net/ipv4/tcp_input.c

46  *		Andrey Savochkin:	Check sequence numbers correctly when
236 		 * when we update icsk_ack.rcv_mss.
412  * 1. Tuning sk->sk_sndbuf, when connection enters established state.
462  * - to enforce header prediction at sender, even when application
467  * The scheme does not work when sender sends good segments opening
796 /* There is something which you must keep in mind when you analyze the
877 	 * These formulae increase RTO, when it should be decreased, increase
878 	 * too slowly, when it should be increased quickly, decrease too quickly
890 			 * Eifel blocks mdev updates when rtt decreases.
1061 /* It's reordering when higher sequence was delivered (i.e. sacked) before
1152 /* This procedure tags the retransmission queue when SACKs arrive.
1166  * (L|S|R is logically valid, it could occur when L|R is sacked,
1176  *	B. SACK arrives sacking SND.NXT at the moment, when the
1182  * when multiple events arrive simultaneously. (see the function below).
1191  *    when segment was retransmitted.
1194  * Both of these heuristics are not used in Loss state, when we cannot
1204  * SACK reneging when it should advance SND.UNA. Such SACK block this is
1216  * happens when start_seq resides between end_seq wrap (e_w) and snd_nxt
1479 	 * tcp_highest_sack_seq() when skb is highest_sack.
1685 	 * useful when hole on every nth skb pattern happens
2247  * counter when SACK is enabled (without SACK, sacked_out is used for
2253  * but when e.g. out-of-window ACKs or packet duplication occurs,
2267  *		but requires a bit more attention. It is entered when
2277  * - when arrived ACK is unusual, namely:
2306  *	F.e. after RTO, when all the queue is considered as lost,
2339  * when we decide that hole is caused by loss, rather than by a reorder.
2353 /* This function decides, when we should leave Disordered state
2438 static bool tcp_tsopt_ecr_before(const struct tcp_sock *tp, u32 when)
2441 	       before(tp->rx_opt.rcv_tsecr, when);
2465 /* We can clear retrans_stamp when there are no retransmissions in the
2468  * what will happen if errors occur when sending retransmission for the
2646  *      But when SND_UNA is acked without further losses,
2992  * Besides that it updates the congestion state when packet loss or ECN
3025 	 *    when high_seq is ACKed. */
3127 		 * prop. delay when it expires. Skip suspected delayed ACKs.
3220 			 * when the retrans timer fires and is rescheduled.
3444 		 * after when the head was last (re)transmitted. Otherwise the
3502 		unsigned long when = tcp_probe0_when(sk, TCP_RTO_MAX);
3504 		when = tcp_clamp_probe0_to_user_timeout(sk, when);
3505 		tcp_reset_xmit_timer(sk, ICSK_TIME_PROBE0, when, TCP_RTO_MAX);
3987 	/* If needed, reset TLP/RTO timer when RACK doesn't set. */
4115  * But, this can also be called on packets in the established flow when
4351  * on networks with high bandwidth, when sequence space is recycled fastly,
4357  * states that events when retransmit arrives after original data are rare.
4419  * of RCV.NXT. Peer still did not advance his SND.UNA when we
4472  *	and the FIN takes effect when it is validly part of sequence
4473  *	space. Not before when we get holes.
4512 		/* This case occurs when a simultaneous close
5208 			/* RFC5681. 4.2. SHOULD send immediate ACK, when
5445 		/* Range is terminated when we see a gap or when
5737  *	This routine is only called when we have urgent data
5779 	/* We may be adding urgent data when the last byte read was
5979  * 	disabled when:
5996  *	tcp_data_queue when everything is OK.
6032 	 *  turn it off	(when there are holes in the receive
6199 	 * initRTO, we only reset cwnd when more than 1 SYN/SYN-ACK
6324 	/* undo_marker is set when SYN or SYNACK times out. The timeout is
6606 	 * when new data has just been ack'ed.
6609 	 * retransmitting any data sooner based on when they