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         /* 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_ct_refresh_acct(ct, ctinfo, skb, nf_ct_icmp_timeout);
  95         }
  96
  97         return NF_ACCEPT;
  98 }
  99
 100 /* Called when a new connection for this protocol found. */
 101 static bool icmp_new(struct nf_conn *ct, const struct sk_buff *skb,
 102                      unsigned int dataoff)
 103 {
 104         static const u_int8_t valid_new[] = {
 105                 [ICMP_ECHO] = 1,
 106                 [ICMP_TIMESTAMP] = 1,
 107                 [ICMP_INFO_REQUEST] = 1,
 108                 [ICMP_ADDRESS] = 1
 109         };
 110
 111         if (ct->tuplehash[0].tuple.dst.u.icmp.type >= sizeof(valid_new)
 112             || !valid_new[ct->tuplehash[0].tuple.dst.u.icmp.type]) {
 113                 /* Can't create a new ICMP `conn' with this. */
 114                 pr_debug("icmp: can't create new conn with type %u\n",
 115                          ct->tuplehash[0].tuple.dst.u.icmp.type);
 116                 nf_ct_dump_tuple_ip(&ct->tuplehash[0].tuple);
 117                 return false;
 118         }
 119         atomic_set(&ct->proto.icmp.count, 0);
 120         return true;
 121 }
 122
 123 /* Returns conntrack if it dealt with ICMP, and filled in skb fields */
 124 static int
 125 icmp_error_message(struct net *net, struct sk_buff *skb,
 126                  enum ip_conntrack_info *ctinfo,
 127                  unsigned int hooknum)
 128 {
 129         struct nf_conntrack_tuple innertuple, origtuple;
 130         const struct nf_conntrack_l4proto *innerproto;
 131         const struct nf_conntrack_tuple_hash *h;
 132
 133         NF_CT_ASSERT(skb->nfct == NULL);
 134
 135         /* Are they talking about one of our connections? */
 136         if (!nf_ct_get_tuplepr(skb,
 137                                skb_network_offset(skb) + ip_hdrlen(skb)
 138                                                        + sizeof(struct icmphdr),
 139                                PF_INET, &origtuple)) {
 140                 pr_debug("icmp_error_message: failed to get tuple\n");
 141                 return -NF_ACCEPT;
 142         }
 143
 144         /* rcu_read_lock()ed by nf_hook_slow */
 145         innerproto = __nf_ct_l4proto_find(PF_INET, origtuple.dst.protonum);
 146
 147         /* Ordinarily, we'd expect the inverted tupleproto, but it's
 148            been preserved inside the ICMP. */
 149         if (!nf_ct_invert_tuple(&innertuple, &origtuple,
 150                                 &nf_conntrack_l3proto_ipv4, innerproto)) {
 151                 pr_debug("icmp_error_message: no match\n");
 152                 return -NF_ACCEPT;
 153         }
 154
 155         *ctinfo = IP_CT_RELATED;
 156
 157         h = nf_conntrack_find_get(net, &innertuple);
 158         if (!h) {
 159                 pr_debug("icmp_error_message: no match\n");
 160                 return -NF_ACCEPT;
 161         }
 162
 163         if (NF_CT_DIRECTION(h) == IP_CT_DIR_REPLY)
 164                 *ctinfo += IP_CT_IS_REPLY;
 165
 166         /* Update skb to refer to this connection */
 167         skb->nfct = &nf_ct_tuplehash_to_ctrack(h)->ct_general;
 168         skb->nfctinfo = *ctinfo;
 169         return -NF_ACCEPT;
 170 }
 171
 172 /* Small and modified version of icmp_rcv */
 173 static int
 174 icmp_error(struct net *net, struct sk_buff *skb, unsigned int dataoff,
 175            enum ip_conntrack_info *ctinfo, u_int8_t pf, unsigned int hooknum)
 176 {
 177         const struct icmphdr *icmph;
 178         struct icmphdr _ih;
 179
 180         /* Not enough header? */
 181         icmph = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_ih), &_ih);
 182         if (icmph == NULL) {
 183                 if (LOG_INVALID(net, IPPROTO_ICMP))
 184                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 185                                       "nf_ct_icmp: short packet ");
 186                 return -NF_ACCEPT;
 187         }
 188
 189         /* See ip_conntrack_proto_tcp.c */
 190         if (net->ct.sysctl_checksum && hooknum == NF_INET_PRE_ROUTING &&
 191             nf_ip_checksum(skb, hooknum, dataoff, 0)) {
 192                 if (LOG_INVALID(net, IPPROTO_ICMP))
 193                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 194                                       "nf_ct_icmp: bad HW ICMP checksum ");
 195                 return -NF_ACCEPT;
 196         }
 197
 198         /*
 199          *      18 is the highest 'known' ICMP type. Anything else is a mystery
 200          *
 201          *      RFC 1122: 3.2.2  Unknown ICMP messages types MUST be silently
 202          *                discarded.
