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 static inline int gre_key_cmpfn(const struct nf_ct_gre_keymap *km, 59 const struct nf_conntrack_tuple *t) 60 { 61 return km->tuple.src.l3num == t->src.l3num && 62 !memcmp(&km->tuple.src.u3, &t->src.u3, sizeof(t->src.u3)) && 63 !memcmp(&km->tuple.dst.u3, &t->dst.u3, sizeof(t->dst.u3)) && 64 km->tuple.dst.protonum == t->dst.protonum && 65 km->tuple.dst.u.all == t->dst.u.all; 66 } 67 68 /* look up the source key for a given tuple */ 69 static __be16 gre_keymap_lookup(struct net *net, struct nf_conntrack_tuple *t) 70 { 71 struct nf_gre_net *net_gre = gre_pernet(net); 72 struct nf_ct_gre_keymap *km; 73 __be16 key = 0; 74 75 list_for_each_entry_rcu(km, &net_gre->keymap_list, list) { 76 if (gre_key_cmpfn(km, t)) { 77 key = km->tuple.src.u.gre.key; 78 break; 79 } 80 } 81 82 pr_debug("lookup src key 0x%x for ", key); 83 nf_ct_dump_tuple(t); 84 85 return key; 86 } 87 88 /* add a single keymap entry, associate with specified master ct */ 89 int nf_ct_gre_keymap_add(struct nf_conn *ct, enum ip_conntrack_dir dir, 90 struct nf_conntrack_tuple *t) 91 { 92 struct net *net = nf_ct_net(ct); 93 struct nf_gre_net *net_gre = gre_pernet(net); 94 struct nf_ct_pptp_master *ct_pptp_info = nfct_help_data(ct); 95 struct nf_ct_gre_keymap **kmp, *km; 96 97 kmp = &ct_pptp_info->keymap[dir]; 98 if (*kmp) { 99 /* check whether it's a retransmission */ 100 list_for_each_entry_rcu(km, &net_gre->keymap_list, list) { 101 if (gre_key_cmpfn(km, t) && km == *kmp) 102 return 0; 103 } 104 pr_debug("trying to override keymap_%s for ct %p\n", 105 dir == IP_CT_DIR_REPLY ? "reply" : "orig", ct); 106 return -EEXIST; 107 } 108 109 km = kmalloc(sizeof(*km), GFP_ATOMIC); 110 if (!km) 111 return -ENOMEM; 112 memcpy(&km->tuple, t, sizeof(*t)); 113 *kmp = km; 114 115 pr_debug("adding new entry %p: ", km); 116 nf_ct_dump_tuple(&km->tuple); 117 118 spin_lock_bh(&keymap_lock); 119 list_add_tail(&km->list, &net_gre->keymap_list); 120 spin_unlock_bh(&keymap_lock); 121 122 return 0; 123 } 124 EXPORT_SYMBOL_GPL(nf_ct_gre_keymap_add); 125 126 /* destroy the keymap entries associated with specified master ct */ 127 void nf_ct_gre_keymap_destroy(struct nf_conn *ct) 128 { 129 struct nf_ct_pptp_master *ct_pptp_info = nfct_help_data(ct); 130 enum ip_conntrack_dir dir; 131 132 pr_debug("entering for ct %p\n", ct); 133 134 spin_lock_bh(&keymap_lock); 135 for (dir = IP_CT_DIR_ORIGINAL; dir < IP_CT_DIR_MAX; dir++) { 136 if (ct_pptp_info->keymap[dir]) { 137 pr_debug("removing %p from list\n", 138 ct_pptp_info->keymap[dir]); 139 list_del_rcu(&ct_pptp_info->keymap[dir]->list); 140 kfree_rcu(ct_pptp_info->keymap[dir], rcu); 141 ct_pptp_info->keymap[dir] = NULL; 142 } 143 } 144 spin_unlock_bh(&keymap_lock); 145 } 146 EXPORT_SYMBOL_GPL(nf_ct_gre_keymap_destroy); 147 148 /* PUBLIC CONNTRACK PROTO HELPER FUNCTIONS */ 149 150 /* gre hdr info to tuple */ 151 bool gre_pkt_to_tuple(const struct sk_buff *skb, unsigned int dataoff, 152 struct net *net, struct nf_conntrack_tuple *tuple) 153 { 154 const struct pptp_gre_header *pgrehdr; 155 struct pptp_gre_header _pgrehdr; 156 __be16 srckey; 157 const struct gre_base_hdr *grehdr; 158 struct gre_base_hdr _grehdr; 159 160 /* first only delinearize old RFC1701 GRE header */ 161 grehdr = skb_header_pointer(skb, dataoff, sizeof(_grehdr), &_grehdr); 162 if (!grehdr || (grehdr->flags & GRE_VERSION) != GRE_VERSION_1) { 163 /* try to behave like "nf_conntrack_proto_generic" */ 164 tuple->src.u.all = 0; 165 tuple->dst.u.all = 0; 166 return true; 167 } 168 169 /* PPTP header is variable length, only need up to the call_id field */ 170 pgrehdr = skb_header_pointer(skb, dataoff, 8, &_pgrehdr); 171 if (!pgrehdr) 172 return true; 173 174 if (grehdr->protocol != GRE_PROTO_PPP) { 175 pr_debug("Unsupported GRE proto(0x%x)\n", ntohs(grehdr->protocol)); 176 return false; 177 } 178 179 tuple->dst.u.gre.key = pgrehdr->call_id; 180 srckey = gre_keymap_lookup(net, tuple); 181 tuple->src.u.gre.key = srckey; 182 183 return true; 184 } 185 186 #ifdef CONFIG_NF_CONNTRACK_PROCFS 187 /* print private data for conntrack */ 188 static void gre_print_conntrack(struct seq_file *s, struct nf_conn *ct) 189 { 190 seq_printf(s, "timeout=%u, stream_timeout=%u ", 191 (ct->proto.gre.timeout / HZ), 192 (ct->proto.gre.stream_timeout / HZ)); 193 } 194 #endif 195 196 static unsigned int *gre_get_timeouts(struct net *net) 197 { 198 return gre_pernet(net)->timeouts; 199 } 200 201 /* Returns verdict for packet, and may modify conntrack */ 202 int nf_conntrack_gre_packet(struct nf_conn *ct, 203 struct sk_buff *skb, 204 unsigned int dataoff, 205 enum ip_conntrack_info ctinfo, 206 const struct nf_hook_state *state) 207 { 208 if (!nf_ct_is_confirmed(ct)) { 209 unsigned int *timeouts = nf_ct_timeout_lookup(ct); 210 211 if (!timeouts) 212 timeouts = gre_get_timeouts(nf_ct_net(ct)); 213 214 /* initialize to sane value. Ideally a conntrack helper 215 * (e.g. in case of pptp) is increasing them */ 216 ct->proto.gre.stream_timeout = timeouts[GRE_CT_REPLIED]; 217 ct->proto.gre.timeout = timeouts[GRE_CT_UNREPLIED]; 218 } 219 220 /* If we've seen traffic both ways, this is a GRE connection. 