/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _INET_ECN_H_
#define _INET_ECN_H_

#include <linux/ip.h>
#include <linux/skbuff.h>
#include <linux/if_vlan.h>

#include <net/inet_sock.h>
#include <net/dsfield.h>
#include <net/checksum.h>

enum {
	INET_ECN_NOT_ECT = 0,
	INET_ECN_ECT_1 = 1,
	INET_ECN_ECT_0 = 2,
	INET_ECN_CE = 3,
	INET_ECN_MASK = 3,
};

extern int sysctl_tunnel_ecn_log;

static inline int INET_ECN_is_ce(__u8 dsfield)
{
	return (dsfield & INET_ECN_MASK) == INET_ECN_CE;
}

static inline int INET_ECN_is_not_ect(__u8 dsfield)
{
	return (dsfield & INET_ECN_MASK) == INET_ECN_NOT_ECT;
}

static inline int INET_ECN_is_capable(__u8 dsfield)
{
	return dsfield & INET_ECN_ECT_0;
}


static inline __u8 INET_ECN_encapsulate(__u8 outer, __u8 inner)
{
	outer &= ~INET_ECN_MASK;
	outer |= !INET_ECN_is_ce(inner) ? (inner & INET_ECN_MASK) :
					  INET_ECN_ECT_0;
	return outer;
}

static inline void INET_ECN_xmit(struct sock *sk)
{
	inet_sk(sk)->tos |= INET_ECN_ECT_0;
	if (inet6_sk(sk) != NULL)
		inet6_sk(sk)->tclass |= INET_ECN_ECT_0;
}

static inline void INET_ECN_dontxmit(struct sock *sk)
{
	inet_sk(sk)->tos &= ~INET_ECN_MASK;
	if (inet6_sk(sk) != NULL)
		inet6_sk(sk)->tclass &= ~INET_ECN_MASK;
}

#define IP6_ECN_flow_init(label) do {		\
      (label) &= ~htonl(INET_ECN_MASK << 20);	\
    } while (0)

#define	IP6_ECN_flow_xmit(sk, label) do {				\
	if (INET_ECN_is_capable(inet6_sk(sk)->tclass))			\
		(label) |= htonl(INET_ECN_ECT_0 << 20);			\
    } while (0)

static inline int IP_ECN_set_ce(struct iphdr *iph)
{
	u32 ecn = (iph->tos + 1) & INET_ECN_MASK;
	__be16 check_add;

	
	if (!(ecn & 2))
		return !ecn;

	
	check_add = (__force __be16)((__force u16)htons(0xFFFB) +
				     (__force u16)htons(ecn));

	iph->check = csum16_add(iph->check, check_add);
	iph->tos |= INET_ECN_CE;
	return 1;
}

static inline int IP_ECN_set_ect1(struct iphdr *iph)
{
	if ((iph->tos & INET_ECN_MASK) != INET_ECN_ECT_0)
		return 0;

	iph->check = csum16_add(iph->check, htons(0x1));
	iph->tos ^= INET_ECN_MASK;
	return 1;
}

static inline void IP_ECN_clear(struct iphdr *iph)
{
	iph->tos &= ~INET_ECN_MASK;
}

static inline void ipv4_copy_dscp(unsigned int dscp, struct iphdr *inner)
{
	dscp &= ~INET_ECN_MASK;
	ipv4_change_dsfield(inner, INET_ECN_MASK, dscp);
}

struct ipv6hdr;


static inline int IP6_ECN_set_ce(struct sk_buff *skb, struct ipv6hdr *iph)
{
	__be32 from, to;

	if (INET_ECN_is_not_ect(ipv6_get_dsfield(iph)))
		return 0;

	from = *(__be32 *)iph;
	to = from | htonl(INET_ECN_CE << 20);
	*(__be32 *)iph = to;
	if (skb->ip_summed == CHECKSUM_COMPLETE)
		skb->csum = csum_add(csum_sub(skb->csum, (__force __wsum)from),
				     (__force __wsum)to);
	return 1;
}

static inline int IP6_ECN_set_ect1(struct sk_buff *skb, struct ipv6hdr *iph)
{
	__be32 from, to;

