include/linux/tcp.h

0001 /* SPDX-License-Identifier: GPL-2.0-or-later */
0002 /*
0003  * INET     An implementation of the TCP/IP protocol suite for the LINUX
0004  *      operating system.  INET is implemented using the  BSD Socket
0005  *      interface as the means of communication with the user level.
0006  *
0007  *      Definitions for the TCP protocol.
0008  *
0009  * Version: @(#)tcp.h   1.0.2   04/28/93
0010  *
0011  * Author:  Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
0012  */
0013 #ifndef _LINUX_TCP_H
0014 #define _LINUX_TCP_H
0015
0016
0017 #include <linux/skbuff.h>
0018 #include <linux/win_minmax.h>
0019 #include <net/sock.h>
0020 #include <net/inet_connection_sock.h>
0021 #include <net/inet_timewait_sock.h>
0022 #include <uapi/linux/tcp.h>
0023
0024 static inline struct tcphdr *tcp_hdr(const struct sk_buff *skb)
0025 {
0026     return (struct tcphdr *)skb_transport_header(skb);
0027 }
0028
0029 static inline unsigned int __tcp_hdrlen(const struct tcphdr *th)
0030 {
0031     return th->doff * 4;
0032 }
0033
0034 static inline unsigned int tcp_hdrlen(const struct sk_buff *skb)
0035 {
0036     return __tcp_hdrlen(tcp_hdr(skb));
0037 }
0038
0039 static inline struct tcphdr *inner_tcp_hdr(const struct sk_buff *skb)
0040 {
0041     return (struct tcphdr *)skb_inner_transport_header(skb);
0042 }
0043
0044 static inline unsigned int inner_tcp_hdrlen(const struct sk_buff *skb)
0045 {
0046     return inner_tcp_hdr(skb)->doff * 4;
0047 }
0048
0049 /**
0050  * skb_tcp_all_headers - Returns size of all headers for a TCP packet
0051  * @skb: buffer
0052  *
0053  * Used in TX path, for a packet known to be a TCP one.
0054  *
0055  * if (skb_is_gso(skb)) {
0056  *         int hlen = skb_tcp_all_headers(skb);
0057  *         ...
0058  */
0059 static inline int skb_tcp_all_headers(const struct sk_buff *skb)
0060 {
0061     return skb_transport_offset(skb) + tcp_hdrlen(skb);
0062 }
0063
0064 /**
0065  * skb_inner_tcp_all_headers - Returns size of all headers for an encap TCP packet
0066  * @skb: buffer
0067  *
0068  * Used in TX path, for a packet known to be a TCP one.
0069  *
0070  * if (skb_is_gso(skb) && skb->encapsulation) {
0071  *         int hlen = skb_inner_tcp_all_headers(skb);
0072  *         ...
