2 * INET An implementation of the TCP/IP protocol suite for the LINUX
3 * operating system. INET is implemented using the BSD Socket
4 * interface as the means of communication with the user level.
6 * Definitions for the TCP protocol.
8 * Version: @(#)tcp.h 1.0.2 04/28/93
10 * Author: Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
12 * This program is free software; you can redistribute it and/or
13 * modify it under the terms of the GNU General Public License
14 * as published by the Free Software Foundation; either version
15 * 2 of the License, or (at your option) any later version.
21 #include <linux/skbuff.h>
22 #include <linux/win_minmax.h>
24 #include <net/inet_connection_sock.h>
25 #include <net/inet_timewait_sock.h>
26 #include <uapi/linux/tcp.h>
28 static inline struct tcphdr
*tcp_hdr(const struct sk_buff
*skb
)
30 return (struct tcphdr
*)skb_transport_header(skb
);
33 static inline unsigned int __tcp_hdrlen(const struct tcphdr
*th
)
38 static inline unsigned int tcp_hdrlen(const struct sk_buff
*skb
)
40 return __tcp_hdrlen(tcp_hdr(skb
));
43 static inline struct tcphdr
*inner_tcp_hdr(const struct sk_buff
*skb
)
45 return (struct tcphdr
*)skb_inner_transport_header(skb
);
48 static inline unsigned int inner_tcp_hdrlen(const struct sk_buff
*skb
)
50 return inner_tcp_hdr(skb
)->doff
* 4;
53 static inline unsigned int tcp_optlen(const struct sk_buff
*skb
)
55 return (tcp_hdr(skb
)->doff
- 5) * 4;
59 #define TCP_FASTOPEN_COOKIE_MIN 4 /* Min Fast Open Cookie size in bytes */
60 #define TCP_FASTOPEN_COOKIE_MAX 16 /* Max Fast Open Cookie size in bytes */
61 #define TCP_FASTOPEN_COOKIE_SIZE 8 /* the size employed by this impl. */
63 /* TCP Fast Open Cookie as stored in memory */
64 struct tcp_fastopen_cookie
{
66 u8 val
[TCP_FASTOPEN_COOKIE_MAX
];
67 #if IS_ENABLED(CONFIG_IPV6)
72 bool exp
; /* In RFC6994 experimental option format */
75 /* This defines a selective acknowledgement block. */
76 struct tcp_sack_block_wire
{
81 struct tcp_sack_block
{
86 /*These are used to set the sack_ok field in struct tcp_options_received */
87 #define TCP_SACK_SEEN (1 << 0) /*1 = peer is SACK capable, */
88 #define TCP_FACK_ENABLED (1 << 1) /*1 = FACK is enabled locally*/
89 #define TCP_DSACK_SEEN (1 << 2) /*1 = DSACK was received from peer*/
91 struct tcp_options_received
{
93 long ts_recent_stamp
;/* Time we stored ts_recent (for aging) */
94 u32 ts_recent
; /* Time stamp to echo next */
95 u32 rcv_tsval
; /* Time stamp value */
96 u32 rcv_tsecr
; /* Time stamp echo reply */
97 u16 saw_tstamp
: 1, /* Saw TIMESTAMP on last packet */
98 tstamp_ok
: 1, /* TIMESTAMP seen on SYN packet */
99 dsack
: 1, /* D-SACK is scheduled */
100 wscale_ok
: 1, /* Wscale seen on SYN packet */
101 sack_ok
: 4, /* SACK seen on SYN packet */
102 snd_wscale
: 4, /* Window scaling received from sender */
103 rcv_wscale
: 4; /* Window scaling to send to receiver */
104 u8 num_sacks
; /* Number of SACK blocks */
105 u16 user_mss
; /* mss requested by user in ioctl */
106 u16 mss_clamp
; /* Maximal mss, negotiated at connection setup */
109 static inline void tcp_clear_options(struct tcp_options_received
*rx_opt
)
111 rx_opt
->tstamp_ok
= rx_opt
->sack_ok
= 0;
112 rx_opt
->wscale_ok
= rx_opt
->snd_wscale
= 0;
115 /* This is the max number of SACKS that we'll generate and process. It's safe
116 * to increase this, although since:
117 * size = TCPOLEN_SACK_BASE_ALIGNED (4) + n * TCPOLEN_SACK_PERBLOCK (8)
118 * only four options will fit in a standard TCP header */
119 #define TCP_NUM_SACKS 4
121 struct tcp_request_sock_ops
;
123 struct tcp_request_sock
{
124 struct inet_request_sock req
;
125 const struct tcp_request_sock_ops
*af_specific
;
126 struct skb_mstamp snt_synack
; /* first SYNACK sent time */
132 u32 last_oow_ack_time
; /* last SYNACK */
133 u32 rcv_nxt
; /* the ack # by SYNACK. For
134 * FastOpen it's the seq#
139 static inline struct tcp_request_sock
*tcp_rsk(const struct request_sock
*req
)
141 return (struct tcp_request_sock
*)req
;
145 /* inet_connection_sock has to be the first member of tcp_sock */
146 struct inet_connection_sock inet_conn
;
147 u16 tcp_header_len
; /* Bytes of tcp header to send */
148 u16 gso_segs
; /* Max number of segs per GSO packet */
151 * Header prediction flags
152 * 0x5?10 << 16 + snd_wnd in net byte order
157 * RFC793 variables by their proper names. This means you can
158 * read the code and the spec side by side (and laugh ...)