	if ((ipv6_get_dsfield(iph) & INET_ECN_MASK) != INET_ECN_ECT_0)
		return 0;

	from = *(__be32 *)iph;
	to = from ^ htonl(INET_ECN_MASK << 20);
	*(__be32 *)iph = to;
	if (skb->ip_summed == CHECKSUM_COMPLETE)
		skb->csum = csum_add(csum_sub(skb->csum, (__force __wsum)from),
				     (__force __wsum)to);
	return 1;
}

static inline void ipv6_copy_dscp(unsigned int dscp, struct ipv6hdr *inner)
{
	dscp &= ~INET_ECN_MASK;
	ipv6_change_dsfield(inner, INET_ECN_MASK, dscp);
}

static inline int INET_ECN_set_ce(struct sk_buff *skb)
{
	switch (skb_protocol(skb, true)) {
	case cpu_to_be16(ETH_P_IP):
		if (skb_network_header(skb) + sizeof(struct iphdr) <=
		    skb_tail_pointer(skb))
			return IP_ECN_set_ce(ip_hdr(skb));
		break;

	case cpu_to_be16(ETH_P_IPV6):
		if (skb_network_header(skb) + sizeof(struct ipv6hdr) <=
		    skb_tail_pointer(skb))
			return IP6_ECN_set_ce(skb, ipv6_hdr(skb));
		break;
	}

	return 0;
}

static inline int INET_ECN_set_ect1(struct sk_buff *skb)
{
	switch (skb_protocol(skb, true)) {
	case cpu_to_be16(ETH_P_IP):
		if (skb_network_header(skb) + sizeof(struct iphdr) <=
		    skb_tail_pointer(skb))
			return IP_ECN_set_ect1(ip_hdr(skb));
		break;

	case cpu_to_be16(ETH_P_IPV6):
		if (skb_network_header(skb) + sizeof(struct ipv6hdr) <=
		    skb_tail_pointer(skb))
			return IP6_ECN_set_ect1(skb, ipv6_hdr(skb));
		break;
	}

	return 0;
}


static inline int __INET_ECN_decapsulate(__u8 outer, __u8 inner, bool *set_ce)
{
	if (INET_ECN_is_not_ect(inner)) {
		switch (outer & INET_ECN_MASK) {
		case INET_ECN_NOT_ECT:
			return 0;
		case INET_ECN_ECT_0:
		case INET_ECN_ECT_1:
			return 1;
		case INET_ECN_CE:
			return 2;
		}
	}

	*set_ce = INET_ECN_is_ce(outer);
	return 0;
}

static inline int INET_ECN_decapsulate(struct sk_buff *skb,
				       __u8 outer, __u8 inner)
{
	bool set_ce = false;
	int rc;

	rc = __INET_ECN_decapsulate(outer, inner, &set_ce);
	if (!rc) {
		if (set_ce)
			INET_ECN_set_ce(skb);
		else if ((outer & INET_ECN_MASK) == INET_ECN_ECT_1)
			INET_ECN_set_ect1(skb);
	}

	return rc;
}

static inline int IP_ECN_decapsulate(const struct iphdr *oiph,
				     struct sk_buff *skb)
{
	__u8 inner;

	switch (skb_protocol(skb, true)) {
	case htons(ETH_P_IP):
		inner = ip_hdr(skb)->tos;
		break;
	case htons(ETH_P_IPV6):
		inner = ipv6_get_dsfield(ipv6_hdr(skb));
		break;
	default:
		return 0;
	}

	return INET_ECN_decapsulate(skb, oiph->tos, inner);
}

static inline int IP6_ECN_decapsulate(const struct ipv6hdr *oipv6h,
				      struct sk_buff *skb)
{
	__u8 inner;

	switch (skb_protocol(skb, true)) {
	case htons(ETH_P_IP):
		inner = ip_hdr(skb)->tos;
		break;
	case htons(ETH_P_IPV6):
		inner = ipv6_get_dsfield(ipv6_hdr(skb));
		break;
	default:
		return 0;
	}

	return INET_ECN_decapsulate(skb, ipv6_get_dsfield(oipv6h), inner);
}
#endif
