Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1 | /* |
| 2 | * This is a module which is used for rejecting packets. |
| 3 | * Added support for customized reject packets (Jozsef Kadlecsik). |
| 4 | * Added support for ICMP type-3-code-13 (Maciej Soltysiak). [RFC 1812] |
| 5 | */ |
| 6 | |
| 7 | /* (C) 1999-2001 Paul `Rusty' Russell |
| 8 | * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org> |
| 9 | * |
| 10 | * This program is free software; you can redistribute it and/or modify |
| 11 | * it under the terms of the GNU General Public License version 2 as |
| 12 | * published by the Free Software Foundation. |
| 13 | */ |
| 14 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 15 | #include <linux/module.h> |
| 16 | #include <linux/skbuff.h> |
| 17 | #include <linux/ip.h> |
| 18 | #include <linux/udp.h> |
| 19 | #include <linux/icmp.h> |
| 20 | #include <net/icmp.h> |
| 21 | #include <net/ip.h> |
| 22 | #include <net/tcp.h> |
| 23 | #include <net/route.h> |
| 24 | #include <net/dst.h> |
| 25 | #include <linux/netfilter_ipv4/ip_tables.h> |
| 26 | #include <linux/netfilter_ipv4/ipt_REJECT.h> |
| 27 | #ifdef CONFIG_BRIDGE_NETFILTER |
| 28 | #include <linux/netfilter_bridge.h> |
| 29 | #endif |
| 30 | |
| 31 | MODULE_LICENSE("GPL"); |
| 32 | MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>"); |
| 33 | MODULE_DESCRIPTION("iptables REJECT target module"); |
| 34 | |
| 35 | #if 0 |
| 36 | #define DEBUGP printk |
| 37 | #else |
| 38 | #define DEBUGP(format, args...) |
| 39 | #endif |
| 40 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 41 | /* Send RST reply */ |
| 42 | static void send_reset(struct sk_buff *oldskb, int hook) |
| 43 | { |
| 44 | struct sk_buff *nskb; |
Patrick McHardy | 6150bac | 2005-06-21 14:03:46 -0700 | [diff] [blame] | 45 | struct iphdr *iph = oldskb->nh.iph; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 46 | struct tcphdr _otcph, *oth, *tcph; |
Al Viro | 6a19d61 | 2006-09-28 14:22:24 -0700 | [diff] [blame] | 47 | __be16 tmp_port; |
| 48 | __be32 tmp_addr; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 49 | int needs_ack; |
Patrick McHardy | 9d02002 | 2006-10-02 16:12:20 -0700 | [diff] [blame^] | 50 | unsigned int addr_type; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 51 | |
| 52 | /* IP header checks: fragment. */ |
| 53 | if (oldskb->nh.iph->frag_off & htons(IP_OFFSET)) |
| 54 | return; |
| 55 | |
| 56 | oth = skb_header_pointer(oldskb, oldskb->nh.iph->ihl * 4, |
| 57 | sizeof(_otcph), &_otcph); |
| 58 | if (oth == NULL) |
| 59 | return; |
| 60 | |
| 61 | /* No RST for RST. */ |
| 62 | if (oth->rst) |
| 63 | return; |
| 64 | |
Patrick McHardy | 6150bac | 2005-06-21 14:03:46 -0700 | [diff] [blame] | 65 | /* Check checksum */ |
Patrick McHardy | 96f6bf8 | 2006-04-06 14:19:24 -0700 | [diff] [blame] | 66 | if (nf_ip_checksum(oldskb, hook, iph->ihl * 4, IPPROTO_TCP)) |
Patrick McHardy | 6150bac | 2005-06-21 14:03:46 -0700 | [diff] [blame] | 67 | return; |
| 68 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 69 | /* We need a linear, writeable skb. We also need to expand |
| 70 | headroom in case hh_len of incoming interface < hh_len of |
| 71 | outgoing interface */ |
Patrick McHardy | 9d02002 | 2006-10-02 16:12:20 -0700 | [diff] [blame^] | 72 | nskb = skb_copy_expand(oldskb, LL_MAX_HEADER, skb_tailroom(oldskb), |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 73 | GFP_ATOMIC); |
Patrick McHardy | 9d02002 | 2006-10-02 16:12:20 -0700 | [diff] [blame^] | 74 | if (!nskb) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 75 | return; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 76 | |
| 77 | /* This packet will not be the same as the other: clear nf fields */ |
| 78 | nf_reset(nskb); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 79 | nskb->nfmark = 0; |
