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