release/src-rt/linux/linux-2.6/net/ipv4/netfilter/ipt_REJECT.c

   1 /*
   2  * This is a module which is used for rejecting packets.
   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
  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>
  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>
  28 #endif
  29
  30 MODULE_LICENSE("GPL");
  31 MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
  32 MODULE_DESCRIPTION("iptables REJECT target module");
  33
  34 #if 0
  35 #define DEBUGP printk
  36 #else
  37 #define DEBUGP(format, args...)
  38 #endif
  39
  40 /* Send RST reply */
  41 static void send_reset(struct sk_buff *oldskb, int hook)
  42 {
  43         struct sk_buff *nskb;
  44         struct iphdr *oiph, *niph;
  45         struct tcphdr _otcph, *oth, *tcph;
  46         unsigned int addr_type;
  47
  48         /* IP header checks: fragment. */
  49         if (ip_hdr(oldskb)->frag_off & htons(IP_OFFSET))
  50                 return;
  51
  52         oth = skb_header_pointer(oldskb, ip_hdrlen(oldskb),
  53                                  sizeof(_otcph), &_otcph);
  54         if (oth == NULL)
  55                 return;
  56
  57         /* No RST for RST. */
  58         if (oth->rst)
  59                 return;
  60
  61         /* Check checksum */
  62         if (nf_ip_checksum(oldskb, hook, ip_hdrlen(oldskb), IPPROTO_TCP))
  63                 return;
  64         oiph = ip_hdr(oldskb);
  65
  66         nskb = alloc_skb(sizeof(struct iphdr) + sizeof(struct tcphdr) +
  67                          LL_MAX_HEADER, GFP_ATOMIC);
  68         if (!nskb)
  69                 return;
  70
  71         skb_reserve(nskb, LL_MAX_HEADER);
  72
  73         skb_reset_network_header(nskb);
  74         niph = (struct iphdr *)skb_put(nskb, sizeof(struct iphdr));
  75         niph->version   = 4;
  76         niph->ihl       = sizeof(struct iphdr) / 4;
  77         niph->tos       = 0;
  78         niph->id        = 0;
  79         niph->frag_off  = htons(IP_DF);
  80         niph->protocol  = IPPROTO_TCP;
  81         niph->check     = 0;
  82         niph->saddr     = oiph->daddr;
  83         niph->daddr     = oiph->saddr;
  84
  85         tcph = (struct tcphdr *)skb_put(nskb, sizeof(struct tcphdr));
  86         memset(tcph, 0, sizeof(*tcph));
  87         tcph->source    = oth->dest;
  88         tcph->dest      = oth->source;
  89         tcph->doff      = sizeof(struct tcphdr) / 4;
  90
  91         if (oth->ack)
  92                 tcph->seq = oth->ack_seq;
  93         else {
  94                 tcph->ack_seq = htonl(ntohl(oth->seq) + oth->syn + oth->fin +
  95                                       oldskb->len - ip_hdrlen(oldskb) -
  96                                       (oth->doff << 2));
  97                 tcph->ack = 1;
  98         }
  99
 100         tcph->rst       = 1;
 101         tcph->check = ~tcp_v4_check(sizeof(struct tcphdr), niph->saddr,
 102                                     niph->daddr, 0);
 103         nskb->ip_summed = CHECKSUM_PARTIAL;
 104         nskb->csum_start = (unsigned char *)tcph - nskb->head;
 105         nskb->csum_offset = offsetof(struct tcphdr, check);
 106
 107         addr_type = RTN_UNSPEC;
 108         if (hook != NF_IP_FORWARD
 109 #ifdef CONFIG_BRIDGE_NETFILTER
 110             || (nskb->nf_bridge && nskb->nf_bridge->mask & BRNF_BRIDGED)
 111 #endif
 112            )
 113                 addr_type = RTN_LOCAL;
 114
 115         /* ip_route_me_harder expects skb->dst to be set */
 116         nskb->dst = dst_clone(oldskb->dst);
 117
 118         nskb->protocol = htons(ETH_P_IP);
 119         if (ip_route_me_harder(nskb, addr_type))
 120                 goto free_nskb;
 121
 122         niph->ttl       = dst_metric(nskb->dst, RTAX_HOPLIMIT);
 123
 124         /* "Never happens" */
 125         if (nskb->len > dst_mtu(nskb->dst))
 126                 goto free_nskb;
 127
 128         nf_ct_attach(nskb, oldskb);
 129
 130         ip_local_out(nskb);
 131         return;
 132
 133  free_nskb:
 134         kfree_skb(nskb);
 135 }
 136
 137 static inline void send_unreach(struct sk_buff *skb_in, int code)
 138 {
 139         icmp_send(skb_in, ICMP_DEST_UNREACH, code, 0);
 140 }
 141
 142 static unsigned int reject(struct sk_buff *skb,
 143                            const struct net_device *in,
 144                            const struct net_device *out,
 145                            unsigned int hooknum,
 146                            const struct xt_target *target,
 147                            const void *targinfo)
 148 {
 149         const struct ipt_reject_info *reject = targinfo;
 150
 151         /* WARNING: This code causes reentry within iptables.