 203          */
 204         if (icmph->type > NR_ICMP_TYPES) {
 205                 if (LOG_INVALID(net, IPPROTO_ICMP))
 206                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 207                                       "nf_ct_icmp: invalid ICMP type ");
 208                 return -NF_ACCEPT;
 209         }
 210
 211         /* Need to track icmp error message? */
 212         if (icmph->type != ICMP_DEST_UNREACH
 213             && icmph->type != ICMP_SOURCE_QUENCH
 214             && icmph->type != ICMP_TIME_EXCEEDED
 215             && icmph->type != ICMP_PARAMETERPROB
 216             && icmph->type != ICMP_REDIRECT)
 217                 return NF_ACCEPT;
 218
 219         return icmp_error_message(net, skb, ctinfo, hooknum);
 220 }
 221
 222 #if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
 223
 224 #include <linux/netfilter/nfnetlink.h>
 225 #include <linux/netfilter/nfnetlink_conntrack.h>
 226
 227 static int icmp_tuple_to_nlattr(struct sk_buff *skb,
 228                                 const struct nf_conntrack_tuple *t)
 229 {
 230         NLA_PUT_BE16(skb, CTA_PROTO_ICMP_ID, t->src.u.icmp.id);
 231         NLA_PUT_U8(skb, CTA_PROTO_ICMP_TYPE, t->dst.u.icmp.type);
 232         NLA_PUT_U8(skb, CTA_PROTO_ICMP_CODE, t->dst.u.icmp.code);
 233
 234         return 0;
 235
 236 nla_put_failure:
 237         return -1;
 238 }
 239
 240 static const struct nla_policy icmp_nla_policy[CTA_PROTO_MAX+1] = {
 241         [CTA_PROTO_ICMP_TYPE]   = { .type = NLA_U8 },
 242         [CTA_PROTO_ICMP_CODE]   = { .type = NLA_U8 },
 243         [CTA_PROTO_ICMP_ID]     = { .type = NLA_U16 },
 244 };
 245
 246 static int icmp_nlattr_to_tuple(struct nlattr *tb[],
 247                                 struct nf_conntrack_tuple *tuple)
 248 {
 249         if (!tb[CTA_PROTO_ICMP_TYPE]
 250             || !tb[CTA_PROTO_ICMP_CODE]
 251             || !tb[CTA_PROTO_ICMP_ID])
 252                 return -EINVAL;
 253
 254         tuple->dst.u.icmp.type = nla_get_u8(tb[CTA_PROTO_ICMP_TYPE]);
 255         tuple->dst.u.icmp.code = nla_get_u8(tb[CTA_PROTO_ICMP_CODE]);
 256         tuple->src.u.icmp.id = nla_get_be16(tb[CTA_PROTO_ICMP_ID]);
 257
 258         if (tuple->dst.u.icmp.type >= sizeof(invmap)
 259             || !invmap[tuple->dst.u.icmp.type])
 260                 return -EINVAL;
 261
 262         return 0;
 263 }
 264
 265 static int icmp_nlattr_tuple_size(void)
 266 {
 267         return nla_policy_len(icmp_nla_policy, CTA_PROTO_MAX + 1);
 268 }
 269 #endif
 270
 271 #ifdef CONFIG_SYSCTL
 272 static struct ctl_table_header *icmp_sysctl_header;
 273 static struct ctl_table icmp_sysctl_table[] = {
 274         {
 275                 .procname       = "nf_conntrack_icmp_timeout",
 276                 .data           = &nf_ct_icmp_timeout,
 277                 .maxlen         = sizeof(unsigned int),
 278                 .mode           = 0644,
 279                 .proc_handler   = proc_dointvec_jiffies,
 280         },
 281         {
 282                 .ctl_name = 0
 283         }
 284 };
 285 #ifdef CONFIG_NF_CONNTRACK_PROC_COMPAT
 286 static struct ctl_table icmp_compat_sysctl_table[] = {
 287         {
 288                 .procname       = "ip_conntrack_icmp_timeout",
 289                 .data           = &nf_ct_icmp_timeout,
 290                 .maxlen         = sizeof(unsigned int),
 291                 .mode           = 0644,
 292                 .proc_handler   = proc_dointvec_jiffies,
 293         },
 294         {
 295                 .ctl_name = 0
 296         }
 297 };
 298 #endif /* CONFIG_NF_CONNTRACK_PROC_COMPAT */
 299 #endif /* CONFIG_SYSCTL */
 300
 301 struct nf_conntrack_l4proto nf_conntrack_l4proto_icmp __read_mostly =
 302 {
 303         .l3proto                = PF_INET,
 304         .l4proto                = IPPROTO_ICMP,
 305         .name                   = "icmp",
 306         .pkt_to_tuple           = icmp_pkt_to_tuple,
 307         .invert_tuple           = icmp_invert_tuple,
 308         .print_tuple            = icmp_print_tuple,
 309         .packet                 = icmp_packet,
 310         .new                    = icmp_new,
 311         .error                  = icmp_error,
 312         .destroy                = NULL,
 313         .me                     = NULL,
 314 #if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
 315         .tuple_to_nlattr        = icmp_tuple_to_nlattr,
 316         .nlattr_tuple_size      = icmp_nlattr_tuple_size,
 317         .nlattr_to_tuple        = icmp_nlattr_to_tuple,
 318         .nla_policy             = icmp_nla_policy,
 319 #endif
 320 #ifdef CONFIG_SYSCTL
 321         .ctl_table_header       = &icmp_sysctl_header,
 322         .ctl_table              = icmp_sysctl_table,
 323 #ifdef CONFIG_NF_CONNTRACK_PROC_COMPAT
 324         .ctl_compat_table       = icmp_compat_sysctl_table,
 325 #endif
 326 #endif
 327 };