/* 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); 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(const unsigned long *o_flags){	int addend = 4; 	if (test_bit(IP_TUNNEL_CSUM_BIT, o_flags))		addend += 4;	if (test_bit(IP_TUNNEL_KEY_BIT, o_flags))		addend += 4;	if (test_bit(IP_TUNNEL_SEQ_BIT, o_flags))		addend += 4;	return addend;} static inline void gre_flags_to_tnl_flags(unsigned long *dst, __be16 flags){	IP_TUNNEL_DECLARE_FLAGS(res) = { }; 	__assign_bit(IP_TUNNEL_CSUM_BIT, res, flags & GRE_CSUM);	__assign_bit(IP_TUNNEL_ROUTING_BIT, res, flags & GRE_ROUTING);	__assign_bit(IP_TUNNEL_KEY_BIT, res, flags & GRE_KEY);	__assign_bit(IP_TUNNEL_SEQ_BIT, res, flags & GRE_SEQ);	__assign_bit(IP_TUNNEL_STRICT_BIT, res, flags & GRE_STRICT);	__assign_bit(IP_TUNNEL_REC_BIT, res, flags & GRE_REC);	__assign_bit(IP_TUNNEL_VERSION_BIT, res, flags & GRE_VERSION); 	ip_tunnel_flags_copy(dst, res);} static inline __be16 gre_tnl_flags_to_gre_flags(const unsigned long *tflags){	__be16 flags = 0; 	if (test_bit(IP_TUNNEL_CSUM_BIT, tflags))		flags |= GRE_CSUM;	if (test_bit(IP_TUNNEL_ROUTING_BIT, tflags))		flags |= GRE_ROUTING;	if (test_bit(IP_TUNNEL_KEY_BIT, tflags))		flags |= GRE_KEY;	if (test_bit(IP_TUNNEL_SEQ_BIT, tflags))		flags |= GRE_SEQ;	if (test_bit(IP_TUNNEL_STRICT_BIT, tflags))		flags |= GRE_STRICT;	if (test_bit(IP_TUNNEL_REC_BIT, tflags))		flags |= GRE_REC;	if (test_bit(IP_TUNNEL_VERSION_BIT, tflags))		flags |= GRE_VERSION; 	return flags;} static inline void gre_build_header(struct sk_buff *skb, int hdr_len,				    const unsigned long *flags, __be16 proto,				    __be32 key, __be32 seq){	IP_TUNNEL_DECLARE_FLAGS(cond) = { };	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; 	__set_bit(IP_TUNNEL_KEY_BIT, cond);	__set_bit(IP_TUNNEL_CSUM_BIT, cond);	__set_bit(IP_TUNNEL_SEQ_BIT, cond); 	if (ip_tunnel_flags_intersect(flags, cond)) {		__be32 *ptr = (__be32 *)(((u8 *)greh) + hdr_len - 4); 		if (test_bit(IP_TUNNEL_SEQ_BIT, flags)) {			*ptr = seq;			ptr--;		}		if (test_bit(IP_TUNNEL_KEY_BIT, flags)) {			*ptr = key;			ptr--;		}		if (test_bit(IP_TUNNEL_CSUM_BIT, flags) &&		    !(skb_shinfo(skb)->gso_type &		      (SKB_GSO_GRE | SKB_GSO_GRE_CSUM))) {			*ptr = 0;			if (skb->ip_summed == CHECKSUM_PARTIAL) {				*(__sum16 *)ptr = csum_fold(lco_csum(skb));			} else {				skb->ip_summed = CHECKSUM_PARTIAL;				skb->csum_start = skb_transport_header(skb) - skb->head;				skb->csum_offset = sizeof(*greh);			}		}	}} #endif