 152            This means that the iptables jump stack is now crap.  We
 153            must return an absolute verdict. --RR */
 154         switch (reject->with) {
 155         case IPT_ICMP_NET_UNREACHABLE:
 156                 send_unreach(skb, ICMP_NET_UNREACH);
 157                 break;
 158         case IPT_ICMP_HOST_UNREACHABLE:
 159                 send_unreach(skb, ICMP_HOST_UNREACH);
 160                 break;
 161         case IPT_ICMP_PROT_UNREACHABLE:
 162                 send_unreach(skb, ICMP_PROT_UNREACH);
 163                 break;
 164         case IPT_ICMP_PORT_UNREACHABLE:
 165                 send_unreach(skb, ICMP_PORT_UNREACH);
 166                 break;
 167         case IPT_ICMP_NET_PROHIBITED:
 168                 send_unreach(skb, ICMP_NET_ANO);
 169                 break;
 170         case IPT_ICMP_HOST_PROHIBITED:
 171                 send_unreach(skb, ICMP_HOST_ANO);
 172                 break;
 173         case IPT_ICMP_ADMIN_PROHIBITED:
 174                 send_unreach(skb, ICMP_PKT_FILTERED);
 175                 break;
 176         case IPT_TCP_RESET:
 177                 send_reset(skb, hooknum);
 178         case IPT_ICMP_ECHOREPLY:
 179                 /* Doesn't happen. */
 180                 break;
 181         }
 182
 183         return NF_DROP;
 184 }
 185
 186 static int check(const char *tablename,
 187                  const void *e_void,
 188                  const struct xt_target *target,
 189                  void *targinfo,
 190                  unsigned int hook_mask)
 191 {
 192         const struct ipt_reject_info *rejinfo = targinfo;
 193         const struct ipt_entry *e = e_void;
 194
 195         if (rejinfo->with == IPT_ICMP_ECHOREPLY) {
 196                 printk("REJECT: ECHOREPLY no longer supported.\n");
 197                 return 0;
 198         } else if (rejinfo->with == IPT_TCP_RESET) {
 199                 /* Must specify that it's a TCP packet */
 200                 if (e->ip.proto != IPPROTO_TCP
 201                     || (e->ip.invflags & XT_INV_PROTO)) {
 202                         DEBUGP("REJECT: TCP_RESET invalid for non-tcp\n");
 203                         return 0;
 204                 }
 205         }
 206         return 1;
 207 }
 208
 209 static struct xt_target ipt_reject_reg = {
 210         .name           = "REJECT",
 211         .family         = AF_INET,
 212         .target         = reject,
 213         .targetsize     = sizeof(struct ipt_reject_info),
 214         .table          = "filter",
 215         .hooks          = (1 << NF_IP_LOCAL_IN) | (1 << NF_IP_FORWARD) |
 216                           (1 << NF_IP_LOCAL_OUT),
 217         .checkentry     = check,
 218         .me             = THIS_MODULE,
 219 };
 220
 221 static int __init ipt_reject_init(void)
 222 {
 223         return xt_register_target(&ipt_reject_reg);
 224 }
 225
 226 static void __exit ipt_reject_fini(void)
 227 {
 228         xt_unregister_target(&ipt_reject_reg);
 229 }
 230
 231 module_init(ipt_reject_init);
 232 module_exit(ipt_reject_fini);