/*
 * INET         An implementation of the TCP/IP protocol suite for the LINUX
 *              operating system.  INET is implemented using the  BSD Socket
 *              interface as the means of communication with the user level.
 *
 *              Definitions for the TCP protocol.
 *
 * Version:     @(#)tcp.h       1.0.2   04/28/93
 *
 * Author:      Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
 *
 *              This program is free software; you can redistribute it and/or
 *              modify it under the terms of the GNU General Public License
 *              as published by the Free Software Foundation; either version
 *              2 of the License, or (at your option) any later version.
 */
#ifndef _LINUX_TCP_H
#define _LINUX_TCP_H


#include <linux/skbuff.h>
#include <linux/win_minmax.h>
#include <net/sock.h>
#include <net/inet_connection_sock.h>
#include <net/inet_timewait_sock.h>
#include <uapi/linux/tcp.h>

static inline struct tcphdr *tcp_hdr(const struct sk_buff *skb)
{
        return (struct tcphdr *)skb_transport_header(skb);
}

static inline unsigned int __tcp_hdrlen(const struct tcphdr *th)
{
        return th->doff * 4;
}

static inline unsigned int tcp_hdrlen(const struct sk_buff *skb)
{
        return __tcp_hdrlen(tcp_hdr(skb));
}

static inline struct tcphdr *inner_tcp_hdr(const struct sk_buff *skb)
{
        return (struct tcphdr *)skb_inner_transport_header(skb);
}

static inline unsigned int inner_tcp_hdrlen(const struct sk_buff *skb)
{
        return inner_tcp_hdr(skb)->doff * 4;
}

static inline unsigned int tcp_optlen(const struct sk_buff *skb)
{
        return (tcp_hdr(skb)->doff - 5) * 4;
}

/* TCP Fast Open */
#define TCP_FASTOPEN_COOKIE_MIN 4       /* Min Fast Open Cookie size in bytes */
#define TCP_FASTOPEN_COOKIE_MAX 16      /* Max Fast Open Cookie size in bytes */
#define TCP_FASTOPEN_COOKIE_SIZE 8      /* the size employed by this impl. */

/* TCP Fast Open Cookie as stored in memory */
struct tcp_fastopen_cookie {
        union {
                u8      val[TCP_FASTOPEN_COOKIE_MAX];
#if IS_ENABLED(CONFIG_IPV6)
                struct in6_addr addr;
#endif
        };
        s8      len;
        bool    exp;    /* In RFC6994 experimental option format */
};

/* This defines a selective acknowledgement block. */
struct tcp_sack_block_wire {
        __be32  start_seq;
        __be32  end_seq;
};

struct tcp_sack_block {
        u32     start_seq;
        u32     end_seq;
};

/*These are used to set the sack_ok field in struct tcp_options_received */
#define TCP_SACK_SEEN     (1 << 0)   /*1 = peer is SACK capable, */
#define TCP_DSACK_SEEN    (1 << 2)   /*1 = DSACK was received from peer*/

struct tcp_options_received {
/*      PAWS/RTTM data  */
        long    ts_recent_stamp;/* Time we stored ts_recent (for aging) */
        u32     ts_recent;      /* Time stamp to echo next              */
        u32     rcv_tsval;      /* Time stamp value                     */
        u32     rcv_tsecr;      /* Time stamp echo reply                */
        u16     saw_tstamp : 1, /* Saw TIMESTAMP on last packet         */
                tstamp_ok : 1,  /* TIMESTAMP seen on SYN packet         */
                dsack : 1,      /* D-SACK is scheduled                  */
                wscale_ok : 1,  /* Wscale seen on SYN packet            */
                sack_ok : 3,    /* SACK seen on SYN packet              */
                smc_ok : 1,     /* SMC seen on SYN packet               */
                snd_wscale : 4, /* Window scaling received from sender  */
                rcv_wscale : 4; /* Window scaling to send to receiver   */
        u8      num_sacks;      /* Number of SACK blocks                */
        u16     user_mss;       /* mss requested by user in ioctl       */
        u16     mss_clamp;      /* Maximal mss, negotiated at connection setup */
};

static inline void tcp_clear_options(struct tcp_options_received *rx_opt)
{
        rx_opt->tstamp_ok = rx_opt->sack_ok = 0;
        rx_opt->wscale_ok = rx_opt->snd_wscale = 0;
#if IS_ENABLED(CONFIG_SMC)
        rx_opt->smc_ok = 0;
#endif
}

