include/net/gre.h

   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 static inline int gre_calc_hlen(__be16 o_flags)
  41 {
  42         int addend = 4;
  43
  44         if (o_flags & TUNNEL_CSUM)
  45                 addend += 4;
  46         if (o_flags & TUNNEL_KEY)
  47                 addend += 4;
  48         if (o_flags & TUNNEL_SEQ)
  49                 addend += 4;
  50         return addend;
  51 }
  52
  53 static inline __be16 gre_flags_to_tnl_flags(__be16 flags)
  54 {
  55         __be16 tflags = 0;
  56
  57         if (flags & GRE_CSUM)
  58                 tflags |= TUNNEL_CSUM;
  59         if (flags & GRE_ROUTING)
  60                 tflags |= TUNNEL_ROUTING;
  61         if (flags & GRE_KEY)
  62                 tflags |= TUNNEL_KEY;
  63         if (flags & GRE_SEQ)
  64                 tflags |= TUNNEL_SEQ;
  65         if (flags & GRE_STRICT)
  66                 tflags |= TUNNEL_STRICT;
  67         if (flags & GRE_REC)
  68                 tflags |= TUNNEL_REC;
  69         if (flags & GRE_VERSION)
  70                 tflags |= TUNNEL_VERSION;
  71
  72         return tflags;
  73 }
  74
  75 static inline __be16 gre_tnl_flags_to_gre_flags(__be16 tflags)
  76 {
  77         __be16 flags = 0;
  78
  79         if (tflags & TUNNEL_CSUM)
  80                 flags |= GRE_CSUM;
  81         if (tflags & TUNNEL_ROUTING)
  82                 flags |= GRE_ROUTING;
  83         if (tflags & TUNNEL_KEY)
  84                 flags |= GRE_KEY;
  85         if (tflags & TUNNEL_SEQ)
  86                 flags |= GRE_SEQ;
  87         if (tflags & TUNNEL_STRICT)
  88                 flags |= GRE_STRICT;
  89         if (tflags & TUNNEL_REC)
  90                 flags |= GRE_REC;
  91         if (tflags & TUNNEL_VERSION)
  92                 flags |= GRE_VERSION;
  93
  94         return flags;
  95 }
  96
  97 static inline __sum16 gre_checksum(struct sk_buff *skb)
  98 {
  99         __wsum csum;
 100
 101         if (skb->ip_summed == CHECKSUM_PARTIAL)
 102                 csum = lco_csum(skb);
 103         else
 104                 csum = skb_checksum(skb, 0, skb->len, 0);
 105         return csum_fold(csum);
 106 }
 107
 108 static inline void gre_build_header(struct sk_buff *skb, int hdr_len,
 109                                     __be16 flags, __be16 proto,
 110                                     __be32 key, __be32 seq)
 111 {
 112         struct gre_base_hdr *greh;
 113
 114         skb_push(skb, hdr_len);
 115
 116         skb_set_inner_protocol(skb, proto);
 117         skb_reset_transport_header(skb);
 118         greh = (struct gre_base_hdr *)skb->data;
 119         greh->flags = gre_tnl_flags_to_gre_flags(flags);
 120         greh->protocol = proto;
 121
 122         if (flags & (TUNNEL_KEY | TUNNEL_CSUM | TUNNEL_SEQ)) {
 123                 __be32 *ptr = (__be32 *)(((u8 *)greh) + hdr_len - 4);
 124
 125                 if (flags & TUNNEL_SEQ) {
 126                         *ptr = seq;
 127                         ptr--;
 128                 }
 129                 if (flags & TUNNEL_KEY) {
 130                         *ptr = key;
 131                         ptr--;
 132                 }
 133                 if (flags & TUNNEL_CSUM &&
 134                     !(skb_shinfo(skb)->gso_type &
 135                       (SKB_GSO_GRE | SKB_GSO_GRE_CSUM))) {
 136                         *ptr = 0;
 137                         *(__sum16 *)ptr = gre_checksum(skb);
 138                 }
 139         }
 140 }
 141
 142 #endif