1 /* 2 * IP6 tables REJECT target module 3 * Linux INET6 implementation 4 * 5 * Copyright (C)2003 USAGI/WIDE Project 6 * 7 * Authors: 8 * Yasuyuki Kozakai <yasuyuki.kozakai@toshiba.co.jp> 9 * 10 * Based on net/ipv4/netfilter/ipt_REJECT.c 11 * 12 * This program is free software; you can redistribute it and/or 13 * modify it under the terms of the GNU General Public License 14 * as published by the Free Software Foundation; either version 15 * 2 of the License, or (at your option) any later version. 16 */ 17 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 18 19 #include <linux/gfp.h> 20 #include <linux/module.h> 21 #include <linux/skbuff.h> 22 #include <linux/icmpv6.h> 23 #include <linux/netdevice.h> 24 #include <net/ipv6.h> 25 #include <net/tcp.h> 26 #include <net/icmp.h> 27 #include <net/ip6_checksum.h> 28 #include <net/ip6_fib.h> 29 #include <net/ip6_route.h> 30 #include <net/flow.h> 31 #include <linux/netfilter/x_tables.h> 32 #include <linux/netfilter_ipv6/ip6_tables.h> 33 #include <linux/netfilter_ipv6/ip6t_REJECT.h> 34 35 MODULE_AUTHOR("Yasuyuki KOZAKAI <yasuyuki.kozakai@toshiba.co.jp>"); 36 MODULE_DESCRIPTION("Xtables: packet \"rejection\" target for IPv6"); 37 MODULE_LICENSE("GPL"); 38 39 /* Send RST reply */ 40 static void send_reset(struct net *net, struct sk_buff *oldskb) 41 { 42 struct sk_buff *nskb; 43 struct tcphdr otcph, *tcph; 44 unsigned int otcplen, hh_len; 45 int tcphoff, needs_ack; 46 const struct ipv6hdr *oip6h = ipv6_hdr(oldskb); 47 struct ipv6hdr *ip6h; 48 struct dst_entry *dst = NULL; 49 u8 proto; 50 struct flowi6 fl6; 51 52 if ((!(ipv6_addr_type(&oip6h->saddr) & IPV6_ADDR_UNICAST)) || 53 (!(ipv6_addr_type(&oip6h->daddr) & IPV6_ADDR_UNICAST))) { 54 pr_debug("addr is not unicast.\n"); 55 return; 56 } 57 58 proto = oip6h->nexthdr; 59 tcphoff = ipv6_skip_exthdr(oldskb, ((u8*)(oip6h+1) - oldskb->data), &proto); 60 61 if ((tcphoff < 0) || (tcphoff > oldskb->len)) { 62 pr_debug("Cannot get TCP header.\n"); 63 return; 64 } 65 66 otcplen = oldskb->len - tcphoff; 67 68 /* IP header checks: fragment, too short. */ 69 if (proto != IPPROTO_TCP || otcplen < sizeof(struct tcphdr)) { 70 pr_debug("proto(%d) != IPPROTO_TCP, " 71 "or too short. otcplen = %d\n", 72 proto, otcplen); 73 return; 74 } 75 76 if (skb_copy_bits(oldskb, tcphoff, &otcph, sizeof(struct tcphdr))) 77 BUG(); 78 79 /* No RST for RST. */ 80 if (otcph.rst) { 81 pr_debug("RST is set\n"); 82 return; 83 } 84 85 /* Check checksum. */ 86 if (csum_ipv6_magic(&oip6h->saddr, &oip6h->daddr, otcplen, IPPROTO_TCP, 87 skb_checksum(oldskb, tcphoff, otcplen, 0))) { 88 pr_debug("TCP checksum is invalid\n"); 89 return; 90 } 91 92 memset(&fl6, 0, sizeof(fl6)); 93 fl6.flowi6_proto = IPPROTO_TCP; 94 ipv6_addr_copy(&fl6.saddr, &oip6h->daddr); 95 ipv6_addr_copy(&fl6.daddr, &oip6h->saddr); 96 fl6.fl6_sport = otcph.dest; 97 fl6.fl6_dport = otcph.source; 98 security_skb_classify_flow(oldskb, flowi6_to_flowi(&fl6)); 99 dst = ip6_route_output(net, NULL, &fl6); 100 if (dst == NULL || dst->error) { 101 dst_release(dst); 102 return; 103 } 104 dst = xfrm_lookup(net, dst, flowi6_to_flowi(&fl6), NULL, 0); 105 if (IS_ERR(dst)) 106 return; 107 108 hh_len = (dst->dev->hard_header_len + 15)&~15; 109 nskb = alloc_skb(hh_len + 15 + dst->header_len + sizeof(struct ipv6hdr) 110 + sizeof(struct tcphdr) + dst->trailer_len, 111 GFP_ATOMIC); 112 113 if (!nskb) { 114 if (net_ratelimit()) 115 pr_debug("cannot alloc skb\n"); 116 dst_release(dst); 117 return; 118 } 119 120 skb_dst_set(nskb, dst); 121 122 skb_reserve(nskb, hh_len + dst->header_len); 123 124 skb_put(nskb, sizeof(struct ipv6hdr)); 125 skb_reset_network_header(nskb); 126 ip6h = ipv6_hdr(nskb); 127 ip6h->version = 6; 128 ip6h->hop_limit = ip6_dst_hoplimit(dst); 