Commit | Line | Data |
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1da177e4 LT |
1 | /* |
2 | * This is a module which is used for rejecting packets. | |
1da177e4 LT |
3 | */ |
4 | ||
5 | /* (C) 1999-2001 Paul `Rusty' Russell | |
6 | * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org> | |
7 | * | |
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. | |
11 | */ | |
12 | ||
1da177e4 LT |
13 | #include <linux/module.h> |
14 | #include <linux/skbuff.h> | |
15 | #include <linux/ip.h> | |
16 | #include <linux/udp.h> | |
17 | #include <linux/icmp.h> | |
18 | #include <net/icmp.h> | |
19 | #include <net/ip.h> | |
20 | #include <net/tcp.h> | |
21 | #include <net/route.h> | |
22 | #include <net/dst.h> | |
6709dbbb | 23 | #include <linux/netfilter/x_tables.h> |
1da177e4 LT |
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> | |
28 | #endif | |
29 | ||
30 | MODULE_LICENSE("GPL"); | |
31 | MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>"); | |
2ae15b64 | 32 | MODULE_DESCRIPTION("Xtables: packet \"rejection\" target for IPv4"); |
1da177e4 | 33 | |
1da177e4 LT |
34 | /* Send RST reply */ |
35 | static void send_reset(struct sk_buff *oldskb, int hook) | |
36 | { | |
37 | struct sk_buff *nskb; | |
3cf93c96 JE |
38 | const struct iphdr *oiph; |
39 | struct iphdr *niph; | |
40 | const struct tcphdr *oth; | |
41 | struct tcphdr _otcph, *tcph; | |
9d02002d | 42 | unsigned int addr_type; |
1da177e4 LT |
43 | |
44 | /* IP header checks: fragment. */ | |
eddc9ec5 | 45 | if (ip_hdr(oldskb)->frag_off & htons(IP_OFFSET)) |
1da177e4 LT |
46 | return; |
47 | ||
c9bdd4b5 | 48 | oth = skb_header_pointer(oldskb, ip_hdrlen(oldskb), |
1da177e4 LT |
49 | sizeof(_otcph), &_otcph); |
50 | if (oth == NULL) | |
e905a9ed | 51 | return; |
1da177e4 LT |
52 | |
53 | /* No RST for RST. */ | |
54 | if (oth->rst) | |
55 | return; | |
56 | ||
6150bacf | 57 | /* Check checksum */ |
c9bdd4b5 | 58 | if (nf_ip_checksum(oldskb, hook, ip_hdrlen(oldskb), IPPROTO_TCP)) |
6150bacf | 59 | return; |
9ba99b0d | 60 | oiph = ip_hdr(oldskb); |
6150bacf | 61 | |
9ba99b0d DV |
62 | nskb = alloc_skb(sizeof(struct iphdr) + sizeof(struct tcphdr) + |
63 | LL_MAX_HEADER, GFP_ATOMIC); | |
9d02002d | 64 | if (!nskb) |
1da177e4 | 65 | return; |
1da177e4 | 66 | |
9ba99b0d DV |
67 | skb_reserve(nskb, LL_MAX_HEADER); |
68 | ||
69 | skb_reset_network_header(nskb); | |
70 | niph = (struct iphdr *)skb_put(nskb, sizeof(struct iphdr)); | |
71 | niph->version = 4; | |
72 | niph->ihl = sizeof(struct iphdr) / 4; | |
73 | niph->tos = 0; | |
74 | niph->id = 0; | |
75 | niph->frag_off = htons(IP_DF); | |
76 | niph->protocol = IPPROTO_TCP; | |
77 | niph->check = 0; | |
78 | niph->saddr = oiph->daddr; | |
79 | niph->daddr = oiph->saddr; | |
80 | ||