/* This is the max number of SACKS that we'll generate and process. It's safe
 * to increase this, although since:
 *   size = TCPOLEN_SACK_BASE_ALIGNED (4) + n * TCPOLEN_SACK_PERBLOCK (8)
 * only four options will fit in a standard TCP header */
#define TCP_NUM_SACKS 4

struct tcp_request_sock_ops;

struct tcp_request_sock {
        struct inet_request_sock        req;
        const struct tcp_request_sock_ops *af_specific;
        u64                             snt_synack; /* first SYNACK sent time */
        bool                            tfo_listener;
        u32                             txhash;
        u32                             rcv_isn;
        u32                             snt_isn;
        u32                             ts_off;
        u32                             last_oow_ack_time; /* last SYNACK */
        u32                             rcv_nxt; /* the ack # by SYNACK. For
                                                  * FastOpen it's the seq#
                                                  * after data-in-SYN.
                                                  */
};

static inline struct tcp_request_sock *tcp_rsk(const struct request_sock *req)
{
        return (struct tcp_request_sock *)req;
}

struct tcp_sock {
        /* inet_connection_sock has to be the first member of tcp_sock */
        struct inet_connection_sock     inet_conn;
        u16     tcp_header_len; /* Bytes of tcp header to send          */
        u16     gso_segs;       /* Max number of segs per GSO packet    */

/*
 *      Header prediction flags
 *      0x5?10 << 16 + snd_wnd in net byte order
 */
        __be32  pred_flags;

/*
 *      RFC793 variables by their proper names. This means you can
 *      read the code and the spec side by side (and laugh ...)
 *      See RFC793 and RFC1122. The RFC writes these in capitals.
 */
        u64     bytes_received; /* RFC4898 tcpEStatsAppHCThruOctetsReceived
                                 * sum(delta(rcv_nxt)), or how many bytes
                                 * were acked.
                                 */
        u32     segs_in;        /* RFC4898 tcpEStatsPerfSegsIn
                                 * total number of segments in.
                                 */
        u32     data_segs_in;   /* RFC4898 tcpEStatsPerfDataSegsIn
                                 * total number of data segments in.
                                 */
        u32     rcv_nxt;        /* What we want to receive next         */
        u32     copied_seq;     /* Head of yet unread data              */
        u32     rcv_wup;        /* rcv_nxt on last window update sent   */
        u32     snd_nxt;        /* Next sequence we send                */
        u32     segs_out;       /* RFC4898 tcpEStatsPerfSegsOut
                                 * The total number of segments sent.
                                 */
        u32     data_segs_out;  /* RFC4898 tcpEStatsPerfDataSegsOut
                                 * total number of data segments sent.
                                 */
        u64     bytes_acked;    /* RFC4898 tcpEStatsAppHCThruOctetsAcked
                                 * sum(delta(snd_una)), or how many bytes
                                 * were acked.
                                 */
        u32     snd_una;        /* First byte we want an ack for        */
        u32     snd_sml;        /* Last byte of the most recently transmitted small packet */
        u32     rcv_tstamp;     /* timestamp of last received ACK (for keepalives) */
        u32     lsndtime;       /* timestamp of last sent data packet (for restart window) */
        u32     last_oow_ack_time;  /* timestamp of last out-of-window ACK */

        u32     tsoffset;       /* timestamp offset */

        struct list_head tsq_node; /* anchor in tsq_tasklet.head list */
        struct list_head tsorted_sent_queue; /* time-sorted sent but un-SACKed skbs */

        u32     snd_wl1;        /* Sequence for window update           */
        u32     snd_wnd;        /* The window we expect to receive      */
        u32     max_window;     /* Maximal window ever seen from peer   */
        u32     mss_cache;      /* Cached effective mss, not including SACKS */

        u32     window_clamp;   /* Maximal window to advertise          */
        u32     rcv_ssthresh;   /* Current window clamp                 */