0073  */
0074 static inline int skb_inner_tcp_all_headers(const struct sk_buff *skb)
0075 {
0076     return skb_inner_transport_offset(skb) + inner_tcp_hdrlen(skb);
0077 }
0078
0079 static inline unsigned int tcp_optlen(const struct sk_buff *skb)
0080 {
0081     return (tcp_hdr(skb)->doff - 5) * 4;
0082 }
0083
0084 /* TCP Fast Open */
0085 #define TCP_FASTOPEN_COOKIE_MIN 4   /* Min Fast Open Cookie size in bytes */
0086 #define TCP_FASTOPEN_COOKIE_MAX 16  /* Max Fast Open Cookie size in bytes */
0087 #define TCP_FASTOPEN_COOKIE_SIZE 8  /* the size employed by this impl. */
0088
0089 /* TCP Fast Open Cookie as stored in memory */
0090 struct tcp_fastopen_cookie {
0091     __le64  val[DIV_ROUND_UP(TCP_FASTOPEN_COOKIE_MAX, sizeof(u64))];
0092     s8  len;
0093     bool    exp;    /* In RFC6994 experimental option format */
0094 };
0095
0096 /* This defines a selective acknowledgement block. */
0097 struct tcp_sack_block_wire {
0098     __be32  start_seq;
0099     __be32  end_seq;
0100 };
0101
0102 struct tcp_sack_block {
0103     u32 start_seq;
0104     u32 end_seq;
0105 };
0106
0107 /*These are used to set the sack_ok field in struct tcp_options_received */
0108 #define TCP_SACK_SEEN     (1 << 0)   /*1 = peer is SACK capable, */
0109 #define TCP_DSACK_SEEN    (1 << 2)   /*1 = DSACK was received from peer*/
0110
0111 struct tcp_options_received {
0112 /*  PAWS/RTTM data  */
0113     int ts_recent_stamp;/* Time we stored ts_recent (for aging) */
0114     u32 ts_recent;  /* Time stamp to echo next      */
0115     u32 rcv_tsval;  /* Time stamp value                 */
0116     u32 rcv_tsecr;  /* Time stamp echo reply            */
0117     u16     saw_tstamp : 1, /* Saw TIMESTAMP on last packet     */
0118         tstamp_ok : 1,  /* TIMESTAMP seen on SYN packet     */
0119         dsack : 1,  /* D-SACK is scheduled          */
0120         wscale_ok : 1,  /* Wscale seen on SYN packet        */
0121         sack_ok : 3,    /* SACK seen on SYN packet      */
0122         smc_ok : 1, /* SMC seen on SYN packet       */
0123         snd_wscale : 4, /* Window scaling received from sender  */
0124         rcv_wscale : 4; /* Window scaling to send to receiver   */
0125     u8  saw_unknown:1,  /* Received unknown option      */
0126         unused:7;
0127     u8  num_sacks;  /* Number of SACK blocks        */
0128     u16 user_mss;   /* mss requested by user in ioctl   */
0129     u16 mss_clamp;  /* Maximal mss, negotiated at connection setup */
0130 };
0131
0132 static inline void tcp_clear_options(struct tcp_options_received *rx_opt)
0133 {
0134     rx_opt->tstamp_ok = rx_opt->sack_ok = 0;
0135     rx_opt->wscale_ok = rx_opt->snd_wscale = 0;
0136 #if IS_ENABLED(CONFIG_SMC)
0137     rx_opt->smc_ok = 0;
0138 #endif
0139 }
0140
0141 /* This is the max number of SACKS that we'll generate and process. It's safe
0142  * to increase this, although since:
0143  *   size = TCPOLEN_SACK_BASE_ALIGNED (4) + n * TCPOLEN_SACK_PERBLOCK (8)
0144  * only four options will fit in a standard TCP header */
0145 #define TCP_NUM_SACKS 4
0146
0147 struct tcp_request_sock_ops;
0148
0149 struct tcp_request_sock {
0150     struct inet_request_sock    req;
0151     const struct tcp_request_sock_ops *af_specific;
0152     u64             snt_synack; /* first SYNACK sent time */
0153     bool                tfo_listener;
0154     bool                is_mptcp;
0155 #if IS_ENABLED(CONFIG_MPTCP)
0156     bool                drop_req;
0157 #endif
0158     u32             txhash;
0159     u32             rcv_isn;
0160     u32             snt_isn;
0161     u32             ts_off;
0162     u32             last_oow_ack_time; /* last SYNACK */
0163     u32             rcv_nxt; /* the ack # by SYNACK. For
0164                           * FastOpen it's the seq#
0165                           * after data-in-SYN.
0166                           */
0167     u8              syn_tos;
0168 };
0169
0170 static inline struct tcp_request_sock *tcp_rsk(const struct request_sock *req)
0171 {
0172     return (struct tcp_request_sock *)req;
0173 }
0174
0175 struct tcp_sock {
0176     /* inet_connection_sock has to be the first member of tcp_sock */
0177     struct inet_connection_sock inet_conn;
0178     u16 tcp_header_len; /* Bytes of tcp header to send      */
0179     u16 gso_segs;   /* Max number of segs per GSO packet    */
0180
0181 /*
0182  *  Header prediction flags
0183  *  0x5?10 << 16 + snd_wnd in net byte order
0184  */
0185     __be32  pred_flags;
0186
0187 /*
0188  *  RFC793 variables by their proper names. This means you can
0189  *  read the code and the spec side by side (and laugh ...)
