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>
23 #include <net/inet_connection_sock.h>
24 #include <net/inet_timewait_sock.h>
25 #include <uapi/linux/tcp.h>
27 static inline struct tcphdr *tcp_hdr(const struct sk_buff *skb)
29 return (struct tcphdr *)skb_transport_header(skb);
32 static inline unsigned int tcp_hdrlen(const struct sk_buff *skb)
34 return tcp_hdr(skb)->doff * 4;
37 static inline struct tcphdr *inner_tcp_hdr(const struct sk_buff *skb)
39 return (struct tcphdr *)skb_inner_transport_header(skb);
42 static inline unsigned int inner_tcp_hdrlen(const struct sk_buff *skb)
44 return inner_tcp_hdr(skb)->doff * 4;
47 static inline unsigned int tcp_optlen(const struct sk_buff *skb)
49 return (tcp_hdr(skb)->doff - 5) * 4;
53 #define TCP_FASTOPEN_COOKIE_MIN 4 /* Min Fast Open Cookie size in bytes */
54 #define TCP_FASTOPEN_COOKIE_MAX 16 /* Max Fast Open Cookie size in bytes */
55 #define TCP_FASTOPEN_COOKIE_SIZE 8 /* the size employed by this impl. */
57 /* TCP Fast Open Cookie as stored in memory */
58 struct tcp_fastopen_cookie {
60 u8 val[TCP_FASTOPEN_COOKIE_MAX];
61 #if IS_ENABLED(CONFIG_IPV6)
66 bool exp; /* In RFC6994 experimental option format */
69 /* This defines a selective acknowledgement block. */
70 struct tcp_sack_block_wire {
75 struct tcp_sack_block {
80 /*These are used to set the sack_ok field in struct tcp_options_received */
81 #define TCP_SACK_SEEN (1 << 0) /*1 = peer is SACK capable, */
82 #define TCP_FACK_ENABLED (1 << 1) /*1 = FACK is enabled locally*/
83 #define TCP_DSACK_SEEN (1 << 2) /*1 = DSACK was received from peer*/
85 struct tcp_options_received {
87 long ts_recent_stamp;/* Time we stored ts_recent (for aging) */
88 u32 ts_recent; /* Time stamp to echo next */
89 u32 rcv_tsval; /* Time stamp value */
90 u32 rcv_tsecr; /* Time stamp echo reply */
91 u16 saw_tstamp : 1, /* Saw TIMESTAMP on last packet */
92 tstamp_ok : 1, /* TIMESTAMP seen on SYN packet */
93 dsack : 1, /* D-SACK is scheduled */
94 wscale_ok : 1, /* Wscale seen on SYN packet */
95 sack_ok : 4, /* SACK seen on SYN packet */
96 snd_wscale : 4, /* Window scaling received from sender */
97 rcv_wscale : 4; /* Window scaling to send to receiver */
98 u8 num_sacks; /* Number of SACK blocks */
99 u16 user_mss; /* mss requested by user in ioctl */
100 u16 mss_clamp; /* Maximal mss, negotiated at connection setup */
103 static inline void tcp_clear_options(struct tcp_options_received *rx_opt)
105 rx_opt->tstamp_ok = rx_opt->sack_ok = 0;
106 rx_opt->wscale_ok = rx_opt->snd_wscale = 0;
109 /* This is the max number of SACKS that we'll generate and process. It's safe
110 * to increase this, although since:
111 * size = TCPOLEN_SACK_BASE_ALIGNED (4) + n * TCPOLEN_SACK_PERBLOCK (8)
112 * only four options will fit in a standard TCP header */
113 #define TCP_NUM_SACKS 4
115 struct tcp_request_sock_ops;
117 struct tcp_request_sock {
118 struct inet_request_sock req;
119 const struct tcp_request_sock_ops *af_specific;
120 struct skb_mstamp snt_synack; /* first SYNACK sent time */
125 u32 last_oow_ack_time; /* last SYNACK */
126 u32 rcv_nxt; /* the ack # by SYNACK. For
127 * FastOpen it's the seq#
132 static inline struct tcp_request_sock *tcp_rsk(const struct request_sock *req)
134 return (struct tcp_request_sock *)req;
138 /* inet_connection_sock has to be the first member of tcp_sock */
139 struct inet_connection_sock inet_conn;
140 u16 tcp_header_len; /* Bytes of tcp header to send */
141 u16 gso_segs; /* Max number of segs per GSO packet */
144 * Header prediction flags
145 * 0x5?10 << 16 + snd_wnd in net byte order
150 * RFC793 variables by their proper names. This means you can
151 * read the code and the spec side by side (and laugh ...)
152 * See RFC793 and RFC1122. The RFC writes these in capitals.
154 u64 bytes_received; /* RFC4898 tcpEStatsAppHCThruOctetsReceived
155 * sum(delta(rcv_nxt)), or how many bytes
158 u32 segs_in; /* RFC4898 tcpEStatsPerfSegsIn
159 * total number of segments in.
