/* SPDX-License-Identifier: GPL-2.0 */#ifndef __LINUX_GRE_H#define __LINUX_GRE_H #include <linux/skbuff.h>#include <net/ip_tunnels.h> struct gre_base_hdr {	__be16 flags;	__be16 protocol;} __packed; struct gre_full_hdr {	struct gre_base_hdr fixed_header;	__be16 csum;	__be16 reserved1;	__be32 key;	__be32 seq;} __packed;#define GRE_HEADER_SECTION 4 #define GREPROTO_CISCO		0#define GREPROTO_PPTP		1#define GREPROTO_MAX		2#define GRE_IP_PROTO_MAX	2 struct gre_protocol {	int  (*handler)(struct sk_buff *skb);	void (*err_handler)(struct sk_buff *skb, u32 info);}; int gre_add_protocol(const struct gre_protocol *proto, u8 version);int gre_del_protocol(const struct gre_protocol *proto, u8 version); struct net_device *gretap_fb_dev_create(struct net *net, const char *name,				       u8 name_assign_type);int gre_parse_header(struct sk_buff *skb, struct tnl_ptk_info *tpi,		     bool *csum_err, __be16 proto, int nhs); static inline bool netif_is_gretap(const struct net_device *dev){	return dev->rtnl_link_ops &&	       !strcmp(dev->rtnl_link_ops->kind, "gretap");} static inline bool netif_is_ip6gretap(const struct net_device *dev){	return dev->rtnl_link_ops &&	       !strcmp(dev->rtnl_link_ops->kind, "ip6gretap");} static inline int gre_calc_hlen(__be16 o_flags){	int addend = 4; 	if (o_flags & TUNNEL_CSUM)		addend += 4;	if (o_flags & TUNNEL_KEY)		addend += 4;	if (o_flags & TUNNEL_SEQ)		addend += 4;	return addend;} static inline __be16 gre_flags_to_tnl_flags(__be16 flags){	__be16 tflags = 0; 	if (flags & GRE_CSUM)		tflags |= TUNNEL_CSUM;	if (flags & GRE_ROUTING)		tflags |= TUNNEL_ROUTING;	if (flags & GRE_KEY)		tflags |= TUNNEL_KEY;	if (flags & GRE_SEQ)		tflags |= TUNNEL_SEQ;	if (flags & GRE_STRICT)		tflags |= TUNNEL_STRICT;	if (flags & GRE_REC)		tflags |= TUNNEL_REC;	if (flags & GRE_VERSION)		tflags |= TUNNEL_VERSION; 	return tflags;} static inline __be16 gre_tnl_flags_to_gre_flags(__be16 tflags){	__be16 flags = 0; 	if (tflags & TUNNEL_CSUM)		flags |= GRE_CSUM;	if (tflags & TUNNEL_ROUTING)		flags |= GRE_ROUTING;	if (tflags & TUNNEL_KEY)		flags |= GRE_KEY;	if (tflags & TUNNEL_SEQ)		flags |= GRE_SEQ;	if (tflags & TUNNEL_STRICT)		flags |= GRE_STRICT;	if (tflags & TUNNEL_REC)		flags |= GRE_REC;	if (tflags & TUNNEL_VERSION)		flags |= GRE_VERSION; 	return flags;} static inline __sum16 gre_checksum(struct sk_buff *skb){	__wsum csum; 	if (skb->ip_summed == CHECKSUM_PARTIAL)		csum = lco_csum(skb);	else		csum = skb_checksum(skb, 0, skb->len, 0);	return csum_fold(csum);} static inline void gre_build_header(struct sk_buff *skb, int hdr_len,				    __be16 flags, __be16 proto,				    __be32 key, __be32 seq){	struct gre_base_hdr *greh; 	skb_push(skb, hdr_len); 	skb_set_inner_protocol(skb, proto);	skb_reset_transport_header(skb);	greh = (struct gre_base_hdr *)skb->data;	greh->flags = gre_tnl_flags_to_gre_flags(flags);	greh->protocol = proto; 	if (flags & (TUNNEL_KEY | TUNNEL_CSUM | TUNNEL_SEQ)) {		__be32 *ptr = (__be32 *)(((u8 *)greh) + hdr_len - 4); 		if (flags & TUNNEL_SEQ) {			*ptr = seq;			ptr--;		}		if (flags & TUNNEL_KEY) {			*ptr = key;			ptr--;		}		if (flags & TUNNEL_CSUM &&		    !(skb_shinfo(skb)->gso_type &		      (SKB_GSO_GRE | SKB_GSO_GRE_CSUM))) {			*ptr = 0;			*(__sum16 *)ptr = gre_checksum(skb);		}	}} #endif