0190  *  See RFC793 and RFC1122. The RFC writes these in capitals.
0191  */
0192     u64 bytes_received; /* RFC4898 tcpEStatsAppHCThruOctetsReceived
0193                  * sum(delta(rcv_nxt)), or how many bytes
0194                  * were acked.
0195                  */
0196     u32 segs_in;    /* RFC4898 tcpEStatsPerfSegsIn
0197                  * total number of segments in.
0198                  */
0199     u32 data_segs_in;   /* RFC4898 tcpEStatsPerfDataSegsIn
0200                  * total number of data segments in.
0201                  */
0202     u32 rcv_nxt;    /* What we want to receive next     */
0203     u32 copied_seq; /* Head of yet unread data      */
0204     u32 rcv_wup;    /* rcv_nxt on last window update sent   */
0205     u32 snd_nxt;    /* Next sequence we send        */
0206     u32 segs_out;   /* RFC4898 tcpEStatsPerfSegsOut
0207                  * The total number of segments sent.
0208                  */
0209     u32 data_segs_out;  /* RFC4898 tcpEStatsPerfDataSegsOut
0210                  * total number of data segments sent.
0211                  */
0212     u64 bytes_sent; /* RFC4898 tcpEStatsPerfHCDataOctetsOut
0213                  * total number of data bytes sent.
0214                  */
0215     u64 bytes_acked;    /* RFC4898 tcpEStatsAppHCThruOctetsAcked
0216                  * sum(delta(snd_una)), or how many bytes
0217                  * were acked.
0218                  */
0219     u32 dsack_dups; /* RFC4898 tcpEStatsStackDSACKDups
0220                  * total number of DSACK blocks received
0221                  */
0222     u32 snd_una;    /* First byte we want an ack for    */
0223     u32 snd_sml;    /* Last byte of the most recently transmitted small packet */
0224     u32 rcv_tstamp; /* timestamp of last received ACK (for keepalives) */
0225     u32 lsndtime;   /* timestamp of last sent data packet (for restart window) */
0226     u32 last_oow_ack_time;  /* timestamp of last out-of-window ACK */
0227     u32 compressed_ack_rcv_nxt;
0228
0229     u32 tsoffset;   /* timestamp offset */
0230
0231     struct list_head tsq_node; /* anchor in tsq_tasklet.head list */
0232     struct list_head tsorted_sent_queue; /* time-sorted sent but un-SACKed skbs */
0233
0234     u32 snd_wl1;    /* Sequence for window update       */
0235     u32 snd_wnd;    /* The window we expect to receive  */
0236     u32 max_window; /* Maximal window ever seen from peer   */
0237     u32 mss_cache;  /* Cached effective mss, not including SACKS */
0238
0239     u32 window_clamp;   /* Maximal window to advertise      */
0240     u32 rcv_ssthresh;   /* Current window clamp         */
0241
0242     /* Information of the most recently (s)acked skb */
0243     struct tcp_rack {
0244         u64 mstamp; /* (Re)sent time of the skb */
0245         u32 rtt_us;  /* Associated RTT */
0246         u32 end_seq; /* Ending TCP sequence of the skb */
0247         u32 last_delivered; /* tp->delivered at last reo_wnd adj */
0248         u8 reo_wnd_steps;   /* Allowed reordering window */
0249 #define TCP_RACK_RECOVERY_THRESH 16
0250         u8 reo_wnd_persist:5, /* No. of recovery since last adj */
0251            dsack_seen:1, /* Whether DSACK seen after last adj */
