tcp: remove early retransmit

This patch removes the support of RFC5827 early retransmit (i.e.,
fast recovery on small inflight with <3 dupacks) because it is
subsumed by the new RACK loss detection. More specifically when
RACK receives DUPACKs, it'll arm a reordering timer to start fast
recovery after a quarter of (min)RTT, hence it covers the early
retransmit except RACK does not limit itself to specific inflight
or dupack numbers.

Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 0 insertions, 19 deletions

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 423438dd6fe9..c55d65f74f7f 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -565,7 +565,6 @@ void tcp_skb_collapse_tstamp(struct sk_buff *skb,
                              const struct sk_buff *next_skb);
 
 /* tcp_input.c */
-void tcp_resume_early_retransmit(struct sock *sk);
 void tcp_rearm_rto(struct sock *sk);
 void tcp_synack_rtt_meas(struct sock *sk, struct request_sock *req);
 void tcp_reset(struct sock *sk);
@@ -1037,24 +1036,6 @@ static inline void tcp_enable_fack(struct tcp_sock *tp)
         tp->rx_opt.sack_ok |= TCP_FACK_ENABLED;
 }
 
-/* TCP early-retransmit (ER) is similar to but more conservative than
- * the thin-dupack feature.  Enable ER only if thin-dupack is disabled.
- */
-static inline void tcp_enable_early_retrans(struct tcp_sock *tp)
-{
-        struct net *net = sock_net((struct sock *)tp);
-
-        tp->do_early_retrans = sysctl_tcp_early_retrans &&
-                sysctl_tcp_early_retrans < 4 && !sysctl_tcp_thin_dupack &&
-                !(sysctl_tcp_recovery & TCP_RACK_LOSS_DETECTION) &&
-                net->ipv4.sysctl_tcp_reordering == 3;
-}
-
-static inline void tcp_disable_early_retrans(struct tcp_sock *tp)
-{
-        tp->do_early_retrans = 0;
-}
-
 static inline unsigned int tcp_left_out(const struct tcp_sock *tp)
 {
         return tp->sacked_out + tp->lost_out;