161 u32 rcv_nxt; /* What we want to receive next */
162 u32 copied_seq; /* Head of yet unread data */
163 u32 rcv_wup; /* rcv_nxt on last window update sent */
164 u32 snd_nxt; /* Next sequence we send */
165 u32 segs_out; /* RFC4898 tcpEStatsPerfSegsOut
166 * The total number of segments sent.
168 u64 bytes_acked; /* RFC4898 tcpEStatsAppHCThruOctetsAcked
169 * sum(delta(snd_una)), or how many bytes
172 struct u64_stats_sync syncp; /* protects 64bit vars (cf tcp_get_info()) */
174 u32 snd_una; /* First byte we want an ack for */
175 u32 snd_sml; /* Last byte of the most recently transmitted small packet */
176 u32 rcv_tstamp; /* timestamp of last received ACK (for keepalives) */
177 u32 lsndtime; /* timestamp of last sent data packet (for restart window) */
178 u32 last_oow_ack_time; /* timestamp of last out-of-window ACK */
180 u32 tsoffset; /* timestamp offset */
182 struct list_head tsq_node; /* anchor in tsq_tasklet.head list */
183 unsigned long tsq_flags;
185 /* Data for direct copy to user */
187 struct sk_buff_head prequeue;
188 struct task_struct *task;
194 u32 snd_wl1; /* Sequence for window update */
195 u32 snd_wnd; /* The window we expect to receive */
196 u32 max_window; /* Maximal window ever seen from peer */
197 u32 mss_cache; /* Cached effective mss, not including SACKS */
199 u32 window_clamp; /* Maximal window to advertise */
200 u32 rcv_ssthresh; /* Current window clamp */
202 /* Information of the most recently (s)acked skb */
204 struct skb_mstamp mstamp; /* (Re)sent time of the skb */
205 u8 advanced; /* mstamp advanced since last lost marking */
206 u8 reord; /* reordering detected */
208 u16 advmss; /* Advertised MSS */
210 u8 nonagle : 4,/* Disable Nagle algorithm? */
211 thin_lto : 1,/* Use linear timeouts for thin streams */
212 thin_dupack : 1,/* Fast retransmit on first dupack */
214 frto : 1;/* F-RTO (RFC5682) activated in CA_Loss */
216 u8 do_early_retrans:1,/* Enable RFC5827 early-retransmit */
217 syn_data:1, /* SYN includes data */
218 syn_fastopen:1, /* SYN includes Fast Open option */
219 syn_fastopen_exp:1,/* SYN includes Fast Open exp. option */
220 syn_data_acked:1,/* data in SYN is acked by SYN-ACK */
221 save_syn:1, /* Save headers of SYN packet */
222 is_cwnd_limited:1;/* forward progress limited by snd_cwnd? */
223 u32 tlp_high_seq; /* snd_nxt at the time of TLP retransmit. */
225 /* RTT measurement */
226 u32 srtt_us; /* smoothed round trip time << 3 in usecs */
227 u32 mdev_us; /* medium deviation */
228 u32 mdev_max_us; /* maximal mdev for the last rtt period */
229 u32 rttvar_us; /* smoothed mdev_max */
230 u32 rtt_seq; /* sequence number to update rttvar */
232 u32 rtt, ts; /* RTT in usec and sampling time in jiffies. */
235 u32 packets_out; /* Packets which are "in flight" */
236 u32 retrans_out; /* Retransmitted packets out */
237 u32 max_packets_out; /* max packets_out in last window */
238 u32 max_packets_seq; /* right edge of max_packets_out flight */
240 u16 urg_data; /* Saved octet of OOB data and control flags */
241 u8 ecn_flags; /* ECN status bits. */
242 u8 keepalive_probes; /* num of allowed keep alive probes */
243 u32 reordering; /* Packet reordering metric. */
244 u32 snd_up; /* Urgent pointer */
247 * Options received (usually on last packet, some only on SYN packets).
249 struct tcp_options_received rx_opt;
252 * Slow start and congestion control (see also Nagle, and Karn & Partridge)
254 u32 snd_ssthresh; /* Slow start size threshold */
255 u32 snd_cwnd; /* Sending congestion window */
256 u32 snd_cwnd_cnt; /* Linear increase counter */
257 u32 snd_cwnd_clamp; /* Do not allow snd_cwnd to grow above this */
260 u32 prior_cwnd; /* Congestion window at start of Recovery. */
261 u32 prr_delivered; /* Number of newly delivered packets to
262 * receiver in Recovery. */
263 u32 prr_out; /* Total number of pkts sent during Recovery. */
265 u32 rcv_wnd; /* Current receiver window */
266 u32 write_seq; /* Tail(+1) of data held in tcp send buffer */
267 u32 notsent_lowat; /* TCP_NOTSENT_LOWAT */
268 u32 pushed_seq; /* Last pushed seq, required to talk to windows */
269 u32 lost_out; /* Lost packets */
270 u32 sacked_out; /* SACK'd packets */
271 u32 fackets_out; /* FACK'd packets */
273 /* from STCP, retrans queue hinting */
274 struct sk_buff* lost_skb_hint;
275 struct sk_buff *retransmit_skb_hint;
277 /* OOO segments go in this list. Note that socket lock must be held,
278 * as we do not use sk_buff_head lock.
