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
   9 #include <linux/types.h>
  10 #include <linux/timer.h>
  11 #include <linux/netfilter.h>
  12 #include <linux/in.h>
  13 #include <linux/icmp.h>
  14 #include <linux/seq_file.h>
  15 #include <net/ip.h>
  16 #include <net/checksum.h>
  17 #include <linux/netfilter_ipv4.h>
  18 #include <net/netfilter/nf_conntrack_tuple.h>
  19 #include <net/netfilter/nf_conntrack_l4proto.h>
  20 #include <net/netfilter/nf_conntrack_core.h>
  21 #include <net/netfilter/nf_log.h>
  22
  23 static unsigned long nf_ct_icmp_timeout __read_mostly = 30*HZ;
  24
  25 static int icmp_pkt_to_tuple(const struct sk_buff *skb,
  26                              unsigned int dataoff,
  27                              struct nf_conntrack_tuple *tuple)
  28 {
  29         const struct icmphdr *hp;
  30         struct icmphdr _hdr;
  31
  32         hp = skb_header_pointer(skb, dataoff, sizeof(_hdr), &_hdr);
  33         if (hp == NULL)
  34                 return 0;
  35
  36         tuple->dst.u.icmp.type = hp->type;
  37         tuple->src.u.icmp.id = hp->un.echo.id;
  38         tuple->dst.u.icmp.code = hp->code;
  39
  40         return 1;
  41 }
  42
  43 /* Add 1; spaces filled with 0. */
  44 static const u_int8_t invmap[] = {
  45         [ICMP_ECHO] = ICMP_ECHOREPLY + 1,
  46         [ICMP_ECHOREPLY] = ICMP_ECHO + 1,
  47         [ICMP_TIMESTAMP] = ICMP_TIMESTAMPREPLY + 1,
  48         [ICMP_TIMESTAMPREPLY] = ICMP_TIMESTAMP + 1,
  49         [ICMP_INFO_REQUEST] = ICMP_INFO_REPLY + 1,
  50         [ICMP_INFO_REPLY] = ICMP_INFO_REQUEST + 1,
  51         [ICMP_ADDRESS] = ICMP_ADDRESSREPLY + 1,
  52         [ICMP_ADDRESSREPLY] = ICMP_ADDRESS + 1
  53 };
  54
  55 static int icmp_invert_tuple(struct nf_conntrack_tuple *tuple,
  56                              const struct nf_conntrack_tuple *orig)
  57 {
  58         if (orig->dst.u.icmp.type >= sizeof(invmap)
  59             || !invmap[orig->dst.u.icmp.type])
  60                 return 0;
  61
  62         tuple->src.u.icmp.id = orig->src.u.icmp.id;
  63         tuple->dst.u.icmp.type = invmap[orig->dst.u.icmp.type] - 1;
  64         tuple->dst.u.icmp.code = orig->dst.u.icmp.code;
  65         return 1;
  66 }
  67
  68 /* Print out the per-protocol part of the tuple. */
  69 static int icmp_print_tuple(struct seq_file *s,
  70                             const struct nf_conntrack_tuple *tuple)
  71 {
  72         return seq_printf(s, "type=%u code=%u id=%u ",
  73                           tuple->dst.u.icmp.type,
  74                           tuple->dst.u.icmp.code,
  75                           ntohs(tuple->src.u.icmp.id));
  76 }
  77
  78 /* Returns verdict for packet, or -1 for invalid. */
  79 static int icmp_packet(struct nf_conn *ct,
  80                        const struct sk_buff *skb,
  81                        unsigned int dataoff,
  82                        enum ip_conntrack_info ctinfo,
  83                        int pf,
  84                        unsigned int hooknum)
  85 {
  86         /* Try to delete connection immediately after all replies:
  87            won't actually vanish as we still have skb, and del_timer
  88            means this will only run once even if count hits zero twice
  89            (theoretically possible with SMP) */
  90         if (CTINFO2DIR(ctinfo) == IP_CT_DIR_REPLY) {
  91                 if (atomic_dec_and_test(&ct->proto.icmp.count)
  92                     && del_timer(&ct->timeout))
  93                         ct->timeout.function((unsigned long)ct);
  94         } else {
  95                 atomic_inc(&ct->proto.icmp.count);
  96                 nf_conntrack_event_cache(IPCT_PROTOINFO_VOLATILE, skb);
  97                 nf_ct_refresh_acct(ct, ctinfo, skb, nf_ct_icmp_timeout);
  98         }
  99
 100         return NF_ACCEPT;
 101 }
 102
 103 /* Called when a new connection for this protocol found. */
 104 static int icmp_new(struct nf_conn *ct,
 105                     const struct sk_buff *skb, unsigned int dataoff)
 106 {
 107         static const u_int8_t valid_new[] = {
 108                 [ICMP_ECHO] = 1,
