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_conntrack_zones.h>
  22 #include <net/netfilter/nf_log.h>
  23
  24 static unsigned int nf_ct_icmp_timeout __read_mostly = 30*HZ;
  25
  26 static bool icmp_pkt_to_tuple(const struct sk_buff *skb, 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 false;
  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 true;
  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 bool 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 false;
  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 true;
  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                        u_int8_t pf,
  84                        unsigned int hooknum)
  85 {
  86         /* Do not immediately delete the connection after the first
  87            successful reply to avoid excessive conntrackd traffic
  88            and also to handle correctly ICMP echo reply duplicates. */
  89         nf_ct_refresh_acct(ct, ctinfo, skb, nf_ct_icmp_timeout);
  90
  91         return NF_ACCEPT;
  92 }
  93
  94 /* Called when a new connection for this protocol found. */
  95 static bool icmp_new(struct nf_conn *ct, const struct sk_buff *skb,
  96                      unsigned int dataoff)
  97 {
  98         static const u_int8_t valid_new[] = {
  99                 [ICMP_ECHO] = 1,
 100                 [ICMP_TIMESTAMP] = 1,
 101                 [ICMP_INFO_REQUEST] = 1,
 102                 [ICMP_ADDRESS] = 1
 103         };
 104
 105         if (ct->tuplehash[0].tuple.dst.u.icmp.type >= sizeof(valid_new) ||
 106             !valid_new[ct->tuplehash[0].tuple.dst.u.icmp.type]) {
 107                 /* Can't create a new ICMP `conn' with this. */
 108                 pr_debug("icmp: can't create new conn with type %u\n",
 109                          ct->tuplehash[0].tuple.dst.u.icmp.type);
 110                 nf_ct_dump_tuple_ip(&ct->tuplehash[0].tuple);
 111                 return false;
 112         }
 113         return true;
 114 }
 115
 116 /* Returns conntrack if it dealt with ICMP, and filled in skb fields */
 117 static int
 118 icmp_error_message(struct net *net, struct nf_conn *tmpl, struct sk_buff *skb,
 119                  enum ip_conntrack_info *ctinfo,
 120                  unsigned int hooknum)
 121 {
 122         struct nf_conntrack_tuple innertuple, origtuple;
 123         const struct nf_conntrack_l4proto *innerproto;
 124         const struct nf_conntrack_tuple_hash *h;
 125         u16 zone = tmpl ? nf_ct_zone(tmpl) : NF_CT_DEFAULT_ZONE;
 126
 127         NF_CT_ASSERT(skb->nfct == NULL);
 128
 129         /* Are they talking about one of our connections? */
 130         if (!nf_ct_get_tuplepr(skb,
 131                                skb_network_offset(skb) + ip_hdrlen(skb)
 132                                                        + sizeof(struct icmphdr),
 133                                PF_INET, &origtuple)) {
 134                 pr_debug("icmp_error_message: failed to get tuple\n");
 135                 return -NF_ACCEPT;
 136         }
 137
 138         /* rcu_read_lock()ed by nf_hook_slow */
 139         innerproto = __nf_ct_l4proto_find(PF_INET, origtuple.dst.protonum);
 140
 141         /* Ordinarily, we'd expect the inverted tupleproto, but it's
 142            been preserved inside the ICMP. */
 143         if (!nf_ct_invert_tuple(&innertuple, &origtuple,
 144                                 &nf_conntrack_l3proto_ipv4, innerproto)) {
 145                 pr_debug("icmp_error_message: no match\n");
 146                 return -NF_ACCEPT;
 147         }
 148
 149         *ctinfo = IP_CT_RELATED;
 150
 151         h = nf_conntrack_find_get(net, zone, &innertuple);
 152         if (!h) {
 153                 pr_debug("icmp_error_message: no match\n");
 154                 return -NF_ACCEPT;
 155         }
 156
 157         if (NF_CT_DIRECTION(h) == IP_CT_DIR_REPLY)
 158                 *ctinfo += IP_CT_IS_REPLY;
 159
 160         /* Update skb to refer to this connection */
 161         skb->nfct = &nf_ct_tuplehash_to_ctrack(h)->ct_general;
 162         skb->nfctinfo = *ctinfo;
 163         return NF_ACCEPT;
 164 }
 165
 166 /* Small and modified version of icmp_rcv */
 167 static int
 168 icmp_error(struct net *net, struct nf_conn *tmpl,
 169            struct sk_buff *skb, unsigned int dataoff,
 170            enum ip_conntrack_info *ctinfo, u_int8_t pf, unsigned int hooknum)
 171 {
 172         const struct icmphdr *icmph;
 173         struct icmphdr _ih;
 174
 175         /* Not enough header? */
 176         icmph = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_ih), &_ih);
 177         if (icmph == NULL) {
 178                 if (LOG_INVALID(net, IPPROTO_ICMP))
 179                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 180                                       "nf_ct_icmp: short packet ");
 181                 return -NF_ACCEPT;
 182         }
 183
 184         /* See ip_conntrack_proto_tcp.c */
 185         if (net->ct.sysctl_checksum && hooknum == NF_INET_PRE_ROUTING &&
 186             nf_ip_checksum(skb, hooknum, dataoff, 0)) {
 187                 if (LOG_INVALID(net, IPPROTO_ICMP))
 188                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 189                                       "nf_ct_icmp: bad HW ICMP checksum ");
 190                 return -NF_ACCEPT;
 191         }
 192
 193         /*
 194          *      18 is the highest 'known' ICMP type. Anything else is a mystery
 195          *
 196          *      RFC 1122: 3.2.2  Unknown ICMP messages types MUST be silently
 197          *                discarded.
