net/ipv4/netfilter/ip_conntrack_proto_icmp.c

   1 /* (C) 1999-2001 Paul `Rusty' Russell
   2  * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License version 2 as
   6  * published by the Free Software Foundation.
   7  */
   8
   9 #include <linux/types.h>
  10 #include <linux/sched.h>
  11 #include <linux/timer.h>
  12 #include <linux/netfilter.h>
  13 #include <linux/in.h>
  14 #include <linux/icmp.h>
  15 #include <linux/seq_file.h>
  16 #include <linux/skbuff.h>
  17 #include <net/ip.h>
  18 #include <net/checksum.h>
  19 #include <linux/netfilter_ipv4.h>
  20 #include <linux/netfilter_ipv4/ip_conntrack.h>
  21 #include <linux/netfilter_ipv4/ip_conntrack_core.h>
  22 #include <linux/netfilter_ipv4/ip_conntrack_protocol.h>
  23
  24 unsigned int ip_ct_icmp_timeout __read_mostly = 30*HZ;
  25
  26 #if 0
  27 #define DEBUGP printk
  28 #else
  29 #define DEBUGP(format, args...)
  30 #endif
  31
  32 static int icmp_pkt_to_tuple(const struct sk_buff *skb,
  33                              unsigned int dataoff,
  34                              struct ip_conntrack_tuple *tuple)
  35 {
  36         struct icmphdr _hdr, *hp;
  37
  38         hp = skb_header_pointer(skb, dataoff, sizeof(_hdr), &_hdr);
  39         if (hp == NULL)
  40                 return 0;
  41
  42         tuple->dst.u.icmp.type = hp->type;
  43         tuple->src.u.icmp.id = hp->un.echo.id;
  44         tuple->dst.u.icmp.code = hp->code;
  45
  46         return 1;
  47 }
  48
  49 /* Add 1; spaces filled with 0. */
  50 static const u_int8_t invmap[] = {
  51         [ICMP_ECHO] = ICMP_ECHOREPLY + 1,
  52         [ICMP_ECHOREPLY] = ICMP_ECHO + 1,
  53         [ICMP_TIMESTAMP] = ICMP_TIMESTAMPREPLY + 1,
  54         [ICMP_TIMESTAMPREPLY] = ICMP_TIMESTAMP + 1,
  55         [ICMP_INFO_REQUEST] = ICMP_INFO_REPLY + 1,
  56         [ICMP_INFO_REPLY] = ICMP_INFO_REQUEST + 1,
  57         [ICMP_ADDRESS] = ICMP_ADDRESSREPLY + 1,
  58         [ICMP_ADDRESSREPLY] = ICMP_ADDRESS + 1
  59 };
  60
  61 static int icmp_invert_tuple(struct ip_conntrack_tuple *tuple,
  62                              const struct ip_conntrack_tuple *orig)
  63 {
  64         if (orig->dst.u.icmp.type >= sizeof(invmap)
  65             || !invmap[orig->dst.u.icmp.type])
  66                 return 0;
  67
  68         tuple->src.u.icmp.id = orig->src.u.icmp.id;
  69         tuple->dst.u.icmp.type = invmap[orig->dst.u.icmp.type] - 1;
  70         tuple->dst.u.icmp.code = orig->dst.u.icmp.code;
  71         return 1;
  72 }
  73
  74 /* Print out the per-protocol part of the tuple. */
  75 static int icmp_print_tuple(struct seq_file *s,
  76                             const struct ip_conntrack_tuple *tuple)
  77 {
  78         return seq_printf(s, "type=%u code=%u id=%u ",
  79                           tuple->dst.u.icmp.type,
  80                           tuple->dst.u.icmp.code,
  81                           ntohs(tuple->src.u.icmp.id));
  82 }
  83
  84 /* Print out the private part of the conntrack. */
  85 static int icmp_print_conntrack(struct seq_file *s,
  86                                 const struct ip_conntrack *conntrack)
  87 {
  88         return 0;
  89 }
  90
  91 /* Returns verdict for packet, or -1 for invalid. */
  92 static int icmp_packet(struct ip_conntrack *ct,
  93                        const struct sk_buff *skb,
  94                        enum ip_conntrack_info ctinfo)
  95 {
  96         /* Try to delete connection immediately after all replies:
  97            won't actually vanish as we still have skb, and del_timer
  98            means this will only run once even if count hits zero twice
  99            (theoretically possible with SMP) */
 100         if (CTINFO2DIR(ctinfo) == IP_CT_DIR_REPLY) {
 101                 if (atomic_dec_and_test(&ct->proto.icmp.count)
 102                     && del_timer(&ct->timeout))
 103                         ct->timeout.function((unsigned long)ct);
 104         } else {
 105                 atomic_inc(&ct->proto.icmp.count);
 106                 ip_conntrack_event_cache(IPCT_PROTOINFO_VOLATILE, skb);
 107                 ip_ct_refresh_acct(ct, ctinfo, skb, ip_ct_icmp_timeout);
 108         }
 109
 110         return NF_ACCEPT;
 111 }
 112
 113 /* Called when a new connection for this protocol found. */
 114 static int icmp_new(struct ip_conntrack *conntrack,
 115                     const struct sk_buff *skb)
 116 {
 117         static const u_int8_t valid_new[] = {
 118                 [ICMP_ECHO] = 1,
 119                 [ICMP_TIMESTAMP] = 1,
 120                 [ICMP_INFO_REQUEST] = 1,
 121                 [ICMP_ADDRESS] = 1
 122         };
 123
 124         if (conntrack->tuplehash[0].tuple.dst.u.icmp.type >= sizeof(valid_new)
 125             || !valid_new[conntrack->tuplehash[0].tuple.dst.u.icmp.type]) {
 126                 /* Can't create a new ICMP `conn' with this. */