221 * Extend timeout. */ 222 if (ct->status & IPS_SEEN_REPLY) { 223 nf_ct_refresh_acct(ct, ctinfo, skb, 224 ct->proto.gre.stream_timeout); 225 /* Also, more likely to be important, and not a probe. */ 226 if (!test_and_set_bit(IPS_ASSURED_BIT, &ct->status)) 227 nf_conntrack_event_cache(IPCT_ASSURED, ct); 228 } else 229 nf_ct_refresh_acct(ct, ctinfo, skb, 230 ct->proto.gre.timeout); 231 232 return NF_ACCEPT; 233 } 234 235 #ifdef CONFIG_NF_CONNTRACK_TIMEOUT 236 237 #include <linux/netfilter/nfnetlink.h> 238 #include <linux/netfilter/nfnetlink_cttimeout.h> 239 240 static int gre_timeout_nlattr_to_obj(struct nlattr *tb[], 241 struct net *net, void *data) 242 { 243 unsigned int *timeouts = data; 244 struct nf_gre_net *net_gre = gre_pernet(net); 245 246 if (!timeouts) 247 timeouts = gre_get_timeouts(net); 248 /* set default timeouts for GRE. */ 249 timeouts[GRE_CT_UNREPLIED] = net_gre->timeouts[GRE_CT_UNREPLIED]; 250 timeouts[GRE_CT_REPLIED] = net_gre->timeouts[GRE_CT_REPLIED]; 251 252 if (tb[CTA_TIMEOUT_GRE_UNREPLIED]) { 253 timeouts[GRE_CT_UNREPLIED] = 254 ntohl(nla_get_be32(tb[CTA_TIMEOUT_GRE_UNREPLIED])) * HZ; 255 } 256 if (tb[CTA_TIMEOUT_GRE_REPLIED]) { 257 timeouts[GRE_CT_REPLIED] = 258 ntohl(nla_get_be32(tb[CTA_TIMEOUT_GRE_REPLIED])) * HZ; 259 } 260 return 0; 261 } 262 263 static int 264 gre_timeout_obj_to_nlattr(struct sk_buff *skb, const void *data) 265 { 266 const unsigned int *timeouts = data; 267 268 if (nla_put_be32(skb, CTA_TIMEOUT_GRE_UNREPLIED, 269 htonl(timeouts[GRE_CT_UNREPLIED] / HZ)) || 270 nla_put_be32(skb, CTA_TIMEOUT_GRE_REPLIED, 271 htonl(timeouts[GRE_CT_REPLIED] / HZ))) 272 goto nla_put_failure; 273 return 0; 274 275 nla_put_failure: 276 return -ENOSPC; 277 } 278 279 static const struct nla_policy 280 gre_timeout_nla_policy[CTA_TIMEOUT_GRE_MAX+1] = { 281 [CTA_TIMEOUT_GRE_UNREPLIED] = { .type = NLA_U32 }, 282 [CTA_TIMEOUT_GRE_REPLIED] = { .type = NLA_U32 }, 283 }; 284 #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */ 285 286 void nf_conntrack_gre_init_net(struct net *net) 287 { 288 struct nf_gre_net *net_gre = gre_pernet(net); 289 int i; 290 291 INIT_LIST_HEAD(&net_gre->keymap_list); 292 for (i = 0; i < GRE_CT_MAX; i++) 293 net_gre->timeouts[i] = gre_timeouts[i]; 294 } 295 296 /* protocol helper struct */ 297 const struct nf_conntrack_l4proto nf_conntrack_l4proto_gre = { 298 .l4proto = IPPROTO_GRE, 299 #ifdef CONFIG_NF_CONNTRACK_PROCFS 300 .print_conntrack = gre_print_conntrack, 301 #endif 302 #if IS_ENABLED(CONFIG_NF_CT_NETLINK) 303 .tuple_to_nlattr = nf_ct_port_tuple_to_nlattr, 304 .nlattr_tuple_size = nf_ct_port_nlattr_tuple_size, 305 .nlattr_to_tuple = nf_ct_port_nlattr_to_tuple, 306 .nla_policy = nf_ct_port_nla_policy, 307 #endif 308 #ifdef CONFIG_NF_CONNTRACK_TIMEOUT 309 .ctnl_timeout = { 310 .nlattr_to_obj = gre_timeout_nlattr_to_obj, 311 .obj_to_nlattr = gre_timeout_obj_to_nlattr, 312 .nlattr_max = CTA_TIMEOUT_GRE_MAX, 313 .obj_size = sizeof(unsigned int) * GRE_CT_MAX, 314 .nla_policy = gre_timeout_nla_policy, 315 }, 316 #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */ 317 }; 318