32_t arp_len = sizeof(struct arphdr) + + (2 * (((*skb).nh.arph)->ar_hln)) + + (2 * (((*skb).nh.arph)->ar_pln)); + + // Make sure the packet is long enough. + if ((((*skb).nh.raw) + arp_len) > (*skb).tail) + return 0; + // IPv4 addresses are always 4 bytes. + if (((*skb).nh.arph)->ar_pln != sizeof(uint32_t)) + return 0; + + memcpy(addr, ((*skb).nh.raw) + sizeof(struct arphdr) + + ((((*skb).nh.arph)->ar_hln)), sizeof(uint32_t)); + + return 2; + } + return 0; +} + +static int ebt_target_isnat(struct sk_buff **pskb, unsigned int hooknr, + const struct net_device *in, const struct net_device *out, + const void *data, unsigned int datalen) +{ + struct ebt_inat_info *info = (struct ebt_inat_info *)data; + uint32_t ip; + int index; + struct ebt_inat_tuple *tuple; + + if (!get_ip_src(*pskb, &ip)) { + /* not an ARP or IPV4 packet */ + return info->target; + } + + if ((ip & __constant_htonl(0xffffff00)) != info->ip_subnet) { + + /* outside our range */ + return info->target; + } + + index = ((unsigned char*)&ip)[3]; /* the last byte; network packets are big endian */ + tuple = &info->a[index]; + + if (!tuple->enabled) { + /* we do not want to alter packets with this IP */ + return info->target; + } + + memcpy(((**pskb).mac.ethernet)->h_source, tuple->mac, ETH_ALEN); + + if ((**pskb).mac.ethernet->h_proto == __constant_htons(ETH_P_ARP)) { + /* change the payload */ + memcpy((**pskb).nh.raw + sizeof(struct arphdr), tuple->mac, ETH_ALEN); + } + + return tuple->target; +} + +static int ebt_target_isnat_check(const char *tablename, unsigned int hookmask, + const struct ebt_entry *e, void *data, unsigned int datalen) +{ + struct ebt_inat_info *info = (struct ebt_inat_info *)data; + + if (datalen != sizeof(struct ebt_inat_info)) + return -EINVAL; + if (BASE_CHAIN && info->target == EBT_RETURN) + return -EINVAL; + CLEAR_BASE_CHAIN_BIT; + if (strcmp(tablename, "nat")) + return -EINVAL; + if (hookmask & ~(1 << NF_BR_POST_ROUTING)) + return -EINVAL; + if (INVALID_TARGET) + return -EINVAL; + return 0; +} + +static struct ebt_target isnat = +{ + {NULL, NULL}, EBT_ISNAT_TARGET, ebt_target_isnat, ebt_target_isnat_check, + NULL, THIS_MODULE +}; + +static int __init init(void) +{ + return ebt_register_target(&isnat); +} + +static void __exit fini(void) +{ + ebt_unregister_target(&isnat); +} + +module_init(init); +module_exit(fini); +EXPORT_NO_SYMBOLS; +MODULE_LICENSE("GPL"); |