James Morris | 984bc16 | 2006-06-09 00:29:17 -0700 | [diff] [blame] | 80 | skb_init_secmark(nskb); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 81 | |
| 82 | tcph = (struct tcphdr *)((u_int32_t*)nskb->nh.iph + nskb->nh.iph->ihl); |
| 83 | |
| 84 | /* Swap source and dest */ |
| 85 | tmp_addr = nskb->nh.iph->saddr; |
| 86 | nskb->nh.iph->saddr = nskb->nh.iph->daddr; |
| 87 | nskb->nh.iph->daddr = tmp_addr; |
| 88 | tmp_port = tcph->source; |
| 89 | tcph->source = tcph->dest; |
| 90 | tcph->dest = tmp_port; |
| 91 | |
| 92 | /* Truncate to length (no data) */ |
| 93 | tcph->doff = sizeof(struct tcphdr)/4; |
| 94 | skb_trim(nskb, nskb->nh.iph->ihl*4 + sizeof(struct tcphdr)); |
| 95 | nskb->nh.iph->tot_len = htons(nskb->len); |
| 96 | |
| 97 | if (tcph->ack) { |
| 98 | needs_ack = 0; |
| 99 | tcph->seq = oth->ack_seq; |
| 100 | tcph->ack_seq = 0; |
| 101 | } else { |
| 102 | needs_ack = 1; |
| 103 | tcph->ack_seq = htonl(ntohl(oth->seq) + oth->syn + oth->fin |
| 104 | + oldskb->len - oldskb->nh.iph->ihl*4 |
| 105 | - (oth->doff<<2)); |
| 106 | tcph->seq = 0; |
| 107 | } |
| 108 | |
| 109 | /* Reset flags */ |
| 110 | ((u_int8_t *)tcph)[13] = 0; |
| 111 | tcph->rst = 1; |
| 112 | tcph->ack = needs_ack; |
| 113 | |
| 114 | tcph->window = 0; |
| 115 | tcph->urg_ptr = 0; |
| 116 | |
Patrick McHardy | 9d02002 | 2006-10-02 16:12:20 -0700 | [diff] [blame^] | 117 | /* Set DF, id = 0 */ |
| 118 | nskb->nh.iph->frag_off = htons(IP_DF); |
| 119 | nskb->nh.iph->id = 0; |
| 120 | |
| 121 | addr_type = RTN_UNSPEC; |
| 122 | if (hook != NF_IP_FORWARD |
| 123 | #ifdef CONFIG_BRIDGE_NETFILTER |
| 124 | || (nskb->nf_bridge && nskb->nf_bridge->mask & BRNF_BRIDGED) |
| 125 | #endif |
| 126 | ) |
| 127 | addr_type = RTN_LOCAL; |
| 128 | |
| 129 | if (ip_route_me_harder(&nskb, addr_type)) |
| 130 | goto free_nskb; |
| 131 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 132 | /* Adjust TCP checksum */ |
Patrick McHardy | 4cf411d | 2006-08-05 00:58:33 -0700 | [diff] [blame] | 133 | nskb->ip_summed = CHECKSUM_NONE; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 134 | tcph->check = 0; |
| 135 | tcph->check = tcp_v4_check(tcph, sizeof(struct tcphdr), |
| 136 | nskb->nh.iph->saddr, |
| 137 | nskb->nh.iph->daddr, |
| 138 | csum_partial((char *)tcph, |
| 139 | sizeof(struct tcphdr), 0)); |
Patrick McHardy | 9d02002 | 2006-10-02 16:12:20 -0700 | [diff] [blame^] | 140 | /* Adjust IP TTL */ |
Yasuyuki Kozakai | e8eaedf | 2006-01-05 12:28:57 -0800 | [diff] [blame] | 141 | nskb->nh.iph->ttl = dst_metric(nskb->dst, RTAX_HOPLIMIT); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 142 | |
| 143 | /* Adjust IP checksum */ |
| 144 | nskb->nh.iph->check = 0; |
| 145 | nskb->nh.iph->check = ip_fast_csum((unsigned char *)nskb->nh.iph, |
| 146 | nskb->nh.iph->ihl); |
| 147 | |
| 148 | /* "Never happens" */ |
| 149 | if (nskb->len > dst_mtu(nskb->dst)) |
| 150 | goto free_nskb; |
| 151 | |
| 152 | nf_ct_attach(nskb, oldskb); |
| 153 | |
| 154 | NF_HOOK(PF_INET, NF_IP_LOCAL_OUT, nskb, NULL, nskb->dst->dev, |
| 155 | dst_output); |
| 156 | return; |
| 157 | |
| 158 | free_nskb: |
| 159 | kfree_skb(nskb); |
| 160 | } |
| 161 | |
| 162 | static inline void send_unreach(struct sk_buff *skb_in, int code) |
| 163 | { |
| 164 | icmp_send(skb_in, ICMP_DEST_UNREACH, code, 0); |
| 165 | } |
| 166 | |
| 167 | static unsigned int reject(struct sk_buff **pskb, |
| 168 | const struct net_device *in, |
| 169 | const struct net_device *out, |
| 170 | unsigned int hooknum, |
Patrick McHardy | c498673 | 2006-03-20 18:02:56 -0800 | [diff] [blame] | 171 | const struct xt_target *target, |
Patrick McHardy | fe1cb10 | 2006-08-22 00:35:47 -0700 | [diff] [blame] | 172 | const void *targinfo) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 173 | { |
| 174 | const struct ipt_reject_info *reject = targinfo; |
