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 int 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                        u_int8_t pf,
  83                        unsigned int hooknum)
  84 {
  85         /* Do not immediately delete the connection after the first
  86            successful reply to avoid excessive conntrackd traffic
  87            and also to handle correctly ICMP echo reply duplicates. */
  88         nf_ct_refresh_acct(ct, ctinfo, skb, nf_ct_icmp_timeout);
  89
  90         return NF_ACCEPT;
  91 }
  92
  93 /* Called when a new connection for this protocol found. */
  94 static bool icmp_new(struct nf_conn *ct, const struct sk_buff *skb,
  95                      unsigned int dataoff)
  96 {
  97         static const u_int8_t valid_new[] = {
  98                 [ICMP_ECHO] = 1,
  99                 [ICMP_TIMESTAMP] = 1,
 100                 [ICMP_INFO_REQUEST] = 1,
 101                 [ICMP_ADDRESS] = 1
 102         };
 103
 104         if (ct->tuplehash[0].tuple.dst.u.icmp.type >= sizeof(valid_new) ||
 105             !valid_new[ct->tuplehash[0].tuple.dst.u.icmp.type]) {
 106                 /* Can't create a new ICMP `conn' with this. */
 107                 pr_debug("icmp: can't create new conn with type %u\n",
 108                          ct->tuplehash[0].tuple.dst.u.icmp.type);
 109                 nf_ct_dump_tuple_ip(&ct->tuplehash[0].tuple);
 110                 return false;
 111         }
 112         return true;
 113 }
 114
 115 /* Returns conntrack if it dealt with ICMP, and filled in skb fields */
 116 static int
 117 icmp_error_message(struct net *net, struct sk_buff *skb,
 118                  enum ip_conntrack_info *ctinfo,
 119                  unsigned int hooknum)
 120 {
 121         struct nf_conntrack_tuple innertuple, origtuple;
 122         const struct nf_conntrack_l4proto *innerproto;
 123         const struct nf_conntrack_tuple_hash *h;
 124
 125         NF_CT_ASSERT(skb->nfct == NULL);
 126
 127         /* Are they talking about one of our connections? */
 128         if (!nf_ct_get_tuplepr(skb,
 129                                skb_network_offset(skb) + ip_hdrlen(skb)
 130                                                        + sizeof(struct icmphdr),
 131                                PF_INET, &origtuple)) {
 132                 pr_debug("icmp_error_message: failed to get tuple\n");
 133                 return -NF_ACCEPT;
 134         }
 135
 136         /* rcu_read_lock()ed by nf_hook_slow */
 137         innerproto = __nf_ct_l4proto_find(PF_INET, origtuple.dst.protonum);
 138
 139         /* Ordinarily, we'd expect the inverted tupleproto, but it's
 140            been preserved inside the ICMP. */
 141         if (!nf_ct_invert_tuple(&innertuple, &origtuple,
 142                                 &nf_conntrack_l3proto_ipv4, innerproto)) {
 143                 pr_debug("icmp_error_message: no match\n");
 144                 return -NF_ACCEPT;
 145         }
 146
 147         *ctinfo = IP_CT_RELATED;
 148
 149         h = nf_conntrack_find_get(net, &innertuple);
 150         if (!h) {
 151                 pr_debug("icmp_error_message: no match\n");
 152                 return -NF_ACCEPT;
 153         }
 154
 155         if (NF_CT_DIRECTION(h) == IP_CT_DIR_REPLY)
 156                 *ctinfo += IP_CT_IS_REPLY;
 157
 158         /* Update skb to refer to this connection */
 159         skb->nfct = &nf_ct_tuplehash_to_ctrack(h)->ct_general;
 160         skb->nfctinfo = *ctinfo;
 161         return -NF_ACCEPT;
 162 }
 163
 164 /* Small and modified version of icmp_rcv */
 165 static int
 166 icmp_error(struct net *net, struct sk_buff *skb, unsigned int dataoff,
 167            enum ip_conntrack_info *ctinfo, u_int8_t pf, unsigned int hooknum)
 168 {
 169         const struct icmphdr *icmph;
 170         struct icmphdr _ih;
 171
 172         /* Not enough header? */
 173         icmph = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_ih), &_ih);
 174         if (icmph == NULL) {
 175                 if (LOG_INVALID(net, IPPROTO_ICMP))
 176                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 177                                       "nf_ct_icmp: short packet ");
 178                 return -NF_ACCEPT;
 179         }
 180
 181         /* See ip_conntrack_proto_tcp.c */
 182         if (net->ct.sysctl_checksum && hooknum == NF_INET_PRE_ROUTING &&
 183             nf_ip_checksum(skb, hooknum, dataoff, 0)) {
 184                 if (LOG_INVALID(net, IPPROTO_ICMP))
 185                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 186                                       "nf_ct_icmp: bad HW ICMP checksum ");
 187                 return -NF_ACCEPT;
 188         }
 189
 190         /*
 191          *      18 is the highest 'known' ICMP type. Anything else is a mystery
 192          *
 193          *      RFC 1122: 3.2.2  Unknown ICMP messages types MUST be silently
 194          *                discarded.
