net/ipv4/netfilter/nf_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  * 16 Dec 2003: Yasuyuki Kozakai @USAGI <yasuyuki.kozakai@toshiba.co.jp>
   9  *      - enable working with Layer 3 protocol independent connection tracking.
  10  *
  11  * Derived from net/ipv4/netfilter/ip_conntrack_proto_icmp.c
  12  */
  13
  14 #include <linux/types.h>
  15 #include <linux/sched.h>
  16 #include <linux/timer.h>
  17 #include <linux/netfilter.h>
  18 #include <linux/in.h>
  19 #include <linux/icmp.h>
  20 #include <linux/seq_file.h>
  21 #include <net/ip.h>
  22 #include <net/checksum.h>
  23 #include <linux/netfilter_ipv4.h>
  24 #include <net/netfilter/nf_conntrack_tuple.h>
  25 #include <net/netfilter/nf_conntrack_protocol.h>
  26 #include <net/netfilter/nf_conntrack_core.h>
  27
  28 unsigned long nf_ct_icmp_timeout = 30*HZ;
  29
  30 #if 0
  31 #define DEBUGP printk
  32 #else
  33 #define DEBUGP(format, args...)
  34 #endif
  35
  36 static int icmp_pkt_to_tuple(const struct sk_buff *skb,
  37                              unsigned int dataoff,
  38                              struct nf_conntrack_tuple *tuple)
  39 {
  40         struct icmphdr _hdr, *hp;
  41
  42         hp = skb_header_pointer(skb, dataoff, sizeof(_hdr), &_hdr);
  43         if (hp == NULL)
  44                 return 0;
  45
  46         tuple->dst.u.icmp.type = hp->type;
  47         tuple->src.u.icmp.id = hp->un.echo.id;
  48         tuple->dst.u.icmp.code = hp->code;
  49
  50         return 1;
  51 }
  52
  53 static int icmp_invert_tuple(struct nf_conntrack_tuple *tuple,
  54                              const struct nf_conntrack_tuple *orig)
  55 {
  56         /* Add 1; spaces filled with 0. */
  57         static u_int8_t invmap[]
  58                 = { [ICMP_ECHO] = ICMP_ECHOREPLY + 1,
  59                     [ICMP_ECHOREPLY] = ICMP_ECHO + 1,
  60                     [ICMP_TIMESTAMP] = ICMP_TIMESTAMPREPLY + 1,
  61                     [ICMP_TIMESTAMPREPLY] = ICMP_TIMESTAMP + 1,
  62                     [ICMP_INFO_REQUEST] = ICMP_INFO_REPLY + 1,
  63                     [ICMP_INFO_REPLY] = ICMP_INFO_REQUEST + 1,
  64                     [ICMP_ADDRESS] = ICMP_ADDRESSREPLY + 1,
  65                     [ICMP_ADDRESSREPLY] = ICMP_ADDRESS + 1};
  66
  67         if (orig->dst.u.icmp.type >= sizeof(invmap)
  68             || !invmap[orig->dst.u.icmp.type])
  69                 return 0;
  70
  71         tuple->src.u.icmp.id = orig->src.u.icmp.id;
  72         tuple->dst.u.icmp.type = invmap[orig->dst.u.icmp.type] - 1;
  73         tuple->dst.u.icmp.code = orig->dst.u.icmp.code;
  74         return 1;
  75 }
  76
  77 /* Print out the per-protocol part of the tuple. */
  78 static int icmp_print_tuple(struct seq_file *s,
  79                             const struct nf_conntrack_tuple *tuple)
  80 {
  81         return seq_printf(s, "type=%u code=%u id=%u ",
  82                           tuple->dst.u.icmp.type,
  83                           tuple->dst.u.icmp.code,
  84                           ntohs(tuple->src.u.icmp.id));
  85 }
  86
  87 /* Print out the private part of the conntrack. */
  88 static int icmp_print_conntrack(struct seq_file *s,
  89                                 const struct nf_conn *conntrack)
  90 {
  91         return 0;
  92 }
  93
  94 /* Returns verdict for packet, or -1 for invalid. */
  95 static int icmp_packet(struct nf_conn *ct,
  96                        const struct sk_buff *skb,
  97                        unsigned int dataoff,
  98                        enum ip_conntrack_info ctinfo,
  99                        int pf,
 100                        unsigned int hooknum)
 101 {
 102         /* Try to delete connection immediately after all replies:
 103            won't actually vanish as we still have skb, and del_timer
 104            means this will only run once even if count hits zero twice
 105            (theoretically possible with SMP) */
 106         if (CTINFO2DIR(ctinfo) == IP_CT_DIR_REPLY) {
 107                 if (atomic_dec_and_test(&ct->proto.icmp.count)
 108                     && del_timer(&ct->timeout))
 109                         ct->timeout.function((unsigned long)ct);
