2 * GRE over IPv4 demultiplexer driver
4 * Authors: Dmitry Kozlov (xeb@mail.ru)
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.
13 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
15 #include <linux/module.h>
17 #include <linux/icmp.h>
18 #include <linux/kernel.h>
19 #include <linux/kmod.h>
20 #include <linux/skbuff.h>
23 #include <linux/netdevice.h>
24 #include <linux/if_tunnel.h>
25 #include <linux/spinlock.h>
26 #include <net/protocol.h>
30 #include <net/route.h>
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];
36 int gre_add_protocol(const struct gre_protocol *proto, u8 version)
38 if (version >= GREPROTO_MAX)
41 return (cmpxchg((const struct gre_protocol **)&gre_proto[version], NULL, proto) == NULL) ?
44 EXPORT_SYMBOL_GPL(gre_add_protocol);
46 int gre_del_protocol(const struct gre_protocol *proto, u8 version)
50 if (version >= GREPROTO_MAX)
53 ret = (cmpxchg((const struct gre_protocol **)&gre_proto[version], proto, NULL) == proto) ?
62 EXPORT_SYMBOL_GPL(gre_del_protocol);
64 void gre_build_header(struct sk_buff *skb, const struct tnl_ptk_info *tpi,
67 struct gre_base_hdr *greh;
69 skb_push(skb, hdr_len);
71 greh = (struct gre_base_hdr *)skb->data;
72 greh->flags = tnl_flags_to_gre_flags(tpi->flags);
73 greh->protocol = tpi->proto;
75 if (tpi->flags&(TUNNEL_KEY|TUNNEL_CSUM|TUNNEL_SEQ)) {
76 __be32 *ptr = (__be32 *)(((u8 *)greh) + hdr_len - 4);
78 if (tpi->flags&TUNNEL_SEQ) {
82 if (tpi->flags&TUNNEL_KEY) {
86 if (tpi->flags&TUNNEL_CSUM &&
87 !(skb_shinfo(skb)->gso_type &
88 (SKB_GSO_GRE|SKB_GSO_GRE_CSUM))) {
90 *(__sum16 *)ptr = csum_fold(skb_checksum(skb, 0,
95 EXPORT_SYMBOL_GPL(gre_build_header);
97 static int parse_gre_header(struct sk_buff *skb, struct tnl_ptk_info *tpi,
100 unsigned int ip_hlen = ip_hdrlen(skb);
101 const struct gre_base_hdr *greh;
105 if (unlikely(!pskb_may_pull(skb, sizeof(struct gre_base_hdr))))
108 greh = (struct gre_base_hdr *)(skb_network_header(skb) + ip_hlen);
109 if (unlikely(greh->flags & (GRE_VERSION | GRE_ROUTING)))
112 tpi->flags = gre_flags_to_tnl_flags(greh->flags);
113 hdr_len = ip_gre_calc_hlen(tpi->flags);
115 if (!pskb_may_pull(skb, hdr_len))
118 greh = (struct gre_base_hdr *)(skb_network_header(skb) + ip_hlen);
119 tpi->proto = greh->protocol;
121 options = (__be32 *)(greh + 1);
122 if (greh->flags & GRE_CSUM) {
123 if (skb_checksum_simple_validate(skb)) {
130 if (greh->flags & GRE_KEY) {
136 if (unlikely(greh->flags & GRE_SEQ)) {
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
146 if (greh->flags == 0 && tpi->proto == htons(ETH_P_WCCP)) {
147 tpi->proto = htons(ETH_P_IP);
148 if ((*(u8 *)options & 0xF0) != 0x40) {
150 if (!pskb_may_pull(skb, hdr_len))
155 return iptunnel_pull_header(skb, hdr_len, tpi->proto);
158 static int gre_cisco_rcv(struct sk_buff *skb)
160 struct tnl_ptk_info tpi;
162 bool csum_err = false;
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)))
172 if (parse_gre_header(skb, &tpi, &csum_err) < 0)
176 for (i = 0; i < GRE_IP_PROTO_MAX; i++) {
177 struct gre_cisco_protocol *proto;
180 proto = rcu_dereference(gre_cisco_proto_list[i]);
183 ret = proto->handler(skb, &tpi);
184 if (ret == PACKET_RCVD) {
191 icmp_send(skb, ICMP_DEST_UNREACH, ICMP_PORT_UNREACH, 0);
197 static void gre_cisco_err(struct sk_buff *skb, u32 info)
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.
