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tcp: disable RFC6675 loss detection 

This patch disables RFC6675 loss detection and make sysctl
net.ipv4.tcp_recovery = 1 controls a binary choice between RACK
(1) or RFC6675 (0).

Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Soheil Hassas Yeganeh <soheil@google.com>
Reviewed-by: Priyaranjan Jha <priyarjha@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
hifive-unleashed-5.1
Yuchung Cheng 2018-05-16 16:40:11 -07:00 committed by David S. Miller
parent 20b654dfe1
commit b38a51fec1
2 changed files with 10 additions and 5 deletions
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3
Documentation/networking/ip-sysctl.txt
View File

@ -449,7 +449,8 @@ tcp_recovery - INTEGER
features.
RACK: 0x1 enables the RACK loss detection for fast detection of lost
retransmissions and tail drops.
retransmissions and tail drops. It also subsumes and disables
RFC6675 recovery for SACK connections.
RACK: 0x2 makes RACK's reordering window static (min_rtt/4).
RACK: 0x4 disables RACK's DUPACK threshold heuristic

12
net/ipv4/tcp_input.c
View File

@ -2035,6 +2035,11 @@ static inline int tcp_dupack_heuristics(const struct tcp_sock *tp)
return tp->sacked_out + 1;
}
static bool tcp_is_rack(const struct sock *sk)
{
return sock_net(sk)->ipv4.sysctl_tcp_recovery & TCP_RACK_LOSS_DETECTION;
}
/* Linux NewReno/SACK/ECN state machine.
* --------------------------------------
*
@ -2141,7 +2146,7 @@ static bool tcp_time_to_recover(struct sock *sk, int flag)
return true;
/* Not-A-Trick#2 : Classic rule... */
if (tcp_dupack_heuristics(tp) > tp->reordering)
if (!tcp_is_rack(sk) && tcp_dupack_heuristics(tp) > tp->reordering)
return true;
return false;
@ -2722,8 +2727,7 @@ static void tcp_rack_identify_loss(struct sock *sk, int *ack_flag)
{
struct tcp_sock *tp = tcp_sk(sk);
/* Use RACK to detect loss */
if (sock_net(sk)->ipv4.sysctl_tcp_recovery & TCP_RACK_LOSS_DETECTION) {
if (tcp_is_rack(sk)) {
u32 prior_retrans = tp->retrans_out;
tcp_rack_mark_lost(sk);
@ -2862,7 +2866,7 @@ static void tcp_fastretrans_alert(struct sock *sk, const u32 prior_snd_una,
fast_rexmit = 1;
}
if (do_lost)
if (!tcp_is_rack(sk) && do_lost)
tcp_update_scoreboard(sk, fast_rexmit);
*rexmit = REXMIT_LOST;
}