net/netfilter/nf_conntrack_proto_gre.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * ip_conntrack_proto_gre.c - Version 3.0
   4  *
   5  * Connection tracking protocol helper module for GRE.
   6  *
   7  * GRE is a generic encapsulation protocol, which is generally not very
   8  * suited for NAT, as it has no protocol-specific part as port numbers.
   9  *
  10  * It has an optional key field, which may help us distinguishing two
  11  * connections between the same two hosts.
  12  *
  13  * GRE is defined in RFC 1701 and RFC 1702, as well as RFC 2784
  14  *
  15  * PPTP is built on top of a modified version of GRE, and has a mandatory
  16  * field called "CallID", which serves us for the same purpose as the key
  17  * field in plain GRE.
  18  *
  19  * Documentation about PPTP can be found in RFC 2637
  20  *
  21  * (C) 2000-2005 by Harald Welte <laforge@gnumonks.org>
  22  *
  23  * Development of this code funded by Astaro AG (http://www.astaro.com/)
  24  *
  25  * (C) 2006-2012 Patrick McHardy <kaber@trash.net>
  26  */
  27
  28 #include <linux/module.h>
  29 #include <linux/types.h>
  30 #include <linux/timer.h>
  31 #include <linux/list.h>
  32 #include <linux/seq_file.h>
  33 #include <linux/in.h>
  34 #include <linux/netdevice.h>
  35 #include <linux/skbuff.h>
  36 #include <linux/slab.h>
  37 #include <net/dst.h>
  38 #include <net/net_namespace.h>
  39 #include <net/netns/generic.h>
  40 #include <net/netfilter/nf_conntrack_l4proto.h>
  41 #include <net/netfilter/nf_conntrack_helper.h>
  42 #include <net/netfilter/nf_conntrack_core.h>
  43 #include <net/netfilter/nf_conntrack_timeout.h>
  44 #include <linux/netfilter/nf_conntrack_proto_gre.h>
  45 #include <linux/netfilter/nf_conntrack_pptp.h>
  46
  47 static const unsigned int gre_timeouts[GRE_CT_MAX] = {
  48         [GRE_CT_UNREPLIED]      = 30*HZ,
  49         [GRE_CT_REPLIED]        = 180*HZ,
  50 };
  51
  52 /* used when expectation is added */
  53 static DEFINE_SPINLOCK(keymap_lock);
  54
  55 static inline struct nf_gre_net *gre_pernet(struct net *net)
  56 {
  57         return &net->ct.nf_ct_proto.gre;
  58 }
  59
  60 void nf_ct_gre_keymap_flush(struct net *net)
  61 {
  62         struct nf_gre_net *net_gre = gre_pernet(net);
  63         struct nf_ct_gre_keymap *km, *tmp;
  64
  65         spin_lock_bh(&keymap_lock);
  66         list_for_each_entry_safe(km, tmp, &net_gre->keymap_list, list) {
  67                 list_del_rcu(&km->list);
  68                 kfree_rcu(km, rcu);
  69         }
  70         spin_unlock_bh(&keymap_lock);
  71 }
  72
  73 static inline int gre_key_cmpfn(const struct nf_ct_gre_keymap *km,
  74                                 const struct nf_conntrack_tuple *t)
  75 {
  76         return km->tuple.src.l3num == t->src.l3num &&
  77                !memcmp(&km->tuple.src.u3, &t->src.u3, sizeof(t->src.u3)) &&
  78                !memcmp(&km->tuple.dst.u3, &t->dst.u3, sizeof(t->dst.u3)) &&
  79                km->tuple.dst.protonum == t->dst.protonum &&
  80                km->tuple.dst.u.all == t->dst.u.all;
  81 }
  82
  83 /* look up the source key for a given tuple */