81 | tcph = (struct tcphdr *)skb_put(nskb, sizeof(struct tcphdr)); | |
82 | memset(tcph, 0, sizeof(*tcph)); | |
83 | tcph->source = oth->dest; | |
84 | tcph->dest = oth->source; | |
85 | tcph->doff = sizeof(struct tcphdr) / 4; | |
86 | ||
87 | if (oth->ack) | |
1da177e4 | 88 | tcph->seq = oth->ack_seq; |
9ba99b0d | 89 | else { |
c9bdd4b5 ACM |
90 | tcph->ack_seq = htonl(ntohl(oth->seq) + oth->syn + oth->fin + |
91 | oldskb->len - ip_hdrlen(oldskb) - | |
92 | (oth->doff << 2)); | |
9ba99b0d | 93 | tcph->ack = 1; |
1da177e4 LT |
94 | } |
95 | ||
9ba99b0d DV |
96 | tcph->rst = 1; |
97 | tcph->check = tcp_v4_check(sizeof(struct tcphdr), | |
98 | niph->saddr, niph->daddr, | |
99 | csum_partial(tcph, | |
100 | sizeof(struct tcphdr), 0)); | |
9d02002d PM |
101 | |
102 | addr_type = RTN_UNSPEC; | |
6e23ae2a | 103 | if (hook != NF_INET_FORWARD |
9d02002d PM |
104 | #ifdef CONFIG_BRIDGE_NETFILTER |
105 | || (nskb->nf_bridge && nskb->nf_bridge->mask & BRNF_BRIDGED) | |
106 | #endif | |
107 | ) | |
108 | addr_type = RTN_LOCAL; | |
109 | ||
9ba99b0d DV |
110 | /* ip_route_me_harder expects skb->dst to be set */ |
111 | dst_hold(oldskb->dst); | |
112 | nskb->dst = oldskb->dst; | |
113 | ||
3db05fea | 114 | if (ip_route_me_harder(nskb, addr_type)) |
9d02002d PM |
115 | goto free_nskb; |
116 | ||
9ba99b0d | 117 | niph->ttl = dst_metric(nskb->dst, RTAX_HOPLIMIT); |
4cf411de | 118 | nskb->ip_summed = CHECKSUM_NONE; |
af443b6d | 119 | |
1da177e4 LT |
120 | /* "Never happens" */ |
121 | if (nskb->len > dst_mtu(nskb->dst)) | |
122 | goto free_nskb; | |
123 | ||
124 | nf_ct_attach(nskb, oldskb); | |
125 | ||
c439cb2e | 126 | ip_local_out(nskb); |
1da177e4 LT |
127 | return; |
128 | ||
129 | free_nskb: | |
130 | kfree_skb(nskb); | |
131 | } | |
132 | ||
133 | static inline void send_unreach(struct sk_buff *skb_in, int code) | |
134 | { | |
135 | icmp_send(skb_in, ICMP_DEST_UNREACH, code, 0); | |
e905a9ed | 136 | } |
1da177e4 | 137 | |
d3c5ee6d JE |
138 | static unsigned int |
139 | reject_tg(struct sk_buff *skb, const struct net_device *in, | |
140 | const struct net_device *out, unsigned int hooknum, | |
141 | const struct xt_target *target, const void *targinfo) | |
1da177e4 LT |
142 | { |
143 | const struct ipt_reject_info *reject = targinfo; | |
144 | ||
1da177e4 LT |
145 | /* WARNING: This code causes reentry within iptables. |
146 | This means that the iptables jump stack is now crap. We | |
147 | must return an absolute verdict. --RR */ | |
e905a9ed YH |
148 | switch (reject->with) { |
149 | case IPT_ICMP_NET_UNREACHABLE: | |
3db05fea | 150 | send_unreach(skb, ICMP_NET_UNREACH); |
e905a9ed YH |
151 | break; |
152 | case IPT_ICMP_HOST_UNREACHABLE: | |
3db05fea | 153 | send_unreach(skb, ICMP_HOST_UNREACH); |
e905a9ed YH |
154 | break; |