0252            advanced:1;   /* mstamp advanced since last lost marking */
0253     } rack;
0254     u16 advmss;     /* Advertised MSS           */
0255     u8  compressed_ack;
0256     u8  dup_ack_counter:2,
0257         tlp_retrans:1,  /* TLP is a retransmission */
0258         unused:5;
0259     u32 chrono_start;   /* Start time in jiffies of a TCP chrono */
0260     u32 chrono_stat[3]; /* Time in jiffies for chrono_stat stats */
0261     u8  chrono_type:2,  /* current chronograph type */
0262         rate_app_limited:1,  /* rate_{delivered,interval_us} limited? */
0263         fastopen_connect:1, /* FASTOPEN_CONNECT sockopt */
0264         fastopen_no_cookie:1, /* Allow send/recv SYN+data without a cookie */
0265         is_sack_reneg:1,    /* in recovery from loss with SACK reneg? */
0266         fastopen_client_fail:2; /* reason why fastopen failed */
0267     u8  nonagle     : 4,/* Disable Nagle algorithm?             */
0268         thin_lto    : 1,/* Use linear timeouts for thin streams */
0269         recvmsg_inq : 1,/* Indicate # of bytes in queue upon recvmsg */
0270         repair      : 1,
0271         frto        : 1;/* F-RTO (RFC5682) activated in CA_Loss */
0272     u8  repair_queue;
0273     u8  save_syn:2, /* Save headers of SYN packet */
0274         syn_data:1, /* SYN includes data */
0275         syn_fastopen:1, /* SYN includes Fast Open option */
0276         syn_fastopen_exp:1,/* SYN includes Fast Open exp. option */
0277         syn_fastopen_ch:1, /* Active TFO re-enabling probe */
0278         syn_data_acked:1,/* data in SYN is acked by SYN-ACK */
0279         is_cwnd_limited:1;/* forward progress limited by snd_cwnd? */
0280     u32 tlp_high_seq;   /* snd_nxt at the time of TLP */
0281
0282     u32 tcp_tx_delay;   /* delay (in usec) added to TX packets */
0283     u64 tcp_wstamp_ns;  /* departure time for next sent data packet */
0284     u64 tcp_clock_cache; /* cache last tcp_clock_ns() (see tcp_mstamp_refresh()) */
0285
0286 /* RTT measurement */
0287     u64 tcp_mstamp; /* most recent packet received/sent */
0288     u32 srtt_us;    /* smoothed round trip time << 3 in usecs */
0289     u32 mdev_us;    /* medium deviation         */
0290     u32 mdev_max_us;    /* maximal mdev for the last rtt period */
0291     u32 rttvar_us;  /* smoothed mdev_max            */
0292     u32 rtt_seq;    /* sequence number to update rttvar */
0293     struct  minmax rtt_min;
0294
0295     u32 packets_out;    /* Packets which are "in flight"    */
0296     u32 retrans_out;    /* Retransmitted packets out        */
0297     u32 max_packets_out;  /* max packets_out in last window */
0298     u32 max_packets_seq;  /* right edge of max_packets_out flight */
0299
0300     u16 urg_data;   /* Saved octet of OOB data and control flags */
0301     u8  ecn_flags;  /* ECN status bits.         */
0302     u8  keepalive_probes; /* num of allowed keep alive probes   */
0303     u32 reordering; /* Packet reordering metric.        */
0304     u32 reord_seen; /* number of data packet reordering events */
0305     u32 snd_up;     /* Urgent pointer       */
0306
0307 /*
0308  *      Options received (usually on last packet, some only on SYN packets).
