net/netfilter/nf_conntrack_proto_gre.c

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