        /* Information of the most recently (s)acked skb */
        struct tcp_rack {
                u64 mstamp; /* (Re)sent time of the skb */
                u32 rtt_us;  /* Associated RTT */
                u32 end_seq; /* Ending TCP sequence of the skb */
                u32 last_delivered; /* tp->delivered at last reo_wnd adj */
                u8 reo_wnd_steps;   /* Allowed reordering window */
#define TCP_RACK_RECOVERY_THRESH 16
                u8 reo_wnd_persist:5, /* No. of recovery since last adj */
                   dsack_seen:1, /* Whether DSACK seen after last adj */
                   advanced:1,   /* mstamp advanced since last lost marking */
                   reord:1;      /* reordering detected */
        } rack;
        u16     advmss;         /* Advertised MSS                       */
        u32     chrono_start;   /* Start time in jiffies of a TCP chrono */
        u32     chrono_stat[3]; /* Time in jiffies for chrono_stat stats */
        u8      chrono_type:2,  /* current chronograph type */
                rate_app_limited:1,  /* rate_{delivered,interval_us} limited? */
                fastopen_connect:1, /* FASTOPEN_CONNECT sockopt */
                fastopen_no_cookie:1, /* Allow send/recv SYN+data without a cookie */
                is_sack_reneg:1,    /* in recovery from loss with SACK reneg? */
                unused:2;
        u8      nonagle     : 4,/* Disable Nagle algorithm?             */
                thin_lto    : 1,/* Use linear timeouts for thin streams */
                unused1     : 1,
                repair      : 1,
                frto        : 1;/* F-RTO (RFC5682) activated in CA_Loss */
        u8      repair_queue;
        u8      syn_data:1,     /* SYN includes data */
                syn_fastopen:1, /* SYN includes Fast Open option */
                syn_fastopen_exp:1,/* SYN includes Fast Open exp. option */
                syn_fastopen_ch:1, /* Active TFO re-enabling probe */
                syn_data_acked:1,/* data in SYN is acked by SYN-ACK */
                save_syn:1,     /* Save headers of SYN packet */
                is_cwnd_limited:1,/* forward progress limited by snd_cwnd? */
                syn_smc:1;      /* SYN includes SMC */
        u32     tlp_high_seq;   /* snd_nxt at the time of TLP retransmit. */

/* RTT measurement */
        u64     tcp_mstamp;     /* most recent packet received/sent */
        u32     srtt_us;        /* smoothed round trip time << 3 in usecs */
        u32     mdev_us;        /* medium deviation                     */
        u32     mdev_max_us;    /* maximal mdev for the last rtt period */
        u32     rttvar_us;      /* smoothed mdev_max                    */
        u32     rtt_seq;        /* sequence number to update rttvar     */
        struct  minmax rtt_min;

        u32     packets_out;    /* Packets which are "in flight"        */
        u32     retrans_out;    /* Retransmitted packets out            */
        u32     max_packets_out;  /* max packets_out in last window */
        u32     max_packets_seq;  /* right edge of max_packets_out flight */

        u16     urg_data;       /* Saved octet of OOB data and control flags */
        u8      ecn_flags;      /* ECN status bits.                     */
        u8      keepalive_probes; /* num of allowed keep alive probes   */
        u32     reordering;     /* Packet reordering metric.            */
        u32     snd_up;         /* Urgent pointer               */

/*
 *      Options received (usually on last packet, some only on SYN packets).
 */
        struct tcp_options_received rx_opt;

