1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef __LINUX_GRE_H
3#define __LINUX_GRE_H
4
5#include <linux/skbuff.h>
6#include <net/ip_tunnels.h>
7
8struct gre_base_hdr {
9 __be16 flags;
10 __be16 protocol;
11} __packed;
12
13struct gre_full_hdr {
14 struct gre_base_hdr fixed_header;
15 __be16 csum;
16 __be16 reserved1;
17 __be32 key;
18 __be32 seq;
19} __packed;
20#define GRE_HEADER_SECTION 4
21
22#define GREPROTO_CISCO 0
23#define GREPROTO_PPTP 1
24#define GREPROTO_MAX 2
25#define GRE_IP_PROTO_MAX 2
26
27struct gre_protocol {
28 int (*handler)(struct sk_buff *skb);
29 void (*err_handler)(struct sk_buff *skb, u32 info);
30};
31
32int gre_add_protocol(const struct gre_protocol *proto, u8 version);
33int gre_del_protocol(const struct gre_protocol *proto, u8 version);
34
35struct net_device *gretap_fb_dev_create(struct net *net, const char *name,
36 u8 name_assign_type);
37int gre_parse_header(struct sk_buff *skb, struct tnl_ptk_info *tpi,
38 bool *csum_err, __be16 proto, int nhs);
39
40static inline bool netif_is_gretap(const struct net_device *dev)
41{
42 return dev->rtnl_link_ops &&
43 !strcmp(dev->rtnl_link_ops->kind, "gretap");
44}
45
46static inline bool netif_is_ip6gretap(const struct net_device *dev)
47{
48 return dev->rtnl_link_ops &&
49 !strcmp(dev->rtnl_link_ops->kind, "ip6gretap");
50}
51
52static inline int gre_calc_hlen(const unsigned long *o_flags)
53{
54 int addend = 4;
55
56 if (test_bit(IP_TUNNEL_CSUM_BIT, o_flags))
57 addend += 4;
58 if (test_bit(IP_TUNNEL_KEY_BIT, o_flags))
59 addend += 4;
60 if (test_bit(IP_TUNNEL_SEQ_BIT, o_flags))
61 addend += 4;
62 return addend;
63}
64
65static inline void gre_flags_to_tnl_flags(unsigned long *dst, __be16 flags)
66{
67 IP_TUNNEL_DECLARE_FLAGS(res) = { };
68
69 __assign_bit(IP_TUNNEL_CSUM_BIT, res, flags & GRE_CSUM);
70 __assign_bit(IP_TUNNEL_ROUTING_BIT, res, flags & GRE_ROUTING);
71 __assign_bit(IP_TUNNEL_KEY_BIT, res, flags & GRE_KEY);
72 __assign_bit(IP_TUNNEL_SEQ_BIT, res, flags & GRE_SEQ);
73 __assign_bit(IP_TUNNEL_STRICT_BIT, res, flags & GRE_STRICT);
74 __assign_bit(IP_TUNNEL_REC_BIT, res, flags & GRE_REC);
75 __assign_bit(IP_TUNNEL_VERSION_BIT, res, flags & GRE_VERSION);
76
77 ip_tunnel_flags_copy(dst, res);
78}
79
80static inline __be16 gre_tnl_flags_to_gre_flags(const unsigned long *tflags)
81{
82 __be16 flags = 0;
83
84 if (test_bit(IP_TUNNEL_CSUM_BIT, tflags))
85 flags |= GRE_CSUM;
86 if (test_bit(IP_TUNNEL_ROUTING_BIT, tflags))
87 flags |= GRE_ROUTING;
88 if (test_bit(IP_TUNNEL_KEY_BIT, tflags))
89 flags |= GRE_KEY;
90 if (test_bit(IP_TUNNEL_SEQ_BIT, tflags))
91 flags |= GRE_SEQ;
92 if (test_bit(IP_TUNNEL_STRICT_BIT, tflags))
93 flags |= GRE_STRICT;
94 if (test_bit(IP_TUNNEL_REC_BIT, tflags))
95 flags |= GRE_REC;
96 if (test_bit(IP_TUNNEL_VERSION_BIT, tflags))
97 flags |= GRE_VERSION;
98
99 return flags;
100}
101
102static inline void gre_build_header(struct sk_buff *skb, int hdr_len,
103 const unsigned long *flags, __be16 proto,
104 __be32 key, __be32 seq)
105{
106 IP_TUNNEL_DECLARE_FLAGS(cond) = { };
107 struct gre_base_hdr *greh;
108
109 skb_push(skb, len: hdr_len);
110
111 skb_set_inner_protocol(skb, protocol: proto);
112 skb_reset_transport_header(skb);
113 greh = (struct gre_base_hdr *)skb->data;
114 greh->flags = gre_tnl_flags_to_gre_flags(tflags: flags);
115 greh->protocol = proto;
116
117 __set_bit(IP_TUNNEL_KEY_BIT, cond);
118 __set_bit(IP_TUNNEL_CSUM_BIT, cond);
119 __set_bit(IP_TUNNEL_SEQ_BIT, cond);
120
121 if (ip_tunnel_flags_intersect(flags, cond)) {
122 __be32 *ptr = (__be32 *)(((u8 *)greh) + hdr_len - 4);
123
124 if (test_bit(IP_TUNNEL_SEQ_BIT, flags)) {
125 *ptr = seq;
126 ptr--;
127 }
128 if (test_bit(IP_TUNNEL_KEY_BIT, flags)) {
129 *ptr = key;
130 ptr--;
131 }
132 if (test_bit(IP_TUNNEL_CSUM_BIT, flags) &&
133 !(skb_shinfo(skb)->gso_type &
134 (SKB_GSO_GRE | SKB_GSO_GRE_CSUM))) {
135 *ptr = 0;
136 if (skb->ip_summed == CHECKSUM_PARTIAL) {
137 *(__sum16 *)ptr = csum_fold(csum: lco_csum(skb));
138 } else {
139 skb->ip_summed = CHECKSUM_PARTIAL;
140 skb->csum_start = skb_transport_header(skb) - skb->head;
141 skb->csum_offset = sizeof(*greh);
142 }
143 }
144 }
145}
146
147#endif
148

source code of linux/include/net/gre.h