  84 static __be16 gre_keymap_lookup(struct net *net, struct nf_conntrack_tuple *t)
  85 {
  86         struct nf_gre_net *net_gre = gre_pernet(net);
  87         struct nf_ct_gre_keymap *km;
  88         __be16 key = 0;
  89
  90         list_for_each_entry_rcu(km, &net_gre->keymap_list, list) {
  91                 if (gre_key_cmpfn(km, t)) {
  92                         key = km->tuple.src.u.gre.key;
  93                         break;
  94                 }
  95         }
  96
  97         pr_debug("lookup src key 0x%x for ", key);
  98         nf_ct_dump_tuple(t);
  99
 100         return key;
 101 }
 102
 103 /* add a single keymap entry, associate with specified master ct */
 104 int nf_ct_gre_keymap_add(struct nf_conn *ct, enum ip_conntrack_dir dir,
 105                          struct nf_conntrack_tuple *t)
 106 {
 107         struct net *net = nf_ct_net(ct);
 108         struct nf_gre_net *net_gre = gre_pernet(net);
 109         struct nf_ct_pptp_master *ct_pptp_info = nfct_help_data(ct);
 110         struct nf_ct_gre_keymap **kmp, *km;
 111
 112         kmp = &ct_pptp_info->keymap[dir];
 113         if (*kmp) {
 114                 /* check whether it's a retransmission */
 115                 list_for_each_entry_rcu(km, &net_gre->keymap_list, list) {
 116                         if (gre_key_cmpfn(km, t) && km == *kmp)
 117                                 return 0;
 118                 }
 119                 pr_debug("trying to override keymap_%s for ct %p\n",
 120                          dir == IP_CT_DIR_REPLY ? "reply" : "orig", ct);
 121                 return -EEXIST;
 122         }
 123
 124         km = kmalloc(sizeof(*km), GFP_ATOMIC);
 125         if (!km)
 126                 return -ENOMEM;
 127         memcpy(&km->tuple, t, sizeof(*t));
 128         *kmp = km;
 129
 130         pr_debug("adding new entry %p: ", km);
 131         nf_ct_dump_tuple(&km->tuple);
 132
 133         spin_lock_bh(&keymap_lock);
 134         list_add_tail(&km->list, &net_gre->keymap_list);
 135         spin_unlock_bh(&keymap_lock);
 136
 137         return 0;
 138 }
 139 EXPORT_SYMBOL_GPL(nf_ct_gre_keymap_add);
 140
 141 /* destroy the keymap entries associated with specified master ct */
 142 void nf_ct_gre_keymap_destroy(struct nf_conn *ct)
 143 {
 144         struct nf_ct_pptp_master *ct_pptp_info = nfct_help_data(ct);
 145         enum ip_conntrack_dir dir;
 146
 147         pr_debug("entering for ct %p\n", ct);
 148
 149         spin_lock_bh(&keymap_lock);
 150         for (dir = IP_CT_DIR_ORIGINAL; dir < IP_CT_DIR_MAX; dir++) {
 151                 if (ct_pptp_info->keymap[dir]) {
 152                         pr_debug("removing %p from list\n",
 153                                  ct_pptp_info->keymap[dir]);
 154                         list_del_rcu(&ct_pptp_info->keymap[dir]->list);
 155                         kfree_rcu(ct_pptp_info->keymap[dir], rcu);
 156                         ct_pptp_info->keymap[dir] = NULL;
 157                 }
 158         }
 159         spin_unlock_bh(&keymap_lock);
 160 }
 161 EXPORT_SYMBOL_GPL(nf_ct_gre_keymap_destroy);