 110         } else {
 111                 atomic_inc(&ct->proto.icmp.count);
 112                 nf_conntrack_event_cache(IPCT_PROTOINFO_VOLATILE, skb);
 113                 nf_ct_refresh_acct(ct, ctinfo, skb, nf_ct_icmp_timeout);
 114         }
 115
 116         return NF_ACCEPT;
 117 }
 118
 119 /* Called when a new connection for this protocol found. */
 120 static int icmp_new(struct nf_conn *conntrack,
 121                     const struct sk_buff *skb, unsigned int dataoff)
 122 {
 123         static u_int8_t valid_new[]
 124                 = { [ICMP_ECHO] = 1,
 125                     [ICMP_TIMESTAMP] = 1,
 126                     [ICMP_INFO_REQUEST] = 1,
 127                     [ICMP_ADDRESS] = 1 };
 128
 129         if (conntrack->tuplehash[0].tuple.dst.u.icmp.type >= sizeof(valid_new)
 130             || !valid_new[conntrack->tuplehash[0].tuple.dst.u.icmp.type]) {
 131                 /* Can't create a new ICMP `conn' with this. */
 132                 DEBUGP("icmp: can't create new conn with type %u\n",
 133                        conntrack->tuplehash[0].tuple.dst.u.icmp.type);
 134                 NF_CT_DUMP_TUPLE(&conntrack->tuplehash[0].tuple);
 135                 return 0;
 136         }
 137         atomic_set(&conntrack->proto.icmp.count, 0);
 138         return 1;
 139 }
 140
 141 extern struct nf_conntrack_l3proto nf_conntrack_l3proto_ipv4;
 142 /* Returns conntrack if it dealt with ICMP, and filled in skb fields */
 143 static int
 144 icmp_error_message(struct sk_buff *skb,
 145                  enum ip_conntrack_info *ctinfo,
 146                  unsigned int hooknum)
 147 {
 148         struct nf_conntrack_tuple innertuple, origtuple;
 149         struct {
 150                 struct icmphdr icmp;
 151                 struct iphdr ip;
 152         } _in, *inside;
 153         struct nf_conntrack_protocol *innerproto;
 154         struct nf_conntrack_tuple_hash *h;
 155         int dataoff;
 156
 157         NF_CT_ASSERT(skb->nfct == NULL);
 158
 159         /* Not enough header? */
 160         inside = skb_header_pointer(skb, skb->nh.iph->ihl*4, sizeof(_in), &_in);
 161         if (inside == NULL)
 162                 return -NF_ACCEPT;
 163
 164         /* Ignore ICMP's containing fragments (shouldn't happen) */
 165         if (inside->ip.frag_off & htons(IP_OFFSET)) {
 166                 DEBUGP("icmp_error_message: fragment of proto %u\n",
 167                        inside->ip.protocol);
 168                 return -NF_ACCEPT;
 169         }
 170
 171         innerproto = nf_ct_find_proto(PF_INET, inside->ip.protocol);
 172         dataoff = skb->nh.iph->ihl*4 + sizeof(inside->icmp);
 173         /* Are they talking about one of our connections? */
 174         if (!nf_ct_get_tuple(skb, dataoff, dataoff + inside->ip.ihl*4, PF_INET,
 175                              inside->ip.protocol, &origtuple,
 176                              &nf_conntrack_l3proto_ipv4, innerproto)) {
 177                 DEBUGP("icmp_error_message: ! get_tuple p=%u",
 178                        inside->ip.protocol);
 179                 return -NF_ACCEPT;
 180         }
 181
 182         /* Ordinarily, we'd expect the inverted tupleproto, but it's
 183            been preserved inside the ICMP. */
 184         if (!nf_ct_invert_tuple(&innertuple, &origtuple,
 185                                 &nf_conntrack_l3proto_ipv4, innerproto)) {
 186                 DEBUGP("icmp_error_message: no match\n");
 187                 return -NF_ACCEPT;
 188         }
 189
 190         *ctinfo = IP_CT_RELATED;
 191
 192         h = nf_conntrack_find_get(&innertuple, NULL);
 193         if (!h) {
 194                 /* Locally generated ICMPs will match inverted if they
 195                    haven't been SNAT'ed yet */
 196                 /* FIXME: NAT code has to handle half-done double NAT --RR */
 197                 if (hooknum == NF_IP_LOCAL_OUT)
 198                         h = nf_conntrack_find_get(&origtuple, NULL);
 199
 200                 if (!h) {
 201                         DEBUGP("icmp_error_message: no match\n");
 202                         return -NF_ACCEPT;