 109                 [ICMP_TIMESTAMP] = 1,
 110                 [ICMP_INFO_REQUEST] = 1,
 111                 [ICMP_ADDRESS] = 1
 112         };
 113
 114         if (ct->tuplehash[0].tuple.dst.u.icmp.type >= sizeof(valid_new)
 115             || !valid_new[ct->tuplehash[0].tuple.dst.u.icmp.type]) {
 116                 /* Can't create a new ICMP `conn' with this. */
 117                 pr_debug("icmp: can't create new conn with type %u\n",
 118                          ct->tuplehash[0].tuple.dst.u.icmp.type);
 119                 NF_CT_DUMP_TUPLE(&ct->tuplehash[0].tuple);
 120                 return 0;
 121         }
 122         atomic_set(&ct->proto.icmp.count, 0);
 123         return 1;
 124 }
 125
 126 /* Returns conntrack if it dealt with ICMP, and filled in skb fields */
 127 static int
 128 icmp_error_message(struct sk_buff *skb,
 129                  enum ip_conntrack_info *ctinfo,
 130                  unsigned int hooknum)
 131 {
 132         struct nf_conntrack_tuple innertuple, origtuple;
 133         const struct nf_conntrack_l4proto *innerproto;
 134         const struct nf_conntrack_tuple_hash *h;
 135
 136         NF_CT_ASSERT(skb->nfct == NULL);
 137
 138         /* Are they talking about one of our connections? */
 139         if (!nf_ct_get_tuplepr(skb,
 140                                skb_network_offset(skb) + ip_hdrlen(skb)
 141                                                        + sizeof(struct icmphdr),
 142                                PF_INET, &origtuple)) {
 143                 pr_debug("icmp_error_message: failed to get tuple\n");
 144                 return -NF_ACCEPT;
 145         }
 146
 147         /* rcu_read_lock()ed by nf_hook_slow */
 148         innerproto = __nf_ct_l4proto_find(PF_INET, origtuple.dst.protonum);
 149
 150         /* Ordinarily, we'd expect the inverted tupleproto, but it's
 151            been preserved inside the ICMP. */
 152         if (!nf_ct_invert_tuple(&innertuple, &origtuple,
 153                                 &nf_conntrack_l3proto_ipv4, innerproto)) {
 154                 pr_debug("icmp_error_message: no match\n");
 155                 return -NF_ACCEPT;
 156         }
 157
 158         *ctinfo = IP_CT_RELATED;
 159
 160         h = nf_conntrack_find_get(&innertuple);
 161         if (!h) {
 162                 pr_debug("icmp_error_message: no match\n");
 163                 return -NF_ACCEPT;
 164         }
 165
 166         if (NF_CT_DIRECTION(h) == IP_CT_DIR_REPLY)
 167                 *ctinfo += IP_CT_IS_REPLY;
 168
 169         /* Update skb to refer to this connection */
 170         skb->nfct = &nf_ct_tuplehash_to_ctrack(h)->ct_general;
 171         skb->nfctinfo = *ctinfo;
 172         return -NF_ACCEPT;
 173 }
 174
 175 /* Small and modified version of icmp_rcv */
 176 static int
 177 icmp_error(struct sk_buff *skb, unsigned int dataoff,
 178            enum ip_conntrack_info *ctinfo, int pf, unsigned int hooknum)
 179 {
 180         const struct icmphdr *icmph;
 181         struct icmphdr _ih;
 182
 183         /* Not enough header? */
 184         icmph = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_ih), &_ih);
 185         if (icmph == NULL) {
 186                 if (LOG_INVALID(IPPROTO_ICMP))
 187                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 188                                       "nf_ct_icmp: short packet ");
 189                 return -NF_ACCEPT;
 190         }
 191
 192         /* See ip_conntrack_proto_tcp.c */
 193         if (nf_conntrack_checksum && hooknum == NF_INET_PRE_ROUTING &&
 194             nf_ip_checksum(skb, hooknum, dataoff, 0)) {
 195                 if (LOG_INVALID(IPPROTO_ICMP))
 196                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 197                                       "nf_ct_icmp: bad HW ICMP checksum ");
 198                 return -NF_ACCEPT;
 199         }
 200
 201         /*
 202          *      18 is the highest 'known' ICMP type. Anything else is a mystery
 203          *
 204          *      RFC 1122: 3.2.2  Unknown ICMP messages types MUST be silently
 205          *                discarded.