 198          */
 199         if (icmph->type > NR_ICMP_TYPES) {
 200                 if (LOG_INVALID(net, IPPROTO_ICMP))
 201                         nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
 202                                       "nf_ct_icmp: invalid ICMP type ");
 203                 return -NF_ACCEPT;
 204         }
 205
 206         /* Need to track icmp error message? */
 207         if (icmph->type != ICMP_DEST_UNREACH &&
 208             icmph->type != ICMP_SOURCE_QUENCH &&
 209             icmph->type != ICMP_TIME_EXCEEDED &&
 210             icmph->type != ICMP_PARAMETERPROB &&
 211             icmph->type != ICMP_REDIRECT)
 212                 return NF_ACCEPT;
 213
 214         return icmp_error_message(net, tmpl, skb, ctinfo, hooknum);
 215 }
 216
 217 #if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
 218
 219 #include <linux/netfilter/nfnetlink.h>
 220 #include <linux/netfilter/nfnetlink_conntrack.h>
 221
 222 static int icmp_tuple_to_nlattr(struct sk_buff *skb,
 223                                 const struct nf_conntrack_tuple *t)
 224 {
 225         NLA_PUT_BE16(skb, CTA_PROTO_ICMP_ID, t->src.u.icmp.id);
 226         NLA_PUT_U8(skb, CTA_PROTO_ICMP_TYPE, t->dst.u.icmp.type);
 227         NLA_PUT_U8(skb, CTA_PROTO_ICMP_CODE, t->dst.u.icmp.code);
 228
 229         return 0;
 230
 231 nla_put_failure:
 232         return -1;
 233 }
 234
 235 static const struct nla_policy icmp_nla_policy[CTA_PROTO_MAX+1] = {
 236         [CTA_PROTO_ICMP_TYPE]   = { .type = NLA_U8 },
 237         [CTA_PROTO_ICMP_CODE]   = { .type = NLA_U8 },
 238         [CTA_PROTO_ICMP_ID]     = { .type = NLA_U16 },
 239 };
 240
 241 static int icmp_nlattr_to_tuple(struct nlattr *tb[],
 242                                 struct nf_conntrack_tuple *tuple)
 243 {
 244         if (!tb[CTA_PROTO_ICMP_TYPE] ||
 245             !tb[CTA_PROTO_ICMP_CODE] ||
 246             !tb[CTA_PROTO_ICMP_ID])
 247                 return -EINVAL;
 248
 249         tuple->dst.u.icmp.type = nla_get_u8(tb[CTA_PROTO_ICMP_TYPE]);
 250         tuple->dst.u.icmp.code = nla_get_u8(tb[CTA_PROTO_ICMP_CODE]);
 251         tuple->src.u.icmp.id = nla_get_be16(tb[CTA_PROTO_ICMP_ID]);
 252
 253         if (tuple->dst.u.icmp.type >= sizeof(invmap) ||
 254             !invmap[tuple->dst.u.icmp.type])
 255                 return -EINVAL;
 256
 257         return 0;
 258 }
 259
 260 static int icmp_nlattr_tuple_size(void)
 261 {
 262         return nla_policy_len(icmp_nla_policy, CTA_PROTO_MAX + 1);
 263 }
 264 #endif
 265
 266 #ifdef CONFIG_SYSCTL
 267 static struct ctl_table_header *icmp_sysctl_header;
 268 static struct ctl_table icmp_sysctl_table[] = {
 269         {
 270                 .procname       = "nf_conntrack_icmp_timeout",
 271                 .data           = &nf_ct_icmp_timeout,
 272                 .maxlen         = sizeof(unsigned int),
 273                 .mode           = 0644,
 274                 .proc_handler   = proc_dointvec_jiffies,
 275         },
 276         { }
 277 };
 278 #ifdef CONFIG_NF_CONNTRACK_PROC_COMPAT
 279 static struct ctl_table icmp_compat_sysctl_table[] = {
 280         {
 281                 .procname       = "ip_conntrack_icmp_timeout",
 282                 .data           = &nf_ct_icmp_timeout,
 283                 .maxlen         = sizeof(unsigned int),
 284                 .mode           = 0644,
 285                 .proc_handler   = proc_dointvec_jiffies,
 286         },
 287         { }
 288 };
 289 #endif /* CONFIG_NF_CONNTRACK_PROC_COMPAT */
 290 #endif /* CONFIG_SYSCTL */
 291
 292 struct nf_conntrack_l4proto nf_conntrack_l4proto_icmp __read_mostly =
 293 {
 294         .l3proto                = PF_INET,
 295         .l4proto                = IPPROTO_ICMP,
 296         .name                   = "icmp",
 297         .pkt_to_tuple           = icmp_pkt_to_tuple,
 298         .invert_tuple           = icmp_invert_tuple,
 299         .print_tuple            = icmp_print_tuple,
 300         .packet                 = icmp_packet,
 301         .new                    = icmp_new,
 302         .error                  = icmp_error,
 303         .destroy                = NULL,
 304         .me                     = NULL,
 305 #if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
 306         .tuple_to_nlattr        = icmp_tuple_to_nlattr,
 307         .nlattr_tuple_size      = icmp_nlattr_tuple_size,
 308         .nlattr_to_tuple        = icmp_nlattr_to_tuple,
 309         .nla_policy             = icmp_nla_policy,
 310 #endif
 311 #ifdef CONFIG_SYSCTL
 312         .ctl_table_header       = &icmp_sysctl_header,
 313         .ctl_table              = icmp_sysctl_table,
 314 #ifdef CONFIG_NF_CONNTRACK_PROC_COMPAT
 315         .ctl_compat_table       = icmp_compat_sysctl_table,
 316 #endif
 317 #endif
 318 };