 162
 163 /* PUBLIC CONNTRACK PROTO HELPER FUNCTIONS */
 164
 165 /* gre hdr info to tuple */
 166 bool gre_pkt_to_tuple(const struct sk_buff *skb, unsigned int dataoff,
 167                       struct net *net, struct nf_conntrack_tuple *tuple)
 168 {
 169         const struct pptp_gre_header *pgrehdr;
 170         struct pptp_gre_header _pgrehdr;
 171         __be16 srckey;
 172         const struct gre_base_hdr *grehdr;
 173         struct gre_base_hdr _grehdr;
 174
 175         /* first only delinearize old RFC1701 GRE header */
 176         grehdr = skb_header_pointer(skb, dataoff, sizeof(_grehdr), &_grehdr);
 177         if (!grehdr || (grehdr->flags & GRE_VERSION) != GRE_VERSION_1) {
 178                 /* try to behave like "nf_conntrack_proto_generic" */
 179                 tuple->src.u.all = 0;
 180                 tuple->dst.u.all = 0;
 181                 return true;
 182         }
 183
 184         /* PPTP header is variable length, only need up to the call_id field */
 185         pgrehdr = skb_header_pointer(skb, dataoff, 8, &_pgrehdr);
 186         if (!pgrehdr)
 187                 return true;
 188
 189         if (grehdr->protocol != GRE_PROTO_PPP) {
 190                 pr_debug("Unsupported GRE proto(0x%x)\n", ntohs(grehdr->protocol));
 191                 return false;
 192         }
 193
 194         tuple->dst.u.gre.key = pgrehdr->call_id;
 195         srckey = gre_keymap_lookup(net, tuple);
 196         tuple->src.u.gre.key = srckey;
 197
 198         return true;
 199 }
 200
 201 #ifdef CONFIG_NF_CONNTRACK_PROCFS
 202 /* print private data for conntrack */
 203 static void gre_print_conntrack(struct seq_file *s, struct nf_conn *ct)
 204 {
 205         seq_printf(s, "timeout=%u, stream_timeout=%u ",
 206                    (ct->proto.gre.timeout / HZ),
 207                    (ct->proto.gre.stream_timeout / HZ));
 208 }
 209 #endif
 210
 211 static unsigned int *gre_get_timeouts(struct net *net)
 212 {
 213         return gre_pernet(net)->timeouts;
 214 }
 215
 216 /* Returns verdict for packet, and may modify conntrack */
 217 int nf_conntrack_gre_packet(struct nf_conn *ct,
 218                             struct sk_buff *skb,
 219                             unsigned int dataoff,
 220                             enum ip_conntrack_info ctinfo,
 221                             const struct nf_hook_state *state)
 222 {
 223         if (state->pf != NFPROTO_IPV4)
 224                 return -NF_ACCEPT;
 225
 226         if (!nf_ct_is_confirmed(ct)) {
 227                 unsigned int *timeouts = nf_ct_timeout_lookup(ct);
 228
 229                 if (!timeouts)
 230                         timeouts = gre_get_timeouts(nf_ct_net(ct));
 231
 232                 /* initialize to sane value.  Ideally a conntrack helper
 233                  * (e.g. in case of pptp) is increasing them */
 234                 ct->proto.gre.stream_timeout = timeouts[GRE_CT_REPLIED];
 235                 ct->proto.gre.timeout = timeouts[GRE_CT_UNREPLIED];
 236         }
 237
 238         /* If we've seen traffic both ways, this is a GRE connection.