203 * Moreover, Cisco "wise men" put GRE key to the third word
204 * in GRE header. It makes impossible maintaining even soft
206 * GRE tunnels with enabled checksum. Tell them "thank you".
208 * Well, I wonder, rfc1812 was written by Cisco employee,
209 * what the hell these idiots break standards established
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;
219 if (parse_gre_header(skb, &tpi, &csum_err)) {
220 if (!csum_err) /* ignore csum errors. */
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);
229 if (type == ICMP_REDIRECT) {
230 ipv4_redirect(skb, dev_net(skb->dev), skb->dev->ifindex, 0,
236 for (i = 0; i < GRE_IP_PROTO_MAX; i++) {
237 struct gre_cisco_protocol *proto;
239 proto = rcu_dereference(gre_cisco_proto_list[i]);
243 if (proto->err_handler(skb, info, &tpi) == PACKET_RCVD)
251 static int gre_rcv(struct sk_buff *skb)
253 const struct gre_protocol *proto;
257 if (!pskb_may_pull(skb, 12))
260 ver = skb->data[1]&0x7f;
261 if (ver >= GREPROTO_MAX)
265 proto = rcu_dereference(gre_proto[ver]);
266 if (!proto || !proto->handler)
268 ret = proto->handler(skb);
279 static void gre_err(struct sk_buff *skb, u32 info)
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;
285 if (ver >= GREPROTO_MAX)
289 proto = rcu_dereference(gre_proto[ver]);
290 if (proto && proto->err_handler)
291 proto->err_handler(skb, info);
295 static const struct net_protocol net_gre_protocol = {
297 .err_handler = gre_err,
301 static const struct gre_protocol ipgre_protocol = {
302 .handler = gre_cisco_rcv,
303 .err_handler = gre_cisco_err,
306 int gre_cisco_register(struct gre_cisco_protocol *newp)
308 struct gre_cisco_protocol **proto = (struct gre_cisco_protocol **)
309 &gre_cisco_proto_list[newp->priority];
311 return (cmpxchg(proto, NULL, newp) == NULL) ? 0 : -EBUSY;
313 EXPORT_SYMBOL_GPL(gre_cisco_register);
315 int gre_cisco_unregister(struct gre_cisco_protocol *del_proto)
317 struct gre_cisco_protocol **proto = (struct gre_cisco_protocol **)
318 &gre_cisco_proto_list[del_proto->priority];
321 ret = (cmpxchg(proto, del_proto, NULL) == del_proto) ? 0 : -EINVAL;
329 EXPORT_SYMBOL_GPL(gre_cisco_unregister);
331 static int __init gre_init(void)
333 pr_info("GRE over IPv4 demultiplexor driver\n");
335 if (inet_add_protocol(&net_gre_protocol, IPPROTO_GRE) < 0) {
336 pr_err("can't add protocol\n");
340 if (gre_add_protocol(&ipgre_protocol, GREPROTO_CISCO) < 0) {
341 pr_info("%s: can't add ipgre handler\n", __func__);
347 inet_del_protocol(&net_gre_protocol, IPPROTO_GRE);
352 static void __exit gre_exit(void)
354 gre_del_protocol(&ipgre_protocol, GREPROTO_CISCO);
355 inet_del_protocol(&net_gre_protocol, IPPROTO_GRE);
358 module_init(gre_init);
359 module_exit(gre_exit);
361 MODULE_DESCRIPTION("GRE over IPv4 demultiplexer driver");
362 MODULE_AUTHOR("D. Kozlov (xeb@mail.ru)");
363 MODULE_LICENSE("GPL");