0309  */
0310     struct tcp_options_received rx_opt;
0311
0312 /*
0313  *  Slow start and congestion control (see also Nagle, and Karn & Partridge)
0314  */
0315     u32 snd_ssthresh;   /* Slow start size threshold        */
0316     u32 snd_cwnd;   /* Sending congestion window        */
0317     u32 snd_cwnd_cnt;   /* Linear increase counter      */
0318     u32 snd_cwnd_clamp; /* Do not allow snd_cwnd to grow above this */
0319     u32 snd_cwnd_used;
0320     u32 snd_cwnd_stamp;
0321     u32 prior_cwnd; /* cwnd right before starting loss recovery */
0322     u32 prr_delivered;  /* Number of newly delivered packets to
0323                  * receiver in Recovery. */
0324     u32 prr_out;    /* Total number of pkts sent during Recovery. */
0325     u32 delivered;  /* Total data packets delivered incl. rexmits */
0326     u32 delivered_ce;   /* Like the above but only ECE marked packets */
0327     u32 lost;       /* Total data packets lost incl. rexmits */
0328     u32 app_limited;    /* limited until "delivered" reaches this val */
0329     u64 first_tx_mstamp;  /* start of window send phase */
0330     u64 delivered_mstamp; /* time we reached "delivered" */
0331     u32 rate_delivered;    /* saved rate sample: packets delivered */
0332     u32 rate_interval_us;  /* saved rate sample: time elapsed */
0333
0334     u32 rcv_wnd;    /* Current receiver window      */
0335     u32 write_seq;  /* Tail(+1) of data held in tcp send buffer */
0336     u32 notsent_lowat;  /* TCP_NOTSENT_LOWAT */
0337     u32 pushed_seq; /* Last pushed seq, required to talk to windows */
0338     u32 lost_out;   /* Lost packets         */
0339     u32 sacked_out; /* SACK'd packets           */
0340
0341     struct hrtimer  pacing_timer;
0342     struct hrtimer  compressed_ack_timer;
0343
0344     /* from STCP, retrans queue hinting */
0345     struct sk_buff* lost_skb_hint;
0346     struct sk_buff *retransmit_skb_hint;
0347
0348     /* OOO segments go in this rbtree. Socket lock must be held. */
0349     struct rb_root  out_of_order_queue;
0350     struct sk_buff  *ooo_last_skb; /* cache rb_last(out_of_order_queue) */
0351
0352     /* SACKs data, these 2 need to be together (see tcp_options_write) */
0353     struct tcp_sack_block duplicate_sack[1]; /* D-SACK block */
0354     struct tcp_sack_block selective_acks[4]; /* The SACKS themselves*/
0355
0356     struct tcp_sack_block recv_sack_cache[4];
0357
0358     struct sk_buff *highest_sack;   /* skb just after the highest
0359                      * skb with SACKed bit set
0360                      * (validity guaranteed only if
0361                      * sacked_out > 0)
0362                      */
0363
0364     int     lost_cnt_hint;
0365
0366     u32 prior_ssthresh; /* ssthresh saved at recovery start */
0367     u32 high_seq;   /* snd_nxt at onset of congestion   */
0368
0369     u32 retrans_stamp;  /* Timestamp of the last retransmit,
0370                  * also used in SYN-SENT to remember stamp of
0371                  * the first SYN. */
0372     u32 undo_marker;    /* snd_una upon a new recovery episode. */
0373     int undo_retrans;   /* number of undoable retransmissions. */
0374     u64 bytes_retrans;  /* RFC4898 tcpEStatsPerfOctetsRetrans
0375                  * Total data bytes retransmitted
0376                  */