 195          */
 196         if (icmph->type > NR_ICMP_TYPES) {
 197                 if (LOG_INVALID(net, IPPROTO_ICMP))
 198                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 199                                       "nf_ct_icmp: invalid ICMP type ");
 200                 return -NF_ACCEPT;
 201         }
 202
 203         /* Need to track icmp error message? */
 204         if (icmph->type != ICMP_DEST_UNREACH &&
 205             icmph->type != ICMP_SOURCE_QUENCH &&
 206             icmph->type != ICMP_TIME_EXCEEDED &&
 207             icmph->type != ICMP_PARAMETERPROB &&
 208             icmph->type != ICMP_REDIRECT)
 209                 return NF_ACCEPT;
 210
 211         return icmp_error_message(net, skb, ctinfo, hooknum);
 212 }
 213
 214 #if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
 215
 216 #include <linux/netfilter/nfnetlink.h>
 217 #include <linux/netfilter/nfnetlink_conntrack.h>
 218
 219 static int icmp_tuple_to_nlattr(struct sk_buff *skb,
 220                                 const struct nf_conntrack_tuple *t)
 221 {
 222         NLA_PUT_BE16(skb, CTA_PROTO_ICMP_ID, t->src.u.icmp.id);
 223         NLA_PUT_U8(skb, CTA_PROTO_ICMP_TYPE, t->dst.u.icmp.type);
 224         NLA_PUT_U8(skb, CTA_PROTO_ICMP_CODE, t->dst.u.icmp.code);
 225
 226         return 0;
 227
 228 nla_put_failure:
 229         return -1;
 230 }
 231
 232 static const struct nla_policy icmp_nla_policy[CTA_PROTO_MAX+1] = {
 233         [CTA_PROTO_ICMP_TYPE]   = { .type = NLA_U8 },
 234         [CTA_PROTO_ICMP_CODE]   = { .type = NLA_U8 },
 235         [CTA_PROTO_ICMP_ID]     = { .type = NLA_U16 },
 236 };
 237
 238 static int icmp_nlattr_to_tuple(struct nlattr *tb[],
 239                                 struct nf_conntrack_tuple *tuple)
 240 {
 241         if (!tb[CTA_PROTO_ICMP_TYPE] ||
 242             !tb[CTA_PROTO_ICMP_CODE] ||
 243             !tb[CTA_PROTO_ICMP_ID])
 244                 return -EINVAL;
 245
 246         tuple->dst.u.icmp.type = nla_get_u8(tb[CTA_PROTO_ICMP_TYPE]);
 247         tuple->dst.u.icmp.code = nla_get_u8(tb[CTA_PROTO_ICMP_CODE]);
 248         tuple->src.u.icmp.id = nla_get_be16(tb[CTA_PROTO_ICMP_ID]);
 249
 250         if (tuple->dst.u.icmp.type >= sizeof(invmap) ||
 251             !invmap[tuple->dst.u.icmp.type])
 252                 return -EINVAL;
 253
 254         return 0;
 255 }
 256
 257 static int icmp_nlattr_tuple_size(void)
 258 {
 259         return nla_policy_len(icmp_nla_policy, CTA_PROTO_MAX + 1);
 260 }
 261 #endif
 262
 263 #ifdef CONFIG_SYSCTL
 264 static struct ctl_table_header *icmp_sysctl_header;
 265 static struct ctl_table icmp_sysctl_table[] = {
 266         {
 267                 .procname       = "nf_conntrack_icmp_timeout",
 268                 .data           = &nf_ct_icmp_timeout,
 269                 .maxlen         = sizeof(unsigned int),
 270                 .mode           = 0644,
 271                 .proc_handler   = proc_dointvec_jiffies,
 272         },
 273         { }
 274 };
 275 #ifdef CONFIG_NF_CONNTRACK_PROC_COMPAT
 276 static struct ctl_table icmp_compat_sysctl_table[] = {
 277         {
 278                 .procname       = "ip_conntrack_icmp_timeout",
 279                 .data           = &nf_ct_icmp_timeout,
 280                 .maxlen         = sizeof(unsigned int),
 281                 .mode           = 0644,
 282                 .proc_handler   = proc_dointvec_jiffies,
 283         },
 284         { }
 285 };
 286 #endif /* CONFIG_NF_CONNTRACK_PROC_COMPAT */
 287 #endif /* CONFIG_SYSCTL */
 288
 289 struct nf_conntrack_l4proto nf_conntrack_l4proto_icmp __read_mostly =
 290 {
 291         .l3proto                = PF_INET,
 292         .l4proto                = IPPROTO_ICMP,
 293         .name                   = "icmp",
 294         .pkt_to_tuple           = icmp_pkt_to_tuple,
 295         .invert_tuple           = icmp_invert_tuple,
 296         .print_tuple            = icmp_print_tuple,
 297         .packet                 = icmp_packet,
 298         .new                    = icmp_new,
 299         .error                  = icmp_error,
 300         .destroy                = NULL,
 301         .me                     = NULL,
 302 #if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
 303         .tuple_to_nlattr        = icmp_tuple_to_nlattr,
 304         .nlattr_tuple_size      = icmp_nlattr_tuple_size,
 305         .nlattr_to_tuple        = icmp_nlattr_to_tuple,
 306         .nla_policy             = icmp_nla_policy,
 307 #endif
 308 #ifdef CONFIG_SYSCTL
 309         .ctl_table_header       = &icmp_sysctl_header,
 310         .ctl_table              = icmp_sysctl_table,
 311 #ifdef CONFIG_NF_CONNTRACK_PROC_COMPAT
 312         .ctl_compat_table       = icmp_compat_sysctl_table,
 313 #endif
 314 #endif
 315 };