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                     && del_timer(&ct->timeout))
  92                         ct->timeout.function((unsigned long)ct);
  93         } else {
  94                 atomic_inc(&ct->proto.icmp.count);
  95                 nf_conntrack_event_cache(IPCT_PROTOINFO_VOLATILE, skb);
  96                 nf_ct_refresh_acct(ct, ctinfo, skb, nf_ct_icmp_timeout);
  97         }
  98
  99         return NF_ACCEPT;
 100 }
 101
 102 /* Called when a new connection for this protocol found. */
 103 static bool icmp_new(struct nf_conn *ct, const struct sk_buff *skb,
 104                      unsigned int dataoff)
 105 {
 106         static const u_int8_t valid_new[] = {
 107                 [ICMP_ECHO] = 1,
 108                 [ICMP_TIMESTAMP] = 1,
 109                 [ICMP_INFO_REQUEST] = 1,
 110                 [ICMP_ADDRESS] = 1
 111         };
 112
 113         if (ct->tuplehash[0].tuple.dst.u.icmp.type >= sizeof(valid_new)
 114             || !valid_new[ct->tuplehash[0].tuple.dst.u.icmp.type]) {
 115                 /* Can't create a new ICMP `conn' with this. */
 116                 pr_debug("icmp: can't create new conn with type %u\n",
 117                          ct->tuplehash[0].tuple.dst.u.icmp.type);
 118                 nf_ct_dump_tuple_ip(&ct->tuplehash[0].tuple);
 119                 return false;
 120         }
 121         atomic_set(&ct->proto.icmp.count, 0);
 122         return true;
 123 }
 124
 125 /* Returns conntrack if it dealt with ICMP, and filled in skb fields */
 126 static int
 127 icmp_error_message(struct sk_buff *skb,
 128                  enum ip_conntrack_info *ctinfo,
 129                  unsigned int hooknum)
 130 {
 131         struct nf_conntrack_tuple innertuple, origtuple;
 132         const struct nf_conntrack_l4proto *innerproto;
 133         const struct nf_conntrack_tuple_hash *h;
 134
 135         NF_CT_ASSERT(skb->nfct == NULL);
 136
 137         /* Are they talking about one of our connections? */
 138         if (!nf_ct_get_tuplepr(skb,
 139                                skb_network_offset(skb) + ip_hdrlen(skb)
 140                                                        + sizeof(struct icmphdr),
 141                                PF_INET, &origtuple)) {
 142                 pr_debug("icmp_error_message: failed to get tuple\n");
 143                 return -NF_ACCEPT;
 144         }
 145
 146         /* rcu_read_lock()ed by nf_hook_slow */
 147         innerproto = __nf_ct_l4proto_find(PF_INET, origtuple.dst.protonum);
 148
 149         /* Ordinarily, we'd expect the inverted tupleproto, but it's
 150            been preserved inside the ICMP. */
 151         if (!nf_ct_invert_tuple(&innertuple, &origtuple,
 152                                 &nf_conntrack_l3proto_ipv4, innerproto)) {
 153                 pr_debug("icmp_error_message: no match\n");
 154                 return -NF_ACCEPT;
 155         }
 156
 157         *ctinfo = IP_CT_RELATED;
 158
 159         h = nf_conntrack_find_get(&innertuple);
 160         if (!h) {
 161                 pr_debug("icmp_error_message: no match\n");
 162                 return -NF_ACCEPT;
 163         }
 164
 165         if (NF_CT_DIRECTION(h) == IP_CT_DIR_REPLY)
 166                 *ctinfo += IP_CT_IS_REPLY;
 167
 168         /* Update skb to refer to this connection */
 169         skb->nfct = &nf_ct_tuplehash_to_ctrack(h)->ct_general;
 170         skb->nfctinfo = *ctinfo;
 171         return -NF_ACCEPT;
 172 }
 173
 174 /* Small and modified version of icmp_rcv */
 175 static int
 176 icmp_error(struct sk_buff *skb, unsigned int dataoff,
 177            enum ip_conntrack_info *ctinfo, int pf, unsigned int hooknum)
 178 {
 179         const struct icmphdr *icmph;
 180         struct icmphdr _ih;
 181
 182         /* Not enough header? */
 183         icmph = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_ih), &_ih);
 184         if (icmph == NULL) {
 185                 if (LOG_INVALID(IPPROTO_ICMP))
 186                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 187                                       "nf_ct_icmp: short packet ");
 188                 return -NF_ACCEPT;
 189         }
 190
 191         /* See ip_conntrack_proto_tcp.c */
 192         if (nf_conntrack_checksum && hooknum == NF_INET_PRE_ROUTING &&
 193             nf_ip_checksum(skb, hooknum, dataoff, 0)) {
 194                 if (LOG_INVALID(IPPROTO_ICMP))
 195                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 196                                       "nf_ct_icmp: bad HW ICMP checksum ");
 197                 return -NF_ACCEPT;
 198         }
 199
 200         /*
 201          *      18 is the highest 'known' ICMP type. Anything else is a mystery
 202          *
 203          *      RFC 1122: 3.2.2  Unknown ICMP messages types MUST be silently
 204          *                discarded.
