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net-tcp: add fast_ack_mode=1: skip rwin check in tcp_fast_ack_mode__tcp_ack_snd_check()

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Add logic for an experimental TCP connection behavior, enabled with
tp->fast_ack_mode = 1, which disables checking the receive window
before sending an ack in __tcp_ack_snd_check(). If this behavior is
enabled, the data receiver sends an ACK if the amount of data is >
RCV.MSS.

Change-Id: Iaa0a0fd7108221f883137a79d5bfa724f1b096d4
Signed-off-by: Juhyung Park <qkrwngud825@gmail.com>
This commit is contained in:
Neal Cardwell 2019-11-16 13:16:25 -05:00 committed by Ksawlii
parent 96c42cd35d
commit 54113b9ad5
4 changed files with 7 additions and 3 deletions
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3
include/linux/tcp.h
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@ -226,7 +226,8 @@ struct tcp_sock {
u8 compressed_ack;
u8 dup_ack_counter:2,
tlp_retrans:1, /* TLP is a retransmission */
unused:5;
fast_ack_mode:2, /* which fast ack mode ? */
unused:3;
u32 chrono_start; /* Start time in jiffies of a TCP chrono */
u32 chrono_stat[3]; /* Time in jiffies for chrono_stat stats */
u8 chrono_type:2, /* current chronograph type */

1
net/ipv4/tcp.c
View file

@ -2874,6 +2874,7 @@ int tcp_disconnect(struct sock *sk, int flags)
tp->rx_opt.dsack = 0;
tp->rx_opt.num_sacks = 0;
tp->rcv_ooopack = 0;
tp->fast_ack_mode = 0;
/* Clean up fastopen related fields */

1
net/ipv4/tcp_cong.c
View file

@ -179,6 +179,7 @@ void tcp_init_congestion_control(struct sock *sk)
struct inet_connection_sock *icsk = inet_csk(sk);
tcp_sk(sk)->prior_ssthresh = 0;
tcp_sk(sk)->fast_ack_mode = 0;
if (icsk->icsk_ca_ops->init)
icsk->icsk_ca_ops->init(sk);
if (tcp_ca_needs_ecn(sk))

5
net/ipv4/tcp_input.c
View file

@ -5507,13 +5507,14 @@ static void __tcp_ack_snd_check(struct sock *sk, int ofo_possible)
/* More than one full frame received... */
if (((tp->rcv_nxt - tp->rcv_wup) > inet_csk(sk)->icsk_ack.rcv_mss &&
(tp->fast_ack_mode == 1 ||
/* ... and right edge of window advances far enough.
* (tcp_recvmsg() will send ACK otherwise).
* If application uses SO_RCVLOWAT, we want send ack now if
* we have not received enough bytes to satisfy the condition.
*/
(tp->rcv_nxt - tp->copied_seq < sk->sk_rcvlowat ||
__tcp_select_window(sk) >= tp->rcv_wnd)) ||
(tp->rcv_nxt - tp->copied_seq < sk->sk_rcvlowat ||
__tcp_select_window(sk) >= tp->rcv_wnd))) ||
/* We ACK each frame or... */
tcp_in_quickack_mode(sk) ||
/* Protocol state mandates a one-time immediate ACK */