280 struct sk_buff_head out_of_order_queue;
282 /* SACKs data, these 2 need to be together (see tcp_options_write) */
283 struct tcp_sack_block duplicate_sack[1]; /* D-SACK block */
284 struct tcp_sack_block selective_acks[4]; /* The SACKS themselves*/
286 struct tcp_sack_block recv_sack_cache[4];
288 struct sk_buff *highest_sack; /* skb just after the highest
289 * skb with SACKed bit set
290 * (validity guaranteed only if
295 u32 retransmit_high; /* L-bits may be on up to this seqno */
297 u32 prior_ssthresh; /* ssthresh saved at recovery start */
298 u32 high_seq; /* snd_nxt at onset of congestion */
300 u32 retrans_stamp; /* Timestamp of the last retransmit,
301 * also used in SYN-SENT to remember stamp of
303 u32 undo_marker; /* snd_una upon a new recovery episode. */
304 int undo_retrans; /* number of undoable retransmissions. */
305 u32 total_retrans; /* Total retransmits for entire connection */
307 u32 urg_seq; /* Seq of received urgent pointer */
308 unsigned int keepalive_time; /* time before keep alive takes place */
309 unsigned int keepalive_intvl; /* time interval between keep alive probes */
313 /* Receiver side RTT estimation */
320 /* Receiver queue space */
327 /* TCP-specific MTU probe information. */
332 u32 mtu_info; /* We received an ICMP_FRAG_NEEDED / ICMPV6_PKT_TOOBIG
333 * while socket was owned by user.
336 #ifdef CONFIG_TCP_MD5SIG
337 /* TCP AF-Specific parts; only used by MD5 Signature support so far */
338 const struct tcp_sock_af_ops *af_specific;
340 /* TCP MD5 Signature Option information */
341 struct tcp_md5sig_info __rcu *md5sig_info;
344 /* TCP fastopen related information */
345 struct tcp_fastopen_request *fastopen_req;
346 /* fastopen_rsk points to request_sock that resulted in this big
347 * socket. Used to retransmit SYNACKs etc.
349 struct request_sock *fastopen_rsk;
356 TCP_TSQ_DEFERRED, /* tcp_tasklet_func() found socket was owned */
357 TCP_WRITE_TIMER_DEFERRED, /* tcp_write_timer() found socket was owned */
358 TCP_DELACK_TIMER_DEFERRED, /* tcp_delack_timer() found socket was owned */
359 TCP_MTU_REDUCED_DEFERRED, /* tcp_v{4|6}_err() could not call
360 * tcp_v{4|6}_mtu_reduced()
364 static inline struct tcp_sock *tcp_sk(const struct sock *sk)
366 return (struct tcp_sock *)sk;
369 struct tcp_timewait_sock {
370 struct inet_timewait_sock tw_sk;
371 #define tw_rcv_nxt tw_sk.__tw_common.skc_tw_rcv_nxt
372 #define tw_snd_nxt tw_sk.__tw_common.skc_tw_snd_nxt
377 /* The time we sent the last out-of-window ACK: */
378 u32 tw_last_oow_ack_time;
380 long tw_ts_recent_stamp;
381 #ifdef CONFIG_TCP_MD5SIG
382 struct tcp_md5sig_key *tw_md5_key;
386 static inline struct tcp_timewait_sock *tcp_twsk(const struct sock *sk)
388 return (struct tcp_timewait_sock *)sk;
391 static inline bool tcp_passive_fastopen(const struct sock *sk)
393 return (sk->sk_state == TCP_SYN_RECV &&
394 tcp_sk(sk)->fastopen_rsk != NULL);
397 static inline void fastopen_queue_tune(struct sock *sk, int backlog)
399 struct request_sock_queue *queue = &inet_csk(sk)->icsk_accept_queue;
400 int somaxconn = READ_ONCE(sock_net(sk)->core.sysctl_somaxconn);
402 queue->fastopenq.max_qlen = min_t(unsigned int, backlog, somaxconn);
405 static inline void tcp_move_syn(struct tcp_sock *tp,
406 struct request_sock *req)
408 tp->saved_syn = req->saved_syn;
409 req->saved_syn = NULL;
412 static inline void tcp_saved_syn_free(struct tcp_sock *tp)
414 kfree(tp->saved_syn);
415 tp->saved_syn = NULL;
418 #endif /* _LINUX_TCP_H */