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/*
* This is a module which is used for rejecting packets.
*/
/* (C) 1999-2001 Paul `Rusty' Russell
* (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
*
* 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/udp.h>
#include <linux/icmp.h>
#include <net/icmp.h>
#include <net/ip.h>
#include <net/tcp.h>
#include <net/route.h>
#include <net/dst.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter_ipv4/ip_tables.h>
#include <linux/netfilter_ipv4/ipt_REJECT.h>
#ifdef CONFIG_BRIDGE_NETFILTER
#include <linux/netfilter_bridge.h>
#endif
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
MODULE_DESCRIPTION("Xtables: packet \"rejection\" target for IPv4");
/* Send RST reply */
static void send_reset(struct sk_buff *oldskb, int hook)
{
struct sk_buff *nskb;
const struct iphdr *oiph;
struct iphdr *niph;
const struct tcphdr *oth;
struct tcphdr _otcph, *tcph;
unsigned int addr_type;
/* IP header checks: fragment. */
if (ip_hdr(oldskb)->frag_off & htons(IP_OFFSET))
return;
oth = skb_header_pointer(oldskb, ip_hdrlen(oldskb),
sizeof(_otcph), &_otcph);
if (oth == NULL)
return;
/* No RST for RST. */
if (oth->rst)
return;
/* Check checksum */
if (nf_ip_checksum(oldskb, hook, ip_hdrlen(oldskb), IPPROTO_TCP))
return;
oiph = ip_hdr(oldskb);
nskb = alloc_skb(sizeof(struct iphdr) + sizeof(struct tcphdr) +
LL_MAX_HEADER, GFP_ATOMIC);
if (!nskb)
return;
skb_reserve(nskb, LL_MAX_HEADER);
skb_reset_network_header(nskb);
niph = (struct iphdr *)skb_put(nskb, sizeof(struct iphdr));
niph->version = 4;
niph->ihl = sizeof(struct iphdr) / 4;
niph->tos = 0;
niph->id = 0;
niph->frag_off = htons(IP_DF);
niph->protocol = IPPROTO_TCP;
niph->check = 0;
niph->saddr = oiph->daddr;
niph->daddr = oiph->saddr;
tcph = (struct tcphdr *)skb_put(nskb, sizeof(struct tcphdr));
memset(tcph, 0, sizeof(*tcph));
tcph->source = oth->dest;
tcph->dest = oth->source;
tcph->doff = sizeof(struct tcphdr) / 4;
if (oth->ack)
tcph->seq = oth->ack_seq;
else {
tcph->ack_seq = htonl(ntohl(oth->seq) + oth->syn + oth->fin +
oldskb->len - ip_hdrlen(oldskb) -
(oth->doff << 2));
tcph->ack = 1;
}
tcph->rst = 1;
tcph->check = tcp_v4_check(sizeof(struct tcphdr),
niph->saddr, niph->daddr,
csum_partial(tcph,
sizeof(struct tcphdr), 0));
addr_type = RTN_UNSPEC;
if (hook != NF_INET_FORWARD
#ifdef CONFIG_BRIDGE_NETFILTER
|| (nskb->nf_bridge && nskb->nf_bridge->mask & BRNF_BRIDGED)
#endif
)
addr_type = RTN_LOCAL;
/* ip_route_me_harder expects skb->dst to be set */
skb_dst_set(nskb, dst_clone(skb_dst(oldskb)));
if (ip_route_me_harder(nskb, addr_type))
goto free_nskb;
niph->ttl = dst_metric(skb_dst(nskb), RTAX_HOPLIMIT);
nskb->ip_summed = CHECKSUM_NONE;
/* "Never happens" */
if (nskb->len > dst_mtu(skb_dst(nskb)))
goto free_nskb;
nf_ct_attach(nskb, oldskb);
ip_local_out(nskb);
return;
free_nskb:
kfree_skb(nskb);
}
static inline void send_unreach(struct sk_buff *skb_in, int code)
{
icmp_send(skb_in, ICMP_DEST_UNREACH, code, 0);
}
static unsigned int
reject_tg(struct sk_buff *skb, const struct xt_target_param *par)
{
const struct ipt_reject_info *reject = par->targinfo;
/* WARNING: This code causes reentry within iptables.
This means that the iptables jump stack is now crap. We
must return an absolute verdict. --RR */
switch (reject->with) {
case IPT_ICMP_NET_UNREACHABLE:
send_unreach(skb, ICMP_NET_UNREACH);
break;
case IPT_ICMP_HOST_UNREACHABLE:
send_unreach(skb, ICMP_HOST_UNREACH);
break;
case IPT_ICMP_PROT_UNREACHABLE:
send_unreach(skb, ICMP_PROT_UNREACH);
break;
case IPT_ICMP_PORT_UNREACHABLE:
send_unreach(skb, ICMP_PORT_UNREACH);
break;
case IPT_ICMP_NET_PROHIBITED:
send_unreach(skb, ICMP_NET_ANO);
break;
case IPT_ICMP_HOST_PROHIBITED:
send_unreach(skb, ICMP_HOST_ANO);
break;
case IPT_ICMP_ADMIN_PROHIBITED:
send_unreach(skb, ICMP_PKT_FILTERED);
break;
case IPT_TCP_RESET:
send_reset(skb, par->hooknum);
case IPT_ICMP_ECHOREPLY:
/* Doesn't happen. */
break;
}
return NF_DROP;
}
static bool reject_tg_check(const struct xt_tgchk_param *par)
{
const struct ipt_reject_info *rejinfo = par->targinfo;
const struct ipt_entry *e = par->entryinfo;
if (rejinfo->with == IPT_ICMP_ECHOREPLY) {
printk("ipt_REJECT: ECHOREPLY no longer supported.\n");
return false;
} else if (rejinfo->with == IPT_TCP_RESET) {
/* Must specify that it's a TCP packet */
if (e->ip.proto != IPPROTO_TCP ||
(e->ip.invflags & XT_INV_PROTO)) {
printk("ipt_REJECT: TCP_RESET invalid for non-tcp\n");
return false;
}
}
return true;
}
static struct xt_target reject_tg_reg __read_mostly = {
.name = "REJECT",
.family = NFPROTO_IPV4,
.target = reject_tg,
.targetsize = sizeof(struct ipt_reject_info),
.table = "filter",
.hooks = (1 << NF_INET_LOCAL_IN) | (1 << NF_INET_FORWARD) |
(1 << NF_INET_LOCAL_OUT),
.checkentry = reject_tg_check,
.me = THIS_MODULE,
};
static int __init reject_tg_init(void)
{
return xt_register_target(&reject_tg_reg);
}
static void __exit reject_tg_exit(void)
{
xt_unregister_target(&reject_tg_reg);
}
module_init(reject_tg_init);
module_exit(reject_tg_exit);
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