 127                 DEBUGP("icmp: can't create new conn with type %u\n",
 128                        conntrack->tuplehash[0].tuple.dst.u.icmp.type);
 129                 DUMP_TUPLE(&conntrack->tuplehash[0].tuple);
 130                 return 0;
 131         }
 132         atomic_set(&conntrack->proto.icmp.count, 0);
 133         return 1;
 134 }
 135
 136 static int
 137 icmp_error_message(struct sk_buff *skb,
 138                    enum ip_conntrack_info *ctinfo,
 139                    unsigned int hooknum)
 140 {
 141         struct ip_conntrack_tuple innertuple, origtuple;
 142         struct {
 143                 struct icmphdr icmp;
 144                 struct iphdr ip;
 145         } _in, *inside;
 146         struct ip_conntrack_protocol *innerproto;
 147         struct ip_conntrack_tuple_hash *h;
 148         int dataoff;
 149
 150         IP_NF_ASSERT(skb->nfct == NULL);
 151
 152         /* Not enough header? */
 153         inside = skb_header_pointer(skb, skb->nh.iph->ihl*4, sizeof(_in), &_in);
 154         if (inside == NULL)
 155                 return -NF_ACCEPT;
 156
 157         /* Ignore ICMP's containing fragments (shouldn't happen) */
 158         if (inside->ip.frag_off & htons(IP_OFFSET)) {
 159                 DEBUGP("icmp_error_track: fragment of proto %u\n",
 160                        inside->ip.protocol);
 161                 return -NF_ACCEPT;
 162         }
 163
 164         innerproto = ip_conntrack_proto_find_get(inside->ip.protocol);
 165         dataoff = skb->nh.iph->ihl*4 + sizeof(inside->icmp) + inside->ip.ihl*4;
 166         /* Are they talking about one of our connections? */
 167         if (!ip_ct_get_tuple(&inside->ip, skb, dataoff, &origtuple, innerproto)) {
 168                 DEBUGP("icmp_error: ! get_tuple p=%u", inside->ip.protocol);
 169                 ip_conntrack_proto_put(innerproto);
 170                 return -NF_ACCEPT;
 171         }
 172
 173         /* Ordinarily, we'd expect the inverted tupleproto, but it's
 174            been preserved inside the ICMP. */
 175         if (!ip_ct_invert_tuple(&innertuple, &origtuple, innerproto)) {
 176                 DEBUGP("icmp_error_track: Can't invert tuple\n");
 177                 ip_conntrack_proto_put(innerproto);
 178                 return -NF_ACCEPT;
 179         }
 180         ip_conntrack_proto_put(innerproto);
 181
 182         *ctinfo = IP_CT_RELATED;
 183
 184         h = ip_conntrack_find_get(&innertuple, NULL);
 185         if (!h) {
 186                 /* Locally generated ICMPs will match inverted if they
 187                    haven't been SNAT'ed yet */
 188                 /* FIXME: NAT code has to handle half-done double NAT --RR */
 189                 if (hooknum == NF_IP_LOCAL_OUT)
 190                         h = ip_conntrack_find_get(&origtuple, NULL);
 191
 192                 if (!h) {
 193                         DEBUGP("icmp_error_track: no match\n");
 194                         return -NF_ACCEPT;
 195                 }
 196                 /* Reverse direction from that found */
 197                 if (DIRECTION(h) != IP_CT_DIR_REPLY)
 198                         *ctinfo += IP_CT_IS_REPLY;
 199         } else {
 200                 if (DIRECTION(h) == IP_CT_DIR_REPLY)
 201                         *ctinfo += IP_CT_IS_REPLY;
 202         }
 203
 204         /* Update skb to refer to this connection */
 205         skb->nfct = &tuplehash_to_ctrack(h)->ct_general;
 206         skb->nfctinfo = *ctinfo;
 207         return -NF_ACCEPT;
 208 }
 209
 210 /* Small and modified version of icmp_rcv */
 211 static int
 212 icmp_error(struct sk_buff *skb, enum ip_conntrack_info *ctinfo,
 213            unsigned int hooknum)
 214 {
 215         struct icmphdr _ih, *icmph;
 216
 217         /* Not enough header? */
 218         icmph = skb_header_pointer(skb, skb->nh.iph->ihl*4, sizeof(_ih), &_ih);
 219         if (icmph == NULL) {
 220                 if (LOG_INVALID(IPPROTO_ICMP))
 221                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 222                                       "ip_ct_icmp: short packet ");
 223                 return -NF_ACCEPT;
 224         }
 225
 226         /* See ip_conntrack_proto_tcp.c */
 227         if (ip_conntrack_checksum && hooknum == NF_IP_PRE_ROUTING &&
 228             nf_ip_checksum(skb, hooknum, skb->nh.iph->ihl * 4, 0)) {
 229                 if (LOG_INVALID(IPPROTO_ICMP))
 230                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 231                                       "ip_ct_icmp: bad ICMP checksum ");
 232                 return -NF_ACCEPT;
 233         }
 234
 235         /*
 236          *      18 is the highest 'known' ICMP type. Anything else is a mystery
 237          *
 238          *      RFC 1122: 3.2.2  Unknown ICMP messages types MUST be silently
 239          *                discarded.