159 * See RFC793 and RFC1122. The RFC writes these in capitals.
161 u64 bytes_received
; /* RFC4898 tcpEStatsAppHCThruOctetsReceived
162 * sum(delta(rcv_nxt)), or how many bytes
165 u32 segs_in
; /* RFC4898 tcpEStatsPerfSegsIn
166 * total number of segments in.
168 u32 data_segs_in
; /* RFC4898 tcpEStatsPerfDataSegsIn
169 * total number of data segments in.
171 u32 rcv_nxt
; /* What we want to receive next */
172 u32 copied_seq
; /* Head of yet unread data */
173 u32 rcv_wup
; /* rcv_nxt on last window update sent */
174 u32 snd_nxt
; /* Next sequence we send */
175 u32 segs_out
; /* RFC4898 tcpEStatsPerfSegsOut
176 * The total number of segments sent.
178 u32 data_segs_out
; /* RFC4898 tcpEStatsPerfDataSegsOut
179 * total number of data segments sent.
181 u64 bytes_acked
; /* RFC4898 tcpEStatsAppHCThruOctetsAcked
182 * sum(delta(snd_una)), or how many bytes
185 u32 snd_una
; /* First byte we want an ack for */
186 u32 snd_sml
; /* Last byte of the most recently transmitted small packet */
187 u32 rcv_tstamp
; /* timestamp of last received ACK (for keepalives) */
188 u32 lsndtime
; /* timestamp of last sent data packet (for restart window) */
189 u32 last_oow_ack_time
; /* timestamp of last out-of-window ACK */
191 u32 tsoffset
; /* timestamp offset */
193 struct list_head tsq_node
; /* anchor in tsq_tasklet.head list */
195 /* Data for direct copy to user */
197 struct sk_buff_head prequeue
;
198 struct task_struct
*task
;
204 u32 snd_wl1
; /* Sequence for window update */
205 u32 snd_wnd
; /* The window we expect to receive */
206 u32 max_window
; /* Maximal window ever seen from peer */
207 u32 mss_cache
; /* Cached effective mss, not including SACKS */
209 u32 window_clamp
; /* Maximal window to advertise */
210 u32 rcv_ssthresh
; /* Current window clamp */
212 /* Information of the most recently (s)acked skb */
214 struct skb_mstamp mstamp
; /* (Re)sent time of the skb */
215 u32 rtt_us
; /* Associated RTT */
216 u32 end_seq
; /* Ending TCP sequence of the skb */
217 u8 advanced
; /* mstamp advanced since last lost marking */
218 u8 reord
; /* reordering detected */
220 u16 advmss
; /* Advertised MSS */
221 u32 chrono_start
; /* Start time in jiffies of a TCP chrono */
222 u32 chrono_stat
[3]; /* Time in jiffies for chrono_stat stats */
223 u8 chrono_type
:2, /* current chronograph type */
224 rate_app_limited
:1, /* rate_{delivered,interval_us} limited? */
225 fastopen_connect
:1, /* FASTOPEN_CONNECT sockopt */
227 u8 nonagle
: 4,/* Disable Nagle algorithm? */
228 thin_lto
: 1,/* Use linear timeouts for thin streams */
231 frto
: 1;/* F-RTO (RFC5682) activated in CA_Loss */
233 u8 syn_data
:1, /* SYN includes data */
234 syn_fastopen
:1, /* SYN includes Fast Open option */
235 syn_fastopen_exp
:1,/* SYN includes Fast Open exp. option */
236 syn_data_acked
:1,/* data in SYN is acked by SYN-ACK */
237 save_syn
:1, /* Save headers of SYN packet */
238 is_cwnd_limited
:1;/* forward progress limited by snd_cwnd? */
239 u32 tlp_high_seq
; /* snd_nxt at the time of TLP retransmit. */
241 /* RTT measurement */
242 u32 srtt_us
; /* smoothed round trip time << 3 in usecs */
243 u32 mdev_us
; /* medium deviation */
244 u32 mdev_max_us
; /* maximal mdev for the last rtt period */
245 u32 rttvar_us
; /* smoothed mdev_max */
246 u32 rtt_seq
; /* sequence number to update rttvar */
247 struct minmax rtt_min
;
249 u32 packets_out
; /* Packets which are "in flight" */
250 u32 retrans_out
; /* Retransmitted packets out */
251 u32 max_packets_out
; /* max packets_out in last window */
252 u32 max_packets_seq
; /* right edge of max_packets_out flight */
254 u16 urg_data
; /* Saved octet of OOB data and control flags */
255 u8 ecn_flags
; /* ECN status bits. */
256 u8 keepalive_probes
; /* num of allowed keep alive probes */
257 u32 reordering
; /* Packet reordering metric. */
258 u32 snd_up
; /* Urgent pointer */
261 * Options received (usually on last packet, some only on SYN packets).