/*
 *      Slow start and congestion control (see also Nagle, and Karn & Partridge)
 */
        u32     snd_ssthresh;   /* Slow start size threshold            */
        u32     snd_cwnd;       /* Sending congestion window            */
        u32     snd_cwnd_cnt;   /* Linear increase counter              */
        u32     snd_cwnd_clamp; /* Do not allow snd_cwnd to grow above this */
        u32     snd_cwnd_used;
        u32     snd_cwnd_stamp;
        u32     prior_cwnd;     /* cwnd right before starting loss recovery */
        u32     prr_delivered;  /* Number of newly delivered packets to
                                 * receiver in Recovery. */
        u32     prr_out;        /* Total number of pkts sent during Recovery. */
        u32     delivered;      /* Total data packets delivered incl. rexmits */
        u32     lost;           /* Total data packets lost incl. rexmits */
        u32     app_limited;    /* limited until "delivered" reaches this val */
        u64     first_tx_mstamp;  /* start of window send phase */
        u64     delivered_mstamp; /* time we reached "delivered" */
        u32     rate_delivered;    /* saved rate sample: packets delivered */
        u32     rate_interval_us;  /* saved rate sample: time elapsed */

        u32     rcv_wnd;        /* Current receiver window              */
        u32     write_seq;      /* Tail(+1) of data held in tcp send buffer */
        u32     notsent_lowat;  /* TCP_NOTSENT_LOWAT */
        u32     pushed_seq;     /* Last pushed seq, required to talk to windows */
        u32     lost_out;       /* Lost packets                 */
        u32     sacked_out;     /* SACK'd packets                       */

        struct hrtimer  pacing_timer;

        /* from STCP, retrans queue hinting */
        struct sk_buff* lost_skb_hint;
        struct sk_buff *retransmit_skb_hint;

        /* OOO segments go in this rbtree. Socket lock must be held. */
        struct rb_root  out_of_order_queue;
        struct sk_buff  *ooo_last_skb; /* cache rb_last(out_of_order_queue) */

        /* SACKs data, these 2 need to be together (see tcp_options_write) */
        struct tcp_sack_block duplicate_sack[1]; /* D-SACK block */
        struct tcp_sack_block selective_acks[4]; /* The SACKS themselves*/

        struct tcp_sack_block recv_sack_cache[4];

        struct sk_buff *highest_sack;   /* skb just after the highest
                                         * skb with SACKed bit set
                                         * (validity guaranteed only if
                                         * sacked_out > 0)
                                         */

        int     lost_cnt_hint;

        u32     prior_ssthresh; /* ssthresh saved at recovery start     */
        u32     high_seq;       /* snd_nxt at onset of congestion       */

        u32     retrans_stamp;  /* Timestamp of the last retransmit,
                                 * also used in SYN-SENT to remember stamp of
                                 * the first SYN. */
        u32     undo_marker;    /* snd_una upon a new recovery episode. */
        int     undo_retrans;   /* number of undoable retransmissions. */
        u32     total_retrans;  /* Total retransmits for entire connection */

        u32     urg_seq;        /* Seq of received urgent pointer */
        unsigned int            keepalive_time;   /* time before keep alive takes place */
        unsigned int            keepalive_intvl;  /* time interval between keep alive probes */

        int                     linger2;


/* Sock_ops bpf program related variables */
#ifdef CONFIG_BPF
        u8      bpf_sock_ops_cb_flags;  /* Control calling BPF programs
                                         * values defined in uapi/linux/tcp.h
                                         */
#define BPF_SOCK_OPS_TEST_FLAG(TP, ARG) (TP->bpf_sock_ops_cb_flags & ARG)
#else
#define BPF_SOCK_OPS_TEST_FLAG(TP, ARG) 0
#endif

/* Receiver side RTT estimation */
        struct {
                u32     rtt_us;
                u32     seq;
                u64     time;
        } rcv_rtt_est;

/* Receiver queue space */
        struct {
                u32     space;
                u32     seq;
                u64     time;
        } rcvq_space;

/* TCP-specific MTU probe information. */
        struct {
                u32               probe_seq_start;
                u32               probe_seq_end;
        } mtu_probe;
        u32     mtu_info; /* We received an ICMP_FRAG_NEEDED / ICMPV6_PKT_TOOBIG
                           * while socket was owned by user.
                           */

#ifdef CONFIG_TCP_MD5SIG
/* TCP AF-Specific parts; only used by MD5 Signature support so far */
        const struct tcp_sock_af_ops    *af_specific;