155 | case IPT_ICMP_PROT_UNREACHABLE: | |
3db05fea | 156 | send_unreach(skb, ICMP_PROT_UNREACH); |
e905a9ed YH |
157 | break; |
158 | case IPT_ICMP_PORT_UNREACHABLE: | |
3db05fea | 159 | send_unreach(skb, ICMP_PORT_UNREACH); |
e905a9ed YH |
160 | break; |
161 | case IPT_ICMP_NET_PROHIBITED: | |
3db05fea | 162 | send_unreach(skb, ICMP_NET_ANO); |
e905a9ed | 163 | break; |
1da177e4 | 164 | case IPT_ICMP_HOST_PROHIBITED: |
3db05fea | 165 | send_unreach(skb, ICMP_HOST_ANO); |
e905a9ed YH |
166 | break; |
167 | case IPT_ICMP_ADMIN_PROHIBITED: | |
3db05fea | 168 | send_unreach(skb, ICMP_PKT_FILTERED); |
1da177e4 LT |
169 | break; |
170 | case IPT_TCP_RESET: | |
3db05fea | 171 | send_reset(skb, hooknum); |
1da177e4 LT |
172 | case IPT_ICMP_ECHOREPLY: |
173 | /* Doesn't happen. */ | |
174 | break; | |
175 | } | |
176 | ||
177 | return NF_DROP; | |
178 | } | |
179 | ||
d3c5ee6d JE |
180 | static bool |
181 | reject_tg_check(const char *tablename, const void *e_void, | |
182 | const struct xt_target *target, void *targinfo, | |
183 | unsigned int hook_mask) | |
1da177e4 | 184 | { |
e905a9ed | 185 | const struct ipt_reject_info *rejinfo = targinfo; |
2e4e6a17 | 186 | const struct ipt_entry *e = e_void; |
1da177e4 | 187 | |
1da177e4 | 188 | if (rejinfo->with == IPT_ICMP_ECHOREPLY) { |
0d53778e | 189 | printk("ipt_REJECT: ECHOREPLY no longer supported.\n"); |
e1931b78 | 190 | return false; |
1da177e4 LT |
191 | } else if (rejinfo->with == IPT_TCP_RESET) { |
192 | /* Must specify that it's a TCP packet */ | |
193 | if (e->ip.proto != IPPROTO_TCP | |
6709dbbb | 194 | || (e->ip.invflags & XT_INV_PROTO)) { |
0d53778e | 195 | printk("ipt_REJECT: TCP_RESET invalid for non-tcp\n"); |
e1931b78 | 196 | return false; |
1da177e4 LT |
197 | } |
198 | } | |
e1931b78 | 199 | return true; |
1da177e4 LT |
200 | } |
201 | ||
d3c5ee6d | 202 | static struct xt_target reject_tg_reg __read_mostly = { |
1da177e4 | 203 | .name = "REJECT", |
6709dbbb | 204 | .family = AF_INET, |
d3c5ee6d | 205 | .target = reject_tg, |
1d5cd909 PM |
206 | .targetsize = sizeof(struct ipt_reject_info), |
207 | .table = "filter", | |
6e23ae2a PM |
208 | .hooks = (1 << NF_INET_LOCAL_IN) | (1 << NF_INET_FORWARD) | |
209 | (1 << NF_INET_LOCAL_OUT), | |
d3c5ee6d | 210 | .checkentry = reject_tg_check, |
1da177e4 LT |
211 | .me = THIS_MODULE, |
212 | }; | |
213 | ||
d3c5ee6d | 214 | static int __init reject_tg_init(void) |
1da177e4 | 215 | { |
d3c5ee6d | 216 | return xt_register_target(&reject_tg_reg); |
1da177e4 LT |
217 | } |
218 | ||
d3c5ee6d | 219 | static void __exit reject_tg_exit(void) |
1da177e4 | 220 | { |
d3c5ee6d | 221 | xt_unregister_target(&reject_tg_reg); |
1da177e4 LT |
222 | } |
223 | ||
d3c5ee6d JE |
224 | module_init(reject_tg_init); |
225 | module_exit(reject_tg_exit); |