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 
netif_is_gretap(const struct net_device * dev)40 static 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 
netif_is_ip6gretap(const struct net_device * dev)46 static 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 
gre_calc_hlen(__be16 o_flags)52 static inline int gre_calc_hlen(__be16 o_flags)
53 {
54 	int addend = 4;
55 
56 	if (o_flags & TUNNEL_CSUM)
57 		addend += 4;
58 	if (o_flags & TUNNEL_KEY)
59 		addend += 4;
60 	if (o_flags & TUNNEL_SEQ)
61 		addend += 4;
62 	return addend;
63 }
64 
gre_flags_to_tnl_flags(__be16 flags)65 static inline __be16 gre_flags_to_tnl_flags(__be16 flags)
66 {
67 	__be16 tflags = 0;
68 
69 	if (flags & GRE_CSUM)
70 		tflags |= TUNNEL_CSUM;
71 	if (flags & GRE_ROUTING)
72 		tflags |= TUNNEL_ROUTING;
73 	if (flags & GRE_KEY)
74 		tflags |= TUNNEL_KEY;
75 	if (flags & GRE_SEQ)
76 		tflags |= TUNNEL_SEQ;
77 	if (flags & GRE_STRICT)
78 		tflags |= TUNNEL_STRICT;
79 	if (flags & GRE_REC)
80 		tflags |= TUNNEL_REC;
81 	if (flags & GRE_VERSION)
82 		tflags |= TUNNEL_VERSION;
83 
84 	return tflags;
85 }
86 
gre_tnl_flags_to_gre_flags(__be16 tflags)87 static inline __be16 gre_tnl_flags_to_gre_flags(__be16 tflags)
88 {
89 	__be16 flags = 0;
90 
91 	if (tflags & TUNNEL_CSUM)
92 		flags |= GRE_CSUM;
93 	if (tflags & TUNNEL_ROUTING)
94 		flags |= GRE_ROUTING;
95 	if (tflags & TUNNEL_KEY)
96 		flags |= GRE_KEY;
97 	if (tflags & TUNNEL_SEQ)
98 		flags |= GRE_SEQ;
99 	if (tflags & TUNNEL_STRICT)
100 		flags |= GRE_STRICT;
101 	if (tflags & TUNNEL_REC)
102 		flags |= GRE_REC;
103 	if (tflags & TUNNEL_VERSION)
104 		flags |= GRE_VERSION;
105 
106 	return flags;
107 }
108 
gre_build_header(struct sk_buff * skb,int hdr_len,__be16 flags,__be16 proto,__be32 key,__be32 seq)109 static inline void gre_build_header(struct sk_buff *skb, int hdr_len,
110 				    __be16 flags, __be16 proto,
111 				    __be32 key, __be32 seq)
112 {
113 	struct gre_base_hdr *greh;
114 
115 	skb_push(skb, hdr_len);
116 
117 	skb_set_inner_protocol(skb, proto);
118 	skb_reset_transport_header(skb);
119 	greh = (struct gre_base_hdr *)skb->data;
120 	greh->flags = gre_tnl_flags_to_gre_flags(flags);
121 	greh->protocol = proto;
122 
123 	if (flags & (TUNNEL_KEY | TUNNEL_CSUM | TUNNEL_SEQ)) {
124 		__be32 *ptr = (__be32 *)(((u8 *)greh) + hdr_len - 4);
125 
126 		if (flags & TUNNEL_SEQ) {
127 			*ptr = seq;
128 			ptr--;
129 		}
130 		if (flags & TUNNEL_KEY) {
131 			*ptr = key;
132 			ptr--;
133 		}
134 		if (flags & TUNNEL_CSUM &&
135 		    !(skb_shinfo(skb)->gso_type &
136 		      (SKB_GSO_GRE | SKB_GSO_GRE_CSUM))) {
137 			*ptr = 0;
138 			if (skb->ip_summed == CHECKSUM_PARTIAL) {
139 				*(__sum16 *)ptr = csum_fold(lco_csum(skb));
140 			} else {
141 				skb->ip_summed = CHECKSUM_PARTIAL;
142 				skb->csum_start = skb_transport_header(skb) - skb->head;
143 				skb->csum_offset = sizeof(*greh);
144 			}
145 		}
146 	}
147 }
148 
149 #endif
150