| 175 | |
| 176 | /* Our naive response construction doesn't deal with IP |
| 177 | options, and probably shouldn't try. */ |
| 178 | if ((*pskb)->nh.iph->ihl<<2 != sizeof(struct iphdr)) |
| 179 | return NF_DROP; |
| 180 | |
| 181 | /* WARNING: This code causes reentry within iptables. |
| 182 | This means that the iptables jump stack is now crap. We |
| 183 | must return an absolute verdict. --RR */ |
| 184 | switch (reject->with) { |
| 185 | case IPT_ICMP_NET_UNREACHABLE: |
| 186 | send_unreach(*pskb, ICMP_NET_UNREACH); |
| 187 | break; |
| 188 | case IPT_ICMP_HOST_UNREACHABLE: |
| 189 | send_unreach(*pskb, ICMP_HOST_UNREACH); |
| 190 | break; |
| 191 | case IPT_ICMP_PROT_UNREACHABLE: |
| 192 | send_unreach(*pskb, ICMP_PROT_UNREACH); |
| 193 | break; |
| 194 | case IPT_ICMP_PORT_UNREACHABLE: |
| 195 | send_unreach(*pskb, ICMP_PORT_UNREACH); |
| 196 | break; |
| 197 | case IPT_ICMP_NET_PROHIBITED: |
| 198 | send_unreach(*pskb, ICMP_NET_ANO); |
| 199 | break; |
| 200 | case IPT_ICMP_HOST_PROHIBITED: |
| 201 | send_unreach(*pskb, ICMP_HOST_ANO); |
| 202 | break; |
| 203 | case IPT_ICMP_ADMIN_PROHIBITED: |
| 204 | send_unreach(*pskb, ICMP_PKT_FILTERED); |
| 205 | break; |
| 206 | case IPT_TCP_RESET: |
| 207 | send_reset(*pskb, hooknum); |
| 208 | case IPT_ICMP_ECHOREPLY: |
| 209 | /* Doesn't happen. */ |
| 210 | break; |
| 211 | } |
| 212 | |
| 213 | return NF_DROP; |
| 214 | } |
| 215 | |
| 216 | static int check(const char *tablename, |
Harald Welte | 2e4e6a1 | 2006-01-12 13:30:04 -0800 | [diff] [blame] | 217 | const void *e_void, |
Patrick McHardy | c498673 | 2006-03-20 18:02:56 -0800 | [diff] [blame] | 218 | const struct xt_target *target, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 219 | void *targinfo, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 220 | unsigned int hook_mask) |
| 221 | { |
| 222 | const struct ipt_reject_info *rejinfo = targinfo; |
Harald Welte | 2e4e6a1 | 2006-01-12 13:30:04 -0800 | [diff] [blame] | 223 | const struct ipt_entry *e = e_void; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 224 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 225 | if (rejinfo->with == IPT_ICMP_ECHOREPLY) { |
| 226 | printk("REJECT: ECHOREPLY no longer supported.\n"); |
| 227 | return 0; |
| 228 | } else if (rejinfo->with == IPT_TCP_RESET) { |
| 229 | /* Must specify that it's a TCP packet */ |
| 230 | if (e->ip.proto != IPPROTO_TCP |
| 231 | || (e->ip.invflags & IPT_INV_PROTO)) { |
| 232 | DEBUGP("REJECT: TCP_RESET invalid for non-tcp\n"); |
| 233 | return 0; |
| 234 | } |
| 235 | } |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 236 | return 1; |
| 237 | } |
| 238 | |
| 239 | static struct ipt_target ipt_reject_reg = { |
| 240 | .name = "REJECT", |
| 241 | .target = reject, |
Patrick McHardy | 1d5cd90 | 2006-03-20 18:01:14 -0800 | [diff] [blame] | 242 | .targetsize = sizeof(struct ipt_reject_info), |
| 243 | .table = "filter", |
| 244 | .hooks = (1 << NF_IP_LOCAL_IN) | (1 << NF_IP_FORWARD) | |
| 245 | (1 << NF_IP_LOCAL_OUT), |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 246 | .checkentry = check, |
| 247 | .me = THIS_MODULE, |
| 248 | }; |
| 249 | |
Andrew Morton | 65b4b4e | 2006-03-28 16:37:06 -0800 | [diff] [blame] | 250 | static int __init ipt_reject_init(void) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 251 | { |
| 252 | return ipt_register_target(&ipt_reject_reg); |
| 253 | } |
| 254 | |
Andrew Morton | 65b4b4e | 2006-03-28 16:37:06 -0800 | [diff] [blame] | 255 | static void __exit ipt_reject_fini(void) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 256 | { |
| 257 | ipt_unregister_target(&ipt_reject_reg); |
| 258 | } |
| 259 | |
Andrew Morton | 65b4b4e | 2006-03-28 16:37:06 -0800 | [diff] [blame] | 260 | module_init(ipt_reject_init); |
| 261 | module_exit(ipt_reject_fini); |