263 struct tcp_options_received rx_opt
;
266 * Slow start and congestion control (see also Nagle, and Karn & Partridge)
268 u32 snd_ssthresh
; /* Slow start size threshold */
269 u32 snd_cwnd
; /* Sending congestion window */
270 u32 snd_cwnd_cnt
; /* Linear increase counter */
271 u32 snd_cwnd_clamp
; /* Do not allow snd_cwnd to grow above this */
274 u32 prior_cwnd
; /* Congestion window at start of Recovery. */
275 u32 prr_delivered
; /* Number of newly delivered packets to
276 * receiver in Recovery. */
277 u32 prr_out
; /* Total number of pkts sent during Recovery. */
278 u32 delivered
; /* Total data packets delivered incl. rexmits */
279 u32 lost
; /* Total data packets lost incl. rexmits */
280 u32 app_limited
; /* limited until "delivered" reaches this val */
281 struct skb_mstamp first_tx_mstamp
; /* start of window send phase */
282 struct skb_mstamp delivered_mstamp
; /* time we reached "delivered" */
283 u32 rate_delivered
; /* saved rate sample: packets delivered */
284 u32 rate_interval_us
; /* saved rate sample: time elapsed */
286 u32 rcv_wnd
; /* Current receiver window */
287 u32 write_seq
; /* Tail(+1) of data held in tcp send buffer */
288 u32 notsent_lowat
; /* TCP_NOTSENT_LOWAT */
289 u32 pushed_seq
; /* Last pushed seq, required to talk to windows */
290 u32 lost_out
; /* Lost packets */
291 u32 sacked_out
; /* SACK'd packets */
292 u32 fackets_out
; /* FACK'd packets */
294 /* from STCP, retrans queue hinting */
295 struct sk_buff
* lost_skb_hint
;
296 struct sk_buff
*retransmit_skb_hint
;
298 /* OOO segments go in this rbtree. Socket lock must be held. */
299 struct rb_root out_of_order_queue
;
300 struct sk_buff
*ooo_last_skb
; /* cache rb_last(out_of_order_queue) */
302 /* SACKs data, these 2 need to be together (see tcp_options_write) */
303 struct tcp_sack_block duplicate_sack
[1]; /* D-SACK block */
304 struct tcp_sack_block selective_acks
[4]; /* The SACKS themselves*/
306 struct tcp_sack_block recv_sack_cache
[4];
308 struct sk_buff
*highest_sack
; /* skb just after the highest
309 * skb with SACKed bit set
310 * (validity guaranteed only if
316 u32 prior_ssthresh
; /* ssthresh saved at recovery start */
317 u32 high_seq
; /* snd_nxt at onset of congestion */
319 u32 retrans_stamp
; /* Timestamp of the last retransmit,
320 * also used in SYN-SENT to remember stamp of
322 u32 undo_marker
; /* snd_una upon a new recovery episode. */
323 int undo_retrans
; /* number of undoable retransmissions. */
324 u32 total_retrans
; /* Total retransmits for entire connection */
326 u32 urg_seq
; /* Seq of received urgent pointer */
327 unsigned int keepalive_time
; /* time before keep alive takes place */
328 unsigned int keepalive_intvl
; /* time interval between keep alive probes */
332 /* Receiver side RTT estimation */
339 /* Receiver queue space */
346 /* TCP-specific MTU probe information. */
351 u32 mtu_info
; /* We received an ICMP_FRAG_NEEDED / ICMPV6_PKT_TOOBIG
352 * while socket was owned by user.