 240          */
 241         if (icmph->type > NR_ICMP_TYPES) {
 242                 if (LOG_INVALID(IPPROTO_ICMP))
 243                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 244                                       "ip_ct_icmp: invalid ICMP type ");
 245                 return -NF_ACCEPT;
 246         }
 247
 248         /* Need to track icmp error message? */
 249         if (icmph->type != ICMP_DEST_UNREACH
 250             && icmph->type != ICMP_SOURCE_QUENCH
 251             && icmph->type != ICMP_TIME_EXCEEDED
 252             && icmph->type != ICMP_PARAMETERPROB
 253             && icmph->type != ICMP_REDIRECT)
 254                 return NF_ACCEPT;
 255
 256         return icmp_error_message(skb, ctinfo, hooknum);
 257 }
 258
 259 #if defined(CONFIG_IP_NF_CONNTRACK_NETLINK) || \
 260     defined(CONFIG_IP_NF_CONNTRACK_NETLINK_MODULE)
 261 static int icmp_tuple_to_nfattr(struct sk_buff *skb,
 262                                 const struct ip_conntrack_tuple *t)
 263 {
 264         NFA_PUT(skb, CTA_PROTO_ICMP_ID, sizeof(__be16),
 265                 &t->src.u.icmp.id);
 266         NFA_PUT(skb, CTA_PROTO_ICMP_TYPE, sizeof(u_int8_t),
 267                 &t->dst.u.icmp.type);
 268         NFA_PUT(skb, CTA_PROTO_ICMP_CODE, sizeof(u_int8_t),
 269                 &t->dst.u.icmp.code);
 270
 271         return 0;
 272
 273 nfattr_failure:
 274         return -1;
 275 }
 276
 277 static int icmp_nfattr_to_tuple(struct nfattr *tb[],
 278                                 struct ip_conntrack_tuple *tuple)
 279 {
 280         if (!tb[CTA_PROTO_ICMP_TYPE-1]
 281             || !tb[CTA_PROTO_ICMP_CODE-1]
 282             || !tb[CTA_PROTO_ICMP_ID-1])
 283                 return -EINVAL;
 284
 285         tuple->dst.u.icmp.type =
 286                         *(u_int8_t *)NFA_DATA(tb[CTA_PROTO_ICMP_TYPE-1]);
 287         tuple->dst.u.icmp.code =
 288                         *(u_int8_t *)NFA_DATA(tb[CTA_PROTO_ICMP_CODE-1]);
 289         tuple->src.u.icmp.id =
 290                         *(__be16 *)NFA_DATA(tb[CTA_PROTO_ICMP_ID-1]);
 291
 292         if (tuple->dst.u.icmp.type >= sizeof(invmap)
 293             || !invmap[tuple->dst.u.icmp.type])
 294                 return -EINVAL;
 295
 296         return 0;
 297 }
 298 #endif
 299
 300 struct ip_conntrack_protocol ip_conntrack_protocol_icmp =
 301 {
 302         .proto                  = IPPROTO_ICMP,
 303         .name                   = "icmp",
 304         .pkt_to_tuple           = icmp_pkt_to_tuple,
 305         .invert_tuple           = icmp_invert_tuple,
 306         .print_tuple            = icmp_print_tuple,
 307         .print_conntrack        = icmp_print_conntrack,
 308         .packet                 = icmp_packet,
 309         .new                    = icmp_new,
 310         .error                  = icmp_error,
 311 #if defined(CONFIG_IP_NF_CONNTRACK_NETLINK) || \
 312     defined(CONFIG_IP_NF_CONNTRACK_NETLINK_MODULE)
 313         .tuple_to_nfattr        = icmp_tuple_to_nfattr,
 314         .nfattr_to_tuple        = icmp_nfattr_to_tuple,
 315 #endif
 316 };