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

#include <linux/module.h>
#include <linux/skbuff.h>
#include <net/ip6_checksum.h>
#include <net/ip6_route.h>
#include <net/tcp.h>

#include <net/netfilter/nf_conntrack_seqadj.h>
#include <net/netfilter/nf_conntrack_synproxy.h>

struct synproxy_stats {
        unsigned int                    syn_received;
        unsigned int                    cookie_invalid;
        unsigned int                    cookie_valid;
        unsigned int                    cookie_retrans;
        unsigned int                    conn_reopened;
};

struct synproxy_net {
        struct nf_conn                  *tmpl;
        struct synproxy_stats __percpu  *stats;
        unsigned int                    hook_ref4;
        unsigned int                    hook_ref6;
};

extern unsigned int synproxy_net_id;
static inline struct synproxy_net *synproxy_pernet(struct net *net)
{
        return net_generic(net, synproxy_net_id);
}

struct synproxy_options {
        u8                              options;
        u8                              wscale;
        u16                             mss_option;
        u16                             mss_encode;
        u32                             tsval;
        u32                             tsecr;
};

struct nf_synproxy_info;
bool synproxy_parse_options(const struct sk_buff *skb, unsigned int doff,
                            const struct tcphdr *th,
                            struct synproxy_options *opts);

void synproxy_init_timestamp_cookie(const struct nf_synproxy_info *info,
                                    struct synproxy_options *opts);

void synproxy_send_client_synack(struct net *net, const struct sk_buff *skb,
                                 const struct tcphdr *th,
                                 const struct synproxy_options *opts);

bool synproxy_recv_client_ack(struct net *net,
                              const struct sk_buff *skb,
                              const struct tcphdr *th,
                              struct synproxy_options *opts, u32 recv_seq);

struct nf_hook_state;

unsigned int ipv4_synproxy_hook(void *priv, struct sk_buff *skb,
                                const struct nf_hook_state *nhs);
int nf_synproxy_ipv4_init(struct synproxy_net *snet, struct net *net);
void nf_synproxy_ipv4_fini(struct synproxy_net *snet, struct net *net);

#if IS_ENABLED(CONFIG_IPV6)
void synproxy_send_client_synack_ipv6(struct net *net,
                                      const struct sk_buff *skb,
                                      const struct tcphdr *th,
                                      const struct synproxy_options *opts);

bool synproxy_recv_client_ack_ipv6(struct net *net, const struct sk_buff *skb,
                                   const struct tcphdr *th,
                                   struct synproxy_options *opts, u32 recv_seq);

unsigned int ipv6_synproxy_hook(void *priv, struct sk_buff *skb,
                                const struct nf_hook_state *nhs);
int nf_synproxy_ipv6_init(struct synproxy_net *snet, struct net *net);
void nf_synproxy_ipv6_fini(struct synproxy_net *snet, struct net *net);
#else
static inline int
nf_synproxy_ipv6_init(struct synproxy_net *snet, struct net *net) { return 0; }
static inline void
nf_synproxy_ipv6_fini(struct synproxy_net *snet, struct net *net) {};
#endif /* CONFIG_IPV6 */

#endif /* _NF_SYNPROXY_SHARED_H */