355 #ifdef CONFIG_TCP_MD5SIG
356 /* TCP AF-Specific parts; only used by MD5 Signature support so far */
357 const struct tcp_sock_af_ops
*af_specific
;
359 /* TCP MD5 Signature Option information */
360 struct tcp_md5sig_info __rcu
*md5sig_info
;
363 /* TCP fastopen related information */
364 struct tcp_fastopen_request
*fastopen_req
;
365 /* fastopen_rsk points to request_sock that resulted in this big
366 * socket. Used to retransmit SYNACKs etc.
368 struct request_sock
*fastopen_rsk
;
375 TCP_TSQ_DEFERRED
, /* tcp_tasklet_func() found socket was owned */
376 TCP_WRITE_TIMER_DEFERRED
, /* tcp_write_timer() found socket was owned */
377 TCP_DELACK_TIMER_DEFERRED
, /* tcp_delack_timer() found socket was owned */
378 TCP_MTU_REDUCED_DEFERRED
, /* tcp_v{4|6}_err() could not call
379 * tcp_v{4|6}_mtu_reduced()
384 TSQF_THROTTLED
= (1UL << TSQ_THROTTLED
),
385 TSQF_QUEUED
= (1UL << TSQ_QUEUED
),
386 TCPF_TSQ_DEFERRED
= (1UL << TCP_TSQ_DEFERRED
),
387 TCPF_WRITE_TIMER_DEFERRED
= (1UL << TCP_WRITE_TIMER_DEFERRED
),
388 TCPF_DELACK_TIMER_DEFERRED
= (1UL << TCP_DELACK_TIMER_DEFERRED
),
389 TCPF_MTU_REDUCED_DEFERRED
= (1UL << TCP_MTU_REDUCED_DEFERRED
),
392 static inline struct tcp_sock
*tcp_sk(const struct sock
*sk
)
394 return (struct tcp_sock
*)sk
;
397 struct tcp_timewait_sock
{
398 struct inet_timewait_sock tw_sk
;
399 #define tw_rcv_nxt tw_sk.__tw_common.skc_tw_rcv_nxt
400 #define tw_snd_nxt tw_sk.__tw_common.skc_tw_snd_nxt
405 /* The time we sent the last out-of-window ACK: */
406 u32 tw_last_oow_ack_time
;
408 long tw_ts_recent_stamp
;
409 #ifdef CONFIG_TCP_MD5SIG
410 struct tcp_md5sig_key
*tw_md5_key
;
414 static inline struct tcp_timewait_sock
*tcp_twsk(const struct sock
*sk
)
416 return (struct tcp_timewait_sock
*)sk
;
419 static inline bool tcp_passive_fastopen(const struct sock
*sk
)
421 return (sk
->sk_state
== TCP_SYN_RECV
&&
422 tcp_sk(sk
)->fastopen_rsk
!= NULL
);
425 static inline void fastopen_queue_tune(struct sock
*sk
, int backlog
)
427 struct request_sock_queue
*queue
= &inet_csk(sk
)->icsk_accept_queue
;
428 int somaxconn
= READ_ONCE(sock_net(sk
)->core
.sysctl_somaxconn
);
430 queue
->fastopenq
.max_qlen
= min_t(unsigned int, backlog
, somaxconn
);
433 static inline void tcp_move_syn(struct tcp_sock
*tp
,
434 struct request_sock
*req
)
436 tp
->saved_syn
= req
->saved_syn
;
437 req
->saved_syn
= NULL
;
440 static inline void tcp_saved_syn_free(struct tcp_sock
*tp
)
442 kfree(tp
->saved_syn
);
443 tp
->saved_syn
= NULL
;
446 struct sk_buff
*tcp_get_timestamping_opt_stats(const struct sock
*sk
);
448 static inline u16
tcp_mss_clamp(const struct tcp_sock
*tp
, u16 mss
)
450 /* We use READ_ONCE() here because socket might not be locked.
451 * This happens for listeners.
453 u16 user_mss
= READ_ONCE(tp
->rx_opt
.user_mss
);
455 return (user_mss
&& user_mss
< mss
) ? user_mss
: mss
;
457 #endif /* _LINUX_TCP_H */