/* TCP MD5 Signature Option information */
        struct tcp_md5sig_info  __rcu *md5sig_info;
#endif

/* TCP fastopen related information */
        struct tcp_fastopen_request *fastopen_req;
        /* fastopen_rsk points to request_sock that resulted in this big
         * socket. Used to retransmit SYNACKs etc.
         */
        struct request_sock *fastopen_rsk;
        u32     *saved_syn;
};

enum tsq_enum {
        TSQ_THROTTLED,
        TSQ_QUEUED,
        TCP_TSQ_DEFERRED,          /* tcp_tasklet_func() found socket was owned */
        TCP_WRITE_TIMER_DEFERRED,  /* tcp_write_timer() found socket was owned */
        TCP_DELACK_TIMER_DEFERRED, /* tcp_delack_timer() found socket was owned */
        TCP_MTU_REDUCED_DEFERRED,  /* tcp_v{4|6}_err() could not call
                                    * tcp_v{4|6}_mtu_reduced()
                                    */
};

enum tsq_flags {
        TSQF_THROTTLED                  = (1UL << TSQ_THROTTLED),
        TSQF_QUEUED                     = (1UL << TSQ_QUEUED),
        TCPF_TSQ_DEFERRED               = (1UL << TCP_TSQ_DEFERRED),
        TCPF_WRITE_TIMER_DEFERRED       = (1UL << TCP_WRITE_TIMER_DEFERRED),
        TCPF_DELACK_TIMER_DEFERRED      = (1UL << TCP_DELACK_TIMER_DEFERRED),
        TCPF_MTU_REDUCED_DEFERRED       = (1UL << TCP_MTU_REDUCED_DEFERRED),
};

static inline struct tcp_sock *tcp_sk(const struct sock *sk)
{
        return (struct tcp_sock *)sk;
}

struct tcp_timewait_sock {
        struct inet_timewait_sock tw_sk;
#define tw_rcv_nxt tw_sk.__tw_common.skc_tw_rcv_nxt
#define tw_snd_nxt tw_sk.__tw_common.skc_tw_snd_nxt
        u32                       tw_rcv_wnd;
        u32                       tw_ts_offset;
        u32                       tw_ts_recent;

        /* The time we sent the last out-of-window ACK: */
        u32                       tw_last_oow_ack_time;

        long                      tw_ts_recent_stamp;
#ifdef CONFIG_TCP_MD5SIG
        struct tcp_md5sig_key     *tw_md5_key;
#endif
};

static inline struct tcp_timewait_sock *tcp_twsk(const struct sock *sk)
{
        return (struct tcp_timewait_sock *)sk;
}

static inline bool tcp_passive_fastopen(const struct sock *sk)
{
        return (sk->sk_state == TCP_SYN_RECV &&
                tcp_sk(sk)->fastopen_rsk != NULL);
}

static inline void fastopen_queue_tune(struct sock *sk, int backlog)
{
        struct request_sock_queue *queue = &inet_csk(sk)->icsk_accept_queue;
        int somaxconn = READ_ONCE(sock_net(sk)->core.sysctl_somaxconn);

        queue->fastopenq.max_qlen = min_t(unsigned int, backlog, somaxconn);
}

static inline void tcp_move_syn(struct tcp_sock *tp,
                                struct request_sock *req)
{
        tp->saved_syn = req->saved_syn;
        req->saved_syn = NULL;
}

static inline void tcp_saved_syn_free(struct tcp_sock *tp)
{
        kfree(tp->saved_syn);
        tp->saved_syn = NULL;
}

struct sk_buff *tcp_get_timestamping_opt_stats(const struct sock *sk);

static inline u16 tcp_mss_clamp(const struct tcp_sock *tp, u16 mss)
{
        /* We use READ_ONCE() here because socket might not be locked.
         * This happens for listeners.
         */
        u16 user_mss = READ_ONCE(tp->rx_opt.user_mss);

        return (user_mss && user_mss < mss) ? user_mss : mss;
}
#endif  /* _LINUX_TCP_H */