 205          */
 206         if (icmph->type > NR_ICMP_TYPES) {
 207                 if (LOG_INVALID(IPPROTO_ICMP))
 208                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 209                                       "nf_ct_icmp: invalid ICMP type ");
 210                 return -NF_ACCEPT;
 211         }
 212
 213         /* Need to track icmp error message? */
 214         if (icmph->type != ICMP_DEST_UNREACH
 215             && icmph->type != ICMP_SOURCE_QUENCH
 216             && icmph->type != ICMP_TIME_EXCEEDED
 217             && icmph->type != ICMP_PARAMETERPROB
 218             && icmph->type != ICMP_REDIRECT)
 219                 return NF_ACCEPT;
 220
 221         return icmp_error_message(skb, ctinfo, hooknum);
 222 }
 223
 224 #if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
 225
 226 #include <linux/netfilter/nfnetlink.h>
 227 #include <linux/netfilter/nfnetlink_conntrack.h>
 228
 229 static int icmp_tuple_to_nlattr(struct sk_buff *skb,
 230                                 const struct nf_conntrack_tuple *t)
 231 {
 232         NLA_PUT_BE16(skb, CTA_PROTO_ICMP_ID, t->src.u.icmp.id);
 233         NLA_PUT_U8(skb, CTA_PROTO_ICMP_TYPE, t->dst.u.icmp.type);
 234         NLA_PUT_U8(skb, CTA_PROTO_ICMP_CODE, t->dst.u.icmp.code);
 235
 236         return 0;
 237
 238 nla_put_failure:
 239         return -1;
 240 }
 241
 242 static const struct nla_policy icmp_nla_policy[CTA_PROTO_MAX+1] = {
 243         [CTA_PROTO_ICMP_TYPE]   = { .type = NLA_U8 },
 244         [CTA_PROTO_ICMP_CODE]   = { .type = NLA_U8 },
 245         [CTA_PROTO_ICMP_ID]     = { .type = NLA_U16 },
 246 };
 247
 248 static int icmp_nlattr_to_tuple(struct nlattr *tb[],
 249                                 struct nf_conntrack_tuple *tuple)
 250 {
 251         if (!tb[CTA_PROTO_ICMP_TYPE]
 252             || !tb[CTA_PROTO_ICMP_CODE]
 253             || !tb[CTA_PROTO_ICMP_ID])
 254                 return -EINVAL;
 255
 256         tuple->dst.u.icmp.type = nla_get_u8(tb[CTA_PROTO_ICMP_TYPE]);
 257         tuple->dst.u.icmp.code = nla_get_u8(tb[CTA_PROTO_ICMP_CODE]);
 258         tuple->src.u.icmp.id = nla_get_be16(tb[CTA_PROTO_ICMP_ID]);
 259
 260         if (tuple->dst.u.icmp.type >= sizeof(invmap)
 261             || !invmap[tuple->dst.u.icmp.type])
 262                 return -EINVAL;
 263
 264         return 0;
 265 }
 266 #endif
 267
 268 #ifdef CONFIG_SYSCTL
 269 static struct ctl_table_header *icmp_sysctl_header;
 270 static struct ctl_table icmp_sysctl_table[] = {
 271         {
 272                 .procname       = "nf_conntrack_icmp_timeout",
 273                 .data           = &nf_ct_icmp_timeout,
 274                 .maxlen         = sizeof(unsigned int),
 275                 .mode           = 0644,
 276                 .proc_handler   = &proc_dointvec_jiffies,
 277         },
 278         {
 279                 .ctl_name = 0
 280         }
 281 };
 282 #ifdef CONFIG_NF_CONNTRACK_PROC_COMPAT
 283 static struct ctl_table icmp_compat_sysctl_table[] = {
 284         {
 285                 .procname       = "ip_conntrack_icmp_timeout",
 286                 .data           = &nf_ct_icmp_timeout,
 287                 .maxlen         = sizeof(unsigned int),
 288                 .mode           = 0644,
 289                 .proc_handler   = &proc_dointvec_jiffies,
 290         },
 291         {
 292                 .ctl_name = 0
 293         }
 294 };
 295 #endif /* CONFIG_NF_CONNTRACK_PROC_COMPAT */
 296 #endif /* CONFIG_SYSCTL */
 297
 298 struct nf_conntrack_l4proto nf_conntrack_l4proto_icmp __read_mostly =
 299 {
 300         .l3proto                = PF_INET,
 301         .l4proto                = IPPROTO_ICMP,
 302         .name                   = "icmp",
 303         .pkt_to_tuple           = icmp_pkt_to_tuple,
 304         .invert_tuple           = icmp_invert_tuple,
 305         .print_tuple            = icmp_print_tuple,
 306         .packet                 = icmp_packet,
 307         .new                    = icmp_new,
 308         .error                  = icmp_error,
 309         .destroy                = NULL,
 310         .me                     = NULL,
 311 #if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
 312         .tuple_to_nlattr        = icmp_tuple_to_nlattr,
 313         .nlattr_to_tuple        = icmp_nlattr_to_tuple,
 314         .nla_policy             = icmp_nla_policy,
 315 #endif
 316 #ifdef CONFIG_SYSCTL
 317         .ctl_table_header       = &icmp_sysctl_header,
 318         .ctl_table              = icmp_sysctl_table,
 319 #ifdef CONFIG_NF_CONNTRACK_PROC_COMPAT
 320         .ctl_compat_table       = icmp_compat_sysctl_table,
 321 #endif
 322 #endif
 323 };