 239          * Extend timeout. */
 240         if (ct->status & IPS_SEEN_REPLY) {
 241                 nf_ct_refresh_acct(ct, ctinfo, skb,
 242                                    ct->proto.gre.stream_timeout);
 243                 /* Also, more likely to be important, and not a probe. */
 244                 if (!test_and_set_bit(IPS_ASSURED_BIT, &ct->status))
 245                         nf_conntrack_event_cache(IPCT_ASSURED, ct);
 246         } else
 247                 nf_ct_refresh_acct(ct, ctinfo, skb,
 248                                    ct->proto.gre.timeout);
 249
 250         return NF_ACCEPT;
 251 }
 252
 253 #ifdef CONFIG_NF_CONNTRACK_TIMEOUT
 254
 255 #include <linux/netfilter/nfnetlink.h>
 256 #include <linux/netfilter/nfnetlink_cttimeout.h>
 257
 258 static int gre_timeout_nlattr_to_obj(struct nlattr *tb[],
 259                                      struct net *net, void *data)
 260 {
 261         unsigned int *timeouts = data;
 262         struct nf_gre_net *net_gre = gre_pernet(net);
 263
 264         if (!timeouts)
 265                 timeouts = gre_get_timeouts(net);
 266         /* set default timeouts for GRE. */
 267         timeouts[GRE_CT_UNREPLIED] = net_gre->timeouts[GRE_CT_UNREPLIED];
 268         timeouts[GRE_CT_REPLIED] = net_gre->timeouts[GRE_CT_REPLIED];
 269
 270         if (tb[CTA_TIMEOUT_GRE_UNREPLIED]) {
 271                 timeouts[GRE_CT_UNREPLIED] =
 272                         ntohl(nla_get_be32(tb[CTA_TIMEOUT_GRE_UNREPLIED])) * HZ;
 273         }
 274         if (tb[CTA_TIMEOUT_GRE_REPLIED]) {
 275                 timeouts[GRE_CT_REPLIED] =
 276                         ntohl(nla_get_be32(tb[CTA_TIMEOUT_GRE_REPLIED])) * HZ;
 277         }
 278         return 0;
 279 }
 280
 281 static int
 282 gre_timeout_obj_to_nlattr(struct sk_buff *skb, const void *data)
 283 {
 284         const unsigned int *timeouts = data;
 285
 286         if (nla_put_be32(skb, CTA_TIMEOUT_GRE_UNREPLIED,
 287                          htonl(timeouts[GRE_CT_UNREPLIED] / HZ)) ||
 288             nla_put_be32(skb, CTA_TIMEOUT_GRE_REPLIED,
 289                          htonl(timeouts[GRE_CT_REPLIED] / HZ)))
 290                 goto nla_put_failure;
 291         return 0;
 292
 293 nla_put_failure:
 294         return -ENOSPC;
 295 }
 296
 297 static const struct nla_policy
 298 gre_timeout_nla_policy[CTA_TIMEOUT_GRE_MAX+1] = {
 299         [CTA_TIMEOUT_GRE_UNREPLIED]     = { .type = NLA_U32 },
 300         [CTA_TIMEOUT_GRE_REPLIED]       = { .type = NLA_U32 },
 301 };
 302 #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
 303
 304 void nf_conntrack_gre_init_net(struct net *net)
 305 {
 306         struct nf_gre_net *net_gre = gre_pernet(net);
 307         int i;
 308
 309         INIT_LIST_HEAD(&net_gre->keymap_list);
 310         for (i = 0; i < GRE_CT_MAX; i++)
 311                 net_gre->timeouts[i] = gre_timeouts[i];
 312 }
 313
 314 /* protocol helper struct */
 315 const struct nf_conntrack_l4proto nf_conntrack_l4proto_gre = {
 316         .l4proto         = IPPROTO_GRE,
 317 #ifdef CONFIG_NF_CONNTRACK_PROCFS
 318         .print_conntrack = gre_print_conntrack,
 319 #endif
 320 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
 321         .tuple_to_nlattr = nf_ct_port_tuple_to_nlattr,
 322         .nlattr_tuple_size = nf_ct_port_nlattr_tuple_size,
 323         .nlattr_to_tuple = nf_ct_port_nlattr_to_tuple,
 324         .nla_policy      = nf_ct_port_nla_policy,
 325 #endif
 326 #ifdef CONFIG_NF_CONNTRACK_TIMEOUT
 327         .ctnl_timeout    = {
 328                 .nlattr_to_obj  = gre_timeout_nlattr_to_obj,
 329                 .obj_to_nlattr  = gre_timeout_obj_to_nlattr,
 330                 .nlattr_max     = CTA_TIMEOUT_GRE_MAX,
 331                 .obj_size       = sizeof(unsigned int) * GRE_CT_MAX,
 332                 .nla_policy     = gre_timeout_nla_policy,
 333         },
 334 #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
 335 };