 206          */
 207         if (icmph->type > NR_ICMP_TYPES) {
 208                 if (LOG_INVALID(IPPROTO_ICMP))
 209                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 210                                       "nf_ct_icmp: invalid ICMP type ");
 211                 return -NF_ACCEPT;
 212         }
 213
 214         /* Need to track icmp error message? */
 215         if (icmph->type != ICMP_DEST_UNREACH
 216             && icmph->type != ICMP_SOURCE_QUENCH
 217             && icmph->type != ICMP_TIME_EXCEEDED
 218             && icmph->type != ICMP_PARAMETERPROB
 219             && icmph->type != ICMP_REDIRECT)
 220                 return NF_ACCEPT;
 221
 222         return icmp_error_message(skb, ctinfo, hooknum);
 223 }
 224
 225 #if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
 226
 227 #include <linux/netfilter/nfnetlink.h>
 228 #include <linux/netfilter/nfnetlink_conntrack.h>
 229
 230 static int icmp_tuple_to_nlattr(struct sk_buff *skb,
 231                                 const struct nf_conntrack_tuple *t)
 232 {
 233         NLA_PUT_BE16(skb, CTA_PROTO_ICMP_ID, t->src.u.icmp.id);
 234         NLA_PUT_U8(skb, CTA_PROTO_ICMP_TYPE, t->dst.u.icmp.type);
 235         NLA_PUT_U8(skb, CTA_PROTO_ICMP_CODE, t->dst.u.icmp.code);
 236
 237         return 0;
 238
 239 nla_put_failure:
 240         return -1;
 241 }
 242
 243 static const struct nla_policy icmp_nla_policy[CTA_PROTO_MAX+1] = {
 244         [CTA_PROTO_ICMP_TYPE]   = { .type = NLA_U8 },
 245         [CTA_PROTO_ICMP_CODE]   = { .type = NLA_U8 },
 246         [CTA_PROTO_ICMP_ID]     = { .type = NLA_U16 },
 247 };
 248
 249 static int icmp_nlattr_to_tuple(struct nlattr *tb[],
 250                                 struct nf_conntrack_tuple *tuple)
 251 {
 252         if (!tb[CTA_PROTO_ICMP_TYPE]
 253             || !tb[CTA_PROTO_ICMP_CODE]
 254             || !tb[CTA_PROTO_ICMP_ID])
 255                 return -EINVAL;
 256
 257         tuple->dst.u.icmp.type = nla_get_u8(tb[CTA_PROTO_ICMP_TYPE]);
 258         tuple->dst.u.icmp.code = nla_get_u8(tb[CTA_PROTO_ICMP_CODE]);
 259         tuple->src.u.icmp.id = nla_get_be16(tb[CTA_PROTO_ICMP_ID]);
 260
 261         if (tuple->dst.u.icmp.type >= sizeof(invmap)
 262             || !invmap[tuple->dst.u.icmp.type])
 263                 return -EINVAL;
 264
 265         return 0;
 266 }
 267 #endif
 268
 269 #ifdef CONFIG_SYSCTL
 270 static struct ctl_table_header *icmp_sysctl_header;
 271 static struct ctl_table icmp_sysctl_table[] = {
 272         {
 273                 .procname       = "nf_conntrack_icmp_timeout",
 274                 .data           = &nf_ct_icmp_timeout,
 275                 .maxlen         = sizeof(unsigned int),
 276                 .mode           = 0644,
 277                 .proc_handler   = &proc_dointvec_jiffies,
 278         },
 279         {
 280                 .ctl_name = 0
 281         }
 282 };
 283 #ifdef CONFIG_NF_CONNTRACK_PROC_COMPAT
 284 static struct ctl_table icmp_compat_sysctl_table[] = {
 285         {
 286                 .procname       = "ip_conntrack_icmp_timeout",
 287                 .data           = &nf_ct_icmp_timeout,
 288                 .maxlen         = sizeof(unsigned int),
 289                 .mode           = 0644,
 290                 .proc_handler   = &proc_dointvec_jiffies,
 291         },
 292         {
 293                 .ctl_name = 0
 294         }
 295 };
 296 #endif /* CONFIG_NF_CONNTRACK_PROC_COMPAT */
 297 #endif /* CONFIG_SYSCTL */
 298
 299 struct nf_conntrack_l4proto nf_conntrack_l4proto_icmp __read_mostly =
 300 {
 301         .l3proto                = PF_INET,
 302         .l4proto                = 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         .packet                 = icmp_packet,
 308         .new                    = icmp_new,
 309         .error                  = icmp_error,
 310         .destroy                = NULL,
 311         .me                     = NULL,
 312 #if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
 313         .tuple_to_nlattr        = icmp_tuple_to_nlattr,
 314         .nlattr_to_tuple        = icmp_nlattr_to_tuple,
 315         .nla_policy             = icmp_nla_policy,
 316 #endif
 317 #ifdef CONFIG_SYSCTL
 318         .ctl_table_header       = &icmp_sysctl_header,
 319         .ctl_table              = icmp_sysctl_table,
 320 #ifdef CONFIG_NF_CONNTRACK_PROC_COMPAT
 321         .ctl_compat_table       = icmp_compat_sysctl_table,
 322 #endif
 323 #endif
 324 };