1 /* 2 * GRE over IPv4 demultiplexer driver 3 * 4 * Authors: Dmitry Kozlov (xeb@mail.ru) 5 * 6 * This program is free software; you can redistribute it and/or 7 * modify it under the terms of the GNU General Public License 8 * as published by the Free Software Foundation; either version 9 * 2 of the License, or (at your option) any later version. 10 * 11 */ 12 13 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 14 15 #include <linux/module.h> 16 #include <linux/if.h> 17 #include <linux/icmp.h> 18 #include <linux/kernel.h> 19 #include <linux/kmod.h> 20 #include <linux/skbuff.h> 21 #include <linux/in.h> 22 #include <linux/ip.h> 23 #include <linux/netdevice.h> 24 #include <linux/if_tunnel.h> 25 #include <linux/spinlock.h> 26 #include <net/protocol.h> 27 #include <net/gre.h> 28 29 #include <net/icmp.h> 30 #include <net/route.h> 31 #include <net/xfrm.h> 32 33 static const struct gre_protocol __rcu *gre_proto[GREPROTO_MAX] __read_mostly; 34 static struct gre_cisco_protocol __rcu *gre_cisco_proto_list[GRE_IP_PROTO_MAX]; 35 36 int gre_add_protocol(const struct gre_protocol *proto, u8 version) 37 { 38 if (version >= GREPROTO_MAX) 39 return -EINVAL; 40 41 return (cmpxchg((const struct gre_protocol **)&gre_proto[version], NULL, proto) == NULL) ? 42 0 : -EBUSY; 43 } 44 EXPORT_SYMBOL_GPL(gre_add_protocol); 45 46 int gre_del_protocol(const struct gre_protocol *proto, u8 version) 47 { 48 int ret; 49 50 if (version >= GREPROTO_MAX) 51 return -EINVAL; 52 53 ret = (cmpxchg((const struct gre_protocol **)&gre_proto[version], proto, NULL) == proto) ? 54 0 : -EBUSY; 55 56 if (ret) 57 return ret; 58 59 synchronize_rcu(); 60 return 0; 61 } 62 EXPORT_SYMBOL_GPL(gre_del_protocol); 63 64 void gre_build_header(struct sk_buff *skb, const struct tnl_ptk_info *tpi, 65 int hdr_len) 66 { 67 struct gre_base_hdr *greh; 68 69 skb_push(skb, hdr_len); 70 71 greh = (struct gre_base_hdr *)skb->data; 72 greh->flags = tnl_flags_to_gre_flags(tpi->flags); 73 greh->protocol = tpi->proto; 74 75 if (tpi->flags&(TUNNEL_KEY|TUNNEL_CSUM|TUNNEL_SEQ)) { 76 __be32 *ptr = (__be32 *)(((u8 *)greh) + hdr_len - 4); 77 78 if (tpi->flags&TUNNEL_SEQ) { 79 *ptr = tpi->seq; 80 ptr--; 81 } 82 if (tpi->flags&TUNNEL_KEY) { 83 *ptr = tpi->key; 84 ptr--; 85 } 86 if (tpi->flags&TUNNEL_CSUM && 87 !(skb_shinfo(skb)->gso_type & 88 (SKB_GSO_GRE|SKB_GSO_GRE_CSUM))) { 89 *ptr = 0; 90 *(__sum16 *)ptr = csum_fold(skb_checksum(skb, 0, 91 skb->len, 0)); 92 } 93 } 94 } 95 EXPORT_SYMBOL_GPL(gre_build_header); 96 97 static int parse_gre_header(struct sk_buff *skb, struct tnl_ptk_info *tpi, 98 bool *csum_err) 99 { 100 unsigned int ip_hlen = ip_hdrlen(skb); 101 const struct gre_base_hdr *greh; 102 __be32 *options; 103 int hdr_len; 104 105 if (unlikely(!pskb_may_pull(skb, sizeof(struct gre_base_hdr)))) 106 return -EINVAL; 107 108 greh = (struct gre_base_hdr *)(skb_network_header(skb) + ip_hlen); 109 if (unlikely(greh->flags & (GRE_VERSION | GRE_ROUTING))) 110 return -EINVAL; 111 112 tpi->flags = gre_flags_to_tnl_flags(greh->flags); 113 hdr_len = ip_gre_calc_hlen(tpi->flags); 114 115 if (!pskb_may_pull(skb, hdr_len)) 116 return -EINVAL; 117 118 greh = (struct gre_base_hdr *)(skb_network_header(skb) + ip_hlen); 119 tpi->proto = greh->protocol; 120 121 options = (__be32 *)(greh + 1); 122 if (greh->flags & GRE_CSUM) { 123 if (skb_checksum_simple_validate(skb)) { 124 *csum_err = true; 125 return -EINVAL; 126 } 127 options++; 128 } 129 130 if (greh->flags & GRE_KEY) { 131 tpi->key = *options; 132 options++; 133 } else 134 tpi->key = 0; 135 136 if (unlikely(greh->flags & GRE_SEQ)) { 137 tpi->seq = *options; 138 options++; 139 } else 140 tpi->seq = 0; 141 142 /* WCCP version 1 and 2 protocol decoding. 143 * - Change protocol to IP 144 * - When dealing with WCCPv2, Skip extra 4 bytes in GRE header 145 */ 146 if (greh->flags == 0 && tpi->proto == htons(ETH_P_WCCP)) { 147 tpi->proto = htons(ETH_P_IP); 148 if ((*(u8 *)options & 0xF0) != 0x40) { 149 hdr_len += 4; 150 if (!pskb_may_pull(skb, hdr_len)) 151 return -EINVAL; 152 } 153 } 154 155 return iptunnel_pull_header(skb, hdr_len, tpi->proto); 156 } 157 158 static int gre_cisco_rcv(struct sk_buff *skb) 159 { 160 struct tnl_ptk_info tpi; 161 int i; 162 bool csum_err = false; 163 164 #ifdef CONFIG_NET_IPGRE_BROADCAST 165 if (ipv4_is_multicast(ip_hdr(skb)->daddr)) { 166 /* Looped back packet, drop it! */ 167 if (rt_is_output_route(skb_rtable(skb))) 168 goto drop; 169 } 170 #endif 171 172 if (parse_gre_header(skb, &tpi, &csum_err) < 0) 173 goto drop; 174 175 rcu_read_lock(); 176 for (i = 0; i < GRE_IP_PROTO_MAX; i++) { 177 struct gre_cisco_protocol *proto; 178 int ret; 179 180 proto = rcu_dereference(gre_cisco_proto_list[i]); 181 if (!proto) 182 continue; 183 ret = proto->handler(skb, &tpi); 184 if (ret == PACKET_RCVD) { 185 rcu_read_unlock(); 186 return 0; 187 } 188 } 189 rcu_read_unlock(); 190 191 icmp_send(skb, ICMP_DEST_UNREACH, ICMP_PORT_UNREACH, 0); 192 drop: 193 kfree_skb(skb); 194 return 0; 195 } 196 197 static void gre_cisco_err(struct sk_buff *skb, u32 info) 198 { 199 /* All the routers (except for Linux) return only 200 * 8 bytes of packet payload. It means, that precise relaying of 201 * ICMP in the real Internet is absolutely infeasible. 202 * 203 * Moreover, Cisco "wise men" put GRE key to the third word 204 * in GRE header. It makes impossible maintaining even soft 205 * state for keyed 206 * GRE tunnels with enabled checksum. Tell them "thank you". 207 * 208 * Well, I wonder, rfc1812 was written by Cisco employee, 209 * what the hell these idiots break standards established 210 * by themselves??? 211 */ 212 213 const int type = icmp_hdr(skb)->type; 214 const int code = icmp_hdr(skb)->code; 215 struct tnl_ptk_info tpi; 216 bool csum_err = false; 217 int i; 218 219 if (parse_gre_header(skb, &tpi, &csum_err)) { 220 if (!csum_err) /* ignore csum errors. */ 221 return; 222 } 223 224 if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED) { 225 ipv4_update_pmtu(skb, dev_net(skb->dev), info, 226 skb->dev->ifindex, 0, IPPROTO_GRE, 0); 227 return; 228 } 229 if (type == ICMP_REDIRECT) { 230 ipv4_redirect(skb, dev_net(skb->dev), skb->dev->ifindex, 0, 231 IPPROTO_GRE, 0); 232 return; 233 } 234 235 rcu_read_lock(); 236 for (i = 0; i < GRE_IP_PROTO_MAX; i++) { 237 struct gre_cisco_protocol *proto; 238 239 proto = rcu_dereference(gre_cisco_proto_list[i]); 240 if (!proto) 241 continue; 242 243 if (proto->err_handler(skb, info, &tpi) == PACKET_RCVD) 244 goto out; 245 246 } 247 out: 248 rcu_read_unlock(); 249 } 250 251 static int gre_rcv(struct sk_buff *skb) 252 { 253 const struct gre_protocol *proto; 254 u8 ver; 255 int ret; 256 257 if (!pskb_may_pull(skb, 12)) 258 goto drop; 259 260 ver = skb->data[1]&0x7f; 261 if (ver >= GREPROTO_MAX) 262 goto drop; 263 264 rcu_read_lock(); 265 proto = rcu_dereference(gre_proto[ver]); 266 if (!proto || !proto->handler) 267 goto drop_unlock; 268 ret = proto->handler(skb); 269 rcu_read_unlock(); 270 return ret; 271 272 drop_unlock: 273 rcu_read_unlock(); 274 drop: 275 kfree_skb(skb); 276 return NET_RX_DROP; 277 } 278 279 static void gre_err(struct sk_buff *skb, u32 info) 280 { 281 const struct gre_protocol *proto; 282 const struct iphdr *iph = (const struct iphdr *)skb->data; 283 u8 ver = skb->data[(iph->ihl<<2) + 1]&0x7f; 284 285 if (ver >= GREPROTO_MAX) 286 return; 287 288 rcu_read_lock(); 289 proto = rcu_dereference(gre_proto[ver]); 290 if (proto && proto->err_handler) 291 proto->err_handler(skb, info); 292 rcu_read_unlock(); 293 } 294 295 static const struct net_protocol net_gre_protocol = { 296 .handler = gre_rcv, 297 .err_handler = gre_err, 298 .netns_ok = 1, 299 }; 300 301 static const struct gre_protocol ipgre_protocol = { 302 .handler = gre_cisco_rcv, 303 .err_handler = gre_cisco_err, 304 }; 305 306 int gre_cisco_register(struct gre_cisco_protocol *newp) 307 { 308 struct gre_cisco_protocol **proto = (struct gre_cisco_protocol **) 309 &gre_cisco_proto_list[newp->priority]; 310 311 return (cmpxchg(proto, NULL, newp) == NULL) ? 0 : -EBUSY; 312 } 313 EXPORT_SYMBOL_GPL(gre_cisco_register); 314 315 int gre_cisco_unregister(struct gre_cisco_protocol *del_proto) 316 { 317 struct gre_cisco_protocol **proto = (struct gre_cisco_protocol **) 318 &gre_cisco_proto_list[del_proto->priority]; 319 int ret; 320 321 ret = (cmpxchg(proto, del_proto, NULL) == del_proto) ? 0 : -EINVAL; 322 323 if (ret) 324 return ret; 325 326 synchronize_net(); 327 return 0; 328 } 329 EXPORT_SYMBOL_GPL(gre_cisco_unregister); 330 331 static int __init gre_init(void) 332 { 333 pr_info("GRE over IPv4 demultiplexor driver\n"); 334 335 if (inet_add_protocol(&net_gre_protocol, IPPROTO_GRE) < 0) { 336 pr_err("can't add protocol\n"); 337 goto err; 338 } 339 340 if (gre_add_protocol(&ipgre_protocol, GREPROTO_CISCO) < 0) { 341 pr_info("%s: can't add ipgre handler\n", __func__); 342 goto err_gre; 343 } 344 345 return 0; 346 err_gre: 347 inet_del_protocol(&net_gre_protocol, IPPROTO_GRE); 348 err: 349 return -EAGAIN; 350 } 351 352 static void __exit gre_exit(void) 353 { 354 gre_del_protocol(&ipgre_protocol, GREPROTO_CISCO); 355 inet_del_protocol(&net_gre_protocol, IPPROTO_GRE); 356 } 357 358 module_init(gre_init); 359 module_exit(gre_exit); 360 361 MODULE_DESCRIPTION("GRE over IPv4 demultiplexer driver"); 362 MODULE_AUTHOR("D. Kozlov (xeb@mail.ru)"); 363 MODULE_LICENSE("GPL"); 364