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 
8 struct gre_base_hdr {
9 	__be16 flags;
10 	__be16 protocol;
11 } __packed;
12 
13 struct 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 
27 struct gre_protocol {
28 	int  (*handler)(struct sk_buff *skb);
29 	void (*err_handler)(struct sk_buff *skb, u32 info);
30 };
31 
32 int gre_add_protocol(const struct gre_protocol *proto, u8 version);
33 int gre_del_protocol(const struct gre_protocol *proto, u8 version);
34 
35 struct net_device *gretap_fb_dev_create(struct net *net, const char *name,
36 				       u8 name_assign_type);
37 int gre_parse_header(struct sk_buff *skb, struct tnl_ptk_info *tpi,
38 		     bool *csum_err, __be16 proto, int nhs);
39 
40 bool is_gretap_dev(const struct net_device *dev);
41 bool is_ip6gretap_dev(const struct net_device *dev);
42 
gre_calc_hlen(__be16 o_flags)43 static inline int gre_calc_hlen(__be16 o_flags)
44 {
45 	int addend = 4;
46 
47 	if (o_flags & TUNNEL_CSUM)
48 		addend += 4;
49 	if (o_flags & TUNNEL_KEY)
50 		addend += 4;
51 	if (o_flags & TUNNEL_SEQ)
52 		addend += 4;
53 	return addend;
54 }
55 
gre_flags_to_tnl_flags(__be16 flags)56 static inline __be16 gre_flags_to_tnl_flags(__be16 flags)
57 {
58 	__be16 tflags = 0;
59 
60 	if (flags & GRE_CSUM)
61 		tflags |= TUNNEL_CSUM;
62 	if (flags & GRE_ROUTING)
63 		tflags |= TUNNEL_ROUTING;
64 	if (flags & GRE_KEY)
65 		tflags |= TUNNEL_KEY;
66 	if (flags & GRE_SEQ)
67 		tflags |= TUNNEL_SEQ;
68 	if (flags & GRE_STRICT)
69 		tflags |= TUNNEL_STRICT;
70 	if (flags & GRE_REC)
71 		tflags |= TUNNEL_REC;
72 	if (flags & GRE_VERSION)
73 		tflags |= TUNNEL_VERSION;
74 
75 	return tflags;
76 }
77 
gre_tnl_flags_to_gre_flags(__be16 tflags)78 static inline __be16 gre_tnl_flags_to_gre_flags(__be16 tflags)
79 {
80 	__be16 flags = 0;
81 
82 	if (tflags & TUNNEL_CSUM)
83 		flags |= GRE_CSUM;
84 	if (tflags & TUNNEL_ROUTING)
85 		flags |= GRE_ROUTING;
86 	if (tflags & TUNNEL_KEY)
87 		flags |= GRE_KEY;
88 	if (tflags & TUNNEL_SEQ)
89 		flags |= GRE_SEQ;
90 	if (tflags & TUNNEL_STRICT)
91 		flags |= GRE_STRICT;
92 	if (tflags & TUNNEL_REC)
93 		flags |= GRE_REC;
94 	if (tflags & TUNNEL_VERSION)
95 		flags |= GRE_VERSION;
96 
97 	return flags;
98 }
99 
gre_checksum(struct sk_buff * skb)100 static inline __sum16 gre_checksum(struct sk_buff *skb)
101 {
102 	__wsum csum;
103 
104 	if (skb->ip_summed == CHECKSUM_PARTIAL)
105 		csum = lco_csum(skb);
106 	else
107 		csum = skb_checksum(skb, 0, skb->len, 0);
108 	return csum_fold(csum);
109 }
110 
gre_build_header(struct sk_buff * skb,int hdr_len,__be16 flags,__be16 proto,__be32 key,__be32 seq)111 static inline void gre_build_header(struct sk_buff *skb, int hdr_len,
112 				    __be16 flags, __be16 proto,
113 				    __be32 key, __be32 seq)
114 {
115 	struct gre_base_hdr *greh;
116 
117 	skb_push(skb, hdr_len);
118 
119 	skb_set_inner_protocol(skb, proto);
120 	skb_reset_transport_header(skb);
121 	greh = (struct gre_base_hdr *)skb->data;
122 	greh->flags = gre_tnl_flags_to_gre_flags(flags);
123 	greh->protocol = proto;
124 
125 	if (flags & (TUNNEL_KEY | TUNNEL_CSUM | TUNNEL_SEQ)) {
126 		__be32 *ptr = (__be32 *)(((u8 *)greh) + hdr_len - 4);
127 
128 		if (flags & TUNNEL_SEQ) {
129 			*ptr = seq;
130 			ptr--;
131 		}
132 		if (flags & TUNNEL_KEY) {
133 			*ptr = key;
134 			ptr--;
135 		}
136 		if (flags & TUNNEL_CSUM &&
137 		    !(skb_shinfo(skb)->gso_type &
138 		      (SKB_GSO_GRE | SKB_GSO_GRE_CSUM))) {
139 			*ptr = 0;
140 			*(__sum16 *)ptr = gre_checksum(skb);
141 		}
142 	}
143 }
144 
145 #endif
146