0377     u32 total_retrans;  /* Total retransmits for entire connection */
0378
0379     u32 urg_seq;    /* Seq of received urgent pointer */
0380     unsigned int        keepalive_time;   /* time before keep alive takes place */
0381     unsigned int        keepalive_intvl;  /* time interval between keep alive probes */
0382
0383     int         linger2;
0384
0385
0386 /* Sock_ops bpf program related variables */
0387 #ifdef CONFIG_BPF
0388     u8  bpf_sock_ops_cb_flags;  /* Control calling BPF programs
0389                      * values defined in uapi/linux/tcp.h
0390                      */
0391 #define BPF_SOCK_OPS_TEST_FLAG(TP, ARG) (TP->bpf_sock_ops_cb_flags & ARG)
0392 #else
0393 #define BPF_SOCK_OPS_TEST_FLAG(TP, ARG) 0
0394 #endif
0395
0396     u16 timeout_rehash; /* Timeout-triggered rehash attempts */
0397
0398     u32 rcv_ooopack; /* Received out-of-order packets, for tcpinfo */
0399
0400 /* Receiver side RTT estimation */
0401     u32 rcv_rtt_last_tsecr;
0402     struct {
0403         u32 rtt_us;
0404         u32 seq;
0405         u64 time;
0406     } rcv_rtt_est;
0407
0408 /* Receiver queue space */
0409     struct {
0410         u32 space;
0411         u32 seq;
0412         u64 time;
0413     } rcvq_space;
0414
0415 /* TCP-specific MTU probe information. */
0416     struct {
0417         u32       probe_seq_start;
0418         u32       probe_seq_end;
0419     } mtu_probe;
0420     u32 mtu_info; /* We received an ICMP_FRAG_NEEDED / ICMPV6_PKT_TOOBIG
0421                * while socket was owned by user.
0422                */
0423 #if IS_ENABLED(CONFIG_MPTCP)
0424     bool    is_mptcp;
0425 #endif
0426 #if IS_ENABLED(CONFIG_SMC)
0427     bool    (*smc_hs_congested)(const struct sock *sk);
0428     bool    syn_smc;    /* SYN includes SMC */
0429 #endif
0430
0431 #ifdef CONFIG_TCP_MD5SIG
0432 /* TCP AF-Specific parts; only used by MD5 Signature support so far */
0433     const struct tcp_sock_af_ops    *af_specific;
0434
0435 /* TCP MD5 Signature Option information */
0436     struct tcp_md5sig_info  __rcu *md5sig_info;
0437 #endif
0438
0439 /* TCP fastopen related information */
0440     struct tcp_fastopen_request *fastopen_req;
0441     /* fastopen_rsk points to request_sock that resulted in this big
0442      * socket. Used to retransmit SYNACKs etc.
0443      */
0444     struct request_sock __rcu *fastopen_rsk;
0445     struct saved_syn *saved_syn;
0446 };
0447
0448 enum tsq_enum {
0449     TSQ_THROTTLED,
0450     TSQ_QUEUED,
0451     TCP_TSQ_DEFERRED,      /* tcp_tasklet_func() found socket was owned */
0452     TCP_WRITE_TIMER_DEFERRED,  /* tcp_write_timer() found socket was owned */
0453     TCP_DELACK_TIMER_DEFERRED, /* tcp_delack_timer() found socket was owned */
0454     TCP_MTU_REDUCED_DEFERRED,  /* tcp_v{4|6}_err() could not call
0455                     * tcp_v{4|6}_mtu_reduced()
0456                     */
0457 };
0458
0459 enum tsq_flags {
0460     TSQF_THROTTLED          = (1UL << TSQ_THROTTLED),
0461     TSQF_QUEUED         = (1UL << TSQ_QUEUED),
0462     TCPF_TSQ_DEFERRED       = (1UL << TCP_TSQ_DEFERRED),
0463     TCPF_WRITE_TIMER_DEFERRED   = (1UL << TCP_WRITE_TIMER_DEFERRED),
0464     TCPF_DELACK_TIMER_DEFERRED  = (1UL << TCP_DELACK_TIMER_DEFERRED),
0465     TCPF_MTU_REDUCED_DEFERRED   = (1UL << TCP_MTU_REDUCED_DEFERRED),
