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 }; 334