 203                 }
 204
 205                 /* Reverse direction from that found */
 206                 if (NF_CT_DIRECTION(h) == IP_CT_DIR_REPLY)
 207                         *ctinfo += IP_CT_IS_REPLY;
 208         } else {
 209                 if (NF_CT_DIRECTION(h) == IP_CT_DIR_REPLY)
 210                         *ctinfo += IP_CT_IS_REPLY;
 211         }
 212
 213         /* Update skb to refer to this connection */
 214         skb->nfct = &nf_ct_tuplehash_to_ctrack(h)->ct_general;
 215         skb->nfctinfo = *ctinfo;
 216         return -NF_ACCEPT;
 217 }
 218
 219 /* Small and modified version of icmp_rcv */
 220 static int
 221 icmp_error(struct sk_buff *skb, unsigned int dataoff,
 222            enum ip_conntrack_info *ctinfo, int pf, unsigned int hooknum)
 223 {
 224         struct icmphdr _ih, *icmph;
 225
 226         /* Not enough header? */
 227         icmph = skb_header_pointer(skb, skb->nh.iph->ihl*4, sizeof(_ih), &_ih);
 228         if (icmph == NULL) {
 229                 if (LOG_INVALID(IPPROTO_ICMP))
 230                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 231                                       "nf_ct_icmp: short packet ");
 232                 return -NF_ACCEPT;
 233         }
 234
 235         /* See ip_conntrack_proto_tcp.c */
 236         if (hooknum != NF_IP_PRE_ROUTING)
 237                 goto checksum_skipped;
 238
 239         switch (skb->ip_summed) {
 240         case CHECKSUM_HW:
 241                 if (!(u16)csum_fold(skb->csum))
 242                         break;
 243                 if (LOG_INVALID(IPPROTO_ICMP))
 244                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 245                                       "nf_ct_icmp: bad HW ICMP checksum ");
 246                 return -NF_ACCEPT;
 247         case CHECKSUM_NONE:
 248                 if ((u16)csum_fold(skb_checksum(skb, 0, skb->len, 0))) {
 249                         if (LOG_INVALID(IPPROTO_ICMP))
 250                                 nf_log_packet(PF_INET, 0, skb, NULL, NULL,
 251                                               NULL,
 252                                               "nf_ct_icmp: bad ICMP checksum ");
 253                         return -NF_ACCEPT;
 254                 }
 255         default:
 256                 break;
 257         }
 258
 259 checksum_skipped:
 260         /*
 261          *      18 is the highest 'known' ICMP type. Anything else is a mystery
 262          *
 263          *      RFC 1122: 3.2.2  Unknown ICMP messages types MUST be silently
 264          *                discarded.
 265          */
 266         if (icmph->type > NR_ICMP_TYPES) {
 267                 if (LOG_INVALID(IPPROTO_ICMP))
 268                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 269                                       "nf_ct_icmp: invalid ICMP type ");
 270                 return -NF_ACCEPT;
 271         }
 272
 273         /* Need to track icmp error message? */
 274         if (icmph->type != ICMP_DEST_UNREACH
 275             && icmph->type != ICMP_SOURCE_QUENCH
 276             && icmph->type != ICMP_TIME_EXCEEDED
 277             && icmph->type != ICMP_PARAMETERPROB
 278             && icmph->type != ICMP_REDIRECT)
 279                 return NF_ACCEPT;
 280
 281         return icmp_error_message(skb, ctinfo, hooknum);
 282 }
 283
 284 struct nf_conntrack_protocol nf_conntrack_protocol_icmp =
 285 {
 286         .list                   = { NULL, NULL },
 287         .l3proto                = PF_INET,
 288         .proto                  = IPPROTO_ICMP,
 289         .name                   = "icmp",
 290         .pkt_to_tuple           = icmp_pkt_to_tuple,
 291         .invert_tuple           = icmp_invert_tuple,
 292         .print_tuple            = icmp_print_tuple,
 293         .print_conntrack        = icmp_print_conntrack,
 294         .packet                 = icmp_packet,
 295         .new                    = icmp_new,
 296         .error                  = icmp_error,
 297         .destroy                = NULL,
 298         .me                     = NULL
 299 };
 300
 301 EXPORT_SYMBOL(nf_conntrack_protocol_icmp);