0466 };
0467
0468 static inline struct tcp_sock *tcp_sk(const struct sock *sk)
0469 {
0470     return (struct tcp_sock *)sk;
0471 }
0472
0473 struct tcp_timewait_sock {
0474     struct inet_timewait_sock tw_sk;
0475 #define tw_rcv_nxt tw_sk.__tw_common.skc_tw_rcv_nxt
0476 #define tw_snd_nxt tw_sk.__tw_common.skc_tw_snd_nxt
0477     u32           tw_rcv_wnd;
0478     u32           tw_ts_offset;
0479     u32           tw_ts_recent;
0480
0481     /* The time we sent the last out-of-window ACK: */
0482     u32           tw_last_oow_ack_time;
0483
0484     int           tw_ts_recent_stamp;
0485     u32           tw_tx_delay;
0486 #ifdef CONFIG_TCP_MD5SIG
0487     struct tcp_md5sig_key     *tw_md5_key;
0488 #endif
0489 };
0490
0491 static inline struct tcp_timewait_sock *tcp_twsk(const struct sock *sk)
0492 {
0493     return (struct tcp_timewait_sock *)sk;
0494 }
0495
0496 static inline bool tcp_passive_fastopen(const struct sock *sk)
0497 {
0498     return sk->sk_state == TCP_SYN_RECV &&
0499            rcu_access_pointer(tcp_sk(sk)->fastopen_rsk) != NULL;
0500 }
0501
0502 static inline void fastopen_queue_tune(struct sock *sk, int backlog)
0503 {
0504     struct request_sock_queue *queue = &inet_csk(sk)->icsk_accept_queue;
0505     int somaxconn = READ_ONCE(sock_net(sk)->core.sysctl_somaxconn);
0506
0507     queue->fastopenq.max_qlen = min_t(unsigned int, backlog, somaxconn);
0508 }
0509
0510 static inline void tcp_move_syn(struct tcp_sock *tp,
0511                 struct request_sock *req)
0512 {
0513     tp->saved_syn = req->saved_syn;
0514     req->saved_syn = NULL;
0515 }
0516
0517 static inline void tcp_saved_syn_free(struct tcp_sock *tp)
0518 {
0519     kfree(tp->saved_syn);
0520     tp->saved_syn = NULL;
0521 }
0522
0523 static inline u32 tcp_saved_syn_len(const struct saved_syn *saved_syn)
0524 {
0525     return saved_syn->mac_hdrlen + saved_syn->network_hdrlen +
0526         saved_syn->tcp_hdrlen;
0527 }
0528
0529 struct sk_buff *tcp_get_timestamping_opt_stats(const struct sock *sk,
0530                            const struct sk_buff *orig_skb,
0531                            const struct sk_buff *ack_skb);
0532
0533 static inline u16 tcp_mss_clamp(const struct tcp_sock *tp, u16 mss)
0534 {
0535     /* We use READ_ONCE() here because socket might not be locked.
0536      * This happens for listeners.
0537      */
0538     u16 user_mss = READ_ONCE(tp->rx_opt.user_mss);
0539
0540     return (user_mss && user_mss < mss) ? user_mss : mss;
0541 }
0542
0543 int tcp_skb_shift(struct sk_buff *to, struct sk_buff *from, int pcount,
0544           int shiftlen);
0545
0546 void __tcp_sock_set_cork(struct sock *sk, bool on);
0547 void tcp_sock_set_cork(struct sock *sk, bool on);
0548 int tcp_sock_set_keepcnt(struct sock *sk, int val);
0549 int tcp_sock_set_keepidle_locked(struct sock *sk, int val);
0550 int tcp_sock_set_keepidle(struct sock *sk, int val);
0551 int tcp_sock_set_keepintvl(struct sock *sk, int val);
0552 void __tcp_sock_set_nodelay(struct sock *sk, bool on);
0553 void tcp_sock_set_nodelay(struct sock *sk);
0554 void tcp_sock_set_quickack(struct sock *sk, int val);
0555 int tcp_sock_set_syncnt(struct sock *sk, int val);
0556 void tcp_sock_set_user_timeout(struct sock *sk, u32 val);
0557
0558 #endif  /* _LINUX_TCP_H */