tcp.h

Go to the documentation of this file.

/*
 * 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, <[email protected]>
 *
 *      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/dmaengine.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 sk_buff *skb)
{
    return 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 {
    s8  len;
    u8  val[TCP_FASTOPEN_COOKIE_MAX];
};

/* 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_FACK_ENABLED  (1 << 1)   /*1 = FACK is enabled locally*/
#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 : 4,    /* SACK seen on SYN packet      */
        snd_wscale : 4, /* Window scaling received from sender  */
        rcv_wscale : 4; /* Window scaling to send to receiver   */
    u8  cookie_plus:6,  /* bytes in authenticator/cookie option */
        cookie_out_never:1,
        cookie_in_always:1;
    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;
    rx_opt->cookie_plus = 0;
}

/* 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_cookie_values;
struct tcp_request_sock_ops;

struct tcp_request_sock {
    struct inet_request_sock    req;
#ifdef CONFIG_TCP_MD5SIG
    /* Only used by TCP MD5 Signature so far. */
    const struct tcp_request_sock_ops *af_specific;
#endif
    struct sock         *listener; /* needed for TFO */
    u32             rcv_isn;
    u32             snt_isn;
    u32             snt_synack; /* synack sent time */
    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 xmit_size_goal_segs; /* Goal for segmenting output packets */

/*
 *  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.
 */
    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 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) */

    struct list_head tsq_node; /* anchor in tsq_tasklet.head list */
    unsigned long   tsq_flags;

    /* Data for direct copy to user */
    struct {
        struct sk_buff_head prequeue;
        struct task_struct  *task;
        struct iovec        *iov;
        int         memory;
        int         len;
#ifdef CONFIG_NET_DMA
        /* members for async copy */
        struct dma_chan     *dma_chan;
        int         wakeup;
        struct dma_pinned_list  *pinned_list;
        dma_cookie_t        dma_cookie;
#endif
    } ucopy;

    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         */

    u32 frto_highmark;  /* snd_nxt when RTO occurred */
    u16 advmss;     /* Advertised MSS           */
    u8  frto_counter;   /* Number of new acks after RTO */
    u8  nonagle     : 4,/* Disable Nagle algorithm?             */
        thin_lto    : 1,/* Use linear timeouts for thin streams */
        thin_dupack : 1,/* Fast retransmit on first dupack      */
        repair      : 1,
        unused      : 1;
    u8  repair_queue;
    u8  do_early_retrans:1,/* Enable RFC5827 early-retransmit  */
        early_retrans_delayed:1, /* Delayed ER timer installed */
        syn_data:1, /* SYN includes data */
        syn_fastopen:1, /* SYN includes Fast Open option */
        syn_data_acked:1;/* data in SYN is acked by SYN-ACK */

/* RTT measurement */
    u32 srtt;       /* smoothed round trip time << 3    */
    u32 mdev;       /* medium deviation         */
    u32 mdev_max;   /* maximal mdev for the last rtt period */
    u32 rttvar;     /* smoothed mdev_max            */
    u32 rtt_seq;    /* sequence number to update rttvar */

    u32 packets_out;    /* Packets which are "in flight"    */
    u32 retrans_out;    /* Retransmitted packets out        */

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

    u8  keepalive_probes; /* num of allowed keep alive probes   */
/*
 *      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; /* Congestion window at start of Recovery. */
    u32 prr_delivered;  /* Number of newly delivered packets to
                 * receiver in Recovery. */
    u32 prr_out;    /* Total number of pkts sent during Recovery. */

    u32 rcv_wnd;    /* Current receiver window      */
    u32 write_seq;  /* Tail(+1) of data held in tcp send buffer */
    u32 pushed_seq; /* Last pushed seq, required to talk to windows */
    u32 lost_out;   /* Lost packets         */
    u32 sacked_out; /* SACK'd packets           */
    u32 fackets_out;    /* FACK'd packets           */
    u32 tso_deferred;
    u32 bytes_acked;    /* Appropriate Byte Counting - RFC3465 */

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

    struct sk_buff_head out_of_order_queue; /* Out of order segments go here */

    /* 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     retransmit_high;    /* L-bits may be on up to this seqno */

    u32 lost_retrans_low;   /* Sent seq after any rxmit (lowest) */

    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;    /* tracking retrans started here. */
    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;

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

/* Receiver queue space */
    struct {
        int space;
        u32 seq;
        u32 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

    /* When the cookie options are generated and exchanged, then this
     * object holds a reference to them (cookie_values->kref).  Also
     * contains related tcp_cookie_transactions fields.
     */
    struct tcp_cookie_values  *cookie_values;

/* 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;
};

enum tsq_flags {
    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()
                    */
};

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;
    u32           tw_rcv_nxt;
    u32           tw_snd_nxt;
    u32           tw_rcv_wnd;
    u32           tw_ts_recent;
    long              tw_ts_recent_stamp;
#ifdef CONFIG_TCP_MD5SIG
    struct tcp_md5sig_key     *tw_md5_key;
#endif
    /* Few sockets in timewait have cookies; in that case, then this
     * object holds a reference to them (tw_cookie_values->kref).
     */
    struct tcp_cookie_values  *tw_cookie_values;
};

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 bool fastopen_cookie_present(struct tcp_fastopen_cookie *foc)
{
    return foc->len != -1;
}

extern void tcp_sock_destruct(struct sock *sk);

static inline int fastopen_init_queue(struct sock *sk, int backlog)
{
    struct request_sock_queue *queue =
        &inet_csk(sk)->icsk_accept_queue;

    if (queue->fastopenq == NULL) {
        queue->fastopenq = kzalloc(
            sizeof(struct fastopen_queue),
            sk->sk_allocation);
        if (queue->fastopenq == NULL)
            return -ENOMEM;

        sk->sk_destruct = tcp_sock_destruct;
        spin_lock_init(&queue->fastopenq->lock);
    }
    queue->fastopenq->max_qlen = backlog;
    return 0;
}

#endif  /* _LINUX_TCP_H */