2 * This is a module which is used for rejecting packets.
5 /* (C) 1999-2001 Paul `Rusty' Russell
6 * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License version 2 as
10 * published by the Free Software Foundation.
13 #include <linux/module.h>
14 #include <linux/skbuff.h>
16 #include <linux/udp.h>
17 #include <linux/icmp.h>
21 #include <net/route.h>
23 #include <linux/netfilter/x_tables.h>
24 #include <linux/netfilter_ipv4/ip_tables.h>
25 #include <linux/netfilter_ipv4/ipt_REJECT.h>
26 #ifdef CONFIG_BRIDGE_NETFILTER
27 #include <linux/netfilter_bridge.h>
30 MODULE_LICENSE("GPL");
31 MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
32 MODULE_DESCRIPTION("Xtables: packet \"rejection\" target for IPv4");
35 static void send_reset(struct sk_buff *oldskb, int hook)
38 struct iphdr *oiph, *niph;
39 struct tcphdr _otcph, *oth, *tcph;
40 unsigned int addr_type;
42 /* IP header checks: fragment. */
43 if (ip_hdr(oldskb)->frag_off & htons(IP_OFFSET))
46 oth = skb_header_pointer(oldskb, ip_hdrlen(oldskb),
47 sizeof(_otcph), &_otcph);
56 if (nf_ip_checksum(oldskb, hook, ip_hdrlen(oldskb), IPPROTO_TCP))
58 oiph = ip_hdr(oldskb);
60 nskb = alloc_skb(sizeof(struct iphdr) + sizeof(struct tcphdr) +
61 LL_MAX_HEADER, GFP_ATOMIC);
65 skb_reserve(nskb, LL_MAX_HEADER);
67 skb_reset_network_header(nskb);
68 niph = (struct iphdr *)skb_put(nskb, sizeof(struct iphdr));
70 niph->ihl = sizeof(struct iphdr) / 4;
73 niph->frag_off = htons(IP_DF);
74 niph->protocol = IPPROTO_TCP;
76 niph->saddr = oiph->daddr;
77 niph->daddr = oiph->saddr;
79 tcph = (struct tcphdr *)skb_put(nskb, sizeof(struct tcphdr));
80 memset(tcph, 0, sizeof(*tcph));
81 tcph->source = oth->dest;
82 tcph->dest = oth->source;
83 tcph->doff = sizeof(struct tcphdr) / 4;
86 tcph->seq = oth->ack_seq;
88 tcph->ack_seq = htonl(ntohl(oth->seq) + oth->syn + oth->fin +
89 oldskb->len - ip_hdrlen(oldskb) -
95 tcph->check = tcp_v4_check(sizeof(struct tcphdr),
96 niph->saddr, niph->daddr,
98 sizeof(struct tcphdr), 0));
100 addr_type = RTN_UNSPEC;
101 if (hook != NF_INET_FORWARD
102 #ifdef CONFIG_BRIDGE_NETFILTER
103 || (nskb->nf_bridge && nskb->nf_bridge->mask & BRNF_BRIDGED)
106 addr_type = RTN_LOCAL;
108 /* ip_route_me_harder expects skb->dst to be set */
109 dst_hold(oldskb->dst);
110 nskb->dst = oldskb->dst;
112 if (ip_route_me_harder(nskb, addr_type))
115 niph->ttl = dst_metric(nskb->dst, RTAX_HOPLIMIT);
116 nskb->ip_summed = CHECKSUM_NONE;
118 /* "Never happens" */
119 if (nskb->len > dst_mtu(nskb->dst))
122 nf_ct_attach(nskb, oldskb);
131 static inline void send_unreach(struct sk_buff *skb_in, int code)
133 icmp_send(skb_in, ICMP_DEST_UNREACH, code, 0);
137 reject_tg(struct sk_buff *skb, const struct net_device *in,
138 const struct net_device *out, unsigned int hooknum,
139 const struct xt_target *target, const void *targinfo)
141 const struct ipt_reject_info *reject = targinfo;
143 /* WARNING: This code causes reentry within iptables.
144 This means that the iptables jump stack is now crap. We
145 must return an absolute verdict. --RR */
146 switch (reject->with) {
147 case IPT_ICMP_NET_UNREACHABLE:
148 send_unreach(skb, ICMP_NET_UNREACH);
150 case IPT_ICMP_HOST_UNREACHABLE:
151 send_unreach(skb, ICMP_HOST_UNREACH);
153 case IPT_ICMP_PROT_UNREACHABLE:
154 send_unreach(skb, ICMP_PROT_UNREACH);
156 case IPT_ICMP_PORT_UNREACHABLE:
157 send_unreach(skb, ICMP_PORT_UNREACH);
159 case IPT_ICMP_NET_PROHIBITED:
160 send_unreach(skb, ICMP_NET_ANO);
162 case IPT_ICMP_HOST_PROHIBITED:
163 send_unreach(skb, ICMP_HOST_ANO);
165 case IPT_ICMP_ADMIN_PROHIBITED:
166 send_unreach(skb, ICMP_PKT_FILTERED);
169 send_reset(skb, hooknum);
170 case IPT_ICMP_ECHOREPLY:
171 /* Doesn't happen. */
179 reject_tg_check(const char *tablename, const void *e_void,
180 const struct xt_target *target, void *targinfo,
181 unsigned int hook_mask)
183 const struct ipt_reject_info *rejinfo = targinfo;
184 const struct ipt_entry *e = e_void;
186 if (rejinfo->with == IPT_ICMP_ECHOREPLY) {
187 printk("ipt_REJECT: ECHOREPLY no longer supported.\n");
189 } else if (rejinfo->with == IPT_TCP_RESET) {
190 /* Must specify that it's a TCP packet */
191 if (e->ip.proto != IPPROTO_TCP
192 || (e->ip.invflags & XT_INV_PROTO)) {
193 printk("ipt_REJECT: TCP_RESET invalid for non-tcp\n");
200 static struct xt_target reject_tg_reg __read_mostly = {
204 .targetsize = sizeof(struct ipt_reject_info),
206 .hooks = (1 << NF_INET_LOCAL_IN) | (1 << NF_INET_FORWARD) |
207 (1 << NF_INET_LOCAL_OUT),
208 .checkentry = reject_tg_check,
212 static int __init reject_tg_init(void)
214 return xt_register_target(&reject_tg_reg);
217 static void __exit reject_tg_exit(void)
219 xt_unregister_target(&reject_tg_reg);
222 module_init(reject_tg_init);
223 module_exit(reject_tg_exit);