1 // SPDX-License-Identifier: GPL-2.0-or-later
3 * GRE over IPv4 demultiplexer driver
5 * Authors: Dmitry Kozlov (xeb@mail.ru)
8 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
10 #include <linux/module.h>
12 #include <linux/icmp.h>
13 #include <linux/kernel.h>
14 #include <linux/kmod.h>
15 #include <linux/skbuff.h>
18 #include <linux/netdevice.h>
19 #include <linux/if_tunnel.h>
20 #include <linux/spinlock.h>
21 #include <net/protocol.h>
23 #include <net/erspan.h>
26 #include <net/route.h>
29 static const struct gre_protocol __rcu *gre_proto[GREPROTO_MAX] __read_mostly;
31 int gre_add_protocol(const struct gre_protocol *proto, u8 version)
33 if (version >= GREPROTO_MAX)
36 return (cmpxchg((const struct gre_protocol **)&gre_proto[version], NULL, proto) == NULL) ?
39 EXPORT_SYMBOL_GPL(gre_add_protocol);
41 int gre_del_protocol(const struct gre_protocol *proto, u8 version)
45 if (version >= GREPROTO_MAX)
48 ret = (cmpxchg((const struct gre_protocol **)&gre_proto[version], proto, NULL) == proto) ?
57 EXPORT_SYMBOL_GPL(gre_del_protocol);
59 /* Fills in tpi and returns header length to be pulled.
60 * Note that caller must use pskb_may_pull() before pulling GRE header.
62 int gre_parse_header(struct sk_buff *skb, struct tnl_ptk_info *tpi,
63 bool *csum_err, __be16 proto, int nhs)
65 const struct gre_base_hdr *greh;
69 if (unlikely(!pskb_may_pull(skb, nhs + sizeof(struct gre_base_hdr))))
72 greh = (struct gre_base_hdr *)(skb->data + nhs);
73 if (unlikely(greh->flags & (GRE_VERSION | GRE_ROUTING)))
76 tpi->flags = gre_flags_to_tnl_flags(greh->flags);
77 hdr_len = gre_calc_hlen(tpi->flags);
79 if (!pskb_may_pull(skb, nhs + hdr_len))
82 greh = (struct gre_base_hdr *)(skb->data + nhs);
83 tpi->proto = greh->protocol;
85 options = (__be32 *)(greh + 1);
86 if (greh->flags & GRE_CSUM) {
87 if (!skb_checksum_simple_validate(skb)) {
88 skb_checksum_try_convert(skb, IPPROTO_GRE,
90 } else if (csum_err) {
98 if (greh->flags & GRE_KEY) {
104 if (unlikely(greh->flags & GRE_SEQ)) {
110 /* WCCP version 1 and 2 protocol decoding.
111 * - Change protocol to IPv4/IPv6
112 * - When dealing with WCCPv2, Skip extra 4 bytes in GRE header
114 if (greh->flags == 0 && tpi->proto == htons(ETH_P_WCCP)) {
117 val = skb_header_pointer(skb, nhs + hdr_len,
118 sizeof(_val), &_val);
122 if ((*val & 0xF0) != 0x40)
125 tpi->hdr_len = hdr_len;
127 /* ERSPAN ver 1 and 2 protocol sets GRE key field
128 * to 0 and sets the configured key in the
129 * inner erspan header field
131 if ((greh->protocol == htons(ETH_P_ERSPAN) && hdr_len != 4) ||
132 greh->protocol == htons(ETH_P_ERSPAN2)) {
133 struct erspan_base_hdr *ershdr;
135 if (!pskb_may_pull(skb, nhs + hdr_len + sizeof(*ershdr)))
138 ershdr = (struct erspan_base_hdr *)(skb->data + nhs + hdr_len);
139 tpi->key = cpu_to_be32(get_session_id(ershdr));
144 EXPORT_SYMBOL(gre_parse_header);
146 static int gre_rcv(struct sk_buff *skb)
148 const struct gre_protocol *proto;
152 if (!pskb_may_pull(skb, 12))
155 ver = skb->data[1]&0x7f;
156 if (ver >= GREPROTO_MAX)
160 proto = rcu_dereference(gre_proto[ver]);
161 if (!proto || !proto->handler)
163 ret = proto->handler(skb);
174 static int gre_err(struct sk_buff *skb, u32 info)
176 const struct gre_protocol *proto;
177 const struct iphdr *iph = (const struct iphdr *)skb->data;
178 u8 ver = skb->data[(iph->ihl<<2) + 1]&0x7f;
181 if (ver >= GREPROTO_MAX)
185 proto = rcu_dereference(gre_proto[ver]);
186 if (proto && proto->err_handler)
187 proto->err_handler(skb, info);
189 err = -EPROTONOSUPPORT;
195 static const struct net_protocol net_gre_protocol = {
197 .err_handler = gre_err,
201 static int __init gre_init(void)
203 pr_info("GRE over IPv4 demultiplexor driver\n");
205 if (inet_add_protocol(&net_gre_protocol, IPPROTO_GRE) < 0) {
206 pr_err("can't add protocol\n");
212 static void __exit gre_exit(void)
214 inet_del_protocol(&net_gre_protocol, IPPROTO_GRE);
217 module_init(gre_init);
218 module_exit(gre_exit);
220 MODULE_DESCRIPTION("GRE over IPv4 demultiplexer driver");
221 MODULE_AUTHOR("D. Kozlov (xeb@mail.ru)");
222 MODULE_LICENSE("GPL");