129 ip6h->nexthdr = IPPROTO_TCP; 130 ipv6_addr_copy(&ip6h->saddr, &oip6h->daddr); 131 ipv6_addr_copy(&ip6h->daddr, &oip6h->saddr); 132 133 tcph = (struct tcphdr *)skb_put(nskb, sizeof(struct tcphdr)); 134 /* Truncate to length (no data) */ 135 tcph->doff = sizeof(struct tcphdr)/4; 136 tcph->source = otcph.dest; 137 tcph->dest = otcph.source; 138 139 if (otcph.ack) { 140 needs_ack = 0; 141 tcph->seq = otcph.ack_seq; 142 tcph->ack_seq = 0; 143 } else { 144 needs_ack = 1; 145 tcph->ack_seq = htonl(ntohl(otcph.seq) + otcph.syn + otcph.fin 146 + otcplen - (otcph.doff<<2)); 147 tcph->seq = 0; 148 } 149 150 /* Reset flags */ 151 ((u_int8_t *)tcph)[13] = 0; 152 tcph->rst = 1; 153 tcph->ack = needs_ack; 154 tcph->window = 0; 155 tcph->urg_ptr = 0; 156 tcph->check = 0; 157 158 /* Adjust TCP checksum */ 159 tcph->check = csum_ipv6_magic(&ipv6_hdr(nskb)->saddr, 160 &ipv6_hdr(nskb)->daddr, 161 sizeof(struct tcphdr), IPPROTO_TCP, 162 csum_partial(tcph, 163 sizeof(struct tcphdr), 0)); 164 165 nf_ct_attach(nskb, oldskb); 166 167 ip6_local_out(nskb); 168 } 169 170 static inline void 171 send_unreach(struct net *net, struct sk_buff *skb_in, unsigned char code, 172 unsigned int hooknum) 173 { 174 if (hooknum == NF_INET_LOCAL_OUT && skb_in->dev == NULL) 175 skb_in->dev = net->loopback_dev; 176 177 icmpv6_send(skb_in, ICMPV6_DEST_UNREACH, code, 0); 178 } 179 180 static unsigned int 181 reject_tg6(struct sk_buff *skb, const struct xt_action_param *par) 182 { 183 const struct ip6t_reject_info *reject = par->targinfo; 184 struct net *net = dev_net((par->in != NULL) ? par->in : par->out); 185 186 pr_debug("%s: medium point\n", __func__); 187 switch (reject->with) { 188 case IP6T_ICMP6_NO_ROUTE: 189 send_unreach(net, skb, ICMPV6_NOROUTE, par->hooknum); 190 break; 191 case IP6T_ICMP6_ADM_PROHIBITED: 192 send_unreach(net, skb, ICMPV6_ADM_PROHIBITED, par->hooknum); 193 break; 194 case IP6T_ICMP6_NOT_NEIGHBOUR: 195 send_unreach(net, skb, ICMPV6_NOT_NEIGHBOUR, par->hooknum); 196 break; 197 case IP6T_ICMP6_ADDR_UNREACH: 198 send_unreach(net, skb, ICMPV6_ADDR_UNREACH, par->hooknum); 199 break; 200 case IP6T_ICMP6_PORT_UNREACH: 201 send_unreach(net, skb, ICMPV6_PORT_UNREACH, par->hooknum); 202 break; 203 case IP6T_ICMP6_ECHOREPLY: 204 /* Do nothing */ 205 break; 206 case IP6T_TCP_RESET: 207 send_reset(net, skb); 208 break; 209 default: 210 if (net_ratelimit()) 211 pr_info("case %u not handled yet\n", reject->with); 212 break; 213 } 214 215 return NF_DROP; 216 } 217 218 static int reject_tg6_check(const struct xt_tgchk_param *par) 219 { 220 const struct ip6t_reject_info *rejinfo = par->targinfo; 221 const struct ip6t_entry *e = par->entryinfo; 222 223 if (rejinfo->with == IP6T_ICMP6_ECHOREPLY) { 224 pr_info("ECHOREPLY is not supported.\n"); 225 return -EINVAL; 226 } else if (rejinfo->with == IP6T_TCP_RESET) { 227 /* Must specify that it's a TCP packet */ 228 if (e->ipv6.proto != IPPROTO_TCP || 229 (e->ipv6.invflags & XT_INV_PROTO)) { 230 pr_info("TCP_RESET illegal for non-tcp\n"); 231 return -EINVAL; 232 } 233 } 234 return 0; 235 } 236 237 static struct xt_target reject_tg6_reg __read_mostly = { 238 .name = "REJECT", 239 .family = NFPROTO_IPV6, 240 .target = reject_tg6, 241 .targetsize = sizeof(struct ip6t_reject_info), 242 .table = "filter", 243 .hooks = (1 << NF_INET_LOCAL_IN) | (1 << NF_INET_FORWARD) | 244 (1 << NF_INET_LOCAL_OUT), 245 .checkentry = reject_tg6_check, 246 .me = THIS_MODULE 247 }; 248 249 static int __init reject_tg6_init(void) 250 { 251 return xt_register_target(&reject_tg6_reg); 252 } 253 254 static void __exit reject_tg6_exit(void) 255 { 256 xt_unregister_target(&reject_tg6_reg); 257 } 258 259 module_init(reject_tg6_init